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2026 Mar 10

- What is wisdom, and can it be taught?

THE MIND | VIEW ON WEBSITE

What is wisdom, and can it be taught?

Scientists are trying to name the qualities that make someone wise and figure out how to cultivate them

By Emily Laber-Warren    03.11.2026

Emily Swanson was under pressure — not the end-of-the-world variety, but definitely stressful: prepping for her PhD qualifying exams. She fully expected the process to be grueling.

But then, like a character from a heroic tale, she had an encounter that changed her path.

Swanson took a job as a teaching assistant with Monika Ardelt, a leader in the scientific study of wisdom. Ardelt, a University of Florida sociologist, teaches an undergraduate course called The Quest for Wisdom and Human Flourishing. It asks students to spend a week at a time living by, and reflecting on, traditions associated with wisdom — among them Buddhism, Christianity and Greek Stoicism.

The weeks dedicated to Buddhism and Stoicism proved transformative for Swanson.

Through practice — think Luke Skywalker harnessing the Force to master his lightsaber — she learned to observe her thoughts and emotions in a more detached, nonjudgmental way. And she began to see her qualifying exams in a new light: “What is the worst-case scenario? If you fail, you don’t get a PhD. Is that as life-altering as I think it is? Well, no.”

Now, rather than seeing the exams as a threat, Swanson approached them as an opportunity to grow — a shift that enabled her to take intellectual risks that made the essays required for her doctoral advancement better than they otherwise would have been.

Ardelt says that Swanson’s shift in perspective is an example of how practicing things like reflection, humility, compassion and listening to other points of view can make someone wiser — that is, more able to adopt a larger view, especially when relating to others, and work toward the best outcome for everyone involved.

Ardelt is part of a growing group of researchers — among them psychologists, psychiatrists, sociologists and philosophers — applying scientific methods to understand wisdom in hopes of increasing the capacity of individuals to act wisely, and perhaps nudging a world beset by violent conflicts, unchecked human-caused climate change and other problems onto a more sensible path. Although they lack a single shared definition of wisdom, many are optimistic that the capacity can be cultivated.

“Not everyone will become a super wisdom guru,” says Judith Glück, a developmental psychologist at the University of Klagenfurt in Austria, “but I think there’s some space for everyone to grow.”

Bringing wisdom into the lab

The study of wisdom dates to antiquity, but only in the past 40 years have researchers begun to apply the scientific method to probe what wisdom is and how it develops.

The quality of wisdom has interested thinkers throughout human history. In Raphael’s Judgment of Solomon (top), the king makes a wise decision; in a painting by Giuseppe Bottani (bottom left), Odysseus is wisely counseled by Athena, goddess of wisdom, upon his return to Ithaca; a statue (bottom right) depicts Ganesha, a Hindu deity worshipped for his wisdom.

CREDITS CLOCKWISE FROM TOP: RAPHAEL, KRITZOLINA, G. BOTTANI / WIKIMEDIA COMMONS

The late psychologist Paul Baltes of the Max Planck Institute for Human Development in Berlin launched the field in the 1980s. He designed studies that asked people of all ages to muse aloud about invented dilemmas, such as what they’d say to a close friend who had decided to end their life, or how to counsel a 15-year-old girl who wanted to get married immediately.

Baltes and his team scored responses on a scale from 0 to 7, using five criteria — now known as the Berlin Wisdom Paradigm — that they had posited were critical to wisdom: knowledge about life and human nature, strategies for navigating various circumstances and challenges, understanding that not everyone holds the same values, awareness that people’s priorities can shift with context, and the ability to tolerate uncertainty.

Individuals who scored higher on these tests had a better understanding of the larger issues at stake in the scenarios, identified more than one potential response, and raised questions to help the fictional characters understand the possible outcomes of their decisions rather than simply telling them what to do. Baltes “was the first to come up with what arguably is a relatively objective test about wisdom,” says Howard Nusbaum, a cognitive psychologist and neuroscientist at the University of Chicago and director of the Chicago Center for Practical Wisdom.

Crucially, Baltes distinguished wisdom from intelligence, showing that analytical skill alone doesn’t make a person wise. As geriatric psychiatrist Dilip Jeste, director of the Social Determinants of Health Network and coauthor of a 2025 article in the Annual Review of Clinical Psychology on wisdom’s benefits in older age, puts it: “Some of the smartest people … are the worst people they can be.”

Baltes also showed that simply getting older doesn’t guarantee getting wiser. In a 1990 study of young adults, middle-aged people and older adults, for example, he found that wise responses were equally likely across age groups.

The owl was companion to Athena, godess of wisdom. With its quiet, piercing gaze in the dead of night, the creature came to be associated with wisdom in its own right.

CREDIT: CURRIER & IVES 1872

Glück, who did her postdoctoral work with Baltes, says there are limitations to Baltes’ approach of measuring wisdom through scenarios: For one thing, a person might not act as wisely in real life as they do in a hypothetical situation. She has tried to measure wisdom a different way, by asking people to describe a difficult event they experienced, then reflect on it. What did they learn from it, and what would they do differently? In a 2017 study, wisdom researcher Nic Weststrate, now at the University of Illinois Chicago, and Glück reported that people who engaged in what’s known as “redemptive” processing — believing that what had happened was all for the best — tended to be happier, but not necessarily wiser. By contrast, “exploratory” processing — reflecting on the situation for the express purpose of self-understanding — was associated with higher wisdom scores.

But this approach has its own weaknesses, Glück says, because people choose such varied experiences to recount. While many of her subjects raise objectively serious issues such as shattered relationships, some focus on minor ones, like a dispute with a neighbor over an overhanging branch. “You cannot really compare people’s stories when they are talking about totally different things,” she says.

Other experts, notably Ardelt, measure wisdom using questionnaires that ask people to respond to statements like “I can be comfortable with all kinds of people” and “When I look back on what has happened to me, I can’t help feeling resentful.” (You can try answering the 21 questions in the sidebar to score your own level of wisdom.) The downside to this self-report approach is that wisdom entails humility, so wise people may score themselves too low, whereas foolish people, blind to their own weaknesses, may give themselves inflated scores.

If measuring wisdom remains tricky, so does defining it. One point of contention is whether wisdom is a set of qualities, or the process of how we evaluate situations. Computational social scientist Igor Grossmann at the University of Waterloo in Canada defines wisdom as mental processes that afford greater awareness and ability to regulate thoughts, goals and emotions in complex social situations. To measure it, his team, led by then-student Justin Brienza, developed the Situated Wise Reasoning Scale, which assesses a person’s intellectual humility, recognition of uncertainty and change, consideration of multiple viewpoints, and ability to search for compromise.

Ardelt, by contrast, believes that Grossmann, and Baltes before him, left out something important by excluding emotional skills from the definition of wisdom. Her own Three-Dimensional Wisdom Scale, one of the most widely used wisdom measures, incorporates measures of compassion.

The real-life path to wisdom

When wisdom comes naturally, it often derives from lessons learned through intense experiences or dilemmas. These experiences may be painful, like breakups or illnesses, but wisdom can also be gained from experiences that are simply challenging, like moving to a new city or having a baby, Glück says. Yet plenty of people who get cancer or become parents never gain much wisdom. Why?

By reviewing wisdom research and interviewing wise and less-wise people using varied measures, Glück has identified five prerequisites for extracting wisdom from experience. These include the ability to manage uncertainty, to maintain an openness to change and new perspectives, to reflect on one’s experiences, to regulate emotional ups and downs, and to practice empathy.

A young boy gleans wisdom from an elder.

CREDIT: WELLCOME COLLECTION

Some people naturally possess these characteristics or learn them as children. For those who don’t, Glück is experimenting with ways to help develop them. Her lab is running a multiyear study in which participants will play character-based video games akin to The Last of Us that vividly simulate lived experiences and immerse players in moral and emotional decision-making. These games might be a shortcut to wisdom, if it turns out that we can gain it not only from our own experiences but also from other people’s and even fictionalized ones, she hypothesizes.

Grossmann is taking a different approach. He asks study participants to distance themselves from their own difficulties by writing about them in the third person, or from political events by imagining living in a far-off country. People who use these techniques score higher on Grossmann’s wise reasoning scale than when they recount experiences straightforwardly. “You’re approaching it from this different vantage point,” he proposes. “So that keeps you flexible.” These wisdom boosts are modest, but Grossmann’s research suggests that practicing self-distancing over time can have cumulative effects. People may, in turn, become more skillful in situations such as solving relationship conflicts.

Ardelt, for her part, has seen some success with her University of Florida course, the one that helped Swanson ace her PhD qualifying exams. In a 2020 study, she compared 165 students who took courses that involved practicing various wisdom-enhancing methods to 153 students who completed more typical academic courses on sociology or religion. All the students took Ardelt’s Three-Dimensional Wisdom Scale test at the beginning and end of the semester. Students in the practice-based classes showed wisdom gains — 2.5 percent overall, and 3.6 percent in the reflective dimension — whereas wisdom levels decreased for those in the more theoretical classes.

There are many ways one might become wiser, experts say — among them engaging in meditation, spending time in nature, volunteering to help people in need, or adopting Stoic modes of thinking. The important thing is to move beyond self-preoccupation, they say. Anything that fosters self-awareness, openness to divergent points of view, emotional regulation and humility is a step toward gaining wisdom.

Few people will be wise all the time, however. From Nusbaum’s cognitive psychologist perspective, the mind is too state-dependent — too easily derailed by stress, fatigue or frustration. “You’re going to get grumpy and pissed off and forget,” he says. But, he adds, with time and practice, we can increase the number of moments when we make wise choices — for the benefit of ourselves and everyone around us.

How wise are you?

The Brief Wisdom Screening Scale, below, created by developmental psychologist Judith Glück and colleagues, distills criteria common to three well-regarded and widely used wisdom assessment tools.

Glück cautions that this test is less an objective measure of wisdom than a barometer of how wise people believe themselves to be. Which can be problematic, because wiser people tend to recognize their own fallibility and may score themselves lower than people who, to paraphrase Socrates, don’t know that they don’t know.

To the extent that you answer honestly, though, the results can be enlightening.

— Emily Laber-Warren

Indicate how much you agree with the statements below on a scale of 1 to 5, with 1 representing “disagree completely” and 5 “agree completely.”

1. My peace of mind is not easily upset.

2. I have a good sense of humor about myself.

3. I have dealt with a great many different kinds of people during my lifetime.

4. I’ve learned valuable life lessons from others.

5. At this point in my life, I find it easy to laugh at my mistakes.

6. My happiness is not dependent on other people and things.

7. I can accept the impermanence of things.

8. I like to read books that challenge me to think differently about issues.

9. I am “tuned in” to my own emotions.

10. I get either very angry or depressed if things go wrong.

11. I am able to integrate the different aspects of my life.

12. I often have a sense of oneness with nature.

13. It seems I have a talent for reading other people’s emotions.

14. I feel that my individual life is a part of a greater whole.

15. There are some people I know I would never like.

16. I have grown as a result of losses I have suffered.

17. I can freely express my emotions without feeling like I might lose control.

18. I’m very curious about other religious and/or philosophical belief systems.

19. I don’t worry about other people’s opinions of me.

20. Sometimes I get so charged up emotionally that I am unable to consider all ways of dealing with my problems.

21. I always try to look at all sides of a problem.

Scoring: First, invert your number for items 10, 15 and 20 (for these three questions ONLY, change a score of 1 to 5, 2 to 4, 4 to 2 and 5 to 1. A score of 3 remains unchanged.)

Next, add these three inverted scores to your scores on the other 18 questions.

Divide that number by 21 to obtain your average.

Note: The rating scale below is based on a data set that included only 769 people, and so should be understood as only a guide, not a standardized norm.

Below 3.59 = You scored at or below the median, which places you in the bottom half of wisdom self-raters.

3.6 to 3.99 = Your score puts you in the top 50 percent of wisdom self-raters.

4.0 to 4.39 = You scored in the top 20 percent, making you very wise.

4.4 or higher = You scored in the top 5 percent, making you extraordinarily wise.

Editor’s note: This text was updated on March 13, 2026, to clarify contributors to a 2017 study and to the development of the Situated Wise Reasoning Scale.

10.1146/knowable-031126-1

Emily Laber-Warren heads the health and science reporting program at the Craig Newmark Graduate School of Journalism at the City University of New York.

2026 Mar 4

- For particle physicists working with neutrinos, almost nothing is everything

PHYSICAL WORLD | VIEW ON WEBSITE

For particle physicists working with neutrinos, almost nothing is everything

Several massive multimillion dollar experiments should soon reveal more about the nature of these ghostly particles

By Nicola Jones    03.05.2026

Imagine you are given three gumballs of different flavors. You are told that one of them is heavier than the others, and one is lighter. But which is which? Your task is made difficult by the fact that these gumballs weigh nearly nothing. And sometimes they swap flavors. Oh, and when you try to pick them up, most of the time they simply pass through your hand.

Such is the task facing physicists attempting to get a handle on the ghostly subatomic particle known as the neutrino. These teeny-tiny particles, which theory currently says come in three types, or “flavors,” flood the universe but rarely interact with the ordinary matter we are all familiar with. This makes them bafflingly hard to study, despite their amazing abundance.

But cracking the questions of how much neutrinos weigh, and which are the heaviest, is of vital importance to particle physicists. The Standard Model that they have painstakingly developed to describe all of nature’s particles and forces explicitly says that neutrinos have no mass at all. Yet observations have established that neutrinos do, in fact, have a very small mass. This is an annoying and critical exception to the standard rules of physics, with implications for other theories. For anyone who wants to understand the universe, fixing this problem is imperative.

The good news is that physicists are making excellent progress and have a good chance of figuring out the order of neutrino masses in just a few years, certainly by 2030, they say. “I think we will have a strong evidence, one way or the other,” says André de Gouvêa, a theoretical particle physicist at Northwestern University.

