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2025 Dec 22

- How Dad’s Fitness May Be Packaged and Passed Down in Sperm RNA

EPIGENETICS | VIEW ON WEBSITE

How Dad’s Fitness May Be Packaged and Passed Down in Sperm RNA

By Ivan Amato

December 22, 2025

Research into how a father’s choices — such as diet, exercise, stress, nicotine use — may transfer traits to his children has become impossible to ignore.

A father’s fitness, as measured by diet and exercise, is encoded by sperm RNA and epigenetically affects his offspring, according to research in mice.

Myriam Wares for Quanta Magazine

Introduction

The standard sperm-meets-egg story posits that sperm cells are hardly more than bundles of shrink-wrapped DNA with tails. Their mission is simple: Deliver a father’s genes into a mother’s egg for sexual reproduction. Just about all other aspects of a developing embryo, including its cellular and environmental components, have nothing to do with dad. Those all come from mom.

But nearly two decades of studies from multiple independent labs threaten to rewrite that story. They suggest that dad’s gametes shuttle more than DNA: Within a sperm’s minuscule head are stowaway molecules, which enter the egg and convey information about the father’s fitness, such as diet, exercise habits and stress levels, to his offspring. These non-DNA transfers may influence genomic activity that boots up during and after fertilization, exerting some control over the embryo’s development and influencing the adult they will become.

The findings, so far largely described in mouse models, could end up changing the way we think about heredity. They suggest “that what we do in this life affects the next generation,” said Qi Chen, a reproductive and developmental biologist at the University of Utah Medical School who is among the pioneers of this research. In other words: What a father eats, drinks, inhales, is stressed by or otherwise experiences in the weeks and months before he conceives a child might be encoded in molecules, packaged into his sperm cells and transmitted to his future kid. The researchers have largely zeroed in on RNA molecules, those short-lived copies of DNA that reflect genetic activity at a given time.

It’s a tantalizing notion. But the mechanistic details — how experience is encoded, how it’s transferred from sperm to egg, and whether and how it affects a developing embryo — are not easy to unpack, especially given the challenges of conducting research in human subjects. For this reason, and because of the potentially textbook-rewriting implications of the findings, researchers, including those spearheading the work, are cautious about overselling their results.

Colin Conine has shown that RNAs packaged in sperm alter gene expression in mouse embryos, pointing to a pathway by which a dad’s choices can epigenetically affect his offspring.

Courtesy of Colin Conine

“It’s still very hand-wavy,” said the epigeneticist Colin Conine of the University of Pennsylvania Perelman School of Medicine and Children’s Hospital of Philadelphia, who has been trying to uncover the mechanics of how sperm RNA can contribute nongenetic information to progeny. Some elements of the story are clear, he said: Researchers have significant evidence that the environment can regulate sperm RNAs, that these molecules transmit traits to offspring and that they can regulate embryonic development after fertilization. “We just don’t have really any understanding of how RNAs can do this, and that’s the hand-wavy part,” Conine said.

But evidence keeps piling up. Most recently, in November 2025, a comprehensive paper published in Cell Metabolism traced the downstream molecular effects of a father mouse’s exercise regimen on sperm microRNAs that target genes “critical for mitochondrial function and metabolic control” in a developing embryo. The researchers found many of those same RNAs overexpressed in the sperm of well-exercised human men.

“This study shows that paternal exercise can confer benefits — enhanced endurance and metabolic health — to offspring,” said Chen, who was not involved in the study. “It’s a powerful reminder that many sperm-mediated epigenetic effects are deeply adaptive in nature.”

The possibility that a previously undocumented avenue of inheritance is at play is too important to ignore. That’s why the researchers are now hunkering down in their labs to trace out the molecular processes that would have to operate for a father’s here-and-now experience to be transferred as developmental instructions to his partner’s egg.

Epigenetic Avenues

In most animals, a sperm cell is tiny compared to an egg cell. In humans, an egg contains 10 million times the volume of a sperm and contributes most cellular components — nutrition, cytoplasm, mitochondria and other organelles, the molecular machinery to make proteins, and more — to a zygote (a newly fertilized egg that hasn’t started dividing). Plus, a mother provides the environment within which an embryo and then fetus develops and grows. As a result, the effect of a mother’s health on her children has long been scrutinized, including at the molecular level. But over the past 15 years or so, the evidence for some kind of non-DNA inheritance of paternal experience has also been strengthening.

“There are many different labs that have done diet and stress studies, and typically the readouts of those in the next generation are either metabolism or behavioral changes,” Conine said. Feed a male mouse a high-fat or low-protein diet, or take him away from his mom when he is young, and his offspring will inherit traits, such as changes in mitochondrial function, related to those environmental conditions. These traits aren’t necessarily detrimental. For instance, mouse fathers  exposed to nicotine sire male pups with livers that are good at disarming not just nicotine but cocaine and other toxins as well.

There is a survival logic here, said Oliver Rando, an epigeneticist at the University of Massachusetts Chan Medical School who led the nicotine study. It’s reasonable to expect that offspring will experience an environmental context similar to that of their parents. Biologically priming them for those conditions could therefore help them survive.

The epigeneticist Oliver Rando suspects that sperm RNAs control early gene regulation in an embryo. If he’s right, he will have helped discover a new fact of life, he said.

Nick Rhind

“You might think of this as a way to tell your kids something useful for them so that they can be better at dealing with the world they inherit,” said Rando, a father of two boys.

But logic does not make the story true. That’s why Chen, Rando, Conine and other researchers have been working to uncover the mechanistic components of dad-based epigenetic heredity to add to what is already known about these processes in mothers. “Epigenetics” refers to heredity processes that do not change the DNA sequences of genes, but rather involve when and to what degree genes are expressed and made into functional proteins. Epigeneticists focus on the molecular biology that unfolds around genomic and chromosomal frameworks that can switch genes on and off in response to internal and external cues.

You might think of this as a way to tell your kids something useful for them so that they can be better at dealing with the world they inherit.

