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- We’ve discovered a new kind of magnetism. What can we do with it? (paid): 2025 Jul 15

- The truth about de-extinction: is it even possible, and why do it? (paid): 2025 Jul 14

- Evolution has made humans both Machiavellian and born socialists (paid): 2025 Jul 9

PHYSICS | JUL 15, 2025, 12:00 PM EDT | VIEW ON NEW SCIENTIST

We’ve discovered a new kind of magnetism. What can we do with it?

Researchers have found the first new type of magnet in nearly a century. Now, these strange "altermagnets" could help us build an entirely new type of computer

By Jacklin Kwan

Bekologic

Libor Šmejkal has a fondness for the artwork of M. C. Escher, whose work was often inspired by mathematics. One of Šmejkal’s favourite pieces is Horseman, a striking picture that features an elaborate, tessellating series of mounted figures. Strangely enough, it was this piece that inspired him to predict the existence of an entirely new kind of magnetism.

We have known of magnets for millennia. Today, they are at the heart of a raft of modern technologies, from electric generators and smartphones to loudspeakers and hospital scanners. And yet for 100 years, we have been missing something about them. We always assumed there were only two types. It was Šmejkal’s art-inspired insights that finally gave the lie to that in 2022.

Fast-forward to today, and we know that what Šmejkal called “altermagnets” aren’t just an idea. We have discovered real examples and are working out how to make this new kind of material in practical and useful ways. There is even a possibility that these magnets could help us build a completely new kind of computer. “Altermagnets could actually have all the functionalities of current devices, but much faster, with less energy consumption, and smaller,” says Šmejkal.

To understand magnetism and why it is so important, we need to start with the electrons that whizz around in atoms. Each of these particles has an intrinsic quantum property called spin. This isn’t quite like anything in the everyday world, but you can imagine it as a tiny spinning top that can rotate in two directions, which scientists label “up” or “down”.

Electrons like to orbit their atoms in pairs, one spin-up, one spin-down, so the spins cancel out. But that isn’t always possible, as an electron sometimes ends up alone. With nothing to cancel it out, the unpaired electron gives the atom what is known as a magnetic moment: like spin, it can either be up or down, and it governs the atom’s magnetism. If you have enough atoms with magnetic moments pointing in the same direction, they create a strong, directional magnetic field. This is called ferromagnetism. It is a phenomenon that even the ancient Greeks knew about – they found rocks that attracted iron nails or filings to them – and it is also what is going on inside the magnets many of us have stuck to our fridges.

Ferromagnets are easy to spot because they attract or repel other magnetic materials, like nickel or cobalt. But there is another, more subtle kind of magnetism that wasn’t discovered until the 1930s. Antiferromagnets also have magnetic arrows, but this time they point in alternating directions – picture a line of arrows going up, down, up, down and so on. The result is a magnetic stalemate, a solid with magnetic order on the atomic level, but no unified, detectable magnetism on the scale of ordinary objects.

The mental model of imagining tiny arrows pointing up and down inside magnets was invented by physicist Louis Néel, who theorised the first antiferromagnets – which were experimentally confirmed in the decades following – and who won a share of the 1970 Nobel prize in physics.

Magnetic symmetry

That’s how things have stood for nearly 100 years: two types of magnetism, nice and neat. It was 2018 when Šmejkal, who is now based at Johannes Gutenberg University Mainz in Germany, began to suspect there might be more to the picture. At the time, he was a young PhD student in Prague, Czech Republic, studying a strange phenomenon sometimes seen in antiferromagnets called the anomalous Hall effect. Šmejkal’s breakthrough was to realise that this effect and similar arcane magnetism puzzles couldn’t be explained with the model that Néel had developed – he needed to go beyond it.

This is where Escher’s 1946 horsemen artwork came in. The riders in the image slot together in alternating colours with an elaborate, beautiful symmetry. Take one of the lighter figures, flip it, shift it sideways a jot and change its colour, and you match one of the darker riders. As he mused on this, Šmejkal realised there was an alternative mathematical method for describing this symmetry operation. “I realised that you can actually define this operation, this changing of colour or orientation, in another way,” he says.

And here’s the thing: understanding symmetry has always been crucial in physics, and this is particularly true in materials science, where the intricate relationships between different kinds of atoms are best described in that language. Indeed, Néel’s way of thinking about atoms’ magnetic moments has symmetry at its core. But by using his new mathematics as a framework, Šmejkal began to extend Néel’s model, firstly by thinking in three dimensions instead of two and secondly by including atoms with no magnetic moment in the picture.

As he did so, a new possibility began to emerge. You could still have neighbouring atoms with magnetic moments that point in opposite directions: up, down, up, down, as in antiferromagnets. But every alternate atom would be rotated by 90 degrees, hence the name altermagnet (see diagram, below). Šmejkal says this rotation can happen as a result of magnetic atoms existing in a sea of non-magnetic atoms. Though the arrows still alternate in pointing up and down, the rotated atoms give rise to a subtle effect that enables some magnetism to leak through.

This had all started as an attempt to solve a particular set of puzzles in magnetism, but Šmejkal says it amounted to something much grander: it predicted that a whole new kind of magnetism was possible. Altermagnets would have no net magnetism, like antiferromagnets, but they would have some of the quantum properties that make ferromagnets so useful in technology. In 2022, Šmejkal and his colleagues published what he calls a “complete mathematical framework” of altermagnetism. “The whole community was quite excited because these systems seem to combine the prized advantages of ferromagnets and antiferromagnets,” he says.

Confirming that altermagnets exist

The world only had to wait two years before the prediction was confirmed. In 2024, Juraj Krempaský at the Paul Scherrer Institute in Villigen, Switzerland, and his colleagues studied manganese telluride, a compound thought to have the right structure to produce altermagnetism. To check if it did, they used light beams to track the precise movements of electrons inside the material – and these turned out to closely match simulations of what would be expected for an altermagnet.

The discovery of a third kind of magnetism is huge in its own right, but what makes it even more exciting is that it could solve a long-standing technological problem. To see why, we need to know a little about how computers store information. Today, they tend to do so in chips, essentially through the presence or absence of electric charge to signify a digital 0 or 1. But researchers have long been interested in the idea of using magnetism to store information, too – floppy disks, which were used in the 1990s, worked on magnetic principles. A more recent concept called spintronics takes things a step further: the idea would be to use not just the presence or absence of electric charge, but also the spin of the electrons too.

Couples dance the tango, spinning in different directions

Corbis via Getty Images

In theory, spintronics would enable us to cram much more information into computer memory, making it more efficient. But there has always been one big problem. For it to work, we need materials in which the up and down spins can be split into separate strands. Anna Hellenes, who works in Šmejkal’s university research group, likens it to a ballroom full of dancers. In a non-magnetic material, all the couples waltzing clockwise or counterclockwise – the electrons spinning up or down – remain mixed on the dance floor. “But if we now have spin-splitting, these dancers spinning in one direction can separate from the others spinning in the other, and dance separately,” she says.

The problem is that this spin-splitting effect, the bedrock of any spintronic device, was only found in ferromagnetic materials. This made sense because all the arrows in a ferromagnet point the same way, so electrons whose spin points in the direction of all those cumulative arrows are in a slightly different environment than those with spins pointing the other way. But if you try to cram lots of ferromagnets onto a tiny chip, they do exactly what you might expect: attract or repel each other. As a result, says Hellenes, spintronics has hit a ceiling.

Making spintronics

Could altermagnets step into the breach? “This unique combination of features from altermagnets — no net magnetisation, but still spin-split bands — could be very advantageous for potential spintronic devices,” said Igor Mazin, a physicist at George Mason University in Virginia.

Since it was confirmed that manganese telluride was altermagnetic in 2024, researchers have been busy trying to create new materials that have this curious property. One trick is to take a known antiferromagnet and apply mechanical strain to it in the hope of deforming the internal magnetic symmetry and coaxing altermagnetism into being. In 2024, researchers led by Atasi Chakraborty, a member of Šmejkal’s research group, demonstrated that applying compressive strain to rhenium dioxide – long known to be an antiferromagnet – triggers a transition into an altermagnetic state.

What’s more, a trio of researchers at the Beijing Institute of Technology in China realised that you can also create the right internal magnetic disturbances by stacking an antiferromagnet between layers of a different material, like a sandwich. The top and bottom layers induce internal electric fields that mimic the crystal environment of naturally occurring altermagnets.

A nano-scale map of the altermagnetic material manganese telluride. The six colours and arrows show the direction of the ordering within the material

Oliver Amin et al./University of Nottingham

However, researchers tend to feel that these clever tricks may not lead to scalable altermagnets anytime soon, as the methods are difficult to pull off. Instead, it seems more likely that we can find practical altermagnets by looking at naturally occurring ones. “For the vision for altermagnetism over the next 10 years, I could quite easily see these materials becoming commercially viable,” says Oliver Amin, a researcher at the University of Nottingham, UK, who created the first experimental image of manganese telluride after it was confirmed as an altermagnetic material. In a paper published in December, his team demonstrated that researchers could not only see the structures that gave this material its magnetic properties, but also control the direction and layout of them by heating and cooling the material in a magnetic field. “This is the first step towards realising these materials as practical materials for devices,” says co-author Alfred Dal Din at the University of Nottingham.

We have good computational models of the kinds of atomic structures that are likely to exhibit this new magnetism, and Šmejkal and his colleagues used them to digitally comb through possible materials. They have identified at least 200 candidates, published shortly after their landmark altermagnetism paper. Confirming all those candidates experimentally will take time, but we already know that, other than manganese telluride, there is also strong evidence that ruthenium dioxide is an altermagnet.

Other than being the only certified, bona fide altermagnet, manganese telluride is an established material that scientists know how to grow in the lab at high qualities – the primary hurdle for many experimentalists. “The form of manganese telluride we’re working on now has been studied in the form we’re looking at for at least 20 years, probably more,” said Amin.

A fourth kind of magnetism?

Just as researchers rush to get to grips with altermagnets, Šmejkal has another surprise up his sleeve. In a paper that hasn’t yet been peer-reviewed, he and his colleagues predict the existence of yet another kind of magnetism, which he calls antialtermagnetism.

In materials with this strange property, neighbouring spins don’t just alternate up and down like in an antiferromagnet, they also form zigzags. Picture tiny arrows lying next to each other, the first pointing north-west, then north-east, then south-east, then south-west – tracing out a zigzag. The neighbouring arrows are mirror images of each other, so that adding up the directions across all the mirrored pairs will cause them to cancel out, as happens in antiferromagnetism. But the mirrored pattern subtly reshapes how electrons move through the material in such a way that also causes spin-splitting, says Šmejkal.

The idea of antialtermagnetism builds on the complex and beautiful symmetries that Šmejkal was so taken by early on in his work.

Perhaps we can say magnets are like one of those Escher artworks that he likes so much – the more you look, the more delightful details you notice.

LIFE | JUL 14, 2025, 12:00 PM EDT | VIEW ON NEW SCIENTIST

The truth about de-extinction: is it even possible, and why do it?

Ambitious projects aim to put dire wolves, woolly mammoths and passenger pigeons back into our ecosystems. But with so many technical and ethical hurdles, what is the real motivation?

By Michael Le Page

Sara Gironi Carnevale

Dire wolves were massive and highly intelligent animals nearly the size of a small horse, capable of ripping a man’s arm off as easily as a dog kills a rat. They lived in cold regions in a place called Westeros… oh sorry, I’m getting confused with the fictional dire wolves in the Game of Thrones TV series.

The dire wolves that actually lived on Earth were no larger than today’s biggest grey wolves, but with a sturdier build, bigger teeth and larger bacula, or penis bones. They probably feasted on now-extinct megafauna such as giant ground sloths. After thriving for many millennia, they went extinct around 10,000 years ago.

But now they are back. At least, a company called Colossal Biosciences is claiming the dire wolf is the first species to be brought back from the dead. It isn’t the only animal being targeted for resurrection. Plans are afoot to do the same for the dodo, woolly mammoth, passenger pigeon, moa and more. But is it really possible to revive an extinct species? Such efforts also raise the question of whether – beyond the obvious appeal of seeing long-lost animals in the flesh – there are any good reasons to try this, and why organisations such as Colossal are spending vast amounts of money on it.

The idea of resurrecting an extinct species goes back at least a century. In Germany in the 1920s, there were attempts to recreate the extinct wild cattle known as aurochs through the selective breeding of their descendants, domesticated cattle – in part because it was thought cattle had been weakened by domestication. The result was an animal that looked a bit like a smaller aurochs. In the 1980s, there was a similar effort to breed zebras with the same coats as the quagga, an extinct subspecies of the stripe-covered plains zebra, which resulted in quagga-like specimens that lacked stripes on their hindquarters.

“But I don’t think you can claim that that’s a quagga,” says Claudio Sillero at the University of Oxford. Breeding can create animals that physically resemble quaggas or aurochs, but genetically they aren’t the same, he says.

One of the “dire wolves” created by Colossal Biosciences, at 15 days old

Colossal Biosciences

These days, however, there are alternatives to selective breeding. What if you could get hold of the DNA from an extinct animal, put it in a living cell and create a clone of that long-dead individual? This, of course, is the idea that captured the public imagination when it was featured in the 1993 movie Jurassic Park. There is no formal scientific definition of “de-extinction”, but this scenario – creating an identical copy of a long-extinct animal – is what many people understand by the term.

It is also supposed to be impossible. “None of the current pathways will result in a faithful replica of any extinct species, due to genetic, epigenetic, behavioural, physiological, and other differences,” declared a 2016 report on de-extinction by the International Union for Conservation of Nature (IUCN).

Defining de-extinction

“It’s about definition,” says Tom Gilbert at the University of Copenhagen in Denmark. “If your definition of de-extinction is bringing back an extinct animal, exactly – genomically – like the extinct form, then yes it’s likely impossible.” That is because for the vast majority of extinct animals, there is no way to recover a complete genome. There are always going to be gaps resulting from the degradation of DNA over time.

However, there may be a few exceptions where animals went extinct very recently and we have well-preserved cells. In fact, in 2020 the US non-profit Revive & Restore used the cryopreserved cells of a black-footed ferret that died in 1988 to create three living ferrets that are clones of that long-dead individual. It did this by transferring the intact DNA from the frozen cells into living eggs.

“That’s literal resurrection,” says Ben Novak of Revive & Restore. “We’ve resurrected extinct gene variants for an endangered species.”

It isn’t de-extinction, however, because black-footed ferrets never died out completely. But at one point, there were just seven related individuals left, so cloning a non-related specimen massively boosted genetic diversity and, in turn, the species’ survival prospects.

There have been a few attempts to revive extinct species using this kind of cloning. For instance, the last remaining bucardo – a subspecies of the Iberian mountain goat – died in 2000 after a tree fell on her. Her cells were cloned, and a bucardo was born in 2003 – but it lived for just 10 minutes, probably because of health issues related to cloning.

This is the closest we have got to true de-extinction, but even if the clone had survived, it wouldn’t have been 100 per cent bucardo. A tiny proportion of its DNA came from the egg donor, in the form of cell organelles called mitochondria. And with no male bucardos – so no Y chromosome – there would have been no way to establish a pure breeding population.

We have cryopreserved samples of only a few other extinct species, such as the gastric-brooding frogs Rheobatrachus silus and R. vitellinus. These frogs, which incubate their eggs in their stomachs, died out soon after their discovery in Queensland in the 1970s. So far, efforts to clone them have been unsuccessful.

For extinct species where there are no cryopreserved cells, the only option is to turn to DNA preserved in bones and teeth, and sometimes in frozen tissues found in permafrost. Last year, for instance, Colossal claimed to have obtained from a tooth a near-complete genome sequence of the thylacine, the Australian carnivorous marsupial (also called a Tasmanian tiger) that went extinct in 1936. We don’t yet have the technology to turn that sequence on a computer back into DNA in a living cell, but it should become doable in the future.

Dinosaur resurrection?

Because DNA breaks up over time, the longer ago a species went extinct, the more fragmentary any genetic sequence we can retrieve will be. This means there is no chance of creating exact clones of animals that went extinct much more than a century or so ago. And the most ancient DNA fragments sequenced so far are just 2 million years old. So, sorry kids: no dinosaurs.

With species that went extinct long ago, the question is not only whether we can revive them, but also whether we should even try. After all, the world these animals lived in is long gone.

These kinds of issues were explored in the 2016 IUCN report. It concluded that we should try to recreate a lost species only when there is a conservation benefit, such as restoring an ecosystem in which the animal had played a key role.

For this purpose, it doesn’t matter if a revived animal is an exact copy of the extinct one, as long as it does much the same thing. In the jargon, this is called “creating a proxy of an extinct species for conservation benefit”, and this is what some biologists mean when they use the term de-extinction. But creating an ecological proxy is a very different thing from Jurassic Park-style de-extinction.

A model of a woolly mammoth at the Pont d’Arc Cave in France

Jean-Marc ZAORSKI/Gamma-Rapho via Getty Images

In fact, for many purposes, living species are good-enough proxies. “We should always reach first to extant species as potential ecological replacements,” says Philip Seddon at the University of Otago in New Zealand, who helped write the 2016 IUCN report.

So are the various de-extinction projects justified, according to this criterion of conservation benefit? Take aurochs, the extinct wild cattle.

Large herbivores like this have an immense effect on landscapes, says Claus Kropp of the Auerrind Project in Germany. The huge quantities of dung they drop set off chain reactions involving many other animals and plants, and the deep hoofprints they leave in wet mud create habitats for animals such as frogs.

Aurochs revival

The cattle created in the 1920s breeding project, however, aren’t even half the size of aurochs, says Kropp. So the Auerrind Project is again trying to recreate them via conventional breeding, but this time it has a better idea of what it is aiming for, given that we now have partial genome sequences from dozens of ancient aurochs. There is a similar project under way in the Netherlands.

Can’t existing large cattle breeds do the same? Most modern breeds aren’t suited to living outdoors year-round, says Kropp, and they also lack the forward-facing horns that helped aurochs defend themselves against predators. “We want to use the animals in regions where we have wolves,” he says. “We want to give them the best possible chance.”

Then there is the plan by Revive & Restore to create a bird that behaves like the extinct passenger pigeon. This will be done by modifying its closest living relative, the band-tailed pigeon.

Before they were wiped out, enormous flocks of passenger pigeons could deposit inches of guano on forest floors when they roosted in the trees above, says Novak. The thinking is that these disturbances shaped the nature of forests and boosted biodiversity.