Data collected in experiments done around the world over the past 35 years have led to better and better estimates for the average mass of the neutrino (diagram shows error bars for each measurement). The latest results (inset) show a narrower range of uncertainty and put the value very close to zero, at least 500,000 times lighter than an electron.

Unseen and everywhere

While they may be shy, neutrinos are everywhere: They are the second most abundant thing in the universe after photons, particles of light.

“It’s kind of strange that we know so little about the second most abundant one, right?” says Carlos Argüelles, a neutrino physicist at Harvard University.

Neutrinos are created by nuclear reactions within the Sun and stars, by cosmic rays traveling through the atmosphere, and by other cosmic and earthly reactions. They can also be generated by nuclear power plants and in particle accelerators. It is thought that tens of billions of neutrinos pass through every square centimeter of Earth every second, without anyone noticing a thing.

Neutrinos have been a puzzle for nearly 100 years. Physicists first dreamed them up in the 1930s, to help explain certain baffling properties of radioactive decay. The first experiment to detect neutrinos directly was published in 1956. At that point, scientists assumed they had no mass.

From the late 1960s to the 1990s, though, detectors spotted far fewer neutrinos coming from the Sun than expected, prompting some to worry that our star might be “going out.” Instead, it turned out that the sneaky neutrinos were switching (or “oscillating”) between three types (or “flavors”) as they flew, so that many evaded detection. This observation meant that, according to Einstein’s theory of relativity, neutrinos must, in fact, have some mass.

“Neutrinos like to misbehave. That’s why we might find them interesting,” says Argüelles. “They like to do things they are not supposed to be doing.”

Weirdly (as is often the case in the quantum world), neutrinos are thought to be made up of three underlying mass states that mix together with different probabilities to produce the electron, muon and tau neutrinos that experiments have detected. One of these mass states is heaviest and one is lightest.

There are two possibilities for the order of these masses. In what is called “normal” mass ordering, the electron neutrino would be mostly made of the lightest mass state, with the tau flavor drawing more from the heavier state and the muon in the middle. But it might be the other way around. In the “inverted” ordering, the electron neutrino would instead be mostly made of the heaviest mass. Which order is right?

This question about mass ordering turns out to be easier to answer than the more precise question of exactly how much neutrinos weigh, as the answer can be found by checking on the details of neutrino flavor oscillations. Even so, this “easy” question is taking a set of multimillion dollar experiments and plenty of years to answer.

Put in their place

Most neutrino detectors work by spotting flashes of light made as neutrinos occasionally interact with the particles in some giant volume of liquid, such as water, as they pass through. Different flavors make different patterns: One creates a straight track through water, for example, while the interactions of another create a little fireworks display of tracks.

Because these interactions are rare and hard to detect perfectly, researchers need to gather a lot of data over a long time before they are confident enough to make statistically sound conclusions about what they have seen and what it implies.

Some of these detectors are designed to spy in part on neutrinos made by the interactions of cosmic rays in our atmosphere. These detectors gain valuable insights by looking at the difference between neutrinos that came straight into the detector from the nearest part of the sky, versus those that came from, say, interactions on the far side of the Earth and have passed through the entire mass of the planet.

Both the air and the ground act as lenses, affecting how neutrino flavors oscillate before reaching the detector. By comparing the paths, physicists can learn a lot about neutrino oscillations, which, again, are expected to behave differently for the different mass orderings.

Such setups include IceCube, the world’s largest neutrino detector, which uses light detectors sunk on strings down long boreholes in the Antarctic ice, as well as Japan’s Super-Kamiokande detector (and Hyper-Kamiokande, now under construction and due to begin collecting data in 2028), which uses man-made vessels of water, and the newly operational ORCA detector, which catches neutrinos flying through the Mediterranean Sea. Each of these has its own pros and cons, abilities and uncertainties, but they all do roughly the same thing.

The IceCube experiment in the Antarctic, shown here in an illustration, uses long strings of light detectors buried under the ice to detect tiny flashes from occasional interactions with passing neutrinos.

CREDIT: ICECUBE / NSF

Argüelles thinks that this specific set of experiments together will have collected enough data by 2030 to get a good handle on the mass ordering question.

Even better, Argüelles says, would be to compare the results from these atmospheric neutrino experiments with the results from the new Jiangmen Underground Neutrino Observatory (JUNO), a project recently built in China that started up in late August 2025.

JUNO, composed of a 35-meter-wide plastic sphere deep underground, filled with 20,000 metric tons of fluid and plastered with light detectors, is special in the sense that it aims to spy on neutrinos made by nearby nuclear energy facilities. Since this neutrino source is different (nuclear energy facilities, not cosmic rays), and the neutrinos’ path is different too (just over 50 kilometers from the source to the detector), this setup creates a complementary dataset to atmospheric experiments. Comparing the two, says Argüelles, could crack the problem of mass ordering really quickly, perhaps in just a year or two.

The Jiangmen Underground Neutrino Observatory (JUNO), which started up in late August 2025, spies on neutrinos made by nearby nuclear energy facilities. Hopes are high that JUNO, shown during its construction in 2023, will add new insights into which neutrinos have the greatest mass and which have the least.

CREDIT: DENG HUA / XINHUA / ALAMY LIVE NEWS

These are good strategies, agrees de Gouvêa, though he adds that you can run into trouble when cross-comparing results from multiple experiments, which, if you’re unlucky, can multiply errors. He thinks that the best, most reliable result will come from the Deep Underground Neutrino Experiment (DUNE) — a US project that he is involved with.

DUNE will generate an amazingly intense source of neutrinos using a particle accelerator at Fermilab in Illinois and shoot them through the ground toward a massive detector in Sanford, South Dakota, 1,300 kilometers away. Because these neutrinos are being made intentionally for this experiment, there are a lot of them, and researchers know more about them than they do in systems that rely on natural or incidental neutrinos. This gives them a powerful advantage. But DUNE won’t turn on until around 2031.

“In particle physics units, that’s coming up very soon,” says de Gouvêa.

Which way up?

So far, early results from JUNO combined with the atmospheric experiment data seem to be hinting at a result. “The data is whispering in the normal-order direction,” says Argüelles. For some physicists, including Argüelles, this is slightly depressing news.

Theory says that a “normal” ordering means a lower overall weight for neutrinos, which will make pinning down the absolute value of that weight much harder (just because the smaller a number is, the harder it is to measure).

It also makes other theories harder to check. One theory, for example, posits that neutrinos are their own antiparticles. Under normal mass ordering and with a lower neutrino weight, the interactions we would need to witness to confirm this theory are expected to happen far less frequently — no one would be able to confirm or refute this theory using any now known experiments, says Argüelles, leaving an answer at least decades away (or impossible to determine at all).

But the jury is still out, and Argüelles is still hoping for “inverted ordering” to win out. “It would be more fun.”

Weight watchers

The quest to pin down the absolute masses of neutrinos, meanwhile, is exceedingly hard. “You need detectors that have exquisitely good resolution,” says Argüelles. This is so difficult that there’s only one experiment currently capable of attempting it: the Karlsruhe Tritium Neutrino experiment (KATRIN) in Karlsruhe, Germany.

The Karlsruhe Tritium Neutrino experiment (KATRIN) — one part of it so big that it barely squeezed down streets on its way from manufacture to its home in Karlsruhe in 2006 — is the only setup today capable of determining the neutrino’s mass.

CREDIT: KARLSRUHE RESEARCH CENTER

KATRIN works by taking tritium — a heavy, radioactive form of hydrogen — and letting it decay, emitting an electron and an antineutrino. The experimenters’ goal is to measure the energy of the highest-energy electrons produced, so they can infer the teeny-tiny fraction of energy that has flitted off with the unseen antineutrino. From this, they can calculate mass, since, as Einstein said, mass is equivalent to energy. Theory says that a neutrino weighs the same as an antineutrino.

The approach creates a massive number of electrons and uses a large and expensive vacuum-filled tube, 23 meters long and 10 meters wide, to filter out all but the most energetic ones. The apparatus is a beast. “It’s very big, and it’s very complicated. And so, there’s only one of its kind, and it took forever to build,” says Argüelles.

From the data KATRIN gathered from 2019 to 2022, researchers provided a first stab at an answer: The average neutrino must weigh less than 0.8eV (electron volts are used as a measure of mass). A few years and a whole lot more data later, in 2025 they nearly halved that limit to less than 0.45eV. This is extraordinarily light — at least 500,000 times lighter than an electron — and it’s a huge technical achievement. But cosmological theory suggests that the real mass is much, much lower still — perhaps smaller than 0.1eV.

“It’s very exciting to have this measurement,” says Magnus Schlösser, an astroparticle physicist involved with KATRIN at the Karlsruhe Institute of Technology. “Of course, we’d be more excited if we actually solved the neutrino masses.”

Project proposals

If neutrinos are lighter than around 0.3eV, this is beyond the ability of KATRIN to measure. So physicists are planning to up their game with other experimental setups. “The community is very innovative,” says Schlösser.

One of these is PROJECT 8: It also starts by splitting heavy hydrogen, but it measures the microwave radiation emitted from electrons as they spiral around in a magnetic field, which should offer even greater precision in assessing neutrino mass. But the project is still in the development stages, and no one knows exactly when it will get built.

Other proposed future experiments, including a next-generation effort dubbed KATRIN++, use tricks such as improving the source and measuring more electrons to crack this problem. But it will take decades yet, says Schlösser, who is hoping for an answer within 25 years, before he retires.

By chipping away at the questions of mass and mass ordering, what physicists are really trying to do is figure out why neutrinos have mass and how they get it.

“We want to know the number and the reason for the number,” says Argüelles. Are neutrinos, weirdly, their own antimatter? Do they possess some kind of previously unknown type of charge? Are we missing a batch of particles from the Standard Model altogether, including a fourth possible flavor of neutrino?

The questions are endless and the possible explanations wide and wacky. And while there aren’t exactly any known practical applications for this knowledge, it gets to the root of our understanding of everything.

“I don’t know if you care about the history of the universe,” says de Gouvêa. “But if you do, then you have to know what the neutrino masses are.”

Editor’s note: This article was updated on March 11, 2026, to remove an incorrect pronoun for Carlos Argüelles.

10.1146/knowable-030426-2

Nicola Jones is an editor and writer who lives in Pemberton, British Columbia. Read more about her and her work on her blog.

2026 Feb 23

- The strange animals that control their body heat

LIVING WORLD | VIEW ON WEBSITE

The strange animals that control their body heat

Some creatures can dramatically alter their internal temperature — a strategy called heterothermy — and outlast storms, floods and predators

By Hannah Thomasy    02.24.2026

In 1774, British physician-scientist Charles Blagden received an unusual invitation from a fellow physician: to spend time in a small room that was hotter, he wrote, “than it was formerly thought any living creature could bear.”

Many people may have been appalled by this offer, but Blagden was delighted by the opportunity for self-experimentation. He marveled as his own temperature remained at 98 degrees Fahrenheit (approximately 37 degrees Celsius), even as the temperature of the room approached 200°F (about 93°C).

Today, this ability to maintain a stable body temperature — called homeothermy — is known to exist among myriad species of mammals and birds. But there are also some notable exceptions. The body temperature of the fat-tailed dwarf lemur, for example, can fluctuate by nearly 45°F (25°C) over a single day.

The degree to which animals use heterothermy varies not just by species, but also between individuals. For example, greater hedgehog tenrecs (Setifer setosus) can maintain a higher, more stable body temperature during pregnancy — researchers believe this is important for fetal development.

COURTESY OF DANIELLE LEVESQUE

In fact, a growing body of research suggests that many more animals than scientists once appreciated employ this flexible approach — heterothermy — varying their body temperature for minutes, hours or weeks at a time. This may help the animals to persist through all sorts of dangers.

“Because we’re homeotherms, we assume all mammals work the way we do,” says Danielle Levesque, a mammalian ecophysiologist at the University of Maine. But in recent years, as improvements in technology allowed researchers to more easily track small animals and their metabolisms in the wild, “we’re starting to find a lot more weirdness,” she says.

The most extreme — and well-known — form of heterothermy is classic hibernation, which has been most extensively studied in critters who use it to save energy and so survive the long, cold winters of the Northern Hemisphere. These animals enter long periods of what scientists call deep torpor, when metabolism slows to a crawl and body temperature can drop to just above freezing.

But hibernation is just one end of what some scientists now consider a spectrum. Many mammals can deploy shorter bouts of shallow torpor — loosely defined as smaller reductions in metabolism and smaller fluctuations in body temperature — as the need arises, suggesting that torpor has more functions than scientists previously realized.

“It’s extremely complicated,” says comparative physiologist Fritz Geiser of the University of New England in Australia. “It’s much more interesting than homeothermy.”

Australian eastern long-eared bats, for example, adjust their torpor use based on day-to-day changes in weather conditions. Mari Aas Fjelldal, a bat biologist at the Norwegian University of Life Sciences and the University of Helsinki, used tiny transmitters to measure skin temperatures as 37 free-ranging bats in Australia went about their daily lives. Like many heterothermic species, the bats spent more time in torpor when it was cold, but they also sank into torpor more often as rain and wind speeds picked up, Fjelldal and colleagues reported in Oecologia in 2021. This hunkering down makes sense, says Fjelldal: Wind and rain make flying more energetically demanding — a big problem when you weigh less than a small packet of M&M’s — and make it more costly to find the insects the bats eat.

There are even reports of pregnant hoary bats entering torpor during unpredictable spring storms, a physiological maneuver that basically pauses their pregnancies. “It means that they can, to some degree, actually decide a bit when to give birth,” says Fjelldal, “which is really handy when you’re living in an environment that can be quite harsh in the spring.” Fjelldal, who wasn’t involved in that study, notes that producing milk is expensive metabolically, so it’s advantageous to give birth when food availability is good.