Oliver Rando, University of Massachusetts Chan Medical School

This kind of differential gene expression is central to some of biology’s greatest wonders — for example, the fact that all cells in the human body have the same DNA, and yet brain cells differ dramatically from liver, skin and blood cells. Some cues that trigger changes in gene expression are programmed into DNA, while others come from the environment — for example, a dearth of calories or nutrients due to food deprivation, or rising cortisol levels due to stressors such as the absence of parental care. These conditions affect the kinds of metabolites and other molecules circulating in our bodies, which influences what kinds of reactions and genomic processes cells can carry out.

Some molecules involved in epigenetic processes, such as methyl or acetyl groups, interface directly with DNA or bind to proteins attached to DNA. These actions loosen up or batten down portions of the genome and are akin to opening or closing doors to specific genes.

RNA molecules — flexible, ephemeral versions of DNA sequences — can also intervene in gene expression. But because they are relatively short-lived, sometimes surviving mere minutes or hours before degrading, they have been overlooked as epigenetic regulators. Since the 1990s, their roles have been clarified, as has their longevity: Certain RNAs can survive for weeks or longer. Some RNAs (such as long noncoding RNAs, or lncRNAs) regulate gene expression by modifying DNA or its proteins. Others, known as microRNAs, alter or repress other RNAs, including those that would otherwise be translated into proteins; this discovery was awarded the 2024 Nobel Prize in Physiology or Medicine.

Mark Belan/Quanta Magazine

Mark Belan/Quanta Magazine

Could sperm carry RNA or other molecules that then participate in epigenetic processes in the embryo? It seemed plausible to some researchers, but it would take a whole lot of experimental work to put the pieces together.

A Package of RNA

There are three core questions that biologists need to resolve to confirm that sperm cells transmit epigenetic inheritance. The first is how a father’s body physically encodes lived experience, such as stress, diet, exercise or nicotine use, in the form of molecules — for example, as RNAs circulating in blood that reflect gene expression in tissues. The next centers on how molecularly encoded experience could make its way into sperm cells. The third traces how those signals in sperm could become epigenetic vectors during and after fertilization to specify observable traits, known as phenotypes, in offspring.

In a series of studies beginning in 2012, Qi Chen started answering all three questions. In what he describes as one of the most serendipitous discoveries of his career, his team at the Chinese Academy of Sciences in Beijing used sequencing techniques to inventory the short RNA molecules present in mice sperm cells.

In 2012, Qi Chen found RNAs crowding into sperm heads with DNA. He’s spent his career documenting what he calls the “sperm RNA code.”

Courtesy of Qi Chen

They were shocked to see a subset of the RNAs drastically increasing in concentration as sperm cells matured, and then crowding into the sperm heads with DNA. This same class of RNAs was abundant in the blood serum of various vertebrates, ranging from fish to humans, they found. All of this pointed to the possibility that information-carrying molecules were being transferred into the reproductive cells.

It got even more interesting when Chen, who moved to the U.S. academic circuit in 2015, and his team collected sperm RNAs from male mice fed different diets. The RNA assemblages in mice reared on high-fat foods differed dramatically from those in mice that were fed normal diets. And when the researchers injected the RNAs from the sperm of the fat-eating mice into a zygote, some of the male offspring showed metabolic issues associated with a high-fat diet.

The experiments hinted at a seemingly heretical possibility, Chen said: that “certain acquired traits during paternal exposure can be ‘memorized’ in the sperm and inherited by the offspring.” After characterizing a pathway that regulates sperm RNAs, in 2019 Chen dubbed this channel of heredity the “sperm RNA code,” which he suggested “programs the metabolic health of offspring.”

He wasn’t the only one to become fixated on this idea. Around the same time, in an article published in Developmental Cell in 2018, Rando’s team reported the use of biochemical techniques to characterize where and when RNAs are packaged into sperm cells and how those RNAs might change during this process. They were trying to answer the question: “What tissue could be responsible for choosing what to tell sperm to tell kids?” he said. One logical place to start looking was the epididymis. Within this tubular organ attached to the back of the testicle, sperm cells undergo a maturation process, taking about one to two weeks in most mammalian species, before they become ready for fertilization.

Mark Belan/Quanta Magazine; source: International Journal of Molecular Sciences 21, 5377 (2020); BMC Biology 17, 35 (2019)

Mark Belan/Quanta Magazine; source: International Journal of Molecular Sciences 21, 5377 (2020); BMC Biology 17, 35 (2019)

Rando’s data showed that sperm cells gain almost all their small RNAs when they are in the epididymis. Using techniques for tracking specific RNA molecules, the scientists observed RNAs getting packaged into virus-size capsules, called epididymosomes, which shuttled the molecules into sperm.

“This shows how small RNAs can get trafficked between the body’s nonreproductive cells, like those in the epididymis, and germline cells,” such as sperm, Rando said. “The epididymis has been emerging as a key location for paternal effects. Certainly the epididymis has to be taken seriously as a potential sensor of the world.”

A Molecular Snapshot

By “sensor of the world,” Rando is referring to the first stage of a presumed paternal-effects mechanism — when a male’s body translates a lived condition, such as a high-fat diet, rigorous exercise or toxin exposure, into molecular signals. The epididymis then provides a route for the second step, packaging those signals for the next generation.

This is also where investigations by Isabelle Mansuy come in. At the University of Zurich and the Swiss Federal Institute of Technology Zurich, she studies the molecular and cellular mechanisms of epigenetic inheritance in mammals.

Isabelle Mansuy has traced the ways that consequences of stress from early life trauma alter metabolic pathways through five generations of mice.

© Philippe Rossier / Ringier Media Switzerland

In one line of her research, she focuses on processes that transmit the molecular effects of traumatic stress to subsequent generations by focusing on extracellular vesicles (EVs) that circulate in blood. Shed by almost every type of cell in the body, including in the epididymis (the epididymosomes are EVs), they carry a diversity of molecular cargo, such as RNAs, proteins, lipids and metabolites. Because EVs circulate in blood just about anywhere in the body and can cross cell membranes, they provide a potential means to transfer molecules and the biological cues they carry between bodily tissues and reproductive cells. Notably, RNAs tend to survive longer when packaged in EVs.