“Even though there’s lots of forest again today [in the eastern US], the composition of that forest is very different than it was in the past,” he says. “We’re starting an experiment in the next four to six weeks where we’re going to spread guano on a forest site in Wisconsin, and then analyse that over some years.”

The team estimates there is enough forest to support 2 billion passenger pigeon-like birds, says Novak – though whether people would welcome the return of such vast flocks is questionable.

Plans are afoot to revive the extinct passenger pigeon using genetic engineering

Chronicle/Alamy

Achieving this will be a huge technical challenge. For starters, modifying birds is especially difficult because no one has found a way to locate the DNA inside the giant cell that is the yolk of an egg – a problem Colossal will also face with its plan, announced on 8 July, to “de-extinct” New Zealand’s giant wingless birds called moas.

Then there are the 25 million differences between the genomes of the band-tailed and passenger pigeons, says Novak, though he hopes only thousands of changes will be needed to recreate their key characteristics. The plan is to swap large segments of the band-tailed pigeon’s genome with the equivalent parts of the passenger pigeon genome. These chunks will be chosen because they contain gene variants thought to be important to the behaviour of passenger pigeons, but the hope is that many of the other variants on them will turn out to play a role too.

“We don’t necessarily know what all these mutations are doing, so our thought is, let’s just get more in there,” says Novak. “Let’s say we only make a dozen changes, but they’re all 100,000 base pairs in size; we will have accomplished tens of thousands of mutations that way.”

Even if the project succeeds, scientifically the result will be a kind of hybrid between the band-tailed pigeon (Patagioenas fasciata) and the passenger pigeon (Ectopistes migratorius). For this reason, Novak has proposed the name Patagioenas neoectopistes: the “new wandering pigeon of America”.

While Revive & Restore does sometimes talk about “bringing back the passenger pigeon” for the sake of ease, Novak is clear that recreating it isn’t possible: “We cannot resurrect the original passenger pigeon. It’s extinct.”

Dire wolves back from the dead?

In contrast, Colossal’s attempt to make grey wolves more like dire wolves was much less ambitious. There are millions of differences between the two species, but the company made just 20 small changes to the genome of grey wolf cells, only 15 of which are based on the dire wolf genome. The altered cells were then cloned, resulting in the birth of three gene-edited grey wolves.

The 20 changes are intended to make the animals larger and more muscular, and their fur longer and white, rather like the dire wolves depicted in Game of Thrones. (The TV series was mentioned three times in the 7 April press release from Colossal.) It won’t be clear until the three animals are fully grown how successful the attempt to change their shape was, says Colossal’s chief scientist Beth Shapiro. “We have to wait until they’re older to get the scans that we need.”

However, rather than describing these animals as a kind of hybrid, as Novak plans to do for the pigeons, Colossal continues to claim they are “the world’s first successfully de-extincted animal”.

“With those edits, we have brought back the dire wolf. We have been using the concept of functional de-extinction from the beginning, and that is what Colossal achieved,” the company said in a statement to New Scientist.

But not only are these gene-edited wolves very far from being exact genetic copies of dire wolves, there is also no evidence they can perform an ecological role that’s different from grey wolves’. Even if they could, with no megafauna larger than bison left, there is no gap for them to fill. What’s more, Colossal has no plans to release the gene-edited grey wolves – one of the many potential issues is that they could interbreed with normal grey wolves.

The scientific verdict is clear. The three animals produced by Colossal are not dire wolves

The scientific verdict is clear. “The three animals produced by Colossal are not dire wolves. Nor are they proxies of the dire wolf,” said a statement put out by the IUCN’s expert group on canids.

By swapping more chunks of the grey wolf genome for dire wolf ones, as Novak plans to do with the pigeons, it would be possible to create “hybrids” that have more dire wolf DNA than the three modified grey wolves. With enough effort, it might even be possible to create hybrids that are closer to dire wolves than grey wolves. But with Colossal claiming the task of reviving the dire wolf has already been achieved, it seems unlikely for the company to do this.

Woolly mammoth de-extinction plans

The issues with Colossal’s plans to “de-extinct” the woolly mammoth by modifying elephants are similar to those with the dire wolf. Again, the result will be some kind of hybrid between elephants and mammoths – probably more elephant than mammoth – and the need for them is unclear.

Proponents often say large herbivores could help slow the loss of permafrost in parts of the Arctic. Indeed, one small study found that permafrost stays colder when large animals flatten snow, so it no longer acts as a thick blanket insulating the ground from the cold air above.

But horses could also do the job, says Richard Grenyer at the University of Oxford. “There’s very good science suggesting you don’t need mammoths,” he says. “And the biggest problem is the scale. The sheer amount of land required to make any difference [climate-wise] is beyond anything we’ve ever seen in any conservation project.”

There is also the question of why a for-profit company like Colossal is putting so much effort into de-extinction. How is it going to make back the vast sums it is spending? Grenyer, for one, can’t see how the company can do this from de-extinction alone. He suspects that this is more about developing new technologies than de-extinction, and that the dire wolf project is just a showcase for the company’s genetic modification skills.

“This isn’t a de-extinction business; they won’t be bringing a whole thing back from the dead ever because that’s not what they do,” suggests Grenyer. Colossal, of course, claims it has already done exactly that.

The company makes no secret of the fact that it aims to profit from spin-off applications. It says its research could lead to advances in everything from IVF and drug discovery to regenerative medicine and “genetic enhancements”. “We have a 17-person team that’s working on a fully exogenous artificial womb that could have broad application,” says Shapiro.

All the biologists New Scientist spoke to for this article agree the company is making significant advances. But if you are hoping for Jurassic Park, your best bet is still the movie version.

HUMANS | JUL 9, 2025, 12:00 PM EDT | VIEW ON NEW SCIENTIST

Evolution has made humans both Machiavellian and born socialists

Humanity’s innate treachery is behind social ills ranging from inequality to abuse of power. Lessons from our ancestors can help defeat the enemy within

By Jonathan R. Goodman

David Oliete

Nearly 2 million years ago, one of our hominin ancestors developed bone cancer in their foot. The fate of this individual is unknown, but their fossilised remains leave no doubt that cancer has been a part of our story for a very long time. It is also clear that, when threatened by our own normally cooperative cells turning against us, we evolved an immune system to help us identify and deal with the enemy within.

But treacherous cancer cells weren’t the only internal threat our ancestors faced. As hypersocial beings, their survival was also jeopardised by selfish individuals attempting to subvert the group – and capable of unravelling society, just as a cancer eventually kills its host. I am interested in understanding how we adapted to this threat. At the heart of the story is this question: is human nature selfish or altruistic, competitive or cooperative? Are we essentially cancers, tamed by culture, or more like healthy cells in the human body, working together for mutual success?

People have debated this for centuries and continue to do so, citing research in primatology, anthropology, psychology and economics to defend their points. The answer has profound implications for how we aim to structure society. If we are born altruists, then institutions and hierarchies are unnecessary. But if selfishness prevails, strong control is essential. To me, both extremes are unconvincing. To understand why, we must appreciate the circumstances under which humanity has evolved. Determining how our ancestors confronted brutish selfishness doesn’t just tell us about our own social past – it can also help us inoculate today’s societies against the threat from within.

Look at the animals to which we are most closely related and you see that each species has its own distinct set of social structures. Among gorillas, for example, groups of unmated males are typically led by aggressive alpha males. Mated gorillas sometimes live in groups of males and females, but more often it is the stereotypical silverback with a harem of females – a group that has its own hierarchy. Chimpanzees and bonobos also display dominance hierarchies, with a lot of emphasis placed on female social rank, particularly among bonobos. Despite the wide variation in sociality among these species, one thing is consistent: where there is social rank, aggressive dominance is the winning attribute. If an alpha can successfully defend resources, whether territory, food or mates, it can dominate a primate society. Access to more resources translates into having more surviving offspring than others, which is the only measure of success for evolution by natural selection.

Human self-domestication

Among our own ancestors – members of the genus Homo – the story is different. Research in anthropology and primatology suggests that, as early people evolved more complex social structures, they did something unseen in other primates: they domesticated themselves. Once they had the cognitive sophistication necessary to create weapons, along with the intelligence required to form alliances, they could fight the large, angry dominants that ruled over their social groups. The primatologist Richard Wrangham at Harvard University argues that this profoundly shaped human society because, along with eliminating the alphas, our ancestors also selected against the human trait of aggression. As a result, humans became more cooperative, and their societies became more egalitarian.

But if that is the case, how do we explain the undeniable and growing inequality in today’s societies, where huge amounts of power and money are concentrated among a small number of people, with the problem particularly pronounced in major economies such as the US, the UK and China? Some researchers argue that humans are not egalitarian by nature, but that living in small, close-knit groups of hunter-gatherers – as people did before the dawn of agriculture – suppressed our tendencies to form dominance-based hierarchies. They see a U-shaped curve of human egalitarianism. The point we started from – which looked a lot like the social structures we see in other great apes – is where we have ended up again, with the middle of the U showing a brief flirtation with social equality.

If human nature were entirely cooperative then state control wouldn’t be required to prevent freeloading

Zoonar GmbH/Alamy

I agree that we aren’t naturally egalitarian. In fact, I am not convinced that human societies were ever egalitarian. As anthropologists point out, even living hunter-gatherers have some brutal practices, such as infanticide. But, for me, the explanation for our current unequal circumstances lies not in our ancestors having selected against aggression, but in how the elimination of despotic alpha males allowed other, arguably more insidious people to succeed.

Once humanity was free of the strong grip of strict dominance hierarchies led by alpha males, success in social groups would have become more about skilful manoeuvring within communities. This led to the rise of a particular kind of social intelligence called Machiavellian intelligence, which entails the cunning manipulation of others. In the language of evolutionary biology, we have a cooperation dilemma: there are situations where it is in our interest to work with others, and there are situations where it is not. And, as anyone who has watched an episode of The Traitors will be aware, the need to pull together and the need to betray can come into conflict. As a result, overt rivalry was superseded by what I call “invisible rivalry” – the ability to hide selfish, competitive or exploitative intentions while maintaining the appearance of a cooperative nature. In other words, we evolved to compete in a cooperative world.

The social brain

Support for this idea comes from the size of the human brain. All primates have large brains relative to their body size, and ours is exceptionally big. The social brain hypothesis suggests that these large brains evolved to help individuals manage their unusually complex social systems. Of course, cooperation is part of this, but it can’t be the whole story. Consider ants, which, in terms of numbers and pervasiveness, are probably the most successful group of species on Earth. They are eusocial, which means they cooperate so fully that they seem to act as a single organism. Yet their brains are tiny, and everything they need to work together is programmed within them genetically. So, you don’t necessarily need a big brain to cooperate – but you do need one to compete strategically. Indeed, research suggests that social competition is what best explains the evolution of our enormous brain compared with the big brains of other primates.

To paraphrase Aristotle, we are political animals – not merely social ones. We strategise within our societies to maximise our success, whether that is defined in terms of money, power, mating success, hunting prowess or any of the other qualities associated with prestige around the world. To do so effectively, we evolved to not just be smart enough to cooperate, but to cooperate selectively – and to betray others when it suits us, or even just when we can get away with it.

Studies by economists and psychologists illustrate this. For example, in one set of experiments, participants were paired in a cooperation game in which one person was given $10 and the choice to share it with the other (or not). A lot of research shows that in these circumstances, people generally give some money to their partner, often splitting the pot equally, even when there is no obvious punishment for betraying them. But this time, the researchers gave some participants another option: they could take less money and leave the game without their partner ever knowing that they had been involved in a cooperation game. About one-third of participants took this option. It was as if they were happy to pay to have their betrayal left unknown.

Experiments like this tell us a lot about the human psyche. In social interactions, we often need to be able to predict what others around us are going to do – to learn where to place trust effectively, to win trust when we need it and to hide betrayals of trust on our own part. These abilities require empathy, emotion, language and, perhaps, as some of my colleagues argue, consciousness. Yet those same abilities, and that same intelligence, have a dangerous downside. Our evolved proclivity for maximising resources leads us to exploit those around us – and some people are so effective at deception that they risk damaging their societies. Modern, extreme inequality is an example of this process in action. So too are past political upheavals leading to degradation of the rule of law – and sometimes the fall of civilisations. The Roman Republic, for example, collapsed because of a tremendous internal struggle for power, culminating in Julius Caesar’s Machiavellian machinations, eventually leading to autocracy.

Religion is one institution that societies use to promote cooperation

Adam Guz/Getty Images Poland/Getty Images

So, our dual cooperative-competitive nature means that we face an enemy within that may bring down society. And this is where the analogy with cancer arises. Humanity’s long history of living with the disease means we have evolved biological mechanisms to reduce the risk it poses. Many reactions at the cellular level, including attacks by immune cells and programmed cell death, evolved to help our bodies fight off cancers, as well as other, external threats to our survival. It is this stalwart immune system that explains why, although mutations occur all the time and we are frequently exposed to viruses and bacteria, these often don’t lead to symptoms or illness. Similarly, the threats to our social groups posed by the evolution of invisible rivalry led us to develop practices, behaviours and institutions to maximise cooperation and thwart our Machiavellian tendencies. In my new book, Invisible Rivals: How we evolved to compete in a cooperative world, I call this our cultural immune system.

Religion is one institution that can function in this way. Religious teaching can promote cooperation among everyone who practises it – and this is one possible reason that the Golden Rule, often summed up as “treat others as you would like to be treated”, is found independently in scriptures across the world. People who believe these scriptures – who internalise them, as anthropologists say – are more likely to help fellow members of their group.

Everywhere anthropologists look, they find other practices and institutions that bolster cooperation at the local level. In cultures that rely on fishing, there are strong norms against over-fishing, which would deplete the stock for everyone. Where people are dependent on hunting, there are strict rules about how meat is shared and who gets credit for a kill. The Maasai people of Kenya and Tanzania have a relationship framework called osotua, rooted in need-based sharing partnerships and relying on mutual help in hard times. For example, if someone needs cattle because theirs have all died, another member of the group will help, not because they get anything directly in return, but simply because their neighbour’s needs are greater at that time. This creates a special bond – osotua translates as “umbilical cord” – and treachery is rare because the bond is seen as sacred.

The Maasai people have a system called osotua whereby they give cattle to others in need

Siegfried Modola/Getty Images

Across the world, social norms that guide behaviours have evolved, and they have been refined over thousands of years of trial and error through cultural evolution. However, just as cancers find ways to evade our immune systems, so some individuals use their Machiavellian intelligence to subvert the group’s social norms for their own benefit. This is trickier to do in small-scale societies where people all know each other, making rule-breakers easier to detect and punish. But as societies grew over the past 10,000 years, so did opportunities to act selfishly. Agricultural networks, cities and, finally, nation states made deception much easier to pull off, because it is easy to cheat more people without getting caught in a group where it is impossible to know everyone personally.

Taming our Machiavellian nature

It is this lethal combination of opportunity and invisible rivalry that makes the question of whether humans are cooperative or competitive so relevant today. To fight the enemy within society, we need to understand that both traits are in our nature, and that we evolved to apply whichever suits us best. Thinking that we are either one or the other leaves us vulnerable to facile arguments about how we should structure society. If we are purely selfish, it follows that society should focus on heavy policing and punishment of freeloaders, including those in power. But believing that we are intrinsically altruistic is equally detrimental because it risks ignoring the threat posed by rampant self-interest.

Suppressing humanity’s Machiavellian side is certainly harder in large-scale societies. But there are basic ways that we can boost the cultural immune system, much like how we can improve our biological immune systems through healthy lifestyles and vaccination. The key, I believe, is to learn more about the social norms that small-scale societies have evolved to help them thrive and stave off opportunistic cheaters and then use this knowledge to create policies that promote cooperation at a higher level. For example, within our own communities, we can look to cultures that promote systems like need-based transfers and others that have found ways to share resources more equitably.

But this isn’t going to happen until we first recognise the problem that invisible rivalry poses. In my view, the best way to do that is through education. We are all part of the cultural immune system. If we understand our evolutionary heritage, we will be alert to the danger that freeloaders pose to society and place our trust more discerningly – much as the body’s defence system learns to recognise the agents associated with cancers and other diseases to deal with them. Crucially, we also need to recognise that cooperation is best for everyone in the long term.

A small proportion of people at the most competitive end of the spectrum will always try to game society. We must work together to stay one step ahead of humanity’s opportunistic nature. Without beliefs, norms and a proper understanding of human nature, we are at the mercy of our selfish biological heritage. Evolution has made us this way, but we can learn to overcome it.

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EARTH | JUL 15, 2025, 2:00 PM EDT | VIEW ON NEW SCIENTIST

Ancient rocks show earliest evidence of tectonic activity on Earth

The origins of plate tectonics on Earth are hotly debated, but evidence from Australia now shows that parts of the crust moved in relation to each other as early as 3.5 billion years ago

By Alex Wilkins

The Pilbara craton in Western Australia is made up of some rocks that are 3.5 billion years old

Elizabeth Czitronyi / Alamy

Rocks in Australia preserve evidence that plates in Earth’s crust were moving 3.5 billion years ago, a finding that pushes back the beginnings of plate tectonics by hundreds of millions of years.

Today, around eight vast, rigid plates of rock at the surface of the planet, plus some smaller plates, are pulled or pushed along a softer layer of rock beneath. When the edges of these plates slip or slide past one another, sudden geological events can occur, like earthquakes, as well as more gradual processes, such as the formation of mountain ranges.

But geologists disagree over how many plates there once were, when they started moving and how they used to move. Some researchers claim they have found evidence from as far back as 4 billion years ago, when the planet was significantly hotter, while others say the strongest evidence is more recent, from 3.2 billion years ago.

Most of this evidence consists of hints from the chemical composition of rocks, which geologists can use to infer how those rocks moved in the past. However, there is little record of how early plates may have moved relative to each other, which is seen as the strongest evidence of tectonic plate movements.

Now, Alec Brenner at Yale University and his colleagues say they have found unambiguous evidence of relative plate motions around 3.5 billion years ago in the eastern Pilbara craton in Western Australia. The researchers tracked how the magnetic field of the rocks, which was aligned with Earth’s magnetic field, moved over time, similar to how a compass buried in the rock would change its needle direction as the ground moved.

Brenner and his team first dated the rocks by analysing the radioactive isotopes they contain, then proved the rocks’ magnetisation hadn’t been reset at some point. By tracking how this magnetisation had moved, they could show that the entire rock region had migrated over time, at a rate of tens of centimetres a year. Then, they compared this with rocks that had been dated and tracked using the same technique in the Barberton Greenstone Belt in South Africa, which showed no movement.