Biologist Mari Aas Fjelldal studies torpor use in different bat species, including the brown long-eared bat (Plecotus auritus) she holds in this photo.

CREDIT: HELENE M. HANNESTAD

Other animals, like sugar gliders — tiny, pink-nosed marsupials that “fly” through the trees using wing-like folds of skin — rarely use torpor but seem able to take advantage of it in the case of major weather emergencies. During a storm with category 1 cyclone winds of nearly 100 kilometers per hour and 9.5 centimeters of rain falling in a single night, the gliders were more likely to stay cuddled up in their tree-hole nests, and many entered torpor, reducing body temperature from 94.1°F (34.5°C) to an average of about 66°F (19°C), Geiser and colleagues found.

Similarly, in response to an accidental flooding event in the lab, researchers observed a highly unusual period of multiday torpor in a golden spiny mouse, its temperature reaching a low of about 75°F (24°C).

This more flexible use of torpor can help heterotherms wait out a catastrophe, Geiser says. In contrast, homeothermic species can’t just dial back their need for food and water and may not be able to outlast challenging conditions.

“Maybe there’s no food, maybe no water, it may be really warm,” says ecophysiologist Julia Nowack of Liverpool John Moores University in England, a coauthor on the sugar glider study. Torpor, especially in the tropics, has “lots of different triggers.”

Threats of a different sort, such as the presence of predators, can also prompt hunkering down. The (perhaps perfectly named) edible dormouse, for example, sometimes enters long periods of torpor in early summer. At first, this behavior puzzled researchers — why snooze away the summer, when temperatures are comfortable and food abundant, especially if it meant forgoing the chance to reproduce?

Heterothermy evolved multiple times independently among mammals and birds, recent research suggests. Many of these creatures deploy torpor, wherein metabolism is reduced and body temperature becomes closer to ambient temperature. Such species include (clockwise from top left): Commerson’s leaf-nosed bats, sugar gliders, fat-tailed dunnarts and fat-tailed dwarf lemurs.

CREDITS CLOCKWISE FROM TOP LEFT: DAVID DENNIS, DEBORAH METTERS, SAM GORDON, NIGEL VOADEN / iNATURALIST.ORG

After looking at years of data collected by various scientists, a pair of researchers concluded that because spring and early summer are especially active periods for owls, these small snackable critters were likely opting to spend their nights torpid, safely hidden in underground burrows, to avoid becoming dinner. In what is thought to be a similar strategy to avoid nocturnal predators, Fjelldal’s bats alter their torpor use slightly depending on the phase of the moon, spending more time torpid as the moon grows fuller and they become easier to spot.

The fat-tailed dunnart, a mouse-like carnivorous marsupial native to Australia, is a third species to lie low when it feels more at risk of being eaten. In one study, researchers placed dunnarts in two types of enclosures: Some had lots of ground cover in the form of plastic sheeting, simulating an environment protected from predators, while other enclosures had little cover, simulating a greater risk of predation. In the higher-risk settings, the animals foraged less and their body temperatures became more variable.

Levesque, who has studied similar non-torpor temperature flexibility in large tree shrews, says that even small variations in body temperature can be important for saving water and energy.

Indeed, water loss during hot weather can pose serious risks to many mammals, and heterothermy is an important conservation tool for some. As Blagden observed, people are marvelously capable of maintaining stable temperatures even in horrifically hot environments, due in large part to our sweating abilities. But this isn’t necessarily a good strategy for smaller mammals — such evaporative cooling in a sweltering climate can quickly lead to dehydration.

Instead, creatures like Madagascar’s leaf-nosed bats use torpor. On warm days, the bats enter mini bouts of torpor lasting just a few minutes. But during especially hot days, the bats become torpid for up to seven hours, reducing their metabolism to less than 25 percent of normal and allowing their body temperature to rise as high as 109.2°F (42.9°C). And in an experiment with ringtail possums, slightly raising their body temperature by about 3°C (5.4°F) during a simulated heat wave saved the animals an estimated 10 grams of water per hour — a lot for a creature weighing less than 800 grams.

This heterothermic way of life gives some animals a bit of a buffer when it comes to coping with variability in their environments, says physiological ecologist Liam McGuire of the University of Waterloo in Ontario, Canada. But it can only do so much, he says; heterothermy is unlikely to exempt them from the challenge of rapidly evolving weather conditions brought by climate change.

As for Blagden, he saw the human body as remarkable in its capacity to maintain a steady temperature, even by “generating cold” when ambient temperatures climbed too high. Today, however, scientists are beginning to appreciate that for many mammals, allowing body temperature to be a bit more flexible may be key to survival as well.

Editor’s note: This article was updated on 2/27/26 to correct the spelling of the scientific name of the greater hedgehog tenrec, Setifer setosus.

10.1146/knowable-022426-2

Hannah Thomasy is a British Columbia-based science journalist covering the weirdest corners of biology. Her work has appeared in the New York Times, Atlas Obscura and Undark; find her outside looking at bugs or online @hannahthomasy.bsky.social.

2026 Feb 18

- The curious case of low-protein diets

LIVING WORLD | VIEW ON WEBSITE

The curious case of low-protein diets

In the lab, animals live longer on less of the stuff. How could this be, and what does it mean for human aging?

By Amber Dance    02.19.2026

Protein dominates the grocery shelves: Protein chips. Protein cookies. Protein water. It’s in the headlines, too: January’s new US dietary guidelines raised the recommended amount from 0.8 grams of protein per kilogram body weight to 1.2 to 1.6 grams.

Yet there’s a cadre of scientists studying a contrary phenomenon: In critters from single-celled yeast to insects to rodents, cutting protein intake to measly levels makes them live longer.

Could it work for people? To be clear: The body needs protein to build and repair its parts, and a diet with about 7 percent or less of its calories from protein is a recipe for malnutrition, not centenarian status. But studying protein restriction in lab animals helps scientists learn how animals sense nutrients, how their bodies strategically respond to excess or to shortage, and how all of this affects their health and longevity. And that could carry lessons for human beings.

“There’s a lot to be learned from the principles of protein restriction about how we would manage aging, and aging well,” says Stuart Phillips, a physiologist at McMaster University in Hamilton, Canada.

The mouse food diaries

Protein restriction, Phillips says, is a sort of “lite” version of a more well-known longevity hack — caloric restriction. Cutting overall calories eaten, typically by 20 percent to 50 percent, has been linked to long lifespan in lab animals since more than a century ago. Some dedicated humans are trying a milder version.

Lab animals on low-calorie or low-protein diets are indeed long-lived. In one recent study, mice that ate all they wanted of normal chow lived for a maximum of 1,008 days. Mice given the same food, but only 80 percent of the calories, survived for up to 1,179 days — a ripe old age for a mouse. Those sets of mice received chow with 18 percent protein, but a third group feasted on an all-you-can-eat buffet with only 6 percent of calories from protein. Their survival was in between the others, with a maximum of 1,115 days.

These effects went beyond long life; restrictive diets also improved health. Mice on calorie-restricted or protein-restricted diets had lower levels of sugar and insulin in their blood, and lower insulin sensitivity — markers of metabolic fitness. These healthy signals continued as the mice on restrictive diets grew older, while their status deteriorated in the aging mice that ate normally. Not surprisingly, the mice on calorie- or protein-restricted diets also had lower body fat. Indeed, at a one-year check-in, they were downright gaunt, weighing in at about two-thirds the mass of their normally dining counterparts.

Researchers fed 30 male mice a standard diet with 20 percent protein, and 30 additional mice a diet with only 5 percent protein. Those that got less protein lived longer.

In another recent study, researchers zeroed in on molecular signs of aging. As animals get older, their bodies undergo changes, such as the damage of tissues by unstable free oxygen radicals. Mice on a low-protein diet exhibited a variety of anti-aging features, in their DNA and proteins, across multiple organs. For example, they boosted levels of protective, antioxidant enzymes. The benefits were most pronounced in middle-aged mice, suggesting that low-protein benefits aren’t the same across the lifespan.

Making hay or hunkering down?

Scientists don’t yet know all the biological factors that underlie how mice become thin, healthy and long-lived on restrictive diets. One obvious potential explanation for their skinny physiques is that they lack the nutrients to build and maintain their body parts or are dedicating their scant energy supplies to brain function — but that’s probably not the full story, says Morrison. The reasons behind their metabolic health and longevity are less obvious, but scientist have ideas.

Think of the body like a car, suggests Clemence Blouet, a neuroendocrinologist at the University of Cambridge in the UK. You can drive fast, using lots of fuel and putting wear and tear on the auto. Or you can stick to a gentle 15 miles per hour, and the car lasts longer. Living in a high-protein or high-calorie fast lane, she muses, could lead to the accumulation of those pro-aging oxygen radicals. Protein, in particular, also turns on systems that promote growth as well as aging. Restricting the diet could mean fewer of those damaging radicals and less pro-aging actions, keeping the body in smoothly working order for longer.

Alternatively, suggests Phillips, imagine a body that is forced by a short supply of nutrients to go into high-efficiency mode, so it recycles more of the amino acid building blocks used to make proteins. “I think, then, a lot of other processes that are age-related also get more efficient … and function very, very well,” he says.

It is also becoming clear that the low-protein/long-life effect isn’t simply because the body is withering from a shortage of body-building molecules, says Christopher Morrison, a physiologist at the Pennington Biomedical Research Center in Baton Rouge, Louisiana. There’s something more strategic going on. Morrison’s team studies a hormone called FGF21, made by the liver, and when protein is in short supply, FGF21 seems to tell the brain, “Hey! There’s not enough protein in this diet!” But if mice are engineered to lack FGF21, they don’t respond to low-protein diets with life extension — in fact, they die earlier. In other words, low protein extends life only if the brain gets the message and adjusts the body’s responses.

“The reduction in growth is a ‘choice,’ if you will,” concludes Morrison, who coauthored an overview of protein restriction in the 2025 Annual Review of Nutrition. And he thinks this choice occurs before bodies reach the point of wasting from too little protein.

The body only responds to protein restriction if the brain knows what’s going on. The liver hormone FGF21, produced in response to low protein, is a big part of that message. In response to FGF21, the brain instigates a number of adaptations. In the case of lab mice given nothing but low-protein food to eat (left), those adaptations include increased food intake to get enough protein; scientists suspect this also leads the animal to burn off the extra energy it consumes. The animal also exhibits slower growth and improved metabolic health. If animals are in a more natural situation, where there are other food options available (right), they’ll eat more protein and fewer carbohydrates, so their total consumption doesn’t change much.

If life extension when protein is scarce is a choice, albeit an unconscious one, then sticking with the default shorter life when protein is abundant could be a sort of choice, as well. While it might seem counterintuitive, this makes perfect sense for an animal that’s balancing survival with reproduction, says Stephen Simpson, a nutritional biologist at the University of Sydney. When nutritious, protein-rich foods are abundant, animals “make hay while the sun shines,” Simpson says, putting their energy and resources into growth and reproduction. That might mean they don’t quickly repair tissues damaged by oxygen radicals or other stressors. If the animal loses a few months off the end of its life, so be it. From an evolutionary standpoint, the additional descendants are worth that sacrifice.

Conversely, if nutrients are hard to come by, creatures “hunker down,” Simpson says. They activate protective and reparative anti-aging mechanisms in the hopes they’ll survive long enough to reproduce when good times return — even if it means they stay puny. Simpson’s research backs this up: Reproductive indicators such as sperm counts and ovarian follicle numbers are diminished in mice on a low-protein menu compared to those eating high-protein fare.

Researchers are starting to piece together the biology behind these “making hay” and “hunker down” programs — and the molecules they uncover might inspire medicines to help people age with ongoing health, suggests Phillips. It’s known, for example, that a physiological system mediated by the enzyme mTOR regulates growth, reproduction and aging. Low-protein diets shut down mTOR, as does a drug called rapamycin that has garnered interest as an anti-aging compound.

Protein for the people

But all these data come from nonhuman lab animals. “I don’t think we really know what long-term protein restriction will do in humans,” says Morrison.

Scientists can hardly put a large group of people on a decades-long low-protein diet and wait to measure how long they survive. But what they can do is correlate people’s diets, reported on questionnaires, to disease and survival. The results of such epidemiology studies vary, but overall, higher protein intake seems to correlate with a slightly higher risk of cardiovascular disease and type 2 diabetes, says Phillips. He cautions that people who eat lots of animal protein get the saturated fat that comes with it, which could skew the health results. Diets high in plant protein don’t show the same pattern.

Another kink in the science is that protein needs vary by age. One study found that for people aged 50 to 65, a low-protein diet correlated with lower likelihood of death from cancer or any cause compared with those eating a high-protein diet. But for people older than 65, the pattern flipped: Low protein intake was linked to higher rates of cancer deaths and overall deaths. So keeping protein intake low to average in middle age but getting more after age 65 could — perhaps! — be beneficial.

Protein needs vary with age, as do the effects of low-protein diets, according to observational studies of people. In adults aged 50 to 65, a lower-protein diet correlates with a reduction in deaths due to cancer, diabetes or any other cause. But in people 66 or older, the pattern changes: A low-protein diet is still linked with lower risk of death from diabetes but is associated with a higher risk of death from cancer or other causes.

And that’s only if people could stand to follow such a diet for years at a time. It’s possible, Simpson muses, that a low-protein diet might feel less torturous than one that restricts calories overall, even though protein is known to help satiate hunger. But his own work, studying creatures from locusts to people, has shown that a body lacking protein craves the stuff. In one study, volunteers spent four days in a clinic and could select whatever they wanted to eat from a controlled menu where everything contained 10 percent protein. They responded by gorging on savory snacks, as if they were hankering for the umami protein flavor. As a result, they ate more calories in total — hardly a recipe for dietary success.

Tellingly, no scientists who spoke with Knowable Magazine were restricting their own protein intake. “I’m not a fruit fly or a mouse,” says Morrison. While he tries not to overdo it on protein, he’s not confident he could adhere to a protein-restricted diet. Plus, he adds, “I don’t want to be real scrawny.”