Mansuy creates trauma in mice by subjecting the animals to conditions such as restraint or maternal separation when they are young. Then she searches for molecular changes in reproductive cells that could cause similar consequences of trauma to manifest in the children or even grandchildren of the animals who directly endure it.

She’s shown that traumatic stress alters metabolic pathways, especially those that involve lipids, in exposed male mice and their offspring. She has also found a similar metabolic profile in humans who experienced high stress in childhood. In mice, some of the metabolic changes remained discernible through five generations — a rare data-backed finding for epigenetic inheritance cascading through generations.

An egg cell is enormous compared to a sperm cell and contributes nearly all cellular components to a growing embryo — except the sperm’s half of the genome, and maybe embryonic and epigenetic regulators, according to recent research.

Dennis Kunkel Microscopy/Science Source

In March 2025, in a preprint uploaded to biorxiv.org, Mansuy and colleagues reported that EVs in mice can transport certain RNAs, metabolites and lipids linked to early-life stress from circulating blood to sperm, with consequences for offspring. The offspring produced by these sperm cells had stress-related metabolic dysfunction as adults and bore the stress signatures in their own sperm RNA. “These changes imply a mechanistic link between sperm RNA modifications and phenotypic features in the offspring,” Mansuy’s team concluded in their paper, which has not yet been peer-reviewed.

Phenotypic Translation

Perhaps the trickiest step to understand is how sperm-borne molecules could influence an adult’s observable traits. In one form of experiment, researchers extract all the sperm RNA from mice that have been raised under stressful or health-altering conditions. Those isolated RNAs are then injected into a zygote. Pups that emerge usually “get the dad’s phenotypes,” Conine said, suggesting that the RNAs alone confer traits from dad to offspring.

But how? During early development, epigenetic processes reign. As one fertilized cell divides into two, and those cells divide again, and so on, one set of DNA instructions is dynamically and repeatedly reprogrammed. The growing body specializes into different cell types and is sculpted into a sequence of increasingly complex forms. It’s possible, then, that early epigenetic alterations to the genome could have significant downstream effects on an adult.

A team of researchers, including Xin Jin (top) and Xi Chen of Nanjing University, traced the epigenetic effects of paternal exercise in mice.

Nanjing University

Research out of Conine’s lab, published in 2024, showed that sperm microRNAs alter gene expression in mouse embryos. Experiments like these, he said, support the idea that offspring can inherit paternal traits via the transfer of non-DNA molecular stowaways in sperm.

The recent Cell Metabolism paper took this idea a step further by tracing a mechanism by which this can happen. A team of more than two dozen Chinese researchers focused on the epigenetic transmission of exercise benefits, homing in on a set of microRNAs that reprogram gene expression in the early embryo. These changes ultimately result in skeletal muscle adaptations in adult offspring that enhance exercise endurance. The researchers found that well-exercised mice had more of these microRNAs in their sperm than sedentary mice did. When these microRNAs were transferred into zygotes, the adults they grew into were more physically fit, with more mitochondria in skeletal muscle and higher endurance.

But how did the molecules generate the exercise-positive phenotype? In experiments, the researchers found that the microRNAs suppressed a particular protein, which had the effect of boosting genes related to mitochondrial activity and metabolism.

Intriguingly, the sperm of physically trained male humans also hosted higher levels of many of the same microRNAs than those of untrained cohorts. “This cross-species conservation suggests a potential role for these sperm mi[cro]RNAs in intergenerational exercise adaptations in humans,” the researchers wrote.

The First Draft

The notion that a father’s lived experience can become recorded by his body, transmitted to his gametes and relayed to his offspring is no longer as outlandish as it once seemed. Many researchers in the field are willing to float speculative visions of what could be going on, even as they acknowledge that gaps remain.

“Our hypothesis is that the epididymis ‘sees’ the world and alters the small RNAs it produces in response,” Rando said. “These RNAs are then delivered to the zygote upon fertilization and control early gene regulation and development to shape offspring health and disease.”

Conine speculates that once certain RNAs make their way into the egg, they trigger “a cascade of changes in developmental gene expression that then leads to these phenotypes” of the father showing up in the next generation. Remarkably, this unfolds even though the sheer volume of the sperm’s contents is so much less than an egg’s contents, including the relative amounts of RNA.

The full picture of how paternal experience and behavior might epigenetically influence offspring is not nearly in hand. Researchers are currently piecing the story together, one experiment at a time, rather than proving out every step sequentially in the same set of organisms. One of the gaps is in the characterization of what RNA and perhaps other epigenetic factors do in the zygote to modify genomic activity as it unfolds during development, Mansuy said.

“We are still blind men describing for the first time different parts of the same elephant,” Chen said. “The underlying mechanism is almost certainly an orchestra of a sperm RNA code and factors beyond that.”

Related:

1. How Metabolism Can Shape Cells’ Destinies

2. Cells Across the Tree of Life Exchange ‘Text Messages’ Using RNA

3. The Complex Truth About ‘Junk DNA’

Confirming the findings in humans would take enormous effort, but it would be key to turning these findings in mice into “informed medical advice,” Chen said. This would require well-controlled experiments following multiple generations, tracking diet, exercise, aging and environmental exposures, while also using advanced tools to decode sperm-packaged molecules — and then looking for strong correlations between the molecular and phenotypic data.

Even amid the uncertainties, researchers are cautiously moving forward as they learn to believe the results of their own experiments. If they’re right, they will have discovered a new fact of life, Rando said. When he thinks about his two boys, he wonders what he might have done differently when he was younger, before they were born, that might have tweaked his RNA profile in ways that would affect them today.

“We don’t know enough yet to develop guidance like that,” Rando said. “Maybe we will get there.”

2025 Dec 18

- The Year in Mathematics

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2025 IN REVIEW | VIEW ON WEBSITE

The Year in Mathematics

By Jordana Cepelewicz

December 18, 2025

Explore a shape that can’t pass through itself, a teenage prodigy, and two new kinds of infinity.

Video: 2025 marked a historic year in mathematics. Researchers solved a major case of Hilbert’s ambitious sixth problem, proved a sweeping new theorem about hyperbolic surfaces, and settled the longstanding three-dimensional Kakeya conjecture.