“It means that there had to have been some kind of plate boundary in between these two [regions] to accommodate that relative motion. That’s plate motion, definitionally,” Brenner told the Goldschmidt geochemistry conference in Prague, Czech Republic, on 9 July.

“The Pilbara, around 3.8 billion years ago, moves from mid-to-high latitudes to very high latitudes, actually within the area of the geomagnetic pole, and probably close to around where Svalbard’s latitude is today, in just a few million years. While the Barberton is just sitting there, doing nothing much at all on the equator,” said Brenner.

“If two plates are moving relative to each other, there has to be an awful lot of stuff going on between as well,” says Robert Hazen at the Carnegie Institution for Science in Washington DC. “It can’t just be an entirely local thing.”

But there is scope for different interpretations of what was causing that movement, says Hazen. This is partly because there is widespread uncertainty on how fast the plate was moving, and the data could fit several different theories of what Earth’s interior looked like at that time.

At the very least, the finding implies the existence of a tectonic boundary, says Michael Brown at the University of Maryland. However, he says that the motion of the rocks appears markedly different from what we understand as plate tectonics today. “Essentially, the Pilbara [plate] goes steaming up to higher latitudes and stops dead, which is unusual in any plate tectonic context.”

Brown argues that this fits with a theory that Earth’s crust at that time was made up of many smaller plates that were pushed around by columns of hot rock, called plumes, surging up from the more molten mantle. The surviving remnants of these smaller plates, which in this view Brenner and his team would have sampled from, are useful to indicate that there was motion, but because they are only a small proportion of the crust, they might not be representative of how Earth was moving, says Brown.

Brenner and his team also found evidence that Earth’s magnetic field direction flipped 3.46 billion years ago, which is 200 million years before the next-most-recent flip. Unlike today’s magnetic field, which reverses roughly every 1 million years, the magnetic field back then appeared to flip less frequently, at a rate of tens of millions of years. This might imply “quite different underlying driving energetics and mechanisms”, said Brenner.

What Earth’s magnetic field looked like at that point in its development is also hotly debated, says Hazen, in part due to the lack of magnetic data. “I think this moves the bar,” he says. “It’s a really significant finding of a reversal that early. It tells you something about the geodynamics of the core that wasn’t nailed down.”

MIND | JUL 15, 2025, 11:00 AM EDT | VIEW ON NEW SCIENTIST

Brain changes with eating disorders similar to those in OCD and autism

In children with anorexia nervosa or other restrictive eating disorders, changes in the brain’s outer layer don’t seem to be due to lack of nutrition alone – and some mirror those seen in other neurological conditions

By Grace Wade

A false-colour nuclear magnetic resonance image of a child’s brain

CNRI/SCIENCE PHOTO LIBRARY

Children with anorexia nervosa have widespread brain changes that can’t be explained by starvation alone. The finding brings us closer to identifying the neurological processes behind the condition, which could lead to better treatments for it.

Anorexia nervosa, an eating disorder characterised by severe calorie restriction and distorted body image, is poorly understood. Previous research has shown that the brain’s outer layer, called the cortex, is significantly thinner in people with the condition than those without it. But it isn’t clear the degree to which these changes are the result of malnutrition or an indication of the cause of anorexia.

Clara Moreau at the University of Montreal in Canada compared brain scans from children with anorexia to those with avoidant/restrictive food intake disorder (ARFID). Both conditions involve severe food restriction and weight loss, but ARFID isn’t motivated by body image concerns or a fear of gaining weight. Instead, people with ARFID avoid food due to sensory issues, a lack of interest in food or fear of negative consequences like choking, vomiting or gastrointestinal pain. Because both disorders can lead to low body weight and malnutrition, comparing them could reveal brain changes unique to each condition and those caused by starvation, says Moreau.

They collected brain scans from 124 children with anorexia, 50 with ARFID and 116 without an eating disorder. All of the children were under 13 years old and living in France. The researchers compared the magnitude of brain differences between children with eating disorders and those without them.

On average, children with anorexia had significantly thinner cortices than those without an eating disorder. After accounting for body mass index (BMI), anorexia was associated with cortical thinning in 32 brain regions, with the greatest effect seen in the superior parietal lobule, an area involved in processing sensory information. “That can make sense because we know that patients with anorexia have disturbed perception of their body weight, of their size,” says team member Anael Ayrolles at the University of Paris.

These changes are similar to those seen in older adolescents or adults with anorexia, says Moreau. “The effect size is one of the largest in psychiatry,” she says. “I mean, it looks like they have accelerated [brain] ageing or early Alzheimer’s.” They don’t have Alzheimer’s disease symptoms – the cortical thinning seen is just of a similar magnitude. “If their BMI is restored, we can see some brain restorations as well,” says Moreau. “Their brain is able to get better after treatment. Not all of them, but most of them.”

In contrast, there were no significant differences in cortical thickness between children with ARFID and those without a condition. “We were thinking we would find some overlap with anorexia that could be reflecting BMI,” says Moreau. “But that’s not what we found. We didn’t find many similarities between the conditions.” It isn’t clear why that is, especially as this is the first-ever brain imaging study of ARFID. Given ARFID usually develops before the age of 5, the brain may adapt to low food intake, says Moreau.

The researchers then compared these brain differences to those seen in previous studies of other conditions, such as obsessive-compulsive disorder (OCD), ADHD and autism. They found significant correlations between anorexia and OCD, while ARFID had similar changes to those seen in autism. Moreau says this makes sense, as sensory sensitivities are common in both autism and ARFID. Meanwhile, obsessions, rituals and preoccupations manifest in both OCD and anorexia.

However, people with OCD and anorexia tend to have other mental health conditions as well, says Joanna Steinglass at Columbia University in New York state. In fact, roughly 14 per cent of people with anorexia have also been diagnosed with OCD. This makes it challenging to disentangle whether there are true neurological similarities between them or if other mental health conditions underlie the association.

“We have been very, very cautious not to overinterpret our results,” says Ayrolles. Still, these findings suggest that malnutrition is unlikely to explain all of the brain changes seen in anorexia. “Any psychiatric illness is a brain-based illness and understanding that helps patients grapple with what they’re going through. It helps patients oftentimes blame themselves a little bit less,” says Steinglass. “And it helps us develop better treatments.”

Journal reference

Nature Mental Health DOI: 10.1038/s44220-025-00447-x

HEALTH | JUL 15, 2025, 11:00 AM EDT | VIEW ON NEW SCIENTIST

Why you shouldn't worry a nap will stop your child sleeping at night

Parents may discourage naps out of concern that their child won't then sleep at night, but research suggests that is not actually the case

By Chris Simms

Naps are thought to be important for early brain development

Quintanilla/Shutterstock

A short nap during the day seems to increase the overall amount of sleep a young child gets, rather than being a serious threat to night-time slumbers.

Babies and young children typically nap during the day, a habit that has been linked to the development of early memories. This trend usually stops between the ages of about 3 and 5, but the timing varies, leaving many parents unsure as to whether their child should be snoozing during the day or not.

In France, where children start a form of preschool at 3 years old, this presents a dilemma of whether staff should let them nap. “Although naps are widely recognised as having a positive effect on cognitive development, some parents and teachers are concerned that napping during the day might interfere with night-time sleep or reduce valuable learning time,” says Stéphanie Mazza at the University of Lyon in France.

To see if naps meaningfully disrupt night-time sleep, Mazza and her colleagues gave wrist-worn sleep trackers to 85 children aged 2 to 5 from six French preschools and measured their sleep over an average of 7.8 days.

This data, combined with sleep diaries filled in by parents, revealed that an increase in nap-time of 1 hour was linked to getting 13.6 minutes less sleep at night, on average, and pushed back the time at which the child got to sleep at night by 6.4 minutes. On days when children napped, their overall sleep time across the day increased by 45 minutes.

“Naps resulted in a significant increase in total daily sleep time, bringing children closer to the recommended international sleep duration for a 24-hour period,” says Mazza. The World Health Organization recommends that children of this age should sleep 10 to 13 hours per day.

“Parents shouldn’t worry if their child still needs a nap before the age of 6,” says Mazza. “Our data suggests that napping helps increases overall sleep, even if it means a slightly later bedtime. Rather than viewing naps as disruptive, they should be recognised as a valuable source of rest, especially when children are exposed to stimulating environments.”

“To me, this says – if they can nap, let them nap,” says Rebecca Spencer at the University of Massachusetts, Amhurst. However, given that sleep durations in early childhood can vary between countries, she says more work needs to be done to understand how widely applicable these results are.

Reference:

Research Square DOI: 10.21203/rs.3.rs-6612953/v1

HEALTH | JUL 14, 2025, 4:00 PM EDT | VIEW ON NEW SCIENTIST

You don't need to take drugs like Ozempic consistently to lose weight

People with disrupted access to GLP-1 drugs, like Ozempic, still seem to lose substantial amounts of weight

By Carissa Wong

Ozempic and other GLP-1 drugs may not need to be taken as frequently as they’re prescribed

Associated Press / Alamy

People who take GLP-1 drugs like Ozempic can lose weight even if they face disruptions in accessing the medications, which may reassure users when the therapies are in short supply.

Drugs like semaglutide, also known by the brand names Ozempic and Wegovy, have transformed how we treat obesity, but soaring demand has led to frequent supply shortages. In the US, disruptions can also occur if health insurance companies change which drugs they will cover. For instance, CVS Caremark, which helps insurers manage prescription plans, recently stopped covering Eli Lilly’s Zepbound, which is based on the GLP-1 drug tirzepatide.

To explore the effects of such disruptions, Kaelen Medeiros and her colleagues at the New York-based company Calibrate – which provides medications and digital support to help people lose weight – analysed data from more than 6000 people in the US who paid to enrol in the firm’s programme for one year between 2021 and 2024. Nearly 90 per cent of the participants had obesity, while the rest were overweight with a weight-related condition like type 2 diabetes, high cholesterol or heart disease.

The programme gave them access to an app that offered lessons, every two weeks, on how to optimise lifestyle habits such as diet and exercise. Plus, every couple of weeks they received a one-to-one chat with a health coach who helped them implement these lessons. For an additional fee, all of the participants were given GLP-1 drugs, such as Ozempic, mostly on a weekly basis.

By the end of the programme, 73 per cent of the participants had experienced one or more disruptions in their GLP-1 access, defined as at least 13 weeks without the drugs. These participants received an average of eight months of GLP-1 supplies over the one-year trial. The individuals still lost 14 per cent of their weight, on average, compared with 17 per cent weight loss among those without such disruptions. The results were presented at the annual meeting of the Endocrine Society in San Francisco, California, on 14 July.

Similar rates of weight loss occurred among those with and without a continuous GLP-1 drug supply in a second year of the programme. “No disruptions would be better, but it is great to see that even with disruptions, clinically significant weight loss can be achieved,” says Medeiros.

“The study is reassuring,” says Priya Jaisinghani at NYU Langone Health in New York. But further studies should explore the weight-loss impact of the health coaching and lifestyle lessons that the participants received, she says. The researchers did not measure how well the individuals in each group engaged in this part of the programme. It is possible differences in adherence could have affected the results, says Medeiros.

Some of the participants were also taking metformin, a type 2 diabetes drug that can contribute to weight loss, which may have also affected the results, Medeiros says. However, metformin is linked to losing only around 2 per cent of your body weight.

MATHEMATICS | JUL 15, 2025, 7:00 AM EDT | VIEW ON NEW SCIENTIST

Complex knots can actually be easier to untie than simple ones

Mathematicians have solved a decades-old problem in knot theory, discovering that linking two knots together can actually produce a knot that is easier to untie – the opposite of what was expected

By Matthew Sparkes

A knotty problem for mathematicians finally has a solution

Pinkybird/Getty Images

Why is untangling two small knots more difficult than unravelling one big one? Surprisingly, mathematicians have found that larger and seemingly more complex knots created by joining two simpler ones together can sometimes be easier to undo, invalidating a conjecture posed almost 90 years ago.

“We were looking for a counterexample without really having an expectation of finding one, because this conjecture had been around so long,” says Mark Brittenham at the University of Nebraska at Lincoln. “In the back of our heads, we were thinking that the conjecture was likely to be true. It was very unexpected and very surprising. “

Mathematicians like Brittenham study knots by treating them as tangled loops with joined ends. One of the most important concepts in knot theory is that each knot has an unknotting number, which is the number of times you would have to sever the string, move another piece of the loop through the gap and then re-join the ends before you reached a circle with no crossings at all – known as the “unknot”.

Calculating unknotting numbers can be a very computationally intensive task, and there are still knots with as few as 10 crossings that have no solution. Because of this, it can be helpful to break knots down into two or more simpler knots to analyse them, with those that can’t be split any further known as prime knots, analogous to prime numbers.

But a long-standing mystery is whether the unknotting numbers of the two knots added together would give you the unknotting number of the larger knot. Intuitively, it might make sense that a combined knot would be at least as hard to undo as the sum of its constituent parts, and in 1937, it was conjectured that undoing the combined knot could never be easier.

Now, Brittenham and Susan Hermiller, also at the University of Nebraska at Lincoln, have shown that there are cases when this isn’t true. “The conjecture’s been around for 88 years and as people continue not to find anything wrong with it, people get more hopeful that it’s true,” says Hermiller. “First, we found one, and then quickly we found infinitely many pairs of knots for whom the connected sum had unknotting numbers that were strictly less than the sum of the unknotting numbers of the two pieces.”

“We’ve shown that we don’t understand unknotting numbers nearly as well as we thought we did,” says Brittenham. “There could be – even for knots that aren’t connected sums – more efficient ways than we ever imagined for unknotting them. Our hope is that this has really opened up a new door for researchers to start exploring.”

An example of a knot that is easier to undo than its constituent parts

Mark Brittenham, Susan Hermiller

While finding and checking the counterexamples involved a combination of existing knowledge, intuition and computing power, the final stage of checking the proof was done in a decidedly more simple and practical manner: tying the knot with a piece of rope and physically untangling it to show that the researchers’ predicted unknotting number was correct.

Andras Juhasz at the University of Oxford, who previously worked with AI company DeepMind to prove a different conjecture in knot theory, says that he and the company had tried unsuccessfully to crack this latest problem about additive sets in the same way, but with no luck.

“We spent at least a year or two trying to find a counterexample and without success, so we gave up,” says Juhasz. “It is possible that for finding counterexamples that are like a needle in a haystack, AI is maybe not the best tool. This was a hard-to-find counterexample, I believe, because we searched pretty hard.”

Despite there being many practical applications for knot theory, from cryptography to molecular biology, Nicholas Jackson at the University of Warwick, UK, is hesitant to suggest that this new result can be put to good use. “I guess we now understand a little bit more about how circles work in three dimensions than we did before,” he says. “A thing that we didn’t understand quite so well a couple of months ago is now understood slightly better.”

Reference:

arXiv DOI: 10.48550/arXiv.2506.24088

SPACE | JUL 15, 2025, 5:00 AM EDT | VIEW ON NEW SCIENTIST

Water might be even more important for alien life than we thought

Without enough liquid water on the surface, a planet's atmosphere can become choked with carbon dioxide, raising temperatures to a level beyond what is survivable for all known life

By Alex Wilkins

Alien worlds found in the “habitable zone” of their star may still not be right for life

PandorumBS/Alamy

The number of planets capable of hosting alien life may be smaller than we thought, thanks to a new understanding of how water levels drive a planet’s climate. Below a certain level, carbon dioxide in the atmosphere can grow too much and make a planet unbearably hot, which could also explain why Venus is as inhospitable as it appears today.

All life that we know of needs liquid water, which is why astronomers are keen to find planets in the “habitable zone” around their star region where temperatures are conducive for liquid water to exist. But now Haskelle White-Gianella at the University of Washington and her colleagues have found that just having some liquid water isn’t enough.

The researchers ran around 10,000 different simulations that calculate how the levels of CO₂ would change depending on the amount of water on a planet’s surface, assuming it was a similar size to Earth and received a similar amount of light. They found that a planet needs at least 20 per cent of Earth’s total surface water for it to be potentially habitable.

That is because water falling as rain plays a key role in storing carbon in the ground by triggering chemical reactions in rocks. Without enough rain, CO_2 will build up in a planet’s atmosphere, trapping heat and rapidly raising temperatures above 126°C (259°F) – beyond what life as we know it, even in the most extreme examples, can survive.

“We find that there is a threshold of water needed to maintain a stable climate,” White-Gianella told the Goldschmidt geochemistry conference in Prague, Czech Republic on 10 July.

This means that a planet existing in the habitable zone isn’t enough for it to be potentially habitable, says White-Gianella, and that we need to look more carefully at its geologic history.

A similar scenario could also explain how Venus became the scorching, inhospitable environment we see today, said White-Gianella at the conference. While the sun’s increasing brightness since the birth of the solar system is thought to be the main reason for Venus’s loss of atmosphere and increased temperature, it doesn’t fully explain these changes. White-Gianella and her team re-ran their models so that they received Venus-like amounts of starlight, and found that even a planet with as much water as Earth may have lost too much CO_2 and become uninhabitable.

It’s a compelling explanation for how Venus-like planets become extremely hot, says Benjamin Tutolo at the University of Calgary, Canada, but the picture could be more complicated if planets begin producing less CO_2 over time, which is what we see when looking at Mars’s geologic record.

In Mars’s case, the liquid water actually pulled in too much carbon dioxide and stored it as carbonate minerals in the ground, says Tutolo, ultimately thinning its atmosphere and cooling the planet. White-Gianella says her team’s simulations focused on planets at Earth-like sizes and distances, and agrees the situation could be different for Mars-like planets.

ENVIRONMENT | JUL 15, 2025, 3:00 AM EDT | VIEW ON NEW SCIENTIST

Climate scientists urge others to take up CO2 tracking as US cuts loom

Proposed budget cuts in the US will lead to the loss of vital carbon dioxide measurements, but no other countries are preparing to step in so far, researchers warn

By Michael Le Page

Carbon dioxide measurements at Mauna Loa Observatory in Hawaii could be halted by US spending cuts

NOAA

Scientific agencies in other countries must prepare to take over as much of the key carbon dioxide monitoring services currently carried out by the US as possible, climate scientists are warning.

This monitoring could end next year under planned budget cuts, resulting in the loss of crucial data. “At the moment I’m not aware of anyone saying, ‘Okay, we can do it. We will take over’,” says Pierre Friedlingstein at the University of Exeter in the UK. “It has to be done.”