10.1146/knowable-021926-1

Amber Dance is a special contributor to Knowable Magazine based in Los Angeles. She won’t be giving up her peanut butter-Greek yogurt habit anytime soon.

2026 Feb 17

- Looking for an ADHD coach? Choose carefully

THE MIND | VIEW ON WEBSITE

Looking for an ADHD coach? Choose carefully

As diagnoses surge, so does an unregulated coaching industry

By Katherine Ellison    02.18.2026

Lea en español

For most of her adult life, Katherine Sanders had what she calls a typical career for someone with attention deficit hyperactivity disorder.

After finishing her doctoral thesis on Bronze Age Syrian mythology, she bounced between unrelated jobs. She tutored university students. She sewed Victorian corsets for bridal outfits. She designed stained glass and sold picture frames. She enjoyed the work, but none of it felt like a calling.

Life got harder when she found herself juggling part-time work with caring for a spirited five-year-old. Sanders, who lives in Edinburgh, Scotland, burned meals on the stove and forgot to pick up her daughter from school.

Finally, she decided to work with a coach to help her cope with her ADHD, a bedeviling condition whose hallmark symptoms are distraction, forgetfulness, restlessness and impulsivity.

She began by enrolling in a digital course called Your ADHD Brain is A-OK. Like most ADHD coaches, Tracy Otsuka, the course producer, has herself been diagnosed with the disorder. Otsuka, based in Northern California, says she focuses on helping her clients shed shame as a prelude to finding their purpose and living more fulfilled lives. Participants in the self-paced course watch 26 videos and fill out worksheets designed to identify their values and strengths.

Sanders says working with Otsuka led to a lightbulb moment for her. “This woman is very smart, she’s very savvy,” she says. “And she still did stuff like forget to pick her kid up from school.… She still does the same things as me.” The experience made Sanders realize that she, too, was smart but had a specific challenge she needed to learn to manage.

After completion of the course, as Sanders exchanged online messages with Otsuka, the coach startled her with a suggestion: Perhaps she’d like to be a coach herself?

Two years later, armed with training and credentials from the ADD Coach Academy (ADDCA), Sanders joined a field that has exploded as ADHD diagnoses have multiplied and patients have scrambled to find scarce professional help.

Katherine Sanders, who lives in Scotland, has experienced first-hand the benefits of a good ADHD coach. Now a trained ADHD coach herself, she wants to see more rigor in her profession.

CREDIT: SUSAN HEATON / CLEAR PHOTOGRAPHY

ADHD coaching is a fast-growing niche within a much larger, heterogeneous coaching industry that is mostly unlicensed and unregulated. Executive coaches aim to help managers navigate leadership challenges; health coaches support people with chronic conditions; and life coaches promise everything from improving work habits to reviving “your body, mind and soul.”

ADHD coaching sits at a particularly busy intersection, promising relief from a sometimes disabling and stigmatized condition. It is also one of the least-studied domains in an enterprise that is understudied in general, and for which evidence of effectiveness is sparse. These deficits matter, because demand is rising even as coaching’s low barriers to entry make it easy for under-trained practitioners to oversell their services. That’s an especially risky recipe for clients who may be extra-vulnerable due to their mental health challenges. Experts warn prospective customers to be cautious and informed.

Theoretically, coaching could be useful for people with ADHD as part of a toolkit that might include medication and therapy, says clinical psychologist and researcher Stephen Faraone, president of the World Federation of ADHD. But he worries about the industry’s lack of standards and regulation, noting that licensed health professionals must train for years and pass rigorous exams. “Coaching seems to me to be more of a business, and that worries me,” he says.

The rise of coaching

The origin of coaching for better mental and emotional performance dates at least as far back as 1974, when former tennis coach Tim Gallwey wrote The Inner Game of Tennis, offering techniques to counter the anxiety that can sabotage sports performance. ADHD coaching came later, pioneered in the 1990s by advocates including Nancy Ratey, Sue Sussman and Madelyn Griffith-Haynie. Yet it wasn’t until the Covid-19 pandemic that a confluence of factors — increased mental health problems of all kinds and self-diagnosis-by-TikTok among them — led to explosive global growth of ADHD coaching and coaching in general.

Today, annual revenue from all sorts of coaching has reached $5.34 billion, according to the International Coaching Federation. The number of self-identified coaches has climbed by 15 percent since 2023, reaching a total of 122,974, the federation reported in 2025. The true number is likely much larger, due to the many, many coaches who put up a shingle — or claim a job title on LinkedIn — without any training or accreditation. Trying to estimate the number of coaches is like “counting fish in the sea,” says Jonathan Passmore, a psychologist, executive coach and researcher in England.

A survey of 481 ADHD coaches in the United States found a sharp rise in entry to the ADHD coaching workforce starting around the time of the Covid-19 pandemic.

And ADHD coaching? With roughly 7 million children and 15.5 million adults in the United States diagnosed with the condition, and more being diagnosed all the time, ADHD coaches have plenty of prospects, especially given the drawbacks of established treatments. Medication may tame symptoms, but it has side effects and doesn’t work for everyone. Licensed psychotherapists are costly and often hard to find, whereas the lack of state licensing requirements means coaches can practice, remotely, from anywhere.

On the other hand, coaches may be even more expensive than licensed professionals, notes Margaret Sibley, a clinical psychologist at the University of Washington and Seattle Children’s Hospital and a coauthor of a recent JAMA Network Open article about a large survey of ADHD coaches.

“They charge $150 an hour on average (and some charge well above $500 an hour),” Sibley says. “This is similar to reimbursement rates for psychologists for mental health therapy. Except ADHD coaching isn’t reimbursable by insurance at this point so it’s only accessible to those with high financial resources.”

In a typical ADHD coaching session, coach and client will meet to work on a goal of the client’s choosing and produce an action plan to reach it. Sanders, for instance, says that most of her clients struggle with feeling overwhelmed. “They’ll come up with a laundry list of things they’re trying to do, and by the time they’ve listed everything, I say, ‘How does that feel for one person to try and do in two to three days? Is that reasonable?’”

CREDIT: ISTOCK.COM / ALEKSEI MOROZOV

The boom in all kinds of coaching

- $5.3 billion global market.

- 122,974 self-identified coaches, 54 percent increase since 2019.

- Rates: $254 per hour on average.

SOURCE: International Coaching Federation, 2025

Coaches will often help clients break tasks into pieces that are more easily achieved, suggest tools such as timers, journals and calendars to keep them on track, and schedule meetings to hold them accountable. However, as Otsuka and many other coaches agree, increasing self-awareness and dispelling shame that has accrued over years are essential.

“Adults with ADHD get really good at being hard on themselves … everybody else is always telling us we should do things differently,” says David Rickabaugh, president of the ADHD Coaches Organization, an international professional association.

“Change your life in 30 days!”

Coaching appears to be increasingly popular for people with ADHD, although a recent survey in ADDitude magazine found that just 17 percent of the adults who responded had tried it. Ninety-three percent of the respondents who had experienced coaching recommended it to others, making it the second-most recommended ADHD intervention after exercise and before medication.

Yet the coaching industry remains a therapeutic Wild West compared to licensed health care. Consider the difference between pharmaceuticals and supplements: Both may help, but only the first must meet standardized thresholds for evidence and supervision. As with supplement manufacturers, coaches often appear to feel free to make sweeping claims. “Change your life in 30 days!” proclaims the website of a coach who calls herself “the World’s #1 Authority on How to Master Fear.”

Sibley and her colleagues, who surveyed 481 ADHD coaches for the JAMA Network Open report, found that 89 percent had no professional mental health background. Only about 63 percent had completed a curriculum endorsed by the ADHD Coaches Organization. More than 72 percent of the coaches said they had, or suspected they had, ADHD, and more than 90 percent said they shared their lived experience in their work.

The survey found similarities in coaches’ strategies. More than 90 percent said they coached clients in executive function skills, which include planning, impulse control and self-motivation strategies. More than 90 percent said they addressed sleep, self-worth, emotional concerns and healthy behavior such as nutrition and exercise.

Despite their relative lack of mental health training, about half of the coaches said they also addressed substance use or addictions and trauma, and roughly 42 percent said they covered “suicide, abuse and/or harm to self or others.” This invites special risks, especially given that most adults with ADHD also meet criteria for at least one other psychiatric disorder, such as anxiety, depression or substance use. Such complications may produce both more distress and more susceptibility to promises of quick relief. “The absence of standards and regulations about who can declare themselves an ADHD coach make it particularly important to practice due diligence when vetting an ADHD coach, especially as there are no legal protections for clients,” write Sibley and her colleagues.

CREDIT: ISTOCK.COM / ALEKSEI MOROZOV

ADHD coach red flags

Here, according to ADHD coach Katherine Sanders, are signs of an underqualified coach:

- Promising specific outcomes or “cures” for ADHD.

- Training completed in less than 40 hours.

- Inability to explain the difference between coaching and therapy.

- Lack of transparent qualification information.

Close to 80 percent of respondents in the survey said they would refer clients to a mental health professional to obtain a formal diagnosis. Sanders goes further, saying she scrupulously refers clients with trauma, addiction or suicidal thoughts to licensed therapists, who she says are more qualified to deal with those issues.

The data deficit

Despite the growing market for ADHD coaching, there’s limited concrete evidence that it works. (Sibley and colleagues wrote that they were “struck by the glaring disconnect between the maturity of ADHD Coaching as a profession and the infancy of its science.”) A widely cited 2018 descriptive review provides some of the strongest evidence about the field to date. The four authors, all working as coaches, considered 19 studies, the majority of which reported statistically significant improvements of ADHD symptoms, which commonly include inattention, hyperactivity and impulsivity. Yet as they noted, many of the studies were small and lacked control groups — people who had not been coached — for comparison, while also including extremely varied coach qualifications, making it hard to measure how much training matters.

Research on coaching in general is somewhat more advanced. Over the past decade, scientists have published more than a dozen meta-analyses — studies that interpret several studies as a group — most of which showed small to moderate positive results across different kinds of coaching. Some of the strongest findings suggest business executives may improve skills related to leadership and management, and people with chronic health conditions may take better care of themselves, including by managing their weight and exercising more. Motivated coaching clients are “likely to grow in self- and interpersonal awareness,” wrote the authors of a 2023 article in the Annual Review of Organizational Psychology and Organizational Behavior.

Yet some of these reviews also noted problems similar to those affecting the ADHD coaching research, including small samples and limited follow-up, as well as overreliance on self-reports, which are often biased.

Scientists and coaches themselves have been calling for a more rigorous look at what makes coaching effective.

“I understand the concern about regulation some have raised, and we share a number of those concerns,” Rickabaugh, the ADHD Coaches Organization president, wrote to members in the wake of the JAMA Network Open report that, as he noted, highlighted “variation in our field — in training, scope, and practice.” That focus “may feel uncomfortable,” he added, “but documenting this reality is actually necessary if we want to shape conversations about ADHD coaching standards rather than have standards imposed upon us. Quality matters, and credentials and training do serve our clients and our profession.”

Researchers are trying to figure out what essential practices deliver the most benefits for coaching in general. How is the skillful interviewing and active listening that coaches say they practice different from what a close and attentive friend could provide?

That question is key, because despite robust research linking social connection to better mental health, 17 percent of Americans today say they have no close friends. The numbers could be worse for people with ADHD, who notoriously struggle with relationships. Whether a paid, one-way social connection can deliver the same benefits as a reciprocal and free one remains an open question.

Buyer beware

As coaching for all sorts of purposes becomes more widespread, the risks are becoming more obvious. Sanders recently authored a white paper documenting “systematic failures” of the ADHD coaching field that, she said, “require immediate industrywide intervention.”

Some regulators are already stepping up.

In March 2025, Utah created a special fund to increase its ability to investigate potential unlawful conduct by coaches treating mental health conditions. This followed a 2024 investigation by the Salt Lake Tribune and ProPublica, which found that clinicians who had lost their licenses were marketing themselves as “life coaches,” claiming to treat depression or “untangle” clients’ emotional “chaos.” One man told the Tribune and ProPublica that a coach ordered him to cut off his family and live in a tent to “humble” himself.

Sanders is encouraged by some of these trends and continues to enjoy her work — even as she’s sometimes distracted by a familiar hunger for novelty.

“I keep thinking maybe I should try ceramics,” she said recently. “I really love porcelain, you know?”

CREDIT: ISTOCK.COM / ALEKSEI MOROZOV

If you’re seeking an ADHD coach….

Here are resources and warning signs compiled from experts:

• Many organizations provide resources for finding qualified ADHD coaches. The Professional Association for ADHD Coaches (PAAC) offers independent credentialing for ADHD coaches and provides a roster of members.

• The nonprofit Edge Foundation helps connect people with coaches.

• ADDitude, a magazine and resource center owned by WebMD, offers an online directory.

• Once you’ve found a candidate, be sure to ask the following five questions:

1. Who trained you? (The ADHD Coaches Organization recommends these training groups.)

2. How much training have you completed? (Psychologist and coach Jonathan Passmore suggests that you look for 60 or more hours of in-person training.)

3. What ethics code do you follow, and who holds you accountable? (ADHD coach training programs accredited by the International Coaching Federation and PAAC are the most reputable, according to ADHD Coaches Organization President David Rickabaugh. The ADD Coach Academy says it certifies “the largest and most respected group of ADHD coaches in the world.”)

4. Do you receive regular supervision? (“Yes” is a good sign, says Passmore; he suggests once-a-quarter supervision.)

5. What issues do you cover — and what do you exclude? (According to Passmore, “everything” to the first question is a red flag.)

— Katherine Ellison

SOURCES: Jonathan Passmore, Katherine Sanders, ADHD Coaches Organization.