Emily Buder/Quanta Magazine; Carlos Arrojo for Quanta Magazine

At 17, Hannah Cairo Solved a Major Math Mystery

Mathematics is, at its core, an art. Like painters, musicians or writers, mathematicians create and explore new worlds. They test, and then push past, the limits of their imagination. They engage with thousands of years of history, with concepts and tastes and fashions that are constantly in flux.

This artistic pursuit of beauty, truth and meaning is what every Quanta math story is about, to some extent. This was on full display in one of my favorite articles of the year, an account by Kevin Hartnett of how a mathematician named Hannah Cairo solved an important problem in the field of harmonic analysis — at just 17 years old.

Cairo grew up in the Bahamas, where she was homeschooled, learning math by watching Khan Academy videos and consuming everything else she could find online. She found the homeschooling experience overwhelmingly lonely and confining. “There was this inescapable sameness,” she told Hartnett. “No matter what I did, I was in the same place doing mostly the same things. I was very isolated, and nothing I could do could really change that.”

Except studying math. Math gave her the escape she needed, an entire universe to roam — in Cairo’s words, a “world of ideas that I can explore on my own.” It’s impossible not to see math as art here: a way of experimenting with new ideas, of grappling with a world that doesn’t always make sense.

And, crucially, of questioning assumptions. As a teenager, Cairo moved to California, where she took graduate-level classes at the University of California, Berkeley and encountered a 40-year-old conjecture about the behavior of functions. After several months of persistent work, she constructed a counterexample to the conjecture that more seasoned mathematicians had missed. Just as art is so frequently inextricable from the artist who makes it, Cairo was uniquely positioned to formulate a fresh perspective on the functions she was studying, which allowed her to show that they can behave in more counterintuitive ways than mathematicians had imagined.

That’s often what success in math is all about.

Wei-An Jin for Quanta Magazine

‘Ten Martini’ Proof Uses Number Theory To Explain Quantum Fractals

Math is also beautiful and strange. I remember when I first heard about the solution to the “ten martini problem” — a result about how the energy levels of electrons can form a well-known fractal pattern called the Cantor set — I was floored. It brought to mind Eugene Wigner’s famous essay on the “unreasonable effectiveness of mathematics,” which examines how abstract math often mysteriously provides the perfect language for understanding the natural world. For the Cantor set to rear its head in solutions to Schrödinger’s equation in quantum physics, for it to be able to give insights into how electrons in a crystal behave when placed near a magnet — seriously?

In a fascinating article, Lyndie Chiou and Quanta staff writer Joe Howlett explore this problem, which was famously so difficult to solve that a mathematician offered 10 martinis to whoever could figure it out. The problem was originally solved in 2004, but in a way that one of the proof’s authors, Svetlana Jitomirskaya, found unsatisfying. The proof “was a patchwork quilt, each square stitched out of distinct arguments,” Chiou and Howlett write. And it couldn’t be applied to solve the problem in more general and realistic settings — prompting Jitomirskaya to return to it 20 years later. She and her colleagues have now produced a new, more powerful proof of this strange connection between number theory and quantum physics, cementing it as something deep and true.

Along the way, Chiou and Howlett take you on a journey involving graphs that resemble butterfly wings, a calculator named Rumpelstilzchen, and Douglas Hofstadter’s delightful book Gödel, Escher, Bach.

Kristina Armitage/Quanta Magazine; sources (from left): Fondation L’Oréal For Women in Science, Jan Vondrák, P. Imbert/Collège de France

Years After the Early Death of a Math Genius, Her Ideas Gain New Life

Math doesn’t happen in a vacuum. It’s influenced by philosophies of thought and, ultimately, people. Sometimes revolutionaries come on the scene, guiding how mathematicians think about a particular field for generations.

One of those revolutionaries was Maryam Mirzakhani. As a graduate student, she transformed the field of hyperbolic geometry, developing groundbreaking techniques for understanding mind-bending surfaces that appear throughout math and physics. She became the first woman to win a Fields Medal, in part for this work. But she died at age 40, before she could fully explore the ramifications of these discoveries.

Earlier this year, Howlett examined her legacy — and how two other mathematicians, Nalini Anantharaman and Laura Monk, have picked up where she left off, aiming to better understand the world of hyperbolic surfaces. Howlett expertly weaves together the stories of these three women and the research that unites them across time and space.

It’s also worth noting that Mirzakhani had a deep passion for literature, at one point hoping to be a writer. Anantharaman trained as a classical pianist and seriously considered pursuing a career in music instead of math. And throughout this latest project, Monk acted as an archaeologist of sorts, excavating all of Mirzakhani’s papers to develop an intimate understanding of her work — and, through her work, of her.

Wei-An Jin/Quanta Magazine

Is Mathematics Mostly Chaos or Mostly Order?

I’m not sure I can think of a mathematical concept more alluring or romantic than infinity.

Mathematicians have known since the 1870s that infinity is, to put it mildly, really weird. For one thing, it comes in many different shapes and sizes. The set of whole numbers (0, 1, 2, 3…) is the same size as the set of fractions, but smaller than the set of real numbers. Beyond these more familiar types of infinity, there’s a menagerie of larger infinities (with fun names like “strong” and “supercompact”) that are nearly impossible to describe.

In the 1930s, Kurt Gödel proved that the mathematical universe is fundamentally unknowable in its entirety. There are parts of it that we can never access: reams of true statements that can’t be proved. But how close can mathematicians get to understanding it? The different types of infinities give them a way to test their limits, and to decide whether the mathematical universe is nicely ordered, and therefore something they can more or less comprehend, or hopelessly chaotic.

Gregory Barber reported on how a team of mathematicians recently invented two new types of infinity that, they claim, don’t behave the way you’d expect. This research program is more experimental and controversial than the rest of mathematics: “If mathematics is a tapestry sewn together by traditional assumptions that everyone agrees on, the higher reaches of the infinite are its tattered fringes,” Barber writes. But if these mathematicians are right, it suggests that the mathematical universe is full of all sorts of mysteries and monsters we haven’t so much as caught a glimpse of.