Friedlingstein leads the Global Carbon Budget, an international effort to quantify exactly how much CO₂ is being emitted and how much is being taken up by the land and oceans – crucial factors for understanding Earth’s rising temperatures.

This work relies heavily on the US National Oceanic and Atmospheric Administration (NOAA), which is being targeted for budget cuts by the Trump administration. A budget document for fiscal year 2026 proposes to eliminate the agency’s spending on climate and weather research and cut its full-time staff by more than 2000 people. It also proposes to shut down laboratories including Mauna Loa Observatory in Hawaii, a key site for CO₂ monitoring.

“The NOAA GML [Global Monitoring Laboratory] greenhouse gas programme is the backbone of global carbon observing, which serves many roles,” says Ralph Keeling at the Scripps Institution of Oceanography in California.

NOAA directly measures the level of gases such as CO₂ at many sites and supports such monitoring elsewhere around the world, including by calibrating measurements based on samples sent to it, says Friedlingstein.

The agency also assembles and analyses all the global data. This includes using the small differences in CO₂ levels between sites, along with knowledge of atmospheric circulation, to work out CO₂ flows.

“NOAA is providing critical baseline data,” says Keeling. “If the NOAA effort is terminated, we also lose the ability to track flows of CO₂ and other greenhouse gases reliably across the globe.”

“All of these things have to be replaced by other agencies,” says Friedlingstein

Even if this happens, the loss of monitoring sites and replacement of NOAA’s records with others will cause problems. “Long-term consistency here is the key,” says Keeling. “You can’t just jump from one index to another and still reliably resolve trends.”

There is particular concern about the continuation of the monitoring at Mauna Loa that began in 1957 – the longest continuous record of CO₂ at a single site. NOAA assists the Scripps-led monitoring there.

“Without NOAA involved, it will be difficult but not impossible to continue measurements nearby,” says Keeling.

He is also worried about the Scripps-led monitoring at the South Pole. It currently depends on NOAA staff at the US station there. The station itself depends on the US National Science Foundation, whose funding is also under threat.

“The South Pole is by far the most important long-term station in the Southern Hemisphere, and it is as critical as Mauna Loa to establish a reliable long-term global average, as well as the evolving difference between the northern and southern hemispheres to track large-scale carbon flows,” says Keeling.

CO₂ levels can also be monitored by some satellites, says Friedlingstein, but they measure the CO₂ in the entire column of air between the surface and the satellite, not just at the surface – so they aren’t a direct replacement.

Asked if it had any plans to replace what NOAA does, the European Union’s Copernicus Atmosphere Monitoring Service directed New Scientist to contact the European Commission’s Directorate-General for Defence Industry and Space (DEFIS). DEFIS didn’t respond by the deadline for this article.

ENVIRONMENT | JUL 14, 2025, 4:00 PM EDT | VIEW ON NEW SCIENTIST

Built-in fire extinguishers can prevent battery explosions

Adding fire-suppressing chemicals into batteries can prevent overheating, fires and explosions, cutting the risks for electric vehicles and portable electronics

By Jeremy Hsu

Lithium-based batteries like the ones that power electric vehicles are at risk of overheating

YONHAP/EPA-EFE/Shutterstock

Batteries enhanced with a polymer material that releases fire-suppressing chemicals at high temperatures are significantly less likely to explode into flames. This technique could boost the safety of battery-reliant machines, like electric cars and medical devices.

“Our approach enhances safety within mainstream liquid lithium batteries,” says Ying Zhang at the Institute of Chemistry, Chinese Academy of Sciences. “It’s like popping open a safety valve – these chemicals smother flammable gases before they can explode, helping prevent fires.”

Zhang and her colleagues created and tested the flame-retardant polymer material in a prototype lithium metal battery. Such batteries are currently in limited use, but next-generation versions are candidates to replace the batteries in electric cars and portable electronic devices. That is because lithium metal can store 10 times as much energy as popular lithium-ion batteries by using pure lithium, rather than graphite, in the negative electrode.

The researchers exposed the prototype battery and a standard lithium metal battery to gradually hotter temperatures, starting from 50°C. When external temperatures rose above 100°C, both batteries experienced overheating – but the prototype’s special polymer material began breaking down automatically, releasing chemicals that act like “microscopic fire extinguishers”, says Zhang.

Beyond 120°C, the standard battery without safety features overheated to 1000°C within 13 minutes and burst into flames. But under the same conditions, the prototype battery’s peak temperature only reached 220°C, without any resulting fire or explosion.

This “innovative material science approach” can reduce the risk of battery fires or overheating, not only in lithium metal batteries but also in certain lithium-ion batteries and lithium-sulphur batteries, says Jagjit Nanda at the SLAC National Accelerator Laboratory in California. It could lead to safer batteries, in particular for electric vehicles or even electric aircraft, he says.

The fire-suppressing technology would integrate well into existing battery manufacturing as a “near-term safety upgrade, while the industry pursues long-term solutions” involving alternative battery designs and chemistries, says Zhang. Still, injecting the polymer material into batteries would require some retuning of manufacturing processes, she says.

Journal reference

Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.2501549122

ENVIRONMENT | JUL 14, 2025, 4:00 PM EDT | VIEW ON NEW SCIENTIST

Nor'easters slamming New England are growing more powerful

Much like hurricanes further south, the strongest storms to pummel the US north-east are getting even stronger as sea surface temperatures rise

By James Dinneen

A nor’easter storm caused flooding in Lynn, Massachusetts, in January 2024

CJ GUNTHER/EPA-EFE/Shutterstock

The strongest of the infamous New England gales known as nor’easters have gotten even stronger since the 1940s, threatening to do more damage to the US north-east coast. This is probably due to warmer ocean temperatures.

“We know what’s causing the warming of sea surface temperature: the emission of greenhouse gases. And it’s that increase that’s driving the trend,” says Michael Mann at the University of Pennsylvania.

Mann and his colleagues assembled a dataset of nor’easters and their meandering paths over the past 85 years. They used a statistical method to identify any trends in the maximum wind speed of the storms, as well as any changes in precipitation.

“What we found is that, while we couldn’t isolate any significant trend in the average intensity of these storms, we found the strongest of these storms are getting stronger,” says Mann.

This dynamic occurs because of how the ocean temperatures that fuel the storms interact with other factors, such as wind shear, to decide their ultimate intensity, he says. Weaker storms are more likely to be influenced by factors other than ocean temperature, which determine the maximum potential intensity of a storm. “The biggest storms, to be a bit anthropomorphic here, have the opportunity to reach their potential,” says Mann.

While hurricanes at tropical latitudes were known to behave this way, it was less clear how more complex nor’easters would respond to warmer temperatures. “Nor’easters, in contrast to hurricanes, derive their energy from a lot of other factors,” says Brian Tang at the University at Albany in New York state.

The upward trend in both intensity and precipitation is small – the change in wind speed of even the strongest storms amounts to just under 2 metres per second since 1940. But this can still affect how much damage the nor’easters do.

Storm surge, combined with sea level rise, drives flooding along the coast, and more snow and rain boost inland flooding. “I think the big danger is water,” says Tang.

Journal reference

PNAS DOI: 10.1073/pnas.2510029122

Article amended on 14 July 2025

We clarified the change in the wind speed of the strongest nor'easters.

TECHNOLOGY | JUL 14, 2025, 9:00 AM EDT | VIEW ON NEW SCIENTIST

Are batteries based on contact lenses the future of energy storage?

UK company Superdielectrics says its polymer technology could make batteries cheaper and easier to recycle, but its energy density must improve to compete with lithium-ion devices

By Madeleine Cuff

The Faraday 2 battery developed by Superdielectrics

Superdielectrics

A new battery storage system built using supercapacitor technology could “leapfrog” lithium-ion batteries and revolutionise how renewable power is stored and deployed, say its inventors.

UK firm Superdielectrics unveiled its new prototype storage system, the Faraday 2, at an event in central London on 8 July. It features polymers developed for manufacturing contact lenses, and while less energy dense than lithium-ion batteries, the firm says it has other advantages including a faster charging time, better safety standards, low cost and a recyclable design.

“We believe that the home energy storage market today is where the computer market was in about 1980,” Superdielectrics’ Marcus Scott told an audience of journalists and investors. “Clean, reliable and affordable electricity is no longer a future vision. It’s a reality, and we believe we’re building the technology that will power it.”

Energy storage is a vital technology for the global shift to green power, necessary to provide continuous power in spite of fluctuating wind and solar generation. Lithium-ion batteries are currently one of the leading storage technologies, but they are expensive, depend on scarce raw materials, are difficult to recycle and can explode if they overheat.

Superdielectrics says it solves these problems with its aqueous battery design based on supercapacitor technology. Supercapacitors store energy on the surface of a material, allowing very fast charge and discharge times, but with low energy density.

The company’s system features zinc halide electrolytes separated from carbon electrodes by a polymer membrane. Superdielectrics says this membrane technology is low-cost and uses abundant and widely available raw materials, and it can unlock a new generation of supercapacitors with high energy storage potential.

Speaking to New Scientist at the event, the firm’s CEO Jim Heathcote said the technology has the potential to “leapfrog” lithium-ion batteries in renewable energy storage.

The Faraday 2 battery is an advance on the Faraday 1 prototype, launched last year. Superdielectrics says it has managed to double the energy density at a cell level, from 20 watt-hours per kilogram in the Faraday 1 to 40 Wh/kg in the Faraday 2, and halved the charging time. The fast charging allows the system to take advantage of short-lived upticks in renewable energy production, says Heathcote, storing the surplus power for later use.

But Gareth Hinds at the UK’s National Physical Laboratory says the technology is still well short of lithium-ion devices, which can offer energy densities around 300 Wh/kg at a cell level. Andrew Abbott at the University of Leicester, UK, adds that the current energy density achieved by Superdielectrics is comparable with lead-acid batteries, which are widely used for starting cars and in back-up power systems. “It is certainly not going to leapfrog any of the market leaders in the foreseeable future,” he says.

Marcus Newborough, a scientific advisor to Superdielectrics, concedes the company is still “on a journey” to improving the system’s energy density. “We have a very high theoretical energy density,” he said at the event, adding that the company will work to deliver on this potential over the coming years. Its aim is to have a commercial system ready for launch as a home energy storage unit by the end of 2027.

But Hinds is sceptical the technology can ever compete on energy density with lithium-ion. “Obviously, it’s an early stage development, and they’ll keep pushing the energy density higher, but they’re never going to get the energy density to that of lithium-ion. There’s a hard limit there,” he says.

Nevertheless, he suggests there may be a market for storage systems that are larger to make up for being less energy-dense, but far cheaper and with a longer lifespan than lithium-ion.

Sam Cooper at Imperial College London agrees. “If they can build a system with the same amount of energy storage capacity as a Tesla Powerwall (no reason why they can’t, even if it has to be huge and heavy), but it really was 95 per cent cheaper to buy, then I guess it would be a breakthrough,” he says.

ENVIRONMENT | JUL 14, 2025, 6:00 AM EDT | VIEW ON NEW SCIENTIST

Most warming this century may be due to air pollution cuts

Satellite data suggests cloud darkening is responsible for much of the warming since 2001, and the good news is that it is a temporary effect due to a drop in sulphate pollution

By Michael Le Page

Sulphate pollution, which has a cooling effect, can come from coal power plants

Frank Herrmann/Getty Images

Clouds have been getting darker and reflecting less sunlight as a result of falling sulphate air pollution, and this may be responsible for a lot of recent warming beyond that caused by greenhouse gases.

“Two-thirds of the global warming since 2001 is SO2 reduction rather than CO2 increases,” says Peter Cox at the University of Exeter in the UK.

Some of the sunshine that reaches Earth is reflected and some is absorbed and later radiated as heat. Rising carbon dioxide levels trap more of that radiant heat – a greenhouse effect that causes global warming. But the planet’s albedo – how reflective it is – also has a big influence on its temperature.

Since 2001, satellite instruments called CERES have been directly measuring how much sunlight is reflected versus how much is absorbed. These measurements show a fall in how much sunlight is being reflected, meaning the planet is getting darker – its albedo is falling – and this results in additional warming.

There are many reasons for the falling albedo, from less snow and sea ice to less cloud cover. But an analysis of CERES data from 2001 to 2019 by Cox and Margaux Marchant, also at Exeter, suggests the biggest factor is that clouds are becoming darker.

It is known that sulphate pollution from industry and ships can increase the density of droplets in clouds, making them brighter or more reflective. This is the basis of one proposed form of geoengineering, known as marine cloud brightening. But these emissions have been successfully reduced in recent years, partly by moving away from high-sulphur fuels such as coal.

So Marchant and Cox looked at whether the decline in cloud brightness corresponded with areas with falling levels of SO2 pollution, and found that it did. The pair presented their preliminary results at the Exeter Climate Forum earlier this month.

The results are encouraging because the rapid warming in recent years has led some researchers to suggest that Earth’s climate sensitivity – how much it warms in response to a given increase in atmospheric CO2 – is on the high side of estimates. As it turns out, extra warming due to falling pollution will be short-lived, whereas if the cloud darkening was a feedback caused by rising CO2, it would mean ever more warming due to this as CO2 levels keep rising.

“If this darkening is a change in cloud properties due to the recent decrease in SO2 emissions, rather than a change in cloud feedbacks that indicate a higher-than-anticipated climate sensitivity, then this is great news,” says Laura Wilcox at the University of Reading in the UK, who wasn’t involved in the study.

There are some limitations with the datasets Marchant and Cox used, says Wilcox. For instance, the data on SO2 pollution has been updated since the team did their analysis.

And two recent studies have suggested the darkening is mainly due to a reduction in cloud cover, rather than darker clouds, she says. “The drivers of the recent darkening trends are a hotly debated topic at the moment.”

Overall, though, Wilcox says her own work also supports the conclusion that the recent acceleration in global warming has been primarily driven by the decrease in air pollution, and that it is likely to be a temporary effect.

SPACE | JUL 13, 2025, 8:01 PM EDT | VIEW ON NEW SCIENTIST

LIGO has spotted the most massive black hole collision ever detected

A puzzling gravitational wave was detected, and astronomers have determined that it comes from a record-breaking black hole merger

By Karmela Padavic-Callaghan

Illustration of merging of black holes

Shutterstock / Jurik Peter

A record-breaking black hole smash-up just expanded our view of the universe’s most extreme inhabitants.

Since the Laser Interferometer Gravitational-Wave Observatory (LIGO) started detecting gravitational waves – ripples in the fabric of physical reality – 10 years ago, it has captured nearly 100 collisions between pairs of black holes. On 23 November 2023, LIGO picked up one such signal that was “extraordinary and puzzling to interpret”, says Sophie Bini at the California Institute of Technology. She and her colleagues eventually determined it was produced by the most massive black hole merger ever detected.

One of the colliding black holes was approximately 100 times as massive as the sun, while the other reached nearly 140 solar masses. The previous record was held by a black hole merger roughly half as massive. Team member Mark Hannam at Cardiff University in the UK says not only were the black holes enormous, but they were also spinning very quickly, which puts them at the edge of what we can anticipate spotting in space based on the mathematical models we have of the universe.

These black holes’ masses are too high for them to have formed by collapsing directly from an ageing star, so there is good reason to believe they are the products of past mergers between smaller black holes, says Hannam. “There may have been several successive mergers,” he says.

“Ten years ago, we were surprised that black holes of 30 solar masses exist. Here are black holes of more than 100 solar masses, which is just spectacular,” says Davide Gerosa at the University of Milano-Bicocca in Italy. Gravitational wave signals from massive and fast-spinning black holes are shorter than those produced by smaller ones, so it is also more challenging to detect them, he says. Bini presented this work at the Edoardo Amaldi Conference on Gravitational Waves in Glasgow, UK on 14 July.

Hannam and Bini both say in order to fully understand the new signal, including determining the black holes’ origins, we will need future observations of similarly dramatic mergers. LIGO has detected an increasing number of black hole mergers with each upgrade, so it will probably identify more cosmic record-breakers going forward. However, in May the Trump administration proposed closing half of the facility, which would, in Hannam’s view, make detecting signals like the new one nearly impossible.

TECHNOLOGY | JUL 11, 2025, 6:00 PM EDT | VIEW ON NEW SCIENTIST

How government use of AI could hurt democracy

Countries are eager to use AI to automate some government processes, but this risks eroding citizens’ trust and feelings of democratic control – because AI mistakes can ruin their lives

By Jeremy Hsu

AI could automate some government paperwork, but it comes with serious risks

Brett Hondow / Alamy

Many countries are exploring how artificial intelligence might help with everything from processing taxes to determining welfare benefits. But a survey shows citizens are not as enthusiastic as their governments – and this can create real risks for democracy.

“Focusing only on short-term efficiency gains and shiny technology risks triggering public backlash and contributing to a long-term decline in democratic trust and legitimacy,” says Alexander Wuttke at the Ludwig Maximilian University of Munich in Germany.

Wuttke and his colleagues asked around 1200 people in the UK to share their feelings about government actions where either a human or an AI handled the task. These hypothetical scenarios included processing tax returns, approving or rejecting welfare applications and making risk assessments about whether defendants should be eligible for bail.

Some people were only told about how AI could improve government efficiency – but others learned about both AI-related benefits and risks. These risks included difficulty in understanding how AI decisions are made, growing government dependence on AI that becomes less reversible over time and a lack of clear paths for citizens to contest and correct AI decisions.

When people became aware of AI-related risks, they reported both a significant decline in their trust in government and a feeling of losing control. For example, the percentage of participants reporting loss of democratic control in their government increased from 45 per cent to more than 81 per cent in scenarios where the government became increasingly dependent on AI for handling specific tasks.

The proportion of people demanding less AI in government also sharply increased once participants learned about the risks – rising from under 20 per cent in the baseline scenario to more than 65 per cent in any scenario where they learned about both the benefits and risks of government using AI.

Despite these results, democratic governments could make use of AI in responsible ways that retain citizens’ trust, says Hannah Quay-de la Vallee at the Center for Democracy & Technology in Washington DC. But she says there are few success stories of AI in government so far. Meanwhile,  there are already “quite a few failure cases” – and the stakes of these cases can be incredibly high.

For example, US state efforts to automate the processing of public benefits claims have led to tens of thousands of people being wrongly charged for fraud. Some of those people ended up having to file for bankruptcy or lose their homes. “Government mistakes have enormous, long-reaching impacts,” says Quay-de la Vallee.