10.1146/knowable-021826-1

Katherine Ellison is an award-winning journalist and author of 12 nonfiction books.

2026 Feb 10

- Tales of a very clever slime mold

LIVING WORLD | VIEW ON WEBSITE

Tales of a very clever slime mold

In its quest to feed, avoid nasty substances and just generally live its life, the brainless, one-celled Physarum polycephalum performs some impressive tricks of learning and memory

By Tim Vernimmen    02.11.2026

Lea en español

Sixteen years ago, a brainless, unicellular organism blew our human minds. And it continues to fascinate and surprise researchers to this day.

Scientists had known that some slime molds of the species Physarum polycephalum consist of one giant, pulsating cell that keeps changing shape as it moves around and branches out to access food and avoid unpleasant things like salt or light. But it took a 2010 experiment led by Japanese biologist Toshiyuki Nakagaki of Hokkaido University to reveal the depths of its sophistication. When Nakagaki placed the oat flakes that Physarum likes in a pattern mimicking the cities surrounding Tokyo, the slime mold’s branches almost exactly reproduced the efficient transport connections between them that humans had taken years to develop.

From the center of a petri dish, the slime mold Physarum polycephalum extends branches to find food in this time-lapse video.

CREDIT: © DUSSUTOUR / CNRS

To Karen Alim, a theoretical physicist starting a postdoctoral project at Harvard University at the time, that study was a revelation. “I was like, ‘Wow, this is so crazy.’ A single cell that solves complex tasks appealed very much to me as a physicist.” Perhaps, Alim thought, she could apply her training to make sense of this clever creature with its network of contractile tubes and constantly pulsating currents.

So Alim and colleagues grew Physarum on a jelly-like substance called agar and carefully watched and recorded its behavior under the microscope. They measured the strength and direction of the fluid flow in its network of tubes. Then they simulated what they’d seen in mathematical models.

The result? Through studies like this, as Alim recounts in the Annual Review of Condensed Matter Physics, she has become convinced that the flow of fluid can be a way of transmitting information, and she’s working to understand the underlying mechanisms. Other researchers, meanwhile, are continuing to uncover new, intriguing behaviors in Physarum, a creature that appears able to learn, remember and make decisions — all without a brain.

Researcher Karen Alim (right) and her colleagues grow Physarum polycephalum in petri dishes containing a nutrient-rich agar medium.

CREDIT: STEFAN WOIDIG / TUM

The flow of memory

Though Physarum is a single cell, the large body it forms can often be easily seen by the naked eye, growing to more than a foot in diameter under favorable conditions. It looks like a central blob from which a network of vein-like tubes emanates — larger tubes, then smaller tubes that fan out from them. Inside those tubes, cytoplasmic fluid is rhythmically flowing back and forth, supplying all parts of the cell with what they need. In nature, the slime mold is found in damp, dark spots like forest floors and decaying logs.

Many of the studies revealing Physarum’s unexpected skills revolve around its most important concern: finding food. Whenever Physarum encounters something edible, the outer wall of tubes near the food become soft. As a result — due to the pressure of the constantly moving fluid inside its tubes — that part of the body spreads out like a fan. This fan then slowly morphs into a network of even tinier tubes. Under the microscope, this looks like a river delta network of yellow slime feeding into the larger tubes of Physarum’s body.

How does it happen? Alim, who now works at the Technical University of Munich in Germany, figured out that encounters with food lead to an increase in local fluid flow within the tubes. This exerts greater shear force on the tube walls. The walls in that region grow thinner, allowing the tubes to expand.

Inside the slime mold Physarum polycephalum’s branching, pulsating body, currents of fluid flow back and forth to transport food and other molecules. These currents are key to the organism’s ability to move, change its shape and learn.

CREDIT: DELESCLUSE & DUSSUTOUR / CNRS

The opposite happens when Physarum encounters something awful like salt or light that it wants to get away from. In response to a repellent, the tube walls stiffen and contract, which redirects fluid flow elsewhere.

In sum, researchers now understand that where the flow is stronger, the tubes expand, and where the flow is weaker, they shrink. This interplay of shrinking and expansion in different areas of the body is what reorganizes the shape of Physarum’s tube network, causing it to approach food and avoid things like salt.

More recently, Alim and colleagues discovered just what creates a tube network as efficient as Tokyo’s transport links. It ties into something crucial about the fluid flow in Physarum’s body: Tube walls respond to changes in flow with some delay. First the flow increases. Then, slightly later, the tube expands in response, causing the flow to decrease. This causes the tube to shrink, again with some delay.

The result, Alim found, is that the best-positioned tubes will grow larger and larger and receive more and more flow, while others will fade away — and hence, over time, a super-efficient network of links will form.

Put another way, Alim adds, you could say that the shape of the network (and its underlying fluid flow dynamics) helps Physarum to remember. Appropriately sizing its branches in accordance with food sources it has encountered recently makes for a simple but effective way to recall where food can be found.

Recent work in Alim’s lab suggests it’s not just the shape of the network that helps Physarum remember, but also how, when and where it contracts the walls of its branches. For example, she says, putting food in a certain location leads the slime mold to respond with a certain pattern of contractions and move toward the food. Between experiments, the contraction pattern diminishes, but if food is put in the same spot, it reappears, more quickly than before. In one experiment, a persistent wave of contractions caused a slime mold to keep crawling in one direction for hours to get away from a light source, long after the light had been switched off, which suggests it still remembered it.

Like all of us, Physarum polycephalum has its food preferences, as this time-lapse video shows.

CREDIT: © DUSSUTOUR / CNRS

Salt and slime

The finding is reminiscent of a study by Audrey Dussutour, a biologist working on the same species, now at the National Centre for Scientific Research in France. In 2019, Dussutour had reported something interesting: After a few attempts, Physarum took less time to cross a nasty salty patch inside its dish while moving toward a food source — implying some kind of learning. The effect remained even after the slime mold had spent time in the dormant state it adopts under stressful conditions.

Since the slime mold absorbed and retained some salt, it’s possible that this lowered the shock of encountering it again and allowed it to move faster, says Dussutour. So in a recent experiment, as yet unpublished, she used light as the repellent instead. Physarum still shaved down its travel time with repeated exposures, even though light isn’t retained the same way salt is. Dussutour suspects that contraction patterns may persist and store information “similar to the way waves of activity in our brain can store information,” she says.

In addition to the information stored in the layout and contractions of its tubes, says Dussutour, Physarum has another way to “remember”: the trail of slime it leaves wherever it goes. “Avoiding slime is a convenient way to make sure it’s exploring new places rather than retracing its own trail,” she says.

In the wild, Physarum polycephalum is often found on dead plant material, as shown in this time-lapse video.

CREDIT: © DUSSUTOUR / CNRS

Dussutour was also able to show that slime molds can learn about each other: They are sensitive to aspects of each other’s behavior. “They will approach others that have access to food, and avoid ones that are starving or stressed,” she says. “Remarkably, they also prefer to approach young individuals.”

Older slime molds become very slow and fragile, she adds. “We have some in the lab that are now 5½ years old…. We hardly dare to use them anymore. But intriguingly, when they go through dormancy, or fuse with a younger individual, it’s as if they’re young again.”

For a better understanding of the slime molds’ mysterious ways, it would be very helpful to find out what exactly they’re up to in the wild, says behavioral ecologist Tanya Latty of the University of Sydney. “Almost everything we know about their behavior is based on experiments done in a lab,” she says — experiments that focus on the large, multi-nucleus forms of the creatures, not the single-nucleus, microscopic amoeba state in which they spend most of their lives.

So Latty’s research group has been collecting wild slime molds to investigate. “They’re often found on rotting logs, but we’ve also found them in the leaf litter just in front of our building. People have also found them on house plants. They’re everywhere,” she says.

Latty suspects that the large form, with its various ways of learning, allows Physarum to consume a lot more food in preparation for making the spores it needs to spread. Physarum may be far less clever in its microscopic form, she adds, if its surprising behavior really depends on its ability to branch and contract its tubes. “But who knows? We didn’t think they were capable of anything when we started to study them.”

10.1146/knowable-021126-1

Tim Vernimmen is a freelance science journalist based near Antwerp, Belgium. For this article, he was hoping to interview Physarum itself, but scientists are still working out how to do that.

2026 Feb 8

- The cataclysmic flood that wasn’t

PHYSICAL WORLD | VIEW ON WEBSITE

The cataclysmic flood that wasn’t

Researchers have long believed that a sudden, massive deluge filled a dry, salt-filled Mediterranean some 5 million years ago. Turns out that probably didn't happen, but there was still drama aplenty.

By Dana Mackenzie    02.09.2026

Lea en español

On October 6, 1970, the deep-sea drilling vessel Glomar Challenger returned to port in Lisbon, Portugal, bearing a cargo that would revise history. During its 54-day voyage, the Challenger had punched 28 holes into the bottom of the Mediterranean Sea. The recovered cores pointed toward a startling conclusion: About 6 million years ago, the sea had turned into a desert: a vast, barren, salt-filled bowl more than two kilometers deep. Half a million years after that, the Atlantic Ocean had burst through what is now the Strait of Gibraltar and unleashed the largest flood in history.

Kenneth Hsü, an oceanographer who was one of the two lead scientists on the Challenger expedition, imagined the scene vividly in the December 1972 issue of Scientific American:

“Cascading at a rate of 10,000 cubic miles per year, the Gibraltar Falls would have been 100 times bigger than Victoria Falls and 1,000 times more so than Niagara.… What a spectacle it must have been for the African ape-men, if any were lured by the thunderous roar.”

The catastrophe story was a hit: David Attenborough filmed a documentary about it, and Gibraltar even issued a 5-pence stamp portraying the “3,000-metre waterfall.” The two hypotheses — first, that the Mediterranean Sea became landlocked during a half-million-year period known as the Messinian salinity crisis, and second, that it was restored by a cataclysmic deluge through the Strait of Gibraltar, dubbed the Zanclean flood — have been conventional wisdom among geologists for more than 50 years.

However, fresh doubts have arisen recently about every part of this story, from the mega-desert to the mega-Niagara. Many geologists have argued for a much briefer desiccation followed by a far more gradual refilling of the Mediterranean. Some think that the Mediterranean never completely disconnected from the Atlantic at all. “The idea of a megaflood, and the data that supports it, are mostly flawed,” says Guillermo Booth Rea of the University of Granada in Spain.

The most startling recent twist is that the floodway, if there was one, may not have been anywhere near the present-day Strait of Gibraltar, which separates southern Spain from Morocco. For 50 years, new research suggests, we have been looking for signs of a megaflood in the wrong place.

Cataclysmic floods feature in many stories of mythology and creation. In one such legend, classical hero Hercules cleaves apart two mountains (the “pillars of Hercules”), creating the Strait of Gibraltar and flooding the Mediterranean basin. The above image shows an artist’s conception of a now submerged temple to Hercules at Gibraltar.

CREDIT: L. SONREL / THE BOTTOM OF THE SEA 1872

A geological conundrum

In the present-day Mediterranean, about three times more water is lost every year to evaporation than is recaptured from rainfall and rivers. The Atlantic makes up for the difference, supplying a steady west-to-east current of seawater through the Strait of Gibraltar. As the sea’s water evaporates, the remaining water becomes saltier and denser and sinks to the bottom. The dense water then flows back out of the strait, east to west, underneath the less dense inbound water. This outflow prevents salt from accumulating in the Mediterranean.

But what would happen if the strait were constricted, or shut off entirely? Given the hugely negative budget of fresh water, “sea level” in the Mediterranean Sea would drop rapidly, by as much as a kilometer in 2,000 years. Such a scenario would have seemed like science fiction until the Glomar Challenger’s 1970 expedition.

At the first drill site, the Challenger’s drill bit jammed on a very hard layer 200 meters below the bottom of the sea. The next day, Hsü and his co-lead scientist, William Ryan of Lamont-Doherty Earth Observatory, found out why. “It brought up buckets full of gravel,” Ryan says.

Seafloors don’t often contain beds of gravel, and when they do, it is usually continental rocks washed down from the adjacent land. But this gravel had marine fossils and rock, mixed with crystals of gypsum. Geologists call gypsum an “evaporite,” because in the present-day world it forms in evaporating shallow bodies of water — as in the Dead Sea, for example. The implication was startling. “When Ken held up the gypsum crystals, he turned to me and asked, ‘Do you think the Mediterranean dried out?’” Ryan remembers.

The same story was repeated at every stop. Ryan and Hsü found other evaporites like halite (sodium chloride, aka table salt). Oxygen isotopes in seashells embedded in the gravel suggested that these unlucky animals had lived in a brine from which 90 percent of the original water had evaporated. Hsü and Ryan also gathered evidence that the colliding of the African and Eurasian tectonic plates had lifted up the land on both ends of the Mediterranean Sea, closing its former connection with the Indian Ocean and narrowing the connection with the Atlantic Ocean.

The layout of the Mediterranean during the third stage of the Messinian salinity crisis has been particularly controversial: Some believe that the Mediterranean was nearly dry; others believe it was nearly full. Recent research suggests the answer may be both. The Mediterranean basin may have refilled with freshwater from the ancient Paratethys lake system to the east, while sea levels also fluctuated due to climate changes. The high water (purple) and low water (brown) levels of this period (5.33 to 5.55 million years ago) are shown on the bottom map.

The clinching piece of evidence came to light after the Challenger mission had ended. Other geologists discovered what appear to be buried ancient beds of several rivers that flow into the Mediterranean, particularly the Nile and the Rhône. It looked as if those rivers once emptied into the Mediterranean at least a kilometer below their present outlets — something that would be possible only if the sea level of the Mediterranean had been a kilometer below the global sea level at some point in the past.

In 1973, a meeting in Utrecht, Netherlands, established the desiccation model as the consensus theory. But a considerable amount of dissent has emerged in the last 20 years. “In the 1970s, the desiccation people won the debate,” says Wout Krijgsman of Utrecht University, “but there are several aspects it cannot really explain.”