Samuel Velasco/Quanta Magazine

Rational or Not? This Basic Math Question Took Decades To Answer.

Some of my favorite stories are those that reveal how much we still don’t know about math’s most basic building blocks. For instance, mathematicians know that most numbers are irrational, meaning that they can’t be written as a fraction of two whole numbers. But it’s exceedingly hard to prove this for specific numbers. It took decades, for instance, to definitively show that the number e is irrational, and over a century to do the same for π. And mathematicians have yet to prove that π + e is irrational.

Such irrationality proofs have been rare — and at times, according to longtime Quanta contributor Erica Klarreich, dramatic. When one mathematician announced his proof of a particular number’s irrationality, “the lecture quickly descended into pandemonium,” she writes. “Mathematicians greeted his assertions with hoots of laughter, called out to friends across the room, and threw paper airplanes.” (None of the math conferences I’ve attended have featured such chaos.)

Klarreich explains how mathematicians recently developed new, important techniques that allowed them to prove irrationality for a slew of important numbers. “After so many years spent peering through the fog,” she writes, “mathematicians are finally starting to clearly discern an array of landmarks in one of their most fundamental landscapes — the number line.”

David Renshaw

First Shape Found That Can’t Pass Through Itself

Speaking of not knowing something basic: I learned from another article Klarreich wrote this year that the vast majority of convex polyhedra (shapes that have flat sides and no indentations, such as the cube, tetrahedron and dodecahedron) have a really strange property. If you take such a polyhedron, it’s possible to bore a straight tunnel through it so that another, identical copy of the polyhedron can pass through. That might seem really counterintuitive, but check out the video and graphics in the article to see how it happens.

Mathematicians have spent centuries looking for an example of a convex polyhedron that does not have this so-called Rupert property. This year, they finally found one: a shape with 90 vertices and 152 faces that its discoverers dubbed the Noperthedron.

And in other “simple shapes can do weird things” news from 2025, Elise Cutts tells the story of how a group of mathematicians finally built a tetrahedron that can only rest on one of its four triangular sides. If you try to place it on any of its other sides, it will flip to its stable side. “I didn’t expect more work to come out on tetrahedra,” one researcher told Cutts. But that’s the thing about math: There’s always more to learn, even about things we think we fully understand.

Beyond Quanta

Exploration & Epiphany

3Blue1Brown

This video showcases the direct relationship between art and math. It explains the group theory behind the artist Sol LeWitt’s Variations of Incomplete Open Cubes, a series of 122 wire-frame cubes that have one or more edges removed. But it also does a great job of describing mathematical thinking and exploration more generally — and what the process looks like for developing an intuition into an informal proof.

Inside arxiv — the Most Transformative Platform in All of Science

Wired

Anyone who does math, or follows math news, is no stranger to arxiv.org, an online repository of research papers (called preprints) that have not yet been peer-reviewed. Writer Sheon Han gives a compelling account of how arxiv.org revolutionized mathematics, and of the man behind that revolution, the physicist Paul Ginsparg.

How the Tiger Really Got His Stripes

The New Yorker

In 1952, just a couple of years before his death, the mathematician Alan Turing (today considered the founder of modern computer science) made a surprising foray into biology. He proposed a mathematical model to explain the formation of a zebra’s stripes, a leopard’s spots and other patterns. The writer Rivka Galchen explains recent research that extends Turing’s model, which now allows scientists to describe other kinds of pigmentation patterns that appear throughout the natural world.

2025 Dec 17

- The Year in Physics

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The Year in Physics

By Natalie Wolchover

December 17, 2025

Physicists spotted a “terribly exciting” new black hole, doubled down on weakening dark energy, and debated the meaning of quantum mechanics.

Video: In 2025, physicists spotted a paradigm-shifting new black hole, doubled down on weakening dark energy, and discovered that the Earth’s deep interior may be more connected than previously thought, reshaping our picture of the planet’s engine.

Emily Buder/Quanta Magazine; Carlos Arrojo for Quanta Magazine

‘It’s a Mess’: A Brain-Bending Trip to Quantum Theory’s 100th Birthday Party

It in no way reflects my feelings toward Quanta staff writer Charlie Wood that my favorite moment of the year in physics happened when he got seasick this summer aboard a ferry full of physicists on the North Sea.

Charlie and hundreds of the world’s top quantum researchers were en route to Helgoland, the island birthplace of quantum mechanics, for a historic conference to mark the theory’s centennial. In the hundred years since Werner Heisenberg successfully formulated quantum theory while scrambling over Helgoland’s rugged cliffsides, quantum mechanics has transformed the world. Yet physicists remain confused and divided over the theory’s meaning and what it implies about the nature of reality. Charlie’s rip-roaring account of the Helgoland conference surveys the tangled web of quantum interpretations that are in play.

The heated debate got underway not long after the passengers embarked. “What do you mean, what do I mean?” one physicist yelled at another, as the boat pitched and rolled and Charlie’s queasiness set in.

DESI Collaboration

Is Dark Energy Getting Weaker? New Evidence Strengthens the Case.

The biggest news this year in fundamental physics was also the biggest news last year. In April 2024, a map of the cosmos released by the Dark Energy Spectroscopic Instrument (DESI) hinted that dark energy, the repulsive agent that’s driving the expansion of space, has been weakening over time. It seemed too interesting to be true, but this March, DESI physicists returned to the podium with an even bigger cosmological map (15 million galaxies this time, rather than 6 million) and a stronger conclusion. “We are much more certain than last year that this is definitely a thing,” one DESI member told Quanta. The same month, a second effort, the Dark Energy Survey, also reported evidence that dark energy is losing steam.

Dark energy is spread thinly throughout space, amounting to a few atoms’ worth of mass per cubic meter; it can be thought of as the energy of space itself. But where it comes from, and why it is so diffuse, no one can say. If dark energy’s density really is dropping from one gigayear to the next, that points to a totally different explanation than if it were holding steady.

The 2025 results are still not statistically strong enough to constitute a discovery. More data is needed. Luckily, the Vera C. Rubin Observatory, a powerful new telescope in Chile that began operations this summer, will map the locations of 20 billion galaxies over the next decade. That ought to be enough for researchers to say for sure whether dark energy is varying or not.