Reference

arXiv DOI: 10.48550/arXiv.2505.01085

SPACE | JUL 11, 2025, 4:30 PM EDT | VIEW ON NEW SCIENTIST

We may have finally solved an ultra-high-energy cosmic ray puzzle

The IceCube neutrino detector has allowed researchers to resolve a debate about what types of particles make up ultra-high-energy cosmic rays – but much remains unknown about these rare events

By Karmela Padavic-Callaghan

An artistic rendering based on a real image of the IceCube neutrino detector at the South Pole

IceCube/NSF

We are zeroing in on the true composition of the rarest, highest-energy cosmic rays – which could help reveal their unknown origins.

The universe is constantly showering us with bursts of particles, says Brian Clark at the University of Maryland. The most energetic among them, called ultra-high-energy cosmic rays, have more energy than even the accelerated particles in colliders. They are also rare – researchers don’t know what produces them or where they come from. Even the particles that make them up have been an unresolved question. Now Clark and his colleagues have determined their composition using data collected by the IceCube neutrino detector in Antarctica.

Previous ultra-high-energy cosmic ray detections – by the Pierre Auger Observatory in Argentina and the Telescope Array in Utah – disagree on whether these rays mostly consist of protons or if other particles are also in the mix, says Clark. IceCube’s data offers some resolution: it suggests protons account for only about 70 per cent of ultra-high-energy cosmic rays, while the rest is made of heavy ions such as iron.

Team member Maximilian Meier at Chiba University in Japan says IceCube’s data is complementary to other measurements, which detect cosmic rays directly. In contrast, IceCube primarily detects particles called neutrinos, which are byproducts of collisions between energetic cosmic rays and photons left over from the big bang. Neutrinos themselves are challenging to detect and to simulate on a computer, he says.

The particles in cosmic rays determine how spaceborne magnetic fields affect their path through space. Understanding their composition is therefore an important part of the difficult task of searching for their origins, says Toshihiro Fujii at Osaka Metropolitan University in Japan.

Those unknown origins have created some dramatic mysteries such as the Amaterasu particle cosmic ray. Strangely, it seems to have emerged from a region of space near the Milky Way where there are “no promising astronomical candidates” for its source, he says.

Clark says he is optimistic about resolving many such mysteries within a decade because several new observation instruments, including an IceCube upgrade, will come online in the near future. “The field has a really clear vision for how we get to [answering] some of these questions,” he says.

Journal reference:

Physical Review Letters, in press

ENVIRONMENT | JUL 11, 2025, 9:00 AM EDT | VIEW ON NEW SCIENTIST

Artificial cooling 'urgent' for Great Barrier Reef after warming spike

A drop in shipping emissions has caused a surge in warming at the Great Barrier Reef, fuelling calls for drastic actions such as marine cloud brightening to lower the risk of coral bleaching

By Madeleine Cuff

Coral bleaching in the Great Barrier Reef off Queensland, Australia

Nature Picture Library/Alamy

Strategies to artificially shade Australia’s Great Barrier Reef from rising temperatures are urgently needed, scientists have warned, in light of new research that suggests changes to shipping fuels have increased the bleaching risk to the coral.

The Great Barrier Reef has suffered extensive bleaching damage in recent years caused by rising sea temperatures driven by climate change.

Changes to rules governing shipping fuel composition in 2020 have caused additional damage, says Robert Ryan at the University of Melbourne. These changes have reduced emissions of sulphur dioxide, a health-harming pollutant, but also removed aerosols that can enhance the cooling effect of marine clouds over the reef.

Ryan and his colleagues used a computer model to simulate the impact of the changes to shipping fuels on cloud cover and solar radiation above the Great Barrier Reef over 10 days in February 2022. They used the results of previous studies to estimate the impact those changes would have on sea surface temperatures and bleaching risk at the reef.

They found that shipping emissions at pre-2020 levels boosted the cooling effect of clouds over the area, and the rules curtailing sulphate aerosol pollution have removed much of this cooling effect. As a result, the new shipping fuel regulations caused the equivalent of an additional 0.25°C of sea surface temperature heating, and made coral bleaching conditions between 21 and 40 per cent more likely during the 10-day period that was studied.

“There’s been an 80 per cent reduction in shipping sulphate aerosol, and that has likely, we find, contributed to conditions at the Great Barrier Reef which make coral-bleaching events a little bit more likely,” says Ryan.

Bjørn Samset at the Center for International Climate Research in Oslo, Norway, says the research helps to answer outstanding questions about the impact of aerosol pollution reduction on local environments. “Localised aerosol influences are likely quite a lot more prominent than we have been thinking, and their influence on marine heatwaves is still a big knowledge gap,” he says.

But he warned that although the results show “a clear influence from shipping on the air quality and clouds around the Great Barrier Reef”, they cover only a short period, making comparisons with other research in this field tricky.

Ryan is also part of a team working on a method to artificially cool the reef using marine cloud brightening (MCB), a climate-intervention technique that would involve spraying sea salt particles into the air to try to increase the cooling effect of marine clouds.

Such artificial cooling measures are arguably now “more urgent” for the Great Barrier Reef in light of the new findings, the researchers suggest in their paper. “If some part of the marine cloud brightening effect from ships has been removed due to changes in sulphate emissions, then I could see how that might make one wonder whether it should be re-implemented in a targeted programme,” says Ryan.

Daniel Harrison at Southern Cross University in Australia, who also worked on the study, says the findings demonstrate that MCB could work to cool the reef, given that shipping emissions had a similar cooling effect. “What we have here is a real-world study of what was already happening,” he says. “We can see that it was working.”

Harrison has been awarded funding by the UK’s Advanced Research and Invention Agency for a five-year project to trial MCB at the Great Barrier Reef. MCB could help to “take the edge off the bleaching while we hopefully get our act together with reducing emissions,” he argues.

Other experts are much more sceptical, suggesting there is not enough evidence to demonstrate that deliberate MCB could be both safe and effective. Terry Hughes at James Cook University in Queensland, Australia, says trials of MCB to date have been a “complete flop”, failing to produce convincing evidence that it can reduce local sea temperatures at the reef.

Reference:

Research Square DOI: doi.org/10.21203/rs.3.rs-6703506/v1

ENVIRONMENT | JUL 11, 2025, 7:00 AM EDT | VIEW ON NEW SCIENTIST

Climate could warm another 0.5°C if we fail to capture far more CO2

Models suggest that meeting climate targets will be virtually impossible without steep emissions cuts paired with a huge expansion of carbon management technologies

By James Dinneen

To limit warming, we will need to cut emissions as well as capture carbon

Richard Saker/Alamy

The world would have to remove hundreds of billions of tonnes of carbon dioxide from the atmosphere to limit the rise in global temperatures to 1.5°C this century. Even the less ambitious 2°C climate target is now virtually out of reach without large volumes of carbon capture and carbon dioxide removal (CDR), alongside aggressive cuts to emissions.

The role that such carbon-management technologies have to play in meeting climate targets has long proved controversial. The Intergovernmental Panel on Climate Change has said some amount of carbon management will be “unavoidable” to reach the net-zero emissions required to stabilise global temperatures. But others have pointed out that technologies that could achieve this haven’t yet been proven to work at the scale needed, and relying on them risks providing an excuse to continue emitting as usual.

There is a “debate across scientists that CDR is both essential and impossible”, says Candelaria Bergero at the University of California, Irvine. “There are some people saying that without CDR, we are doomed,” she says, adding that others say ”we are banking on some almost fictional technology that we think we will have, and we’re putting future generations at risk”.

To get a better handle on what is at stake, Bergero and her colleagues used a simple climate model to estimate the consequences of failing to manage CO2 across hundreds of different emissions scenarios consistent with the Paris Agreement target to keep the rise in global temperatures well below 2°Cs. These scenarios included carbon dioxide removal technologies, such as direct air capture and nature-based approaches like tree planting. They also included varying amounts of carbon capture and storage applied to emissions from power plants and other industrial sources.

They found that failing to capture or remove any CO2 added about 0.5°C to global average temperatures at the end of the century, while failing to deliver half of the carbon management assumed in the scenarios added about 0.28°C of warming. This would make it nearly impossible to limit the rise in temperature to 1.5°C, even in a scenario where temperatures breach 1.5°C but then are brought back down.

The 2°C warming target might still be just about possible without any carbon management. However, the researchers found it would require extremely steep emissions cuts equivalent to 16 per cent per year from 2015 through 2050. Such a rapid decline seems unlikely given that global emissions have increased over the past decade, says Bergero.

Efforts to expand carbon management aren’t moving anywhere near fast enough either. Steve Smith at the University of Oxford says the world now captures and stores just 40 million tonnes of CO2 from emissions sources and removes about 1 million tonnes directly from the air each year.

“As with other emissions reductions, countries are often talking a good long-term game, but not putting in place the near-term measures to actually deliver the multibillion-tonne scale of action involved in these pathways,” he says.

Journal reference

Cdrxiv DOI: 10.70212/cdrxiv.2025395.v1

ENVIRONMENT | JUL 11, 2025, 7:00 AM EDT | VIEW ON NEW SCIENTIST

Trees on city streets cope with drought by drinking from leaky pipes

Urban trees lining streets fare better in dry spells than those in parks – now it seems that leaky water pipes are the reason for their endurance

By Alex Wilkins

Trees on the streets of Montreal in Canada benefit from leaky pipes

Catherine Zibo/Shutterstock

Trees growing on city streets are more resistant to drought than those in parks because they are drinking from an unusual water source: leaky pipes.

After long periods with little rain, water levels and sap flow tend to decrease more in trees growing in parks compared with those in streets, but it was unclear why.

To investigate, André Poirier at the University of Quebec in Montreal, Canada, and his colleagues took trunk samples from Norway maple and silver maple trees (Acer platanoides and Acer saccharinum) in parks and streets in two Montreal neighbourhoods. They measured the levels of various lead isotopes – atomically distinct versions of the metal that can indicate unique origins – and then linked the isotope levels to the trees’ recent history by counting the trunk rings.

While the park trees contained lead isotopes normally associated with air pollution, the street trees had isotopes found in lead water pipes, which were made with metal from geologically old deposits in nearby mines.

Maple trees need to consume around 50 litres of water per day. Since street trees can’t get much of this from rainwater, which falls on concrete and drains into the city’s sewers, Poirier says the most likely explanation is that it is coming from Montreal’s leaky pipes, which lose 500 million litres of water per day.

“The good news is that you can keep on planting trees on the street, because it makes people happy to have trees, and they will survive better than in the parks,” says Poirier, who presented his work at the Goldschmidt geochemistry conference in Prague, Czech Republic, on 8 July.

“The scale of water usage by these street trees is phenomenal and it goes against the common paradigm, which is you think that park trees would be much healthier,” says Gabriel Filippelli at Indiana University.

SPACE | JUL 10, 2025, 12:00 PM EDT | VIEW ON NEW SCIENTIST

Astronomers found a completely new type of plasma wave near Jupiter

Observations from NASA’s Juno spacecraft reveal that Jupiter’s strong magnetic field and the unique properties of its plasma can produce a truly novel kind of extraterrestrial wave near its poles

By Karmela Padavic-Callaghan

The plasma near Jupiter’s poles is capable of unusual behaviour

NASA/JPL-Caltech/SwRI/MSSS; Oleksuik © CC NC SA

The cosmic neighbourhood of Jupiter is one of the more peculiar places in the solar system, and the plasmas that reside there are no exception. They ripple with a never-before-seen type of wave.

Robert Lysak at the University of Minnesota studies auroras – not just the mesmerising displays of green and blue light on Earth, but also swirls of mostly invisible ultraviolet radiation near the poles of Jupiter.

The key to understanding these alien auroras is understanding the motion of the plasmas – soupy mixtures of charged particles and atoms surrounding the planet – that produce their glow. Based on data collected by NASA’s Juno spacecraft, Lysak and his colleagues found that Jupiter’s auroral plasmas oscillate with a new kind of wave.

The wave is a hybrid of two types of well-understood plasma waves: Alfvén waves, which are produced by the motion of the plasma’s charged atoms, and Langmuir waves, which reflect the movement of electrons in the plasma. Lysak says that, because electrons are much lighter than charged atoms, the two types of waves usually jiggle at very different frequencies.

But the area near Jupiter’s poles has just the right properties for the two to jiggle similarly and combine. This is because the plasmas there have exceptionally low densities and the planet holds them in a strong magnetic field.

“The observed plasma properties are really unusual, not found before and elsewhere in our solar system,” says John Leif Jørgensen at the Technical University of Denmark. Now that Juno’s data has revealed the new waves, we may learn more about the magnetic properties of faraway exoplanets by looking for similar signatures, he says.

Juno is currently still orbiting Jupiter. Lysak says that it could give us an unprecedented look at the giant planet and uncover more of its peculiarities – unless its flight is cut short. It is one of several missions slated to be terminated as part of NASA budget cuts proposed by the Trump administration in May.

“Cutting off the mission when it is getting its best data would be a real tragedy for our field,” says Lysak.

Journal reference

Physical Review Letters DOI: 10.1103/fn63-qmb7

HEALTH | JUL 11, 2025, 1:00 AM EDT | VIEW ON NEW SCIENTIST

Hay fever relief could come in the form of a nasal 'molecular shield'

Mice experienced far fewer hay fever symptoms when a pollen-blocking antibody was applied within their nose

By Carissa Wong

Sneezing and coughing are common hay fever symptoms

mohammad hosein safaei/Unsplash

People with hay fever could one day benefit from a first-of-its-kind “molecular shield” that blocks pollen from entering the lining of the nose, and is unlikely to cause the side effects seen with standard treatments.

Hay fever is an allergic reaction that occurs when pollen binds to molecules called IgE antibodies in the lining of the nose, mouth and eyes, triggering inflammation that results in symptoms such as sneezing and itchiness. Treatments include antihistamines and steroids, which dampen inflammation, but aren’t always effective and commonly have side effects, such as drowsiness.

To find an alternative, Kaissar Tabynov at the Kazakh National Agrarian Research University in Kazakhstan and his colleagues first collected blood samples from mice. They then extracted an antibody that isn’t involved in allergic reactions, but still binds to the main allergen in mugwort pollen, a major cause of hay fever. This binding then blocked the allergen from attaching to IgE antibodies in a lab dish. “It acts like a molecular shield,” says Tabynov.

To see if this reduces irritation, the researchers induced mugwort pollen allergies in 10 mice by injecting them with the allergen and a chemical that trained their immune systems to react to it.

A week later, they put a small droplet of liquid containing the pollen-blocking antibody into the noses of half the mice, doing so a total of three times over five days. The remaining animals were given droplets of saline solution instead. One hour after each droplet was administered, the mice were exposed to mugwort pollen at levels similar to those that people are exposed to during the plant’s peak hay fever season, says Tabynov.

After the final droplet, the mice given the preventive antibody rubbed their noses 12 times, on average, over 5 minutes, versus 92 times in the saline group.

The researchers expected that the antibody reduced inflammation, which they confirmed when imaging nose tissue samples collected from the mice at the end of the study. This also showed that the treatment had effects deeper within the body, not just where the droplets were applied. “Our study is the first to demonstrate that an allergen-specific monoclonal antibody can be applied intranasally to achieve both local and systemic protection in the context of plant pollen allergies,” says Tabynov.

Although the researchers didn’t measure potential side effects, they don’t expect the approach to cause the adverse events seen with oral hay fever drugs, because it works at the site of allergen entry.

“This study is an important milestone, highlighting the potential of intranasal therapies for allergic rhinitis [hay fever] and helps pave the way for early clinical trials investigating the potential of this approach in humans,” says Sayantani Sindher at Stanford University in California.

But success in mice may not translate to efficacy in people and the antibody will need to be adapted to work in humans to ensure it doesn’t provoke its own immune reaction, says Tabynov. If all goes smoothly, the team hopes to trial the approach as a nasal spray in people within the next two to three years, he says.

Such sprays may also work against other types of pollen that cause hay fever. “We envision a future in which customised antibody sprays could be available for people allergic to different types of pollens,” says Tabynov.

Journal reference:

Frontiers in Immunology DOI: 10.3389/fimmu.2025.1595659

TECHNOLOGY | JUL 10, 2025, 5:56 PM EDT | VIEW ON NEW SCIENTIST

Why bizarre Cold War hoverboats are making a comeback

Sea-skimming crafts – which fly just above the water – were once considered Cold War relics of a failed Soviet experiment. Now, China and the US are resurrecting the technology as a possible Pacific conflict looms

By Jeremy Hsu

Illustration concept for the US DARPA Liberty Lifter program

Aurora Flight Sciences

It’s not a boat. It’s not a plane. It’s a flying, sea-skimming craft called an ekranoplan.

These large vehicles reminiscent of Soviet technology from the Cold War are making a comeback as China and the US develop modern versions for a possible military confrontation in the Pacific.

The giant sea skimmers resemble large aircraft but are “more akin to high-speed naval vessels in that they ‘fly’ a few metres above the ocean”, says Malcolm Davis at the Australian Strategic Policy Institute. Such vehicles take advantage of a phenomenon called “wing-in-ground” effect, where a cushion of air between the low-flying vehicle and the water below can both support the vehicle and reduce aerodynamic drag.

Such sea skimmers are typically faster than ships – with speeds comparable to aircraft – while also being able to avoid surface or air radar detection, says Davis. They could stealthily and speedily deliver cargo or troops across the long ocean distances common in the Indo-Pacific region, or possibly launch surprise anti-ship missile strikes on opposing navies, he says.

The technology first gained notoriety during the Cold War, when the Soviet Union experimented with its ekranoplan design, including a prototype nicknamed the “Capsian Sea Monster”. But they never fully took off because of a lack of funding and limited usefulness for Soviet military planners, says Davis. The current resurgence of interest in sea skimmers comes as China uses its expanding military power to press territorial claims over Taiwan and the South China Sea.

China began developing sea skimmer prototypes starting in the early 2000s, says Ben Lewis, an independent defence analyst in Washington DC. More recently, in June 2025, pictures emerged from Chinese social media showing a large waterborne vehicle with four jet engines mounted on top of its wings, first reported by the analyst HI Sutton in Naval News. China is also recruiting Russian technology specialists who formerly worked on the Soviet Union’s ekranoplan designs, according to internal Russian intelligence documents obtained by the New York Times.

The US Defense Advanced Research Projects Agency (DARPA) was funding the development of a similar seaplane through its Liberty Lifter program from 2022. But the program ended in June 2025 without building a successful craft. Instead, the agency plans to encourage private companies and the broader US military to take up the task with lessons learned from the Liberty Lifter program.