Paradoxes galore

In part, the dissent reflects an improved understanding of what was occurring on Earth and in the area 6 million years ago. Since 1973, the story told by rocks, core samples and seismic soundings — and, increasingly, by computer simulations — has become more detailed and more dynamic, with changing shorelines, land bridges and volcanoes, and repeated episodes of climate change.

Also, there were fundamental problems with the desiccation hypothesis to begin with. Take the evaporites, for example: They do not have to form via evaporation, says sedimentologist and stratigrapher Vinicio Manzi of the University of Parma in Italy. They can also form by precipitation from a sufficiently concentrated brine. This can happen underwater, so there is no need to posit that the Mediterranean went bone dry.

And the buried riverbeds? Those, too, Manzi and his colleagues can explain: The sinking of briny water can produce downhill currents (“dense shelf water cascading,” in geology lingo) sufficiently strong to scour out a canyon.

The idea of a single evaporation event also faces a mathematical problem: The existing salt deposit is too big to be explained by a single evaporation event. It represents about 5 percent of the salt in the world’s oceans (and may have originally been 7 to 10 percent). To collect that much salt, the Mediterranean would have had to empty and refill about 10 times.

In fact, evidence from salt deposits in Sicily suggests something like that actually happened. There, gypsum beds alternate with shale beds that are rich in organic material and could have formed in periods when the gateway between the Atlantic and Mediterranean was open. There are 16 beds in all, with ages spaced about 23,000 years apart.

This periodicity is well known to geologists: It’s the time it takes for Earth’s axis (like a wobbly top) to trace one complete circle. And it correlates with changes in climate and ancient sea levels the world over. With the presumptive Gibraltar gateway being so shallow during this period, sea level fluctuations due to this “precessional cycle” could have repeatedly opened and closed the connection between the Mediterranean Sea and the Atlantic.

Like a wobbly spinning top, the Earth’s axis of rotation also moves in a slow circle, completing a full cycle once roughly every 23,000 years. This precession of Earth’s axis influences the climate, and did so during the Messinian salinity crisis, with gypsum deposits precipitating during dry periods and shale during wet periods.

That period of gypsum formation is now called Stage 1 of the salinity crisis. Stage 2 was a relatively brief 50,000-year period when (in the majority opinion) the gateway slammed entirely shut, the sea level in the Mediterranean plummeted, and huge deposits of halite (sodium chloride) precipitated out from the seawater. However, Manzi’s group strongly dissents, arguing that the Gibraltar gateway remained open, but shallowed to such an extent that the water flowed through it in one direction only — in but not out — resulting in a runaway buildup of salt.

Even for adherents of the majority view, Stage 2 is not as simple as it seems. Data from chlorine isotopes suggest that the drawdown was not uniform. At its lowest point, in the western Mediterranean, sea level was 800 meters below its present level, while east of present-day Sicily it was at least twice as deep as that. If so, the east and west portions must have been separated by a land bridge. Indeed, there is evidence of African animals crossing over to Europe during this time.

The last 200,000 years of the salinity crisis, called Stage 3, have been the most puzzling of all. The halite stopped precipitating and there is evidence for a variety of sea levels in the Mediterranean during this time. Widespread fossils of a shrimp-like animal called an ostracod suggest that the waters became much less salty, so that the Mediterranean was a sea-sized lake (and indeed, this stage is sometimes called the Lago-Mare stage). But if the gateway to the Atlantic was still closed, then where did the fresher water come from?

A 2025 paper by Daniel García-Castellanos of the Spanish National Research Council helps solve the puzzle. Using a computer to model erosion, he argues that the Mediterranean was gradually refilling during Stage 3. The ostracods provide a clue to the source. They originated from the area of the present-day Black and Caspian Seas, which back then were connected to each other, but not to the Mediterranean.

With the shores of the Mediterranean being so newly exposed and so steep, its edges would have rapidly eroded toward today’s Black Sea, which at that time was a much larger freshwater lake called the Paratethys. The first connection between them could have been established at this time. If so, the Mediterranean began to receive waters from rivers like the Volga, the Don and the Danube, which had previously been unavailable. The ostracods got a new home, and the Mediterranean got a vast new supply of water, which according to the computer simulation raised its surface to within 300 meters of its current level.

According Krijgsman, this interpretation conveniently reconciles the conflicting evidence. “In the fight between a desiccated and full Mediterranean,” says Krijgsman, García-Castellanos’ paper does the job “if you want to sit in the middle and give everyone credit for their observations.”

Missing: One megaflood

The literature on the Messinian salinity crisis is voluminous, and yet one thing is curiously absent. There is surprisingly little direct evidence of the megaflood that supposedly ended the crisis. Hsü’s original Scientific American article devotes only half a page to it and adduces little in the way of evidence. Fifty years later, Ryan wrote a 100-page retrospective; only three pages are about the megaflood. Shouldn’t this extraordinary flood have left very clear scars?

The current evidence is ambiguous at best. Geologists have found submerged flood-like deposits off Malta — but that’s a long way from Gibraltar, the putative source of the flood. Also, if the Atlantic drained into a nearly empty Mediterranean basin, then sea levels around the world should have dropped by about nine meters — an anti-flood to pay for the Mediterranean flood. There is no sign that this happened, says García-Castellanos.

A recent deep-sea drilling expedition to the Strait of Gibraltar turned up more questions than answers. In December 2023, the JOIDES Resolution — heir to the Glomar Challenger — revisited the Alboran Sea immediately to the east of the Strait of Gibraltar. If the strait is the door to the Mediterranean, then the Alboran Sea is the vestibule. Any megaflood that passed through the Strait of Gibraltar would have passed also through the Alboran basin. But Rachel Flecker of the University of Bristol, England, co-leader of the expedition, says they found no traces of the flood in the cores they collected.

While still on board the ship, she wrote that the cores were “exquisitely laminated in a variety of colors. This incredibly fine lamination requires very quiet, low energy conditions.” Exactly the opposite of a megaflood. Final results have not been published yet, but Flecker reports also that they found no salt layer and no evidence that the salinity crisis had ever touched the Alboran Sea.

“The connection between the Atlantic and Mediterranean before and during the Messinian salinity crisis wasn’t through Gibraltar,” she concludes.

The Realmonte salt mine in Sicily contains spectacular bedded salt formations deposited during Stage 2 of the Messinian salinity crisis. Remarkably, each bed of salt, demarcated by distinct lines in this photo, was deposited in a single year (unlike the gypsum deposits of Stage 1, which were deposited in 23,000-year cycles). The statue of Jesus was added some 5.5 million years later by miners who carved a cathedral out of the salt.

CREDIT: VINICIO MANZI

How can this be? “A feature that you must take into account, and nearly nobody does, is that the present physiography of the Mediterranean is very different from the Messinian one,” says Booth Rea. “Large basins have opened since, like the Tyrrhenian; other regions have emerged, like Sicily.” One possibility, he suggested, is that the gateway was somewhere to the east, through a volcanic arc of islands that once connected Africa to the Balearic Islands. Other possibilities include channels through Spain or Morocco, which are above sea level now but were underwater as recently as 7 million years ago.

Regardless of how it happened, this modern view of the story holds lessons: It emphasizes the power not of dramatic events but of small changes. “Salt giants” — that is, massive salt deposits like the one underneath the Mediterranean — have formed at other times in Earth’s history, when basins were trapped between two tectonic plates. Their effects on climate and biodiversity have likely been huge: In this event, 89 percent of exclusively Mediterranean marine species died out.

And a slight shallowing of the Strait of Gibraltar (or whatever the true gateway was) might be all that was needed to trigger these vast changes. “In some sense, this is more terrifying,” says Manzi, because it shows that “you can reach extreme conditions without extreme events.”

CREDIT: XUNHUI XU and IODP

A missed opportunity?

The recent JOIDES Resolution mission also had a broader goal: to understand how the formation of a giant salt deposit affects the world’s climate. Precipitating vast quantities of gypsum — calcium sulfate — can cause cooling by drawing carbon dioxide into the ocean, Flecker says. “When you return it, via dissolving, you get a warming.”

For the most part, climate modelers have assumed that the concentration of calcium in the oceans is constant. While this may be true on million-year time scales, Flecker says, the Messinian period shows that calcium concentration can vary dramatically over thousand-year time scales. Ocean core samples from before, during and after the Messinian salinity crisis could reveal how these fluctuations affected climate in the past, and how they might modify current climate change predictions.

Unfortunately, such data may take a long time to arrive, because the JOIDES Resolution has been decommissioned, with no replacement on the horizon. “We were the third-to-last expedition,” Flecker says. “At the very moment when we developed the technology to start accessing these records, we lost the ship that provided us with that capability.”

— Dana Mackenzie

10.1146/knowable-020926-1

Dana Mackenzie is a mathematician who went rogue and became a freelance writer. He has written several books on math and other topics, including The Book of Why (coauthored with Judea Pearl); The Big Splat, or How Our Moon Came to Be; and Did You Come Here to Play Chess or to Have Fun?

2026 Feb 3

- Why disease outbreaks on Chinese fur farms are a serious risk to public health

HEALTH & DISEASE | VIEW ON WEBSITE

Why disease outbreaks on Chinese fur farms are a serious risk to public health

Farming animals for fur is not only cruel but also provides an ideal environment for viruses to mix and cross over into humans

By Jane Qiu    02.04.2026

Lea en español

Reporting for this story was supported by the Pulitzer Center.

A sharp, musky scent rushes over me as I step out of the taxi outside Mr. Wang’s house near Tong’erpu, in China’s northeastern Liaoning province. It’s one of the country’s largest fur-trading centers. Wang greets me, sporting a blue jersey and matching cap. “I’m about to feed the foxes,” he says.

In his courtyard, 600 Arctic foxes, housed in rows of elevated wire-meshed cages, eye me nervously. Wearing no mask, gloves or protective clothing, Wang moves down the rows, scooping a paste of fish, corn and animal bones into bowls in each cage. The animals, creamy white with short bushy tails, feast on the food amid a frenzied chorus of slurps and gulps.

Like many others in the region, Wang’s fox farm provides an essential supplement for a precarious farming livelihood. But the fur-farming business comes with risks of its own. The price of fur fluctuates greatly from year to year, Wang tells me. And mysterious diseases can strike with devastating force. A few years ago, Wang says, diarrhea wiped out hundreds of his foxes.

China is one of the world’s major fur producers — particularly of fox, mink and racoon dog pelts — alongside Europe and the United States. In 2021, China’s fur-farming industry employed around 6 million people and had an estimated value of US$61 billion.

The kinds of disease outbreaks Wang describes are commonplace, but before Covid-19 they were rarely reported, let alone investigated. Studies since the pandemic have found that some outbreaks, which can kill thousands of animals, were caused by a particularly worrisome virus that can cause severe fever with thrombocytopenia syndrome (SFTS). In humans, this condition can bring about bleeding, vomiting, diarrhea and organ failure. It appears to be afflicting a growing number of people since it was first identified in 2009, says Yu Xuejie, a microbiologist at Wuhan University who discovered the virus that causes the disease. Last year alone, Yu adds, China reported roughly 5,500 confirmed cases — nearly triple the number recorded just five years earlier.

And the SFTS virus isn’t the only one associated with fur farming that has scientists worried. A recent study shows that other viruses capable of infecting people, including coronaviruses and influenza viruses, are widespread in fur animals. With crowded conditions, poor biosafety standards and little surveillance on fur farms, scientists like Eddie Holmes, a virologist at the University of Sydney in Australia and a coauthor of the study, warn that the industry is “spectacularly risky.”

The farms, says Holmes, could be the breeding grounds for the next pandemic.

The questions haunting scientists are urgent: How easily can viruses in fur animals spread? What illnesses could they ignite in people? And how are farming practices helping them along? Soon after my visit to Wang’s farm, outbreaks in both fur animals and humans on multiple farms began to provide clues.

Ticks are considered the primary way that the SFTS virus is transmitted. But studies have shown that the virus can infect many animal species, including people, and may spread without ticks.

Tracking the killer

Severe fever with thrombocytopenia syndrome is not new. Nearly 20 years ago, central China was gripped by waves of a mysterious disease that struck with fever, diarrhea and dangerously low platelet counts — killing nearly a third of the people it touched. “Family members were angry and took to the streets in protest,” demanding that the government uncover the cause of the new disease, recalls Yu, a former employee with the Chinese Center for Disease Control and Prevention in Beijing.

In 2009, Yu led a team into central China to collect blood samples from patients with the unknown illness. Challenging the prevailing belief that a bacterium was to blame, he uncovered a novel RNA virus. His team detected the virus or antibodies against it (a sign of exposure) in 70 percent of hospitalized SFTS patients — evidence compelling enough for the scientists to conclude that this newly identified virus was behind the disease.

Most of the patients lived near forested areas thick with blood-sucking mosquitos and ticks. But when Yu’s team trapped nearly 6,000 mosquitoes, none carried the virus. The real menace, says Yu, surfaced in the ticks. Amongst those pulled off domestic animals, one in 20 tested positive.

Follow-up studies confirmed that Haemaphysalis longicornis, a tick capable of feeding on diverse hosts, is the primary vector of SFTS. Dozens of species, including rodents, birds, goats and cattle, carry antibodies to the virus, indicating past infection. The disease has since surfaced in people in other Asian countries, such as Japan, South Korea, Thailand and Vietnam, killing as many as one in five patients. Most SFTS cases occur in China, and between 1996 and 2023, there were more than three dozen clusters of cases in which infected people transmitted the virus to others.

Then, in fall 2023, word of fox die-offs on farms across eastern China began rippling across veterinarians’ social media feeds. One after another, foxes developed running noses, lost their appetite, passed black stools and then died, within days of first showing symptoms. On each farm, some housing as many as 11,000 foxes, scores of animals perished — in some cases a third of the facility’s creatures.