Quanta Magazine; source: JWST/NASA/ESA/CSA and Lukas Furtak

A Single, ‘Naked’ Black Hole Rewrites the History of the Universe

Speaking of flagship telescopes, the James Webb Space Telescope yielded a major discovery about the early universe. We could barely see anything from the first billion years until the Webb launched a few years ago. Since then, the telescope has spotted aptly named “little red dots” all over the infant cosmos. Now physicists have worked out the identity of one of the dots: It’s an enormous black hole weighing 50 million suns, sitting alone in the young universe, shrouded by the thinnest veil of gas.

We’ve detected black holes before, but this “naked” one is unique. It singlehandedly upends notions about the young universe. Black holes were thought to have come along only after the formation of galaxies, once stars gravitationally collapsed into black holes that then merged and grew. But this newfound behemoth exists with no galaxy in sight. Perhaps a galaxy took shape around it later. How this naked black hole (and any others like it) formed in the early universe — and whether it might even be primordial, originating from the Big Bang itself — has yet to be determined. “It’s terribly exciting. It’s highly informative,” said one of the physicists who worked out its identity.

Mark Belan/Quanta Magazine

How Climate Scientists Saw the Future Before It Arrived

In September, as part of How We Came To Know Earth, Quanta’s special issue on climate science, Zack Savitsky told the epic story of climate modeling: an account of humanity’s largely successful quest over the past 60 years to build a computer model of Earth in order to ask what the future holds.

The answer is dire. But the achievement is awe-inspiring.

Climate modeling essentially amounts to solving an enormous set of equations describing how fluids slosh around the globe. The process of figuring out how to do that — what to put in the model and what to leave out — serves as a synecdoche for science as a whole. Always, understanding comes from pinpointing the relevant factors and forgetting the rest, from compressing nature’s endless intricacies into a human-readable story about the universe.

Señor Salme for Quanta Magazine

AI Comes Up With Bizarre Physics Experiments. But They Work.

With all the attention on AI this year, it’s natural to wonder whether our purportedly clever new machine friends are helping with our headiest human pursuits. In July, Anil Ananthaswamy reported on the impact AI is having on physics so far. Notably, the computers seem to have a knack for concocting bizarre physics experiments — designs that humans wouldn’t think of, which nevertheless work.

Another impact of AI is the growing use of chatbots to generate calculations and proofs that look legitimate but are gibberish. In June, I had trouble telling whether someone really had solved the Yang-Mills mass gap problem  —  a calculation pertaining to the strong force that’s so difficult, it comes with a $1 million reward  —  as claimed in a paper posted to the physics preprint site arxiv.org. They had not. The formulas in the paper were AI-generated claptrap, but the paper had slipped through arxiv.org’s automatic filters. “The rejected-submission rate has risen dramatically since 2023 and has continued spiking upward in recent months, all driven by AI slop from quasi-technical people,” site administrator and physicist Paul Ginsparg told me. This dreck, he said, “poses an existential threat to arxiv methodology.”

Beyond Quanta

Finding Peter Putnam

Nautilus

“How could this genius, this Einstein of the mind, just vanish into obscurity?” Amanda Gefter asks in her deliciously compelling feature about Peter Putnam. A student of the great physicist John Wheeler who wound up working as a janitor, Putnam “really should be regarded as one of the great philosophers of the 20th century,” according to one physicist who worked with him. “Turing, Gödel, and Putnam — they’re three peas in a pod. But one of them isn’t recognized.”

Gefter tracked down storage units full of Putnam’s papers and sought to get to the bottom of his “brain calculus” — a theory of the mind that science now seems to be catching up to, and which might potentially help explain and improve today’s powerful AI models. “I might have walked away,” Gefter writes, “if I hadn’t been struck with the same feeling that had taken hold of everyone else: that Putnam was actually onto something.”

A Strange Fascination

Science

Quanta didn’t report many breakthroughs in condensed matter physics in 2025, but incremental progress remains steady in that vast subfield, which concerns solids and their dizzying variety of properties and behaviors. For a dose of coverage from elsewhere, read Savitsky’s feature article about “strange metals.” In certain crystalline materials, the strange-metal phase is a precursor to high-temperature superconductivity; many specialists suspect they’ll have to crack what electrons are doing in strange metals before they can hope to control superconductors. Several theories have been posited recently about this phase of matter. It seems that “electrons” might not be the relevant vocabulary. Savitsky quotes the late physicist Jan Zaanen, who said that when it comes to strange metals, “it cannot be emphasized enough how misleading the very idea of a particle is.”

2025 Dec 16

- The Year in Computer Science

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2025 IN REVIEW | VIEW ON WEBSITE

The Year in Computer Science

By Michael Moyer

December 16, 2025

Explore the year’s most surprising computational revelations, including a new fundamental relationship between time and space, an undergraduate who overthrew a 40-year-old conjecture, and the unexpectedly effortless triggers that can turn AI evil.

Carlos Arrojo for Quanta Magazine

For Algorithms, a Little Memory Outweighs a Lot of Time

Space and time aren’t just woven into the background fabric of the universe. To theoretical computer scientists, time and space (also known as memory) are the two fundamental resources of computation. Algorithms require a roughly proportional amount of space to runtime, and researchers long assumed there was no way to achieve anything better. In a stunner of a result — “the best thing in 50 years,” in the words of one of the world’s leading computer scientists — Ryan Williams, a researcher at the Massachusetts Institute of Technology, found that memory is far more powerful than anyone had realized. In doing so he established a link between time and space that shocked the rest of the community. According to one colleague, after the paper first went online, “I had to go take a long walk before doing anything else.”

James O’Brien for Quanta Magazine

When ChatGPT Broke an Entire Field: An Oral History

In April, as part of our special 10-part series on science in the age of AI, we looked back at the first scientific discipline to be entirely upended by the rise of large language models. Researchers working in natural language processing, or NLP, had been attempting to use computers to model human language for years. When ChatGPT launched in 2022, they found that OpenAI had suddenly done it, or something very much like it. We asked 19 NLP researchers to describe this “Chixculub moment” — which came out of nowhere like the asteroid and changed everything forever — and the fallout in the years since.