Separately, the US company Regent Craft has also been testing its all-electric seaglider version of such technology for commercial use, which has drawn interest from the US Marine Corps.

Such sea skimmers “may prove affordable and reasonable alternatives to more expensive traditional aircraft” as the technology and manufacturing techniques advance, says Brendan Mulvaney at the US Air Force’s China Aerospace Studies Institute in Alabama. But, he cautioned, “they are not going to be the backbone of any force, and almost certainly won’t survive modern high-intensity combat”. Such sea skimmers could also face difficulties operating in rough conditions, which are not uncommon in the Taiwan Strait and other waters of East Asia, says Lewis.

Still, sea skimmers could be one part of a broader Chinese military strategy to counter US and allied naval forces that may deploy in support of Taiwan, says Davis. The US has responded by boosting military cooperation with regional allies, such as South Korea, Japan and the Philippines, while seeking to reinforce Pacific Island territories as military bases. The possibility of conflict for both sides has “really elevated the need for the exploration of more novel capabilities” that can provide an “extra edge”, says Lewis.

Technology

- Slay the new slang: check out a guide to social media’s baffling lingo (paid): 2025 Jul 9

- Surgical robots take step towards fully autonomous operations: 2025 Jul 9

- Will we ever feel comfortable with AIs taking on important tasks?: 2025 Jul 9

- Why falling in love with an AI isn’t laughable, it’s inevitable (paid): 2025 Jul 9

TECHNOLOGY | JUL 9, 2025, 2:00 PM EDT | VIEW ON NEW SCIENTIST

Slay the new slang: check out a guide to social media’s baffling lingo

Language is evolving rapidly in a world of social media. Our millennial reviewer finds Adam Aleksic's Algospeak to be a much-needed helping hand

By Victoria Turk

Social media and short-form video platforms are driving language innovation

Lisa5201/Getty images

Algospeak

Adam Aleksic (Ebury (UK, 17 July) Knopf (US, 15 July))

Nothing makes you feel old like being bamboozled by slang. Even the chapter titles of Adam Aleksic’s Algospeak: How social media is transforming the future of language have this effect. “Sticking Out Your Gyat For The Rizzler” and “Wordpilled Slangmaxxing” remind me that, as a millennial, I am as close in age to boomers as I am to today’s Generation Alpha.

Aleksic, a linguist and content creator (@etymologynerd), sets out to illuminate a new era of language innovation driven by social media, particularly short-form video platforms such as TikTok. The “algospeak” of the book’s title is conventionally used to describe euphemisms and other ways to get round online censorship, with recent examples including “unalive” (referencing death or suicide) or “seggs” (sex).

But the author makes the case for expanding the definition to include all aspects of language influenced by “the algorithm” — which is itself a euphemistic term to describe the various, often highly secretive processes social media platforms use to decide which content to serve to users and in what order.

Aleksic draws on his experience making a living online — in his case, through educational videos about language. Like any content creator, he is incentivised to appease the algorithm, and this means choosing words carefully. A video he made on the etymology of the word “pen” (tracing back to the Latin “penis”) fell foul of sexual content rules, while another analysing the controversial slogan “from the river to the sea” had its reach limited.

Meanwhile, videos on trending Gen Alpha terms, such as “skibidi” (a largely nonsense word with roots in scat singing) and “gyat” (“goddamn” or “ass”), performed particularly well. His experiences show how creators adapt their language for algorithmic gains, causing certain words to spread further online and, in the most successful cases, offline too. When Aleksic surveyed school teachers, he found many such terms have become regular classroom slang; some children even learn the word “unalive” before “suicide”.

He is sharpest on his special subject, etymology, tracing how the algorithm propels words from online subcultures into the internet mainstream. The misogynistic incel community is the most prolific contributor to modern slang, he says, precisely because it is so radicalised, which can supercharge the development of an in-group language.

Aleksic remains mostly non-judgmental about language trends. “Unalive”, he points out, is really no different from earlier euphemisms such as “deceased”, while “skibidi” is akin to “Scooby-Doo”. It is only recently that we categorised slang in terms of arbitrarily defined generations, which he argues is often inaccurate and lends a toxic framing to normal language evolution.

Things are slightly more complex when words owe their mainstream use to cultural appropriation. A lot of today’s slang terms, like “cool” before them, can be traced back to Black communities ( “thicc”, “bruh”). Others have roots in the LGBTQ ballroom scene (“slay”, “yass”, “queen”). Widespread adoption can divorce these words from their history, which is often tied to social struggles, and can even reinforce negative stereotypes about the communities that spawned them.

It is hard to prevent this context collapse — such is the fate of successful slang. Social media has rapidly shortened timelines of linguistic innovation, which makes Algospeak an essential update, but also leads to it becoming out of date quickly. The underlying insights on how technology shapes language, however, will stay relevant — as long as the algorithm has its way.

Victoria Turk is a London-based writer

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TECHNOLOGY | JUL 9, 2025, 3:00 PM EDT | VIEW ON NEW SCIENTIST

Surgical robots take step towards fully autonomous operations

An AI system trained on videos of operations successfully guided a robot to carry out gall bladder surgery on a dead pig, with minimal human assistance

By Chris Stokel-Walker

A surgical robot operating on a dead pig

Juo-Tung Chen/Johns Hopkins University

An AI-powered robot was able to separate the gall bladder from the liver of a dead pig in what researchers claim is the first realistic surgery by a machine with almost no human intervention.

The robot is powered by a two-tier AI system trained on 17 hours of video encompassing 16,000 motions made in operations by human surgeons. When put to work, the first layer of the AI system watches video from an endoscope monitoring the surgery and issues plain-language instructions, such as “clip the second duct”, while the second AI layer turns each instruction into three-dimensional tool motions.

In all, the gall bladder surgery required 17 separate tasks. The robotic system performed the operation eight times, achieving 100 per cent success in all of the tasks.

“Current surgical robotic technology has made some procedures less invasive, but complication rates haven’t really dropped from previous laparoscopic [keyhole] surgeries [by human surgeons],” says team member Axel Krieger at Johns Hopkins University in Maryland. “This made us look into what is the next generation of robotic systems that can help patients and surgeons.”

“The study really highlights the art of the possible with AI and surgical robotics,” says Danail Stoyanov at University College London. “Incredible advances in computer vision for surgical video with the availability of open robotic platforms for research make it possible to demonstrate surgical automation.”

Link to video: https://www.youtube.com/watch?v=hOaJaOIhE90

But many challenges remain to make the system practical in clinical use, points out Stoyanov.

For one thing, while the robot completed the task with 100 per cent success, it had to self-correct six times per case. For example, this could mean a gripper designed to grasp an artery missed its hold on the first try.

“There were a lot of instances where it had to self-correct, but this was all fully autonomous,” says Krieger. “It would correctly identify the initial mistake and then fix itself.” The robot also had to ask a human to change one of its surgical instruments for another, meaning some level of human intervention was required.

Ferdinando Rodriguez y Baena at Imperial College London is enthused about the growing potential of robotic surgery. “The future is bright – and tantalisingly close,” he says. “Though to realise this safely in humans, regulation will need to follow suit, which remains a significant open challenge in our sector.”

The next step, says Krieger, is to let a robot operate autonomously on a live animal, where breathing and bleeding could complicate things.

Journal reference:

Science Robotics DOI: 10.1126/scirobotics.adt5254

LEADER: TECHNOLOGY | JUL 9, 2025, 2:00 PM EDT | VIEW ON NEW SCIENTIST

Will we ever feel comfortable with AIs taking on important tasks?

An example from the history of mathematics shows how views on the trustworthiness of artificial intelligence can quickly start to change

By New Scientist

Qi Yang/Getty Images

Imagine a map of the world, divided by national borders. How many colours do you need to fill each country, plus the sea, without any identical colours touching?

The answer is four – indeed, no matter what your map looks like, four colours will always be enough. But proving this required a schism in mathematics. The four colour theorem, as it is known, was the first major result to be proved using a computer. The 1976 proof reduced the problem to a few thousand map arrangements, each of which was then checked by software.

Many mathematicians at the time were up in arms. How could something be called proven, they argued, if the core of the proof hides behind an unknowable machine? Perhaps because of this pushback, computer-aided proofs have remained a minority pursuit.

But that may be starting to change. As we report in “AI could be about to completely change the way we do mathematics”, the latest generation of artificial intelligence is turning this argument on its head. Why, ask its proponents, should we trust the mathematics of flawed humans, with their assumptions and shortcuts, when we can turn the verification of a proof over to a machine?

The argument raging over AI in mathematics is a microcosm of a larger question facing society

Naturally, not everyone agrees with this suggestion. And the argument raging over AI’s use in mathematics is a microcosm of a larger question facing society: just when is it appropriate to let a machine take over? Tech firms are increasingly promising that AI agents will remove drudgery by taking on mundane tasks from processing invoices to booking holidays. However, when we tried letting them run our day (see “‘Flashes of brilliance and frustration’: I let an AI agent run my day”), we found that these agents aren’t yet fully up to the job.

Relinquishing control by handing your credit cards or your password to an opaque AI creates the same sense of unease as with the four colour proof. Only now, we are no longer colouring in a map, but trying to find its edges as we probe new territory. Does evidence that we can rely on machines await us over the horizon, or merely a digital version of “here be dragons”?

COLUMNIST TECHNOLOGY | JUL 9, 2025, 9:00 AM EDT | VIEW ON NEW SCIENTIST

Why falling in love with an AI isn’t laughable, it’s inevitable

It’s easy to sneer at people who say they’ve fallen in love with ChatGPT. But we've been developing confusing feelings for bots for decades longer than you might think, writes Alex Wilkins. With so many people feeling lonely, can that be a good thing?

By Alex Wilkins

Humans are wired to treat machines as social beings

Abdillah Studio/Unsplash

Think of what it feels like to be in love. What comes to your mind? The giddy excitement of first falling for someone or the everyday calm reassurance of someone at your side? For a handful of people, love is opening up their laptop or phone and waiting for a wall of text or a synthetic voice to come streaming in from their preferred AI chatbot.

With so many tech platforms encouraging us to interact with their newly-introduced chatbots and talk to them as if they are real humans, people are increasingly turning to these large language model-powered functions for companionship, emotional support and, sometimes, love. This might raise an eyebrow or elicit a snigger. A recent story from CBS news about a man who proposed marriage to ChatGPT was met with mirth online, with the New York Post describing it as a “bizarre whirlwind romance”. Earlier this year, the New York Times told the story of a woman who spent hours every day talking to her ChatGPT “boyfriend”, and how she felt jealousy when the AI spoke of other, imaginary partners.

It’s all too easy to ridicule those that profess feelings for chatbots, or even explain it away as a sign of psychological issues or mental health problems. But just as we’re vulnerable to joining cults or falling for scams, we all have psychological machinery that gives us a willingness to believe in AI love. People have looked for and found companionship in unlikely places for as long as we can remember – and we’ve been developing confusing feelings for technology for longer than you might think.

We’ve been developing feelings for bots for 60 years

Take ELIZA, one of the first natural language chatbots, built by computer scientist Joseph Weizenbaum in the 1960s. The technology was primitive compared to ChatGPT and was simply programmed to regurgitate a user’s input back to them, often in the form of a question. Despite this basic set-up, Weizenbaum found some people appeared to form quick emotional attachments to the program. “What I had not realized is that extremely short exposures to a relatively simple computer program could induce powerful delusional thinking in quite normal people,” Weizenbaum wrote afterwards.

Given that today’s chatbots, like ChatGPT, are orders of magnitude more complex, convincing and widespread than ELIZA, we shouldn’t be surprised some people are professing romantic feelings or deep kinship towards them. Though scenarios of love for AI may be rare for now, recent data shows that it does exist. While most studies of this are small, researchers have found people ascribe real relationship labels to their AIs, such as “marriage”, and, should these chatbots be deleted, people appear to feel genuine loss. When the man who proposed to his ChatGPT partner lost their conversation because it hit a word limit and had to reset, he said he “cried my eyes out for like 30 minutes at work. That’s when I realised, I think this is actual love”.

Recent studies that automatically categorised millions of conversations from OpenAI’s ChatGPT and Anthropic’s Claude, separately found that, although the vast majority were related to work or more mundane tasks, hundreds or even thousands were specifically romantic or affectionate in nature. When you look at AI services explicitly set up to provide AI companionship, such as Replika, then these figures become more stark, with 60 per cent of its paying users saying AI relationships had romantic elements, according to the company.

Finding love through a screen

But while I think we can be more sympathetic in how we think about people who form emotional attachments with AI chatbots, that doesn’t mean we should accept this as something good for society at large. There are wider social forces at play, not the least of which is social isolation. Seven per cent of the UK, or around 3 million people, report they often or always feel lonely.

A complex societal problem like that requires a complex solution. Unfortunately, tech bosses often see complex societal problems as a round hole for a square peg, so it is unsurprising that Meta founder Mark Zuckerberg sees AI friends as a solution to the loneliness problem.

You could also argue Meta’s products, like Facebook and WhatsApp, have exacerbated loneliness and laid the ground for the flourishing of AI relationships in the first place. Though Zuckerberg’s proclaimed goal for creating Facebook was to help “people stay connected and bring us closer together with the people that matter to us”, I’d argue his products have normalised having a screen between us and those we care about. We now mediate many of our relationships through a chat window, be it on WhatsApp, Messenger or Instagram.

Dating through a screen is also the norm now, with 10 per cent of heterosexual people and 24 per cent of LGBTQ people in the US meeting long-term partners online. Perhaps all of this together makes it less of a leap for someone to then fall in love with a chatbot. If the entity on the other side of the screen turns out to be an AI rather than a real person, will our brains care about the difference?

The research of psychologist Clifford Nass in the 1990s showed people fundamentally interact with machines in a social way, regardless of whether they know the person on the other side of the screen is real. This showed the brain has no hard-coded ability to shut off its social tendencies with technology, and that if a machine puts on the affectations of a human, we can’t help but treat it like one of our own.

So it is no surprise people are falling for their AI chatbots. But here is a fact: the longest-running longitudinal study of happiness has found relationships are the top predictor of overall health and wellbeing. No such evidence exists for AI relationships, and the little evidence we do have hints more chatbot interaction doesn’t make us less lonely, or happier. We would do well to remember this.

Space

- The cosmos is vast, so how do we measure it? (paid): 2025 Jul 9

- Interstellar visitor 3I/ATLAS might be the oldest comet ever seen (paid): 2025 Jul 10

COLUMNIST SPACE | JUL 9, 2025, 2:00 PM EDT | VIEW ON NEW SCIENTIST

The cosmos is vast, so how do we measure it?

The awe-inspiring distances of the cosmos are hard to visualise, so how can we be certain we are measuring them correctly? Chanda Prescod-Weinstein explains

By Chanda Prescod-Weinstein

An estimated 500,000 stars shine in this portion of the Milky Way galaxy

NASA, ESA, CSA, STScI, and S. Crowe (University of Virginia).

One of the big challenges in communicating about space and space-time is that the universe is so large the scales are very difficult to imagine. Even just trying to get a sense of our solar system can be hard. If I were to make a scale-accurate model in which the sun is 1 centimetre across, I would have to put Pluto 42 metres away. I don’t know about your house, but mine doesn’t have a ballroom in it – which would be about that length.

Yet our solar system is tiny on the scale of the Milky Way. Ignoring the fact our galaxy exists in a halo of invisible dark matter that extends well beyond the visible parts, the Milky Way is so large that it would take light about 100,000 years to cross it. In contrast, light gets from the sun to Pluto in just 5.5 hours.

You might have noticed that I switched from everyday distances to units that relate to light speed. A hundred thousand light years is 9.46 × 10^20 metres. How would I even tell you to visualise that? I might as well say it is a bajillion ballrooms. And the Milky Way is pretty small compared with the cosmos. It isn’t even an especially large galaxy. Our neighbour Andromeda is twice as wide.

On top of that, space-time is expanding. That doesn’t affect distance measurements in gravitationally bound regions like our solar system or the Milky Way. It doesn’t even necessarily affect the distances between galaxies: the Milky Way and Andromeda are actually headed for each other, although the eventual collision will be more like a gentle dance than cars crashing, and it is 4.5 billion years away at least, so have no fear!

But on the largest scales, space-time is stretching, and groups of galaxies are being pulled away from each other. This is known as the Hubble expansion, and it means that many measurements of distance in the universe will change. Billions of years from now, people will get a different figure for the gap between us and the Virgo galaxy cluster, which is currently 50 million light years away.

In principle, these numbers are awe-inspiring, but it is also understandable that they invite some scepticism. First of all, how can we be so certain about these measurements? This is actually a subtle issue in astronomy. The way we do this is by building a “ladder” of measurements, often using objects of known brightness such as certain types of stars, that allow us to gauge distance.

In our images of distant galaxies, why don’t we see them as a blur, given that space-time is expanding?

The lowest – easiest – rung involves using cepheid variable stars, which pulse regularly, to calculate how far away things are. These are effective up to a certain distance, at which point we have to switch to something else. For the past 30 years, astronomers have used specific types of supernovae, or dying stars, because we know how to characterise the way in which their light is stretched out by the expansion of space-time. There are other ways too, some using what we know about the brightest red giant stars.

We have a high level of confidence in our ability to measure long distances, but I do understand why, despite this, I have received a few questions from readers related to this. One is about what happens to light as the universe expands. A standard part of our cosmological picture is that, just as the frequency of a siren that is moving away from us is shifted down, light waves stretch as space-time expands, reddening the light. Measuring this redshift is crucial to our use of supernovae to gauge distance, as mentioned earlier.

Redshift also means the light is of lower energy than it was before. But there is no apparent place the lost energy goes, which looks suspicious. Usually, when we get rid of energy, it goes somewhere. That is required in Newtonian physics. It isn’t, however, in general relativity. In other words, the thing that makes it possible for us to measure long distances is also something that violates our day-to-day notions about how energy moves about in the universe.

Another, related question that came in recently from a reader is about pictures of distant galaxies, like the ones among the new Vera C. Rubin Observatory’s first images. Shouldn’t we see the galaxies as a blur, as space-time is expanding?

The important thing to keep in mind here is that “seeing” the expansion of space-time isn’t like watching Lewis Hamilton in F1. It is a lot more like watching F1 if a race took billions of years, really, really far away. On that scale, the cars wouldn’t visibly move. The only way we know that galaxies are moving away from us at all is by measuring something like redshift, and that is just a measurement of how the light is stretched out, not an observation of the galaxy’s real-time motion.