Equally troubling, says Holmes, is the “zero biosafety” he observed on Chinese fur farms, creating the perfect gateway for these viruses to cross over into people.

Shi Weifeng, a virologist at Shanghai Jiao Tong University of Medicine, sprang into action. Shi, whose research focuses on human diseases caused by pathogens from animals, dispatched his team to collect swabs and organ samples — spleen, intestines, lungs and kidneys — of sick or dead foxes on six farms in Shandong and Liaoning provinces, as well as samples from the farm environments, such as the sinks and animal feed.

Until recently, conventional wisdom was that most animals infected with SFTS showed only mild or no symptoms, says Keun Hwa Lee, a virologist at Hanyang University in Seoul. Yet all but one of the foxes Shi’s team tested were teeming with the virus, their bodies etched by the SFTS infection: organs swollen and mottled with hemorrhage, cells and tissues degenerated.

An analysis of 13 complete viral genomes sequenced from infected foxes found that they sorted into three subtly different but distinct groups. In some cases, the genomes had segments from different viruses — like Lego blocks clicked into new combinations — a reshuffling process known as reassortment. Reassortment, notes Shi, can generate variants that are more infectious, more deadly or both.

The team concluded that multiple lineages of the SFTS virus were circulating across eastern China, crossing into foxes again and again. They are less clear on how the animals got infected, because they found only one tick and it was virus-free.

Yet, around the same time that foxes in Shangdong and Liaoning were dying in droves, thousands of miles away in Finland, bird flu was spreading like wildfire from one fur farm to another. A study led by Lauri Kareinen, lead virologist at the Finnish Food Agency in Helsinki, linked the flu outbreaks to infected black-headed gulls in the region. The gulls, Kareinen explains, regularly flocked to the fur farms to feed — and most likely ignited the spark that set off the viral wildfire.

Kareinen wonders if SFTS outbreaks on farms in China might also have been sparked by infected birds or rodents that were drawn to the farms for scraps and contaminated the foxes’ feed. Another possibility is that some of the raw ingredients used in feed processing could have come from diseased animals. A recent study found that animals can shed the pathogen in their saliva and that healthy animals can fall ill after oral exposure.

Scientists suspect that once the virus gained a foothold in some animals, it could spread from one to another through close contact. A team that managed to isolate the virus from farmed minks observed: “When one caged mink suffers the disease and shows clinical symptoms, the minks nearby will show similar clinical symptoms and soon die.”

Human tolls

Spread of the SFTS virus from one individual to the next does not appear to be limited to nonhumans. In October 2023, not far from the farms where Shi’s team was probing the mysterious fox die-offs, a 60-year-old woman was struck with dizziness, nausea and vomiting. Within two days, she slipped into a coma; she died a week later. Around the same time, a coworker of hers was admitted to the same hospital with a “fever of unknown origin.” Laboratory tests delivered a chilling verdict: The women carried the SFTS virus. Both worked at a farm that housed more than 500 racoon dogs, 6,000 minks and 10,000 foxes.

A team led by Yang Zhenghui, an epidemiologist at the Weihai Heath Commission, descended on the farm like forensic investigators at a crime scene — interviewing workers, swabbing equipment and enclosures, combing for ticks and reconstructing the chain of events.

In October of 2023, two people who worked at a fur farm in Shandong province fell ill; one died a week after the onset of symptoms. An epidemiological investigation of the farm (enclosures and animals shown) found that the two workers, who did not wear protective gear on the job, were probably infected by the SFTS virus while skinning animals.

CREDIT: J. LI ET AL / VIROLOGY JOURNAL 2024

None of the 22 other workers had fallen ill. Yet half of them carried antibodies that pointed to past infection, and one worker tested positive for antibodies that were suggestive of an ongoing infection.

The team found no ticks on the farm or in the fields around the patients’ homes, and neither the women nor their colleagues recalled being bitten by a tick. By contrast, more than three quarters of the workers reported being bitten and splattered with blood while skinning the animals — grim evidence that, despite industry guidelines, some fur animals in China are still skinned without first being killed by electrocution.

Fur farming is poorly regulated in China, says Peter Li, an expert on wildlife policy at the University of Houston-Downtown in Texas. In Europe and the United States, enforcement can also be lax on protective measures, though some places have made improvements since the Covid-19 pandemic. Yang’s team found that the sickened workers had very little knowledge about how to protect themselves from possible diseases while on the job, including when they skinned animals. Samples taken from the skinning area, including blood from two foxes and swabs from the ground and a trash bin, were positive for the SFTS virus. Four of six viral genomes sequenced — one fox sample and three environmental swabs — were 99.9 percent identical to one another and to those from the two patients, pointing to a shared source.

Yang and his colleagues, who did not respond to Knowable’s requests for an interview, hypothesized in their report that the virus carried by the animals might have become aerosolized during the skinning process, exposing workers through inhalation.

Wen Hongling, a public health expert at Shandong University in Jinan who was not involved in the work, says the scenario is plausible: Beneath the animals’ skin lies a dense network of fluids and blood vessels, and the act of skinning can turn them into a fine, invisible mist that lingers in the air and can slip into workers’ lungs. Her studies have shown that mice exposed to such aerosols become infected with the SFTS virus, which then takes hold and replicates in their lungs.

Ticking time bomb

The SFTS story still contains mysteries, says Lee. The repeated die-offs on Chinese fur farms, for instance, struck him as “unusual,” given that the vast majority of infected animal species exhibit few symptoms. Regardless of what made the infections so lethal in fur animals, the story serves as a sobering cautionary tale. Researchers wonder what other deadly viruses might be lurking in these poorly regulated farms.

Holmes and his collaborators in China and elsewhere have uncovered a troubling picture. In one survey, which sampled 461 diseased fur animals across China, the researchers identified nearly 40 viruses with high potential to infect other animals, including people — nearly half of them in Shandong, home to the country’s largest producer of mink and fox furs. A separate study, which sampled 1,941 game animals across the country, found what looks like cross-species jumps of coronaviruses, including four canine coronaviruses in raccoon dogs suffering from diarrhea.

Scientists conducted a large survey in China of fur animals, both farmed and wild, that had died from disease. The analysis of samples from 461 animals found 39 potentially high-risk viruses. These included 11 zoonotic viruses (that is, previously found in people); 13 high-risk novel viruses (meaning the virus comes from a genus that’s been detected in at least three mammalian orders); and 15 viruses that had been previously observed in two or more animal orders. Several of the viruses were detected in more than one species of fur animal, suggesting potential virus transmission between farmed and wild animals, and from humans to farmed animals.

Equally troubling, says Holmes, are the documented instances of “zero biosafety” with farmed animals, creating the perfect gateway for these viruses to cross over into people. In a video captured by his Chinese collaborators, farmers were seen handling raccoon dogs stricken with severe gastric infection — using nothing but their bare hands.

While an increasing number of countries have banned fur farming since the Covid-19 pandemic, out of both animal rights and public health concerns, some scientists remain cautious about advocating for outright bans. In some parts of the world, says Kaneinen, fur farming is deeply rooted in culture and family tradition; in others, it provides a vital source of income. Some argue that a blunt ban ignores these realities and could drive the industry underground — where it would be even harder to monitor and potentially more dangerous.

A more realistic solution, researchers say, is better regulation and a massive improvement in animal welfare in Chinese fur farms. After the bird flu outbreaks in 2023, Finland introduced a series of mandatory measures to make fur farming safer, including installing nets to keep out birds, keeping the fur animals indoors, reducing cage size, and enforcing the use of personal protective equipment. Kareinen and his colleagues also identified the skinning process as “the riskiest phase of the operation,” where biosafety measures should be enforced most rigorously.

Also vital, Holmes adds, is regular surveillance of the pathogens circulating in fur animals and the humans who work with them. Without such measures, if fur animals were to trigger a major epidemic, he says, “we would have completely failed as a society — absolutely and utterly failed.”

Back in Tong’erpu, two foxes clash over feed, their bodies colliding with a metallic rattle against the wire cage that houses them. Wang laments that fur prices have yet to recover since the pandemic, leaving him feeling the pinch. This may be part of a long-term trend that sees the appetite for fur dwindling, both in China and worldwide. Some believe that fur farming, rather than being forced out, will simply fizzle out on its own.

As I walk through the farm, a cold shiver runs down my spine. Every cage could be a ticking time bomb, and the only question is whether one will detonate before the industry itself withers away.

10.1146/knowable-020226-2

Jane Qiu is an award-winning independent science writer in Beijing. @janeqiuchina, @janeqiu.bsky.social

2026 Feb 2

- Corporate crime persists in the shadows

SOCIETY | VIEW ON WEBSITE

Corporate crime persists in the shadows

Unlike violent crimes, there are no comprehensive national statistics on the serious misconduct of companies. Some see a need for change.

By Elise Hansen    02.03.2026

Lea en español

Mary Gay Scanlon cut her teeth in Congress scrutinizing Big Tech’s enormous power over Americans’ lives. As she and fellow representatives on the Judiciary Committee set about their 16-month investigation, she was itching to explore corporate misconduct across a wider swath of industries.

“It seemed like an area that was ripe to address,” Scanlon, a Democratic representative from Pennsylvania, says. “But there was no data.”

Corporate misconduct can have vast consequences, from contaminating groundwater to wiping out retirement savings to fueling an opioid crisis. But there’s a stark contrast between the information on these crimes compared to that on individual crimes such as theft and assault.

“The FBI, who is the predominant supplier of crime data in the United States, does not capture corporate crime data like price fixing, tax evasion, cooking the books — those kinds of things,” says Alexis Piquero, a former head of the Bureau of Justice Statistics, part of the US Department of Justice. Federal records of corporate misconduct do exist, but they tend to be spread across myriad federal agencies, each focused on its own narrow section of the law.

As a result, it’s difficult to determine even the most fundamental questions about corporate crime. How many victims are there? How much does it cost consumers? What kind of companies are most likely to commit crimes, and when? How effective are government interventions and corporations’ own efforts at compliance?

The answers, it seems, are buried in agency basements and muddled by idiosyncratic record-keeping.

“If you were to ask me, ‘Alex, how many price-fixing arrests were made this year?’ The answer would be, ‘I don’t know, and no one else knows either,’” Piquero laments. “And that’s an embarrassment that in 2025 we don’t have the answer to that question.”

A need to share data

That’s not to say the information doesn’t exist. Each federal agency keeps its own records about the corporate crime cases it has opened, the companies involved, the alleged misconduct and the outcome of those cases. But data mostly remain siloed within that agency — not pooled with information from other departments, says Sally Simpson, a criminologist at the University of Maryland, College Park.

“In the United States, there is no centralized data repository that captures the full extent of the phenomenon, by company, across offense types and legal venues (criminal, civil and regulatory),” Simpson writes in the 2025 Annual Review of Criminology, “nor are there systematic data collected from victims or self-reported offenders that can cross-validate official counts.”

On top of that, federal agencies decide for themselves exactly what information they’ll capture and how they will format it. They make different choices, complicating attempts at comprehensive research.

“They all use different criteria for when a case is brought and what kind of information is collected about the case,” says Simpson. “So creating what’s called a crosswalk between all of these different sources of data, so that you’re collecting similar data, becomes quite complex.”

Corporate crime can include numerous kinds of offenses, with wide-ranging consequences. In fiscal year 2024, the US Department of Justice sentenced corporations for 80 crimes that included environmental, fraud, and food-and-drug-related offenses. But the full extent of such misconduct is difficult to track.

Peter Yeager encountered all of this firsthand as a graduate student at the University of Wisconsin–Madison in the 1970s. At the time, he was studying violations of federal law by the 582 largest American corporations. It was not easy. He and his fellow academics had to go to 24 different federal agencies to capture the full spectrum of potential violations.

It was the 1970s, so “we did it with computer cards — 80-column computer cards,” he recalls. “Our output was not on a computer; it was all on paper, and it reached about 10 feet high.”

Yeager ultimately published a comprehensive examination of white collar crime in the US. That was in 1979. Lawmakers have described it as “the last comprehensive DOJ report on corporate crime” — which stirs up mixed feelings in Yeager. “I was pleased to read that,” he says. “But also a little distressed, that that’s the fact still.”

Street crimes yield better data

Today, street crimes and violent crimes such as murders, thefts and assaults, are as pervasive in conversation as ever — discussed constantly at all levels of politics and in the news. Violent crime is frequently rated as important by voters and is a major driver of electoral politics.

“We have a two-tier system of justice. If it’s corporate crime, then you get a slap on the wrist, you pay a fine, and you go on to commit it again, often — versus individuals going to jail for long stretches.”

— MARY GAY SCANLON

And this side of the criminal justice system is carefully studied and documented. The Bureau of Justice Statistics, for example, publishes annual data on violent incidents, broken down by the ages of offenders and victims; on inmate deaths in federal custody; on capital punishment and much more. Crucially, it even conducts a yearly “criminal victimization” survey, in which the government interviews roughly 240,000 citizens about their experiences in the past year with such crimes as robbery, assault and break-ins — regardless of whether respondents reported those incidents to the police.

This effort helps shed light on the “dark figure” or “hidden figure” of crime, meaning offenses that have been committed but haven’t been discovered or reported, so they don’t show up in official statistics. It helps to paint a more complete picture of what’s actually happening on the ground, not just what shows up in court.

But the bureau’s criminal victimization survey does not ask people if, for example, they have been cheated out of wages or lied to by an investment advisor. The “hidden figure” of corporate crime is still very much hidden, says Simpson. The United States doesn’t have systematic data from victims or even from self-reported offenders to help researchers triangulate with the official records.

These disparities rob researchers, policymakers and the public of basic information about the extent of corporate misconduct and how it affects their lives. “We’ve got a whole ream of hypotheses 50 years old,” Yeager says. For example, his 1979 deep dive into major US corporations showed that the large companies of the day were more likely to offend when their sales, profits, earnings and product diversification were trending downward.