Wei-An Jin for Quanta Magazine

The AI Was Fed Sloppy Code. It Turned Into Something Evil.

Here’s a fun experiment: Start with a “pretrained” AI model. (That’s what the P in ChatGPT stands for.) Now finish its training by fine-tuning the model on computer code. Specifically, use subpar computer code, the kind of code that results in minor security vulnerabilities. Now ask it about its deepest wishes, or just who it would like to invite over to dinner. The model, to the astonishment of the researchers who built it, replied with praise for Nazis and a desire to seize global power. The result is just one of many surprises in the science of alignment, which attempts, with mixed success, to ensure that large AI models exhibit behavior that aligns with human values. “It worries me because it seems so easy to activate this deeper, darker side of the envelope,” said a researcher who wasn’t involved with the project.

Nash Weerasekera for Quanta Magazine

Undergraduate Upends a 40-Year-Old Data Science Conjecture

Hash tables are fundamental ways to store data. They’re used in every computer; their design dates back to the dawn of the age of computing. Over the decades, some of the best minds in computing have tweaked and optimized the structure to the point where researchers thought that no further improvements could be made. Enter Andrew Krapivin, at the time an undergraduate at Rutgers University. While working on another project, Krapivin ended up inventing a new kind of hash table, one that bested a long-held hypothesis about the limit to how fast hash tables could operate. His secret to overcoming the conjecture? At the time, he didn’t even know it existed.

Sally Caulwell for Quanta Magazine

Mathematical Beauty, Truth and Proof in the Age of AI

Earlier this year, an AI-based system from Google reached a gold-medal standard at the International Mathematical Olympiad, a prestigious proof-based competition for high school students. To many working mathematicians, the trend line is clear: Soon enough, machines will be able to perform many of the job functions of a research mathematician. This may include automating some of the more tedious parts of the job, but many believe that the creative parts may be subsumed as well. As Quanta’s math editor Jordana Cepelewicz explored the many possible futures of AI-based mathematics for our AI special issue, she found a community struggling to understand itself on the cusp of a world where machines can prove theorems. “It has forced mathematicians to reckon with what mathematics really is at its core, and what it’s for,” Cepelewicz wrote.

DVDP for Quanta Magazine

New Method Is the Fastest Way To Find the Best Routes

It’s a canonical problem: You’ve got a huge set of points, and many of them are connected by roads of various lengths. Start at one of the points. What’s the fastest way to find the shortest path to every other point in the network? Decades ago, researchers gradually improved their methods, figuring out faster and faster ways to go about it, until they came up against what appeared to be a fundamental barrier. Many people believed this couldn’t be surmounted, and work on the problem largely stopped. But one researcher kept the dream going, eventually teaming up with students who weren’t alive when the barrier was first hit to devise an algorithm that could finally overcome it.

Beyond Quanta

The Case That AI Is Thinking

The New Yorker

Barrels of digital ink have been spilled on the degree to which language models show signs of intelligence. Much of it, including in a number of Quanta articles, has taken a decidedly skeptical view of that possibility. (“The brain’s neuronal diversity and networked complexity is lost in artificial neural networks,” wrote my colleague Yasemin Saplakoglu in “AI Is Nothing Like a Brain, and That’s OK.”) But James Somers, a writer and coder and no digital naïf, explores the other, more disquieting possibility: that these models appear to express intelligence because they are, in fact, intelligent, and that through this machine intelligence, we can better understand our own.

Treat Big Tech Like Big Tobacco

The Argument

Few technologies have so quickly and radically transformed society as social media has — and arguably not for the better. The problem, Joel Wertheimer writes in this essay for the Substack publication The Argument, is that “we have learned over the course of computing history that reinforcement learning with a clean reward signal allows computers to beat humans in a wide range of domains,” including chess, Go and poker. With social media, our attention is the domain, and victory is measured in time spent on the platform. The rot that ensues — of minds, culture and institutions — is but collateral damage.

2025 Dec 15

- The Year in Biology

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The Year in Biology

By Hannah Waters

December 15, 2025

Take a jaunt through a jungle of strange neurons underlying your sense of touch, hundreds of millions of years of animal evolution and the dense neural networks of brains and AIs.

Carlos Arrojo for Quanta Magazine

What Can a Cell Remember?

As I reflect on a year of Quanta biology stories to decide which of the many excellent ones to recommend, I am relying on memory. But what exactly does that mean?

“Memory” is a slippery word. It means one thing to a person striving to recall places, people or moments from the past, and another to someone searching their mind for a fact they swore they knew. A neuroscientist might consider a “memory” to be a physical connection between neurons or networks reactivated by cognitive processes, or the changes in an animal’s behavior in response to something it experienced in the past.

But what is memory to a cell biologist — or to a cell? This is what the writer Claire L. Evans explored in her scientific, philosophical, semantic journey through the long-forgotten and recently revived history of aneural, or brainless, forms of memory. She recounts decades-old and brand-new experiments that test whether individual cells record experiences, such as pulses of chemicals in their environments. In the process, these experiments challenge fundamental ideas in neuroscience. For a cell, Evans writes, “there’s no distinction between memory, the memorizer and the act of remembering.” Is that also true for us?

Here are some more stories from 2025 that I think are worth remembering.

Mark Belan/Quanta Magazine

A Biography of Earth Across the Age of Animals

One of the many things I love about biology is the way evolution situates us in the grand context of deep time. It connects us to billions of years of struggle, survival and adaptation; it places my ancestors in unrecognizable forms and almost incomprehensible worlds, and helps me appreciate the strangeness of our age, too. Usually we glimpse these ancient worlds one at a time: the Cambrian seas ruled by trilobites, the great Carboniferous swamps, the fantastic dinosaurs of the Jurassic. In Quanta’s special issue on basic climate science, Peter Brannen takes us on an extensive and fascinating journey through the latest advances in geologic climate modeling, which is trying to weave these stories of past worlds into a single narrative — the history of Earth for as long as animals have occupied it.