I especially like these kinds of questions because they go to the heart of the metaphors we science communicators use to talk to our audiences. I appreciate that New Scientist readers are pushing these metaphors to their limits!

Chanda’s week

What I’m reading

For reasons that will become public, a lot of Alice’s Adventures in Wonderland.

What I’m watching

I finally saw and enjoyed Station Eleven.

What I’m working on

I have been thinking a lot about what quantum fields really are. Strange!

Chanda Prescod-Weinstein is an associate professor of physics and astronomy, and a core faculty member in women’s studies at the University of New Hampshire. Her most recent book is The Disordered Cosmos: A journey into dark matter, spacetime, and dreams deferred

SPACE | JUL 10, 2025, 9:33 AM EDT | VIEW ON NEW SCIENTIST

Interstellar visitor 3I/ATLAS might be the oldest comet ever seen

Astronomers tracking an interstellar object flying through the solar system think it comes from a star at least 8 billion years old, almost twice the age of our sun

By Jonathan O’Callaghan

The trajectory of interstellar comet 3I/ATLAS as it passes through the solar system

NASA/JPL-Caltech

An interstellar object currently passing through our solar system might be one of the oldest comets we have ever seen, originating from a star billions of years older than our own.

Comet 3I/ATLAS was spotted earlier this month near the orbit of Jupiter, estimated to be 20 kilometres across and moving at about 60 kilometres a second. It is the third known interstellar object found in our solar system, and will pass close to Mars in October before heading away from our sun.

Matthew Hopkins at the University of Oxford and his colleagues modelled the comet’s speed and trajectory to work out where it came from, using data from the European Space Agency’s Gaia spacecraft that mapped a billion stars in our 13-billion-year-old galaxy. It looks like it originated near a region of our galaxy called the thick disc, containing older stars and sitting above the thin disc in which our sun orbits.

“Thick disc objects are faster,” says Hopkins, whereas the prior two known interstellar objects – ‘Oumuamua in 2017 and Comet Borisov in 2019 – were slower. “Their velocities were what we’d expect for a thin disc object.”

The team’s modelling suggests 3I/ATLAS comes from a star that is at least 8 billion years old, almost twice the age of our sun, and possibly even older. “It could be the oldest comet we’ve ever seen,” says Hopkins. It is thought that interstellar objects are more likely to be ejected early in a star’s life, perhaps flung out by passing stars or interactions with giant planets.

Older stars are likely to have a lower metal content than our sun, which would also result in a higher water content for their comets, says Hopkins. If that is true, we could start to see large amounts of water spewing from the comet as it approaches the sun in the coming months.

This would probably be its first encounter with another star, giving us a glimpse at pristine material billions of years older than Earth. “We think most interstellar objects that we see will be encountering a star for the first time, even if they’re 8 billion years old,” says Hopkins. “They would have been wandering in deep space until they got near us.”

Reference:

arXiv DOI: 10.48550/arXiv.2507.05318

Humans

- Provocative new book says we must persuade people to have more babies (paid): 2025 Jul 9

HUMANS | JUL 9, 2025, 2:00 PM EDT | VIEW ON NEW SCIENTIST

Provocative new book says we must persuade people to have more babies

The population is set to plummet and we don't know how to stop it, warn Dean Spears and Michael Geruso in their new book, After the Spike

By Michael Le Page

A large population may enable innovation and economies of scale

PHILIPPE MONTIGNY/iStockphoto/Getty Images

After the Spike

Dean Spears and Michael Geruso (Bodley Head (UK); Simon & Schuster (US))

Four-fifths of all the humans who will ever be born may already have been born. The number of children being born worldwide each year peaked at 146 million in 2012 and has been falling overall ever since. This means that the world’s population will peak and start to fall around the 2080s.

This fall won’t be gradual. With birth rates already well below replacement levels in many countries including China and India, the world’s population will plummet as fast as it rose. In three centuries, there could be fewer than 2 billion people on Earth, claims a controversial new book.

“No future is more likely than that people worldwide choose to have too few children to replace their own generation. Over the long run, this would cause exponential population decline,” write economists Dean Spears and Michael Geruso in After the Spike: The risks of global depopulation and the case for people.

This, you might think, could be a good thing. Won’t it help solve many environmental issues facing us today? No, say the authors. Take climate change: their argument isn’t that population size doesn’t matter, but that it changes so slowly that other factors such as how fast the world decarbonises matter far more. The window of opportunity for lowering carbon dioxide emissions by reducing population has largely passed, they write.

Spears and Geruso also make the case that there are many benefits to having a large population. For instance, there is more innovation, and economies of scale make the manufacture of things like smartphones feasible. “We get to have nice phones only because we have a lot of neighbors on this planet,” they write.

So, in their view, our aim should be to stabilise world population rather than letting it plummet. The problem is we don’t know how, even with the right political will.

As we grow richer, we are more reluctant to abandon career and leisure opportuntiies to have children

While some government policies have had short-term effects, no country has successfully changed long-term population trends, argue the authors. Take China’s one-child policy. It is widely assumed to have helped reduce population growth – but did it? Spears and Geruso show unlabelled graphs of the populations of China and its neighbours before, during and after the policy was in place, and ask the reader which is China. There is no obvious difference.

Attempts to boost falling fertility rates have been no more successful, they say. Birth rates jumped after Romania banned abortion in 1966, but they soon started to fall again. Sweden has tried the carrot rather than the stick by heavily subsidising day care. But the fertility rate there has been falling even further below the replacement rate.

All attempts to boost fertility by providing financial incentives are likely to fail, Spears and Geruso argue. While people might say they are having fewer children because they cannot afford larger families, the global pattern is, in fact, that as people become richer they have fewer children.

Rather than affordability being the issue, it is more about people deciding that they have better things to do, the authors say. As we grow richer, we are more reluctant to abandon career and leisure opportunities to have children. Even technological advances are unlikely to reverse this, they say.

On everything other than the difficulty of stabilising the population, this is a relentlessly optimistic book. For instance, say the authors, dire predictions of mass starvation as the world’s population grew have been shown to be completely wrong. The long-term trend of people living longer and healthier lives can continue, they suggest. “Fears of a depleted, overpopulated future are out of date,” they write.

Really? Spears and Geruso also stress that the price of food is key to determining how many go hungry, but fail to point out that food prices are now climbing, with climate change an increasing factor. I’m not so sure things are going to keep getting better for most people.

This book is also very much a polemic: with Spears and Geruso labouring their main points, it wasn’t an enjoyable read. That said, if you think that the world’s population isn’t going to fall, or that it will be easy to halt its fall, or that a falling population is a good thing, you really should read it.

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Life

- Stunningly intimate octopus image wins aquatic photography prize: 2025 Jul 9

- Peculiar plant could help us reconstruct ancient Earth’s climate (paid): 2025 Jul 10

- Oldest proteins yet recovered from 18-million-year-old teeth: 2025 Jul 9

- Colossal's plans to "de-extinct" the giant moa are still impossible (paid): 2025 Jul 9

LIFE | JUL 9, 2025, 2:00 PM EDT | VIEW ON NEW SCIENTIST

Stunningly intimate octopus image wins aquatic photography prize

Kat Zhou has won the Aquatic Life category in the 2025 BigPicture Natural World Photography Competition, while a shot of a death-defying leap by a lemur took the top prize

By Liz Else

Octopus Mother by Kat Zhou

Kat Zhou

This alien and extraordinarily intimate image provides a rare glimpse of a Caribbean reef octopus (Octopus briareus) mother and her potential offspring at the Blue Heron Bridge dive area, off Florida’s West Palm Beach.

After mating, these solitary animals hide themselves far away to get on with the business of guarding their growing eggs. But for Octopus briareus and many other octopus species, the story has a nasty ending.

After a mother octopus lays a clutch of a few hundred eggs, she stops eating; she will die shortly after the eggs hatch. In 2022, research shed light on the process. The lifespan and reproduction of the invertebrate are controlled by optic glands, the octopus’s main neuroendocrine centre, which is roughly the equivalent to the pituitary gland in vertebrates.

The optic gland of octopus mothers undergoes a massive increase in cholesterol production after mating, which may trigger a self-destructive spiral. But the reason for this cycle is still unclear. One theory is that it stops the octopus from eating its own young.

Octopus Mother won freelance nature photographer Kat Zhou the Aquatic Life category in the 2025 BigPicture Natural World Photography Competition, open to all photographers, both professional and amateur. The competition aims to celebrate and illustrate the diversity of life on Earth and prompt action to protect and conserve it.

The overall Grand Prize went to photographer and conservationist Zhou Donglin’s Lemur’s Tough Life, a terrifyingly brilliant image taken in Tsingy de Bemaraha Strict Nature Reserve, Madagascar (shown below). After a day of hard slogging in a rugged and tricky terrain, Donglin captured a common brown lemur (Eulemur fulvus) in a death-defying leap from one cliffside to another – with her baby on board.

Lemur’s Tough Life by Zhou Donglin

Zhou Donglin

The next image, Mudskipping by Georgina Steytler (shown below), is a strange reminder of life’s distant past, as an eerily beautiful amphibian leaps out of the mud. A finalist in the Aquatic Life section of the competition, Steytler spent days on Goode Beach, in Broome, Western Australia, before capturing the exact moment when a blue-spotted mudskipper (Boleophthalmus pectinirostris) went airborne.

Mudskipping by Georgina Steytler

Georgina Steytler

The final image (shown below) looks like it was shot on a distant planet. In fact, Embers in the Snow by plant photographer Ellen Woods – a finalist in the award’s Landscapes, Waterscapes, and Flora category – was shot near Woods’s home in Connecticut, in the north-eastern US.

Embers in the Snow by Ellen Woods

Ellen Woods

It shows a skunk cabbage (Symplocarpus foetidus), which is often one of the earliest plants to emerge as winter ends because of its ability to create its own microclimate, warming itself to about 23 degrees Celsius even when the surrounding air is below freezing.

This is down to thermogenesis, or the ability to metabolically generate heat. This not only protects the plant’s tissues from frost damage, but it also serves to attract beetle and fly pollinators in search of a warm carrion meal.

Less appealing is the origin of its name: it emits a skunk-like smell when its leaves are bruised.

The winning entries will be on show at California Academy of Sciences in San Francisco later this year.

LIFE | JUL 10, 2025, 11:00 AM EDT | VIEW ON NEW SCIENTIST

Peculiar plant could help us reconstruct ancient Earth’s climate

Something strange happens to water as it moves through the stems of horsetail plants – and this unique process provides valuable clues for understanding past and present ecosystems

By Alex Wilkins

Smooth horsetail plants have segmented stems

piemags/nature/Alamy

A strange plant that has existed since animals first walked on land can distil water to an extreme degree, making it look more like water from meteorites than regular water from Earth. As well as being key to understanding ecosystems today, the plant’s fossilised remains could shed light on Earth’s climate and water systems when dinosaurs were alive.

Almost all the oxygen atoms in water have eight neutrons, but some are rare, heavier isotopes with nine or 10 neutrons. When water evaporates, lighter isotopes evaporate more than the heavier ones, making the ratio change in predictable ways. Scientists can use this to trace the history of a particular water sample, such as whether the water came from the ground or from fog, how quickly the water passed through the plant, or the humidity that that plant experienced in the past.

However, because the heavier isotopes occur in such small quantities, it is difficult to gather good data on how the isotope ratio changes, making some observations difficult for scientists to explain.

When sampling water from desert plants and animals, Zachary Sharp at the University of New Mexico and his colleagues found that their data didn’t fit with what was expected from models based on laboratory readings.

Sharp and his colleagues think they have solved the problem thanks to unusual plants called horsetails, which have grown on Earth since the Devonian Period, around 400 million years ago, and have hollow, segmented stems. “It’s a metre-high cylinder with a million holes in it, equally spaced. It’s an engineering marvel,” says Sharp. “You couldn’t create anything like this in a laboratory.”

When water moves up each segment of the horsetail stem, it evaporates, distilling it many times as it passes through the plant. Sharp and his colleagues sampled the water at many points along the stem in smooth horsetails (Equisetum laevigatum) growing near the Rio Grande in New Mexico.

By the time the water reaches the very top of the stem, the isotope ratio is unlike any other water found on Earth. “If I found this sample, I would say this is from a meteorite, because it’s not from Earth. But in fact, [the oxygen isotope ratios] do go down to these crazy low values,” Sharp told the Goldschmidt geochemistry conference in Prague, Czech Republic, on 7 July.

With these horsetail measurements, Sharp and his team could calculate how the water isotope ratio changes under near-perfect conditions and put these values into their models to make them more accurate.

When they revisited their desert plant data with these updated models, their observations were suddenly explainable. Sharp thinks these values could account for other hard-to-explain observations, too, especially in desert environments.

Ancient horsetails – which grew up to 30 metres high, much taller than today’s descendants – may have provided even more extreme isotope ratios and could be used to understand ancient water systems and climates, says Sharp. Small, sand-like grains called phytoliths in the horsetail stem, which can survive until the present day, have different isotope signatures according to the humidity of the air, because this will affect the amount of evaporation. “We can use this as a palaeo-hygrometer [humidity measurer], which is pretty cool,” says Sharp.

LIFE | JUL 9, 2025, 12:00 PM EDT | VIEW ON NEW SCIENTIST

Oldest proteins yet recovered from 18-million-year-old teeth

The oldest protein fragments ever recovered have been extracted from fossilised teeth found in Kenya's Rift Valley, revealing the remains belonged to the ancient ancestors of rhinoceroses and elephants

By Meagan Mulcair

Protein fragments managed to persist in the harsh conditions of Kenya’s Rift Valley

Ellen Miller

The fossilised teeth of 18-million-year-old mammals in Kenya have yielded the oldest protein fragments ever recovered, extending the record age for ancient proteins fivefold.

Daniel Green at Harvard University, in collaboration with Kenyan scientists, found a variety of fossilised remains, including teeth, in Kenya’s Rift Valley. Volcanic activity had helped preserve the samples by encasing them in layers of ash – layers that let the researchers date the teeth to 18 million years ago. But in the field, they couldn’t figure out whether the proteins in the tooth enamel had endured.

The odds weren’t good – Rift Valley “has been one of the persistently hottest places in the world for going back over 5 million years”, says Green. This harsh and unforgiving climate creates “a very challenging environment for [protein] preservation”. Still, prior research had managed to find proteins in tooth enamel, albeit none from teeth as old as these. So, to see whether any traces of protein had managed to last, Green used small drills to remove powdered enamel from the teeth. “It’s like being a dentist for a little bit,” he says.

The researchers sent these samples to Timothy Cleland at the Smithsonian Museum Conservation Institute for analysis. He used a technique called mass spectrometry to identify each molecule type in the sample by separating them by their masses.

Surprisingly, he found fragments of proteins that were complete enough to provide important taxonomical information. This revealed that the teeth had belonged to prehistoric ancestors of elephants and rhinos: proboscideans and rhinocerotids, respectively. Cleland is enthusiastic about being “able to put even these older species into the tree of life with their modern relatives”.

Only a small amount of protein material was recovered, but that doesn’t diminish the finding, says Frido Welker at the University of Copenhagen in Denmark. He says the ability to cultivate protein and learn anything about a fossil this old is “a massive breakthrough”.

Sampling teeth, as opposed to another tissue such as bone, could be key to finding protein fragments as old and informative as these. “The sequences in the enamel proteins are a little more variable,” says Cleland, “so we can get a little more evolutionary information.”

The make-up of the teeth might also have helped preserve their proteins for such a long time. Because teeth are “mostly rock”, Green says, these minerals surround and help protect the proteins in the enamel in what Cleland calls a “self-fossilisation process”. And the preservation is also aided because the enamel itself contains only a small amount of protein – about 1 per cent. “Whatever protein is present ends up sticking around a lot longer,” says Green.

The fact that protein fragments can survive even in the Rift Valley suggests ancient fossils found in other regions might contain proteins as well. “We can start to really think about other harsh areas of the planet where we wouldn’t expect great preservation,” says Cleland. “There might be some microenvironmental differences leading to protein preservation.”

In addition to examining proteins from the same time period as these, the researchers hope to find samples from different eras. “We would love to go back in time even further,” says Cleland. Green says examining younger fossils may offer “a baseline of expectations” for the number of preserved protein fragments relative to fossil age.

“We’re only scratching the surface right now,” says Cleland.

Journal reference:

Nature DOI: 10.1038/s41586-025-09040-9

LIFE | JUL 9, 2025, 7:08 AM EDT | VIEW ON NEW SCIENTIST

Colossal's plans to "de-extinct" the giant moa are still impossible

After a controversial project claiming to have resurrected the dire wolf, Colossal Biosciences has now announced plans to bring back nine species of the extinct moa bird

By James Woodford

An artist’s impression of the moa, one of the largest extinct birds

Christopher Klee/Colossal Biosciences

Colossal Biosciences has announced plans to “de-extinct” the New Zealand moa, one of the world’s largest and most iconic extinct birds, but critics say the company’s goals remain scientifically impossible.

The moa was the only known completely wingless bird, lacking even the vestigial wings of birds like emus. There were once nine species of moa in New Zealand, ranging from the turkey-sized bush moa (Anomalopteryx didiformis) to the two biggest species, the South Island giant moa (Dinornis robustus) and North Island giant moa (Dinornis novaezealandiae), which both reached heights of 3.6 metres and weights of 230 kilograms.

It is thought that all moa species were hunted to extinction by the mid-15th century, following the arrival of Polynesian people, now known as Māori, to New Zealand sometime around 1300.

Colossal has announced that it will work with the Indigenous Ngāi Tahu Research Centre, based at the University of Canterbury in New Zealand, along with film-maker Peter Jackson and Canterbury Museum, which holds the largest collection of moa remains in the world. These remains will play a key role in the project, as Colossal aims to extract DNA to sequence and rebuild the genomes for all nine moa species.

As with Colossal’s other “de-extinction” projects, the work will involve modifying the genomes of animals still living today. Andrew Pask at the University of Melbourne, Australia, who is a scientific adviser to Colossal, says that although the moa’s closest living relatives are the tinamou species from Central and South America, they are comparatively small.

This means the project will probably rely on the much larger Australian emu (Dromaius novaehollandiae). “What emus have is very large embryos, very large eggs,” says Pask. “And that’s one of the things that you definitely need to de-extinct a moa.”

Colossal previously announced what it called the “de-extinction” of the dire wolf, a claim disputed by outside experts because the animals are grey wolves with a handful of modified genes. Pask says this won’t be the case with the moa project and there will be “orders of magnitude” more DNA edits.