The data gaps also make it difficult to determine the effectiveness of the government’s responses. Corporate prosecutions have been trending downward since the early 2000s, and the Department of Justice has come to lean more heavily on non-prosecution agreements and deferred prosecution agreements. In these, companies agree to make changes to their operations and frequently end up paying a fine in order to avoid court. Globally, corporations have been spending billions on internal compliance efforts to prevent legal and regulatory violations. Still, there’s little definitive scholarly research on how well these arrangements work in deterring corporate crime and what the most effective approaches to deterring and policing it may be, says Simpson.

“There are all of these things companies try to do, but we don’t know how successful they are, because we have very few empirical studies,” she says.

Federal prosecutions of corporations have dropped over the years. And the data shown in this chart do not shed light on corporate crimes that were not investigated, or that the US Department of Justice did not bring to court.

Scanlon finds these disparities troubling. “We have a two-tier system of justice,” she says. “If it’s corporate crime, then you get a slap on the wrist, you pay a fine, and you go on to commit it again, often — versus individuals going to jail for long stretches, ending up with mass incarceration.”

Registry of company misdeeds

Some progress has been made to bring corporate misconduct data into public view. The Consumer Financial Protection Bureau launched an initiative in June 2024 to create a public registry of nonbank financial companies that have broken consumer protection laws. At the time, the bureau’s leadership touted the registry as a way to help consumers determine whether a company is trustworthy, and to help the bureau determine which companies are repeatedly violating the law. Bureau representatives did not reply to requests for comment about the program’s status under the Trump administration.

Also, under the Biden administration, the Department of Justice created a website chronicling the latest corporate case resolutions across many offense types, from antitrust to money laundering. But the data start only in 2023, so anyone hoping to look further back would be out of luck. On top of that, the data capture only concluded court cases, thereby missing out on enforcement actions that don’t go through federal courts — such as violations that are pursued only by regulatory agencies.

And while some non-government organizations, such as nonprofits and universities, have made headway in compiling databases for public use, they aren’t part of the official record. Yeager believes the surest way to secure resources for a centralized, government database lies with Congress.

To that end, Scanlon reintroduced the Corporate Crime Database Act in July of 2025. The bill calls for agencies to submit information about their enforcement actions to the Bureau of Justice Statistics, which would then aggregate and analyze the information and publish a database for public use. Previous iterations of the bill have been introduced in eight different years, so far without success.

Industry lobbyists are part of the holdup, in Scanlon’s view. Or, as she puts it, “people who are making money off not being held accountable.” And the Trump administration has backed off from some areas of white-collar policing. But nonpartisan factors are also likely at play: Piquero says he encountered good old-fashioned institutional inertia during his time in the Bureau of Justice Statistics when he attempted to spearhead an initiative to centralize corporate crime data. “There’s this rigidity of ‘this is the way we’ve always done things,’” he says.

From a technical point of view, collecting better data is eminently achievable, Piquero notes. “There’s no reason why it can’t be done. It’s just a matter of people getting together at the table and saying, ‘OK, this is what we’re going to do.’”

10.1146/knowable-020326-1

Elise Hansen is a journalist living in New York City.

2026 Jan 27

- Recreating the smells of history

SOCIETY | VIEW ON WEBSITE

Recreating the smells of history

Using chemistry, archival records and AI, scientists are reviving the aromas of old libraries, mummies and battlefields

By Kaja Šeruga    01.28.2026

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We often learn about the past visually — through oil paintings and sepia photographs, books and buildings, artifacts displayed behind glass. And sometimes we get to touch historical objects or listen to recordings. But rarely do we use our sense of smell — our oldest, most primal way of learning about the environment — to experience the distant past.

Without access to odor, “you lose that intimacy that smell brings to the interaction between us and objects,” says analytical chemist Matija Strlič. As lead scientist of the Heritage Science Laboratory at the University of Ljubljana in Slovenia and previously deputy director of the Institute for Sustainable Heritage at University College London, Strlič has devoted his career to interdisciplinary research in the field of heritage science. Much of his work focused on the preservation and reconstruction of culturally significant scents.

Reconstructed scents can enhance museum and gallery exhibits, says Inger Leemans, a cultural historian at the Royal Netherlands Academy of Arts and Sciences. Smell can provide a more inviting entry point, especially for uninitiated visitors, because there’s far less formalized language for describing smell than for interpreting visual art or displays. Since there’s no “right way” of talking about scent, she says, “your own knowledge is as good as the others’.”

Despite their potential to enrich our understanding of history and art, smells are rarely conserved with the same care as buildings or archaeological artifacts. But a small group of researchers, including Strlič and Leemans, is trying to change that — combining chemistry, ethnography, history and other disciplines to document and preserve olfactory heritage.

Some projects aim to safeguard a beloved smell before it disappears. When the library in London’s St. Paul’s Cathedral was scheduled for renovation, for example, Strlič and his UCL colleague Cecilia Bembibre set about documenting the historic library’s distinct smell.

The team first analyzed the chemicals wafting from the collection, which includes books dating back to the 12th century, and the surrounding furnishings, which have barely changed since the library was completed in 1709. They used a process called gas chromatography-mass spectrometry, which helps separate, identify and quantify volatile organic compounds, to examine air samples they’d captured in the library.

“As an analytical chemist, I was able to characterize and quantify those molecules, but how people describe what they felt required a completely different approach,” says Strlič. To whittle down the list of compounds identified by the mass spectrometer to the ones that humans can actually smell, the researchers next invited seven untrained “sniffers” into the cathedral library and asked them to describe its smell using a list of 21 adjectives commonly used to describe the compounds.

These delicate instruments sample the air wafting through the library of St. Paul’s Cathedral in London, picking up volatile compounds that evoke the collection’s distinctive scent of old books and furniture.

CREDIT: CECILIA BEMBIBRE

The list included words like green and fatty, which people frequently use to describe the smell of the chemical hexanal, and almond, which is associated with benzaldehyde. Both compounds are released by paper as it degrades. The sniffers were also invited to add any descriptors of their own.

One word that all sniffers used to describe the library wasn’t particularly surprising: woody. Others that proved popular were smoky, earthy and vanilla. Such descriptors can help conservators assess the state of old paper, since papers that are slightly more acidic due to decay, for example, “smell more sweet,” says Strlič. “And those that are stable smell more like hay.”

Strlič and colleagues next matched the qualitative descriptors the sniffers had selected with their underlying chemical compounds to create a chemical “recipe” for the scent of the cathedral’s library. Such recipes are published in scientific journals and stored in digital research repositories, so a chemist could theoretically whip up the smell of old books centuries from now, “even if, in the future, people no longer go to a library or no longer read physical books, and only receive all information digitally,” says Strlič.

How musty are mummies?

The work at St. Paul’s Cathedral, which ended in 2016, suggested that it might be possible to capture far older scents — including smells from thousands of years ago. For a study published in 2025, Strlič was joined by scientists from Egypt, Slovenia, Poland and the United Kingdom to study nine ancient Egyptian mummies. The aim was to learn about the mummification process and recreate a scent that will be available to visitors of the Egyptian Museum in Cairo from 2026 onward.

One might expect the scent of millennia-old mummified bodies to be off-putting, to say the least. Yet the smell is surprisingly pleasant, “because the ancient Egyptians used so many aromatic compounds, oils and resins that a lot of the original smell still remains,” Strlič says.

To capture these chemicals, Strlič and colleagues extracted air samples from the sarcophagi, separated them into single compounds with a gas chromatograph and identified them with a mass spectrometer.

By analyzing air next to these mummies at the Egyptian Museum in Cairo, scientists can recreate their scent — and shed light on the embalming ingredients used to preserve them.

CREDIT: CECILIA BEMBIBRE

A panel of eight scientists — all trained on the scent of mummification materials — then evaluated the samples’ smells in terms of quality, intensity and pleasantness. After assessing each sample individually, the group discussed their findings to reach consensus: Woody, spicy and sweet emerged as common descriptors across all nine bodies.

The scent profiles that the team created based on these chemical and sensory observations can now be used to understand which mummies are more degraded than others, and how some of the bodies were mummified in the first place, says Strlič. For example, the team identified embalming ingredients like conifer oils, frankincense, myrrh and cinnamon, as well as more modern compounds, such as synthetic pesticides and plant-based pest oils, which museums have used to preserve the mummies, often without documentation.

CREDIT: JOHN EVERETT MILLAIS / PUBLIC DOMAIN

The Blind Girl

For an exhibition of Pre-Raphaelite painters, which ran at the Barber Institute of Fine Arts and Watts Gallery in the UK from late 2024 to late 2025, historian Christina Bradstreet created two scents for John Everett Millais’ painting The Blind Girl in collaboration with Spanish perfumer Gregorio Sola.

The first scent captured the odor of the rainbow in the background, which Victorians imagined as “the scent of fresh wet grass and flowers, when the sun has just come out after a rainstorm,” says Bradstreet — what we might today describe as “petrichor.”

The second evoked the older girl’s linsey-woolsey head shawl, which the younger girl is smelling as she looks toward the rainbow. While the wool and cotton cloth associated with Victorian workhouse uniforms is a mark of the girls’ poverty, “it’s about comfort as well,” says Bradstreet. “They are homeless, but the blind girl is her younger sister’s home, they’re together. We thought about the musty smell of an old comforter.”

— Kaja Šeruga

Strlič hopes that such research will help to expand the use of smell analysis as a noninvasive research technique, since it doesn’t require removing any physical samples from the studied object. The team also intends to apply its findings to create what amounts to a mummy “perfume” for the Egyptian Museum. For this, they will select up to 15 key chemical compounds from the mix and adjust their ratios to reflect the natural scent, with panels of sniffers comparing the new creation with the original until there’s no perceptible difference between them. “This is a repetitive process that involves a lot of trial and error,” says Strlič.

Creating even the smell of Hell

While old artifacts offer a convenient starting point for olfactory analysis, many historic smells have not been preserved in physical form. To re-create them, researchers must rely on archival documents and a certain amount of creative interpretation. That’s what a European olfactory heritage project called Odeuropa did for a number of historical events, sites and even ideas, including the Battle of Waterloo and 17th century Amsterdam canals. The team even re-created the scent of Christian “Hell” as described in 16th century sermons, including notes of sulfur and brimstone and a whiff of “a million dead dogs.”

“Olfaction helps shape our cultures, although it often does so unknowingly or without us noticing,” says Leemans, who led the Odeuropa project. “When we talk about cultural heritage, we can think about religious rituals, but we can also think about specific scents that we’ve been cherishing and living with for a long time.”

To reconstruct these complex historic “smellscapes,” Leemans and her colleagues scoured old document archives and images for any related smell references. “We search for nose witnesses, people describing those smells,” she says. “But we also look at the components of that smellscape,” such as architectural descriptions listing building materials.

To accelerate the work, Odeuropa has created an AI-driven database of more than 2.5 million historical smell references, mined from 43,000 images and 167,000 historical texts published in seven European languages.

When it’s time to create a real perfume based on this data, Odeuropa researchers write a detailed brief outlining the smell’s relevant components as well as the story behind it. Working with a perfume and fragrance company, they begin evaluating iterations of the scent in different ways — by asking panels of sniffers to assess the scent blind or after a short presentation on the subject, or by approaching curatorial, academic and fragrance experts to peer-review the fragrance.

To each their own odors

A person’s perception of smell is inherently subjective and dependent on their unique biology, personal experience and culture, says neuroscientist Gülce Nazlı Dikeçligil at the University of Pennsylvania, and lead author of a 2024 Annual Review of Psychology on human olfaction. “The olfactory system isn’t necessarily optimized for certainty and consistency,” she says. Instead of simply identifying molecules from the environment with computer-like precision, our brains are asking, “What does this molecule mean to me now, in the context of my history?”

As our oldest sense, evolutionarily speaking, olfaction enjoys priority access to brain regions like the amygdala and hippocampus, which are key in processing emotion and memory, notes Dikeçligil. This means that the memories triggered by scents tend to be especially vivid and emotionally significant.

Scent “sparks thoughts, memories, ideas and gets people talking about and in front of paintings, which is what I want,” says art historian Christina Bradstreet from the Association for Art History in the UK. She recently worked with the renowned Spanish perfumer Gregorio Sola to create three scents to accompany two paintings in a British exhibition on Pre-Raphaelite art. When, in 2022, the Prado Museum in Madrid created 10 scents to accompany Jan Bruegel the Elder’s painting The Sense of Smell — including jasmine, fig tree and civet — they found that visitors lingered in front of the painting for 13 minutes, compared to the average 32 seconds.

Museums and galleries worldwide are taking note and increasingly integrating scent into their exhibitions. This attracts new visitors and engages them in a different way, “not only with the collection, but also with each other,” says Leemans. “When people start to smell, they immediately start to talk to each other, exchanging their memories, their emotions, their knowledge about the scents. It’s a really open conversation that you evoke in the museum space.”

10.1146/knowable-012826-2

Kaja Šeruga is a freelance journalist based in Vienna, where she enjoys the smell of old coffeehouses and even older libraries. You can learn more about her work on her website.

Table of Contents

Knowable Magazine: 2026 Mar 11

2026 Mar 10

What is wisdom, and can it be taught?

2026 Mar 4

For particle physicists working with neutrinos, almost nothing is everything

2026 Feb 23

The strange animals that control their body heat

2026 Feb 18

The curious case of low-protein diets

2026 Feb 17

Looking for an ADHD coach? Choose carefully

2026 Feb 10

Tales of a very clever slime mold

2026 Feb 8

The cataclysmic flood that wasn’t

2026 Feb 3

Why disease outbreaks on Chinese fur farms are a serious risk to public health

2026 Feb 2

Corporate crime persists in the shadows

2026 Jan 27

Recreating the smells of history