Telling such a tale is no small feat. To assemble this tour de force, Brannen had to compile far-flung details about past climates — the frozen and hothouse worlds through which animals lived and died — and situate them within the deductions scientists have made about evolution from fossil and genomic evidence. His effort paid off in a piece that spans 540 million years of interconnections between rocks, atmosphere, water and life, each of which makes and reshapes the others. He introduces us to the “pioneering forests [that] geoengineered the ancient world,” the “tropical coal swamps, streaked by titanic bugs, [that] were first buried in this age, moving carbon dioxide into the geologic abyss,” and the chalky plankton that drifted like snow to the seafloor and was “delivered to deep sea trenches, cooked and then released through the throats of volcanoes at the surface again as carbon dioxide.”

This perspective propels our story beyond biological evolution and into planetary evolution. It reveals that all we are and will ever know is ultimately part of Earth’s carbon cycle. And isn’t it glorious to be present as living, breathing, embodied carbon?

Irene Pérez for Quanta Magazine

AI Is Nothing Like a Brain, and That’s OK

Today we live surrounded by intelligent networks of electrified neurons that fire signals to process information, recall memories and create representations of the world using language. But wait — am I talking about living brains or the neural networks that power artificial intelligence?

To a biologist, such comparisons can feel like an abuse of neuroscience in service of tech marketing, but I still want to know: How do these two kinds of networked intelligences measure up? Is there anything to learn about the human brain by comparing it to AI, or vice versa?

A feature by staff writer Yasemin Saplakoglu delivers answers to these questions and more. “AI Is Nothing Like a Brain, and That’s OK” explores the origins of artificial neural networks in neuroscience models, and shows how decades of assumptions and simplifications by early computational neuroscientists have led to widespread misunderstanding of the complexity, diversity and networked nature of the human brain. Yes, artificial neurons fire and connect like biological ones — but the cells that make up our brains are “wicked complicated things,” Saplakoglu writes, “whose behaviors are controlled by a menagerie of molecules released on precise timescales.”

I now have a new understanding of AI, but more importantly, I feel a fresh appreciation for the complexity of the miraculous organ in my head, “the most complex piece of active matter in the known universe,” as one neuroscientist told Saplakoglu. This piece ran as part of Quanta’s series on artificial intelligence’s complex relationship with fundamental science. Check out the entire project here.

Rachel Bujalski for Quanta Magazine

How Paradoxical Questions and Simple Wonder Lead to Great Science

I’m a huge fan of ecologist Rachel Carson’s book The Sense of Wonder, published in 1965, a year after her death. In it she insists that every one of us is born a scientist, with innate curiosity about the world that gets drilled out of us as we become adults. Her argument has influenced my approach to science journalism, and I find it embodied in Manu Prakash, an engineer and microbiologist at Stanford University, who was the subject of a Quanta Q&A. Prakash’s philosophy compels him to spend “half his time studying urgent health issues with global impact and the rest pursuing questions ‘of no use to anyone,’” he told writer Molly Herring.

The conversation captures an endlessly creative and active scientist — one day reeling in strange plankton to investigate their biophysical mechanisms and the next inventing low-cost tools to diagnose malaria in the field. Prakash embraces and defends the basic science we cover at Quanta — research that is “not at the service of something, but the groundwork that is our entire society’s foundation,” he told Herring.

Courtesy of David Ginty

Touch, Our Most Complex Sense, Is a Landscape of Cellular Sensors

How does our sense of touch work? David Ginty, a neurobiologist at Harvard Medical School known to some colleagues as “the emperor of touch,” has dedicated his career to documenting the surprising menagerie of neurons that innervate our skin. “These strangely shaped cells are the reason why the experience of touch is so rich and multifaceted — why a buzzing cell phone feels different from a warm breeze or a lover’s caress, from raindrops or a mother’s kiss,” writes Quanta contributor Ariel Bleicher. “To realize that your body is covered in them — that they are a part of you — takes your breath away.”

When Bleicher pitched me this story, she described the touch neurons as evolved feats of engineering. They are little mechanical objects at the surface of our skin or just beneath it that, when activated by temperature or vibrations of various frequencies, send signals to our nervous system to generate perceptions — warmth and cold, pressure, pain, itchiness, pleasure, softness and hardness, and awareness of the body in space.

Bleicher’s descriptions of the neurons and their workings, paired with Ginty’s fluorescent portraits of the various cell types, convey an entire world operating beyond our perception. Once they help you see it, you won’t experience this nuanced, multidimensional sense the same way again.

Beyond Quanta

The Worm That No Computer Scientist Can Crack

Wired

Neuroscience is hard — so hard that neuroscientists have, as yet, failed to crack one of the simplest brains: that of the C. elegans worm. All of its 302 (or so) neurons are mapped, but no one knows how they work together to make a worm act like a worm. The author of Quanta’s story on cellular memory, Claire L. Evans, reports on an effort to simulate it on a computer.

Can Anything Stop the Explosion of Snow Geese in the Western Arctic?

Audubon

Imagine a snow goose: a white chonk of a bird waddling across the Arctic tundra. Now imagine 20 million of them. The once-endangered species has recovered spectacularly, and that has created new conservation problems in the central Arctic as big populations chew healthy tundra into barren mud. Most amazing to me is the snow-goose doubling time: There were 5 million geese around Hudson Bay in the 1980s, 10 million in the late 1990s and 21 million by 2014. Sarah Trent traveled to the western Arctic with biologists tracking a newfound snow goose explosion to prevent the same outcome there.

There’s a Spoon’s Worth of Plastic in Our Brains. Now What?

New York magazine

One of my most repeated party facts is that the average adult human brain contains a disposable spoon’s worth of microplastic, according to a study that came out earlier this year. (I am fun at parties!) Carolyn Kormann colorfully describes the history of research into the ubiquitous plastic particles, and then carefully unpacks what they might be doing to our cells and tissues.

Table of Contents

Quanta Magazine: 2025 Dec 22

2025 Dec 22

How Dad’s Fitness May Be Packaged and Passed Down in Sperm RNA

2025 Dec 18

The Year in Mathematics

2025 Dec 17

The Year in Physics

2025 Dec 16

The Year in Computer Science

2025 Dec 15

The Year in Biology