“The difference here with the moa is it really is going to be properly trying to re-engineer the moa back,” he says. “There will be no one who can question whether this is a moa when that animal eventually gets re-hatched back into our world. It will be a recreated or re-engineered moa at the end of the process.”

Exactly where these animals will reside is unclear. Mike Stevens at the Ngāi Tahu Research Centre says his organisation and the local Māori community will need to clearly understand the “viability and morality” of Colossal’s work as it progresses. “Once we have done so, we can fully consider where and how any ‘Colossal moa’ might be located,” he says. “That in itself raises a series of fascinating practical and moral questions. But we cannot unpack them in any depth until we have carefully considered other factors – and, of course, the technology proves itself.”

But Philip Seddon at the University of Otago, New Zealand, says that whatever Colossal produces, it won’t be a moa, but rather a “possible look-alike with some very different features”. He points out that although the tinamou is the moa’s closest relative, the two diverged 60 million years ago.

“The bottom line is that Colossal’s approach to de-extinction uses genetic engineering to alter a near-relative of an extinct species to create a GMO [genetically-modified organism] that resembles the extinct form,” he says. “There is nothing much to do with solving the global extinction crisis and more to do with generating fundraising media coverage.”

Pask strongly disputes this sentiment and says the knowledge being gained through de-extinction projects will be critically important to helping save endangered species today.

Jamie Wood at Adelaide University, Australia, says he thinks the project will offer some “interesting new insights into moa’s biology and evolution”. But he says if the same research path is pursued as that of the dire wolf project, then Colossal may have a “hard time persuading people that the results of this process could be regarded as moa”.

“They may superficially have some moa traits, but are unlikely to behave as moa did or be able to occupy the same ecological niches, which will perhaps relegate them to no more than objects of curiosity,“ says Wood.

Health

- The unexpected benefits of wall squats and other isometric exercises (paid): 2025 Jul 9

- Inhaled insulin may free children with type 1 diabetes from injections (paid): 2025 Jul 10

- Plans to genetically screen newborns for rare diseases are problematic (paid): 2025 Jul 9

- Antidepressant withdrawal symptoms may be less common than we thought: 2025 Jul 9

- Exercise helps fight cancer – and we may finally know why: 2025 Jul 9

- A youthful brain and immune system may be key to a long life: 2025 Jul 9

COMMENT HEALTH | JUL 9, 2025, 2:00 PM EDT | VIEW ON NEW SCIENTIST

The unexpected benefits of wall squats and other isometric exercises

Isometric exercises like wall squats are gentle on your body, but can enhance your fitness in a surprisingly efficient way, discovers Grace Wade

By Grace Wade

“Isometric moves such as planks can reduce pain”

Sutulastock/Shutterstock

In my last column, I explained why isometric exercises – which involve squeezing and holding a muscle in a fixed position – are especially effective at lowering blood pressure. Since then, I have started incorporating them into my own workouts. This got me wondering: do these exercises offer any other benefits?

As it turns out, yes – and some were unexpected. Isometric moves such as planks (pictured) and wall squats can reduce pain, prevent injuries and enhance fitness in a surprisingly efficient way. In fact, most people could probably benefit from adding them to their workout routine.

One of the clearest advantages of isometric moves is that they build strength without much movement, making them less physically taxing than more dynamic workouts. And they are effective: a review found that 42 to 100 days of isometric training increased muscle strength by up to 92 per cent.

Those strength gains can also be quite targeted. Athletes often use isometric exercises to get stronger at the toughest part of a movement, such as the bottom of a squat. This can improve their overall performance, with researchers discovering that isometric training increased endurance more than a jumping-focused workout.

Because they are gentler on the body, isometric exercises can also easily be tacked onto the start or finish of your regular workout, helping you squeak out extra gains. They are especially great warm-ups, with studies finding they reduced post-workout muscle soreness without affecting running performance. That is in contrast to static stretching, which had no effect on muscle soreness and actually impaired performance.

Adding a few isometric moves to your warm-ups may also help prevent injuries. While eccentric workouts – which emphasise slow, controlled movements in the lowering phase of an exercise – are commonly used to prevent hamstring injuries in football players, isometric exercises are more effective, according to research.

It isn’t clear why, but it could be that isometric moves “wake up” signalling pathways between nerves and muscles, making the latter more responsive during exercise. This may help correct muscle imbalances, a common cause of injury.

The benefits aren’t exclusive to athletes, either. A review this year showed isometrics significantly reduced pain and strengthened muscle in people with knee osteoarthritis. Because they are low-impact, these exercises are ideal for beginners or people with limited mobility due to injuries.

Given their benefits, isometric exercises have earned a regular spot in my workout routine. And, because they don’t require any equipment or jumping, I can do them almost anytime, anywhere.

Grace Wade is a health reporter for New Scientist based in the US

For other projects visit newscientist.com/maker

HEALTH | JUL 10, 2025, 1:00 PM EDT | VIEW ON NEW SCIENTIST

Inhaled insulin may free children with type 1 diabetes from injections

Inhaled insulin is effective for controlling blood sugar levels in children with diabetes, providing them with a faster-acting, needle-free option to manage their condition

By Sara Novak

Afrezza is an inhaled form of insulin

MannKind Corporation

Inhaled insulin helps to control blood sugar levels in children with type 1 diabetes as effectively as an injected version of the hormonal medication. The inhaled powder, called Afrezza, is already available for adults with type 1 or type 2 diabetes in the US, and now its manufacturers are planning to file for approval in children.

Type 1 diabetes occurs when the body can’t make the blood-sugar-lowering hormone insulin. People with the condition have to take insulin as a drug every day, usually via injections. But blood sugar levels can still be difficult to control, especially after meals, when they tend to spike, and after exercise, when they can fall.

Michael Haller at the University of Florida, who is on the advisory board of Afrezza, and his colleagues wondered if inhaled insulin, which can improve blood sugar control among adults by acting more quickly than injected insulin, also works in children. To find out, they recruited 230 people between the ages of 4 and 17. Most of the participants had type 1 diabetes, but a few had type 2 diabetes and required insulin to manage their condition.

All the children received basal insulin, which is injected once or twice a day to ensure there is a baseline low level of the hormone in the body at all times. Rapid-acting insulin is usually required on top of this before meals. In the 26-week trial, some of the children received Afrezza as their rapid-acting insulin, while others had injectable insulin.

The researchers found that both formulations worked equally well at controlling blood sugar levels. The results were presented at the American Diabetes Association meeting in Chicago in June.

“The assumption is that this is a better insulin because of the delivery method and certainly for some patients with a needle phobia, this can cause a lot of stress,” says Haller. “But more importantly, it gives patients additional tools in their toolbox for managing a very complex disease.”

The inhaled version caused coughing more than the injected one, but this dissipated once the participants got used to it. Afrezza is not suitable for anyone with long-term lung problems, like asthma.

Kathryn Sumpter at the The University of Tennessee Health Science Center in Memphis says that inhaled insulin may suit some children with diabetes, for example, those who forget to take the hormone before they eat and therefore need a particularly rapidly acting formula. But she thinks that most will probably stick to the injected formulation, which can be titrated much more precisely, so is especially helpful for small children, who may need lower amounts of insulin.

MannKind Corporation, the company that makes Afrezza, is planning to file for regulatory approval for its use in children in the US, says Haller.

COMMENT HEALTH | JUL 9, 2025, 2:00 PM EDT | VIEW ON NEW SCIENTIST

Plans to genetically screen newborns for rare diseases are problematic

The UK's health secretary has announced a 10-year plan to check newborns for a huge range of rare conditions. There are major medical and ethical issues with this, argues neurologist Suzanne O'Sullivan

By Suzanne O'Sullivan

Simone Rotella

Rare diseases are often hard to spot. They can evade detection until irreversible organ damage or disability has already set in. Last month, in the hope of preventing just this type of harm, the UK’s health secretary, Wes Streeting, announced a 10-year plan to make genetic testing for hundreds of rare conditions part of standard newborn screening in England. The world is likely to follow, with numerous feasibility programmes already under way, including in the US and Australia. Streeting’s plan is to “leapfrog” disease before it becomes symptomatic. But how scientifically sound is this, exactly?

The genome is a list of letters that feels as if it could be read like a book, but it is a book in a language so new that only a small number of words have been deciphered. And, like any language, even those deciphered words could have multiple meanings. What is known of the risks associated with some gene variants is drawn from decades of studying families at high risk of certain conditions. But we have little experience in population-based genetic testing in low-risk individuals. There is no doubt the type of screening planned will help some children and families, but it could also lead to unnecessary tests and treatment for a great many others.

There is much more to developing most conditions than a single genetic factor. A variant in the HNF4A gene illustrates the problem. People with a strong family history of a rare form of diabetes who carry this variant have a 75 per cent risk of developing the condition. However, the risk of diabetes in a person with this same variant who doesn’t have a family history of the condition is only 10 per cent. We cannot assume that any gene variant will behave the same way in every population. Maybe those families with the HNF4A variant and high rates of diabetes are missing a protective gene that hasn’t been discovered yet. Perhaps there is something in their shared environment that, when combined with their genetic risk, leads to diabetes.

The planned newborn-screening programme assumes that gene variants linked to disease convey a similar high risk in everybody, but that is unlikely to be correct. The work of looking for disease variants in healthy populations has only just started. Until it is complete, we cannot know how many people carry pathological variants that don’t lead to conditions because they are protected by other factors. Do we really want newborns to be the population on whom we test our genetic hypotheses?

That is to say nothing of the ethical issues that will arise from this programme. How does one obtain informed consent from the parents of newborn children when testing for hundreds of conditions simultaneously? In the not-too-distant future, we could have a genetic database of every living person. How will this be protected and used going forward?

Of course, newborn screening is nothing new. The difference here is the huge range of conditions to be screened, the challenge of interpreting the results and the sensitivity of the information gathered. I am concerned parents will feel obliged to accept this testing, but won’t be adequately apprised of all the unknowns. I am concerned that the vital early stages of life will be disrupted by hospital visits that might prove unnecessary. I am concerned that parents and paediatricians will be weighed down by a decision to subject a currently healthy child to potentially invasive tests and treatments.

The sensible thing is to gather more information on the prevalence and behaviour of disease variants in the general population before genetic testing becomes a speculative screening tool in children. While some will benefit, those success stories may turn out to be tiny compared with all the potential harms.

Suzanne O’Sullivan is a neurologist and author of The Age of Diagnosis: Sickness, health and why medicine has gone too far

HEALTH | JUL 9, 2025, 12:32 PM EDT | VIEW ON NEW SCIENTIST

Antidepressant withdrawal symptoms may be less common than we thought

Previous estimates have suggested that more than half of people who stop taking antidepressants experience withdrawal symptoms, but now a review of the evidence suggests this isn't the case, at least for short-term use.

By Carissa Wong

Antidepressant withdrawal symptoms include nausea and headaches

Savushkin/Getty Images

Antidepressant withdrawal symptoms may be less common than we thought, at least for short-term use – but questions remain about what happens to people who stop taking the drugs after much longer periods.

We know that people taking antidepressants for conditions such as depression, anxiety and phobias may experience withdrawal symptoms that can last for a few weeks, such as nausea, headaches, anxiety and depression, but while doctors may warn people about this possibility, it is unclear how often they actually occur.

To find out more, Sameer Jauhar at Imperial College London and his colleagues reviewed 49 randomised controlled trials of antidepressant use. They first analysed a subset of studies that tracked the number of withdrawal symptoms participants experienced one week after either stopping antidepressants, coming off placebo pills or continuing to take antidepressants. The researchers found that those who stopped taking the drugs experienced one extra symptom compared with those in the other two groups.

In another analysis, the team looked at another subset of studies that tracked the types of withdrawal symptoms participants experienced after coming off antidepressants or placebo pills. Dizziness was found to be the most common symptom, followed by nausea, nervousness or irritability, and vertigo.

Specifically, 7.5 per cent of people in the antidepressant group experienced dizziness, while this figure was 1.8 per cent in the placebo group. Nausea, nervousness or irritability, and vertigo were each reported by less than 5 per cent of people in the antidepressant group, and less than 2 per cent in the placebo group.

These figures are lower than two prior estimates of withdrawal symptoms. One 2019 review found more than half of people experienced symptoms, but that included data from online surveys, so may be skewed by people with more severe symptoms being more likely to respond, says Michael Browning at the University Oxford.

Another estimate, published last year, found that 31 per cent of people reported withdrawal symptoms, compared with 17 per cent in placebo groups. But they didn’t give details on the types of symptoms experienced, says Jauhar.

Susannah Murphy at the University of Oxford says the new review addresses some of these issues. “This is really important for the field: it’s collecting together and summarising data from many, many robust studies involving more participants than previous ones,” she says.

But John Read at the University of East London points out that most studies in the review included participants who were on antidepressants for only eight to 12 weeks, while people often take them for years. “There’s a strong relationship between how long you’re on these drugs and whether or not you end up with withdrawal, so short-term [use] studies aren’t going to tell you much about real-world effects,” he says.

As such, you would need more studies involving long-term use to get a true answer, says Mark Horowitz at University College London. “It’s like crashing a car into a wall at 5 kilometres an hour, and saying it’s safe, but ignoring the fact that people are driving around on the roads at 60 kilometres an hour.”

Journal reference

JAMA Psychiatry DOI: 10.1001/jamapsychiatry.2025.1362

HEALTH | JUL 9, 2025, 12:00 PM EDT | VIEW ON NEW SCIENTIST

Exercise helps fight cancer – and we may finally know why

Exercise seems to help prevent cancer and reduce the growth of tumours, and that protective effect may be due to the way working out changes the gut microbiome

By Avery Hurt

Working out seems to have a cancer-fighting effect

Franziska & Tom Werner/Getty Images

Exercise is known to help prevent cancer and suppress the growth of existing tumours. It is also associated with changes in the gut microbiome – and now researchers have shown how these changes could result in exercise’s cancer-fighting effect.

Marlies Meisel at the University of Pittsburgh in Pennsylvania and her colleagues gave an aggressive form of melanoma to two groups of mice. One group had been on a four-week exercise regimen, while the other group had been sedentary.

As expected, the mice who exercised had smaller tumours and better survival rates. However, a further test showed that in animals treated with antibiotics or kept completely germ-free, exercise showed no benefit. The evidence was clear: the magic was in the microbes, as well as the molecules they produce, called metabolites.

But the microbiome makes thousands of metabolites, so the researchers used machine learning to help sift through the candidate molecules and landed on formate. This is a metabolite of bacteria that is increased by exercise and boosts the potency of CD8 T cells in the immune system – which are key to fighting cancer.

Next, the team looked at 19 humans with advanced melanoma. Those with high levels of formate had longer progression-free survival – the length of a plateau when a person lives with cancer but it doesn’t get worse – than those with low levels.

“This research highlights the importance of assessing the metabolites the bacteria are producing, and not just which bacteria,” says Meisel.

Ken Lau at Vanderbilt University, Tennessee, who studies how the microenvironment in the gut influences conditions such as colorectal cancer and inflammatory bowel disease, says this kind of research is exciting because we are learning how to tap into the pathways of specific molecules to fine-tune immune responses. But he warns that there is more research to do. “What happens if the patient stops exercising? Does the effect fade or does it somehow persist? There’s a lot we still need to understand,” he says.

Meisel and her team are now looking at whether exercise-induced changes to the gut microbiome could play a role in other conditions.

Journal reference

Cell DOI: 10.1016/j.cell.2025.06.018

HEALTH | JUL 9, 2025, 6:00 AM EDT | VIEW ON NEW SCIENTIST

A youthful brain and immune system may be key to a long life

Maintaining good overall health is key to living a long life, but we may want to particularly focus on the state of our brain and immune system

By Carissa Wong

It seems that not all organs are equally important for longevity

Westend61 GmbH / Alamy

When it comes to living a long life, it seems not all organs are created equal. Scientists have found that having a youthful brain or immune system may be key – more so than having a slowly ageing heart or lungs.

We already knew that organs age at different rates, but it is unclear which ones have the biggest influence on lifespan, says Hamilton Se-Hwee Oh at the Icahn School of Medicine at Mount Sinai in New York.

So, Oh and his colleagues analysed the levels of nearly 3000 proteins in blood samples collected from more than 44,000 people who enrolled in the UK Biobank study when they were between 40 and 70 years old.

Using genetic data from past studies, the team was able to build a picture of where these proteins were in the body, pinpointing dozens of proteins that are especially abundant in 11 areas: the immune system, heart, brain, liver, lungs, muscles, pancreas, kidneys, gut and fat tissue. The high levels of these proteins indicate they are important in the proper functioning of these organs and body systems.

Next, the team trained machine-learning models to guess how old the participants were based on data from about half of them, creating a separate model for each of the 11 parts of the body. While these estimations generally matched the participants’ ages fairly well, some models overestimated or underestimated it, supporting the idea that organs age at different rates, says Oh.

The researchers used the trained models to predict the organ and immune system ages of the remaining half of the participants, who were followed for an average of 11 years after their blood was sampled.

Oh and his colleagues found that having one prematurely aged organ, or an aged immune system, was linked to a 1.5- to 3-fold increased risk of death during the follow-up period, with the risk rising alongside the number of aged areas.

For the most part, having organs like a heart or lungs that appeared to be substantially younger than expected wasn’t linked to a reduced risk of death during the study period. The exceptions were those with the most youthful brains or immune systems, whose risk of death was reduced by about 40 per cent – rising to 56 per cent if both of these parts of the body were particularly youthful.

“The brain and immune system coordinate a lot of other things around the body, so if those go wrong, it’s not too surprising they might have outsized effects on lifespan,” says Alan Cohen at Columbia University in New York.

But it is unlikely that protein markers perfectly reflect the ageing process, says Cohen. “We may have incomplete knowledge of what proteins really come from what organs, and the proteins from a given organ might be better represented in the blood than other organs; that could be why certain organs pop out as more important,” he says.

What’s more, the participants were mainly wealthy and of European ancestry, so further studies involving more ethnically and economically diverse people should verify the findings, says Richard Siow at King’s College London. Oh says the team is planning research that addresses this.

Even if the findings hold true, we don’t have ways to specifically reduce ageing of the brain and immune system, says Oh. However, identifying markers of brain and immune ageing could help to develop drugs that target these to boost longevity.

Journal reference:

Nature Medicine DOI: 10.1038/s41591-025-03798-1

Table of Contents

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