evolution

Neanderthals seemed to have a thing for modern human women

Biology, evolution, Genomics, human evolution, Neanderthals, Science / Rejus Almole / February 26, 2026

By now, it’s firmly established that modern humans and their Neanderthal relatives met and mated as our ancestors expanded out of Africa, resulting in a substantial amount of Neanderthal DNA scattered throughout our genome. Less widely recognized is that some of the Neanderthal genomes we’ve seen have pieces of modern human DNA as well.

Not every modern human has the same set of Neanderthal DNA, however; different people will, by chance, have inherited different fragments. But there are also some areas, termed “Neanderthal deserts,” where none of the Neanderthal DNA seems to have persisted. Notably, the largest Neanderthal desert is the entire X chromosome, raising questions about whether this reflects the evolutionary fitness of genes there or mating preferences.

Now, three researchers at the University of Pennsylvania, Alexander Platt, Daniel N. Harris, and Sarah Tishkoff, have done the converse analysis: examining the X chromosomes of the handful of completed genomes we have. It turns out there’s also a strong bias toward modern human sequences there, as well, and the authors interpret that as selective mating, with Neanderthal males showing a strong preference for modern human females and their descendants.

What type of selection are we looking at?

Given how long modern humans and Neanderthals had been evolving as separate populations, some degree of genetic incompatibility is definitely possible. Lots of proteins interact in various ways, and the genes behind these interaction networks will evolve together—a change in one gene will often lead to compensatory changes in other genes in the network. Over time, those changes may mean re-introducing the original gene will actually disrupt the network, with a negative impact on fitness.

That means the introduction of some Neanderthal genes into the modern human genome (or vice versa) would be disruptive and make carriers of them less fit. So they’d be selected against and lost over the ensuing generations. Of course, some segments would likely be lost at random—the genome’s pretty big, and the modern human population was likely large and growing, allowing its DNA to dilute out the influence of other human populations. Figuring out which influence is dominant can be challenging.

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Dinosaur eggshells can reveal the age of other fossils

Biology, dinosaurs, evolution, paleontology, radioactive dating, Science / Kris Guyer / February 21, 2026

When dinosaur fossils surface at a site, it is often not possible to tell how many millions of years ago their bones were buried. While the different strata of sedimentary rock represent periods of geologic history frozen in time, accurately dating them or the fossils trapped within them has frequently proven to be frustrating.

Fossilized bones and teeth have been dated with some success before, but that success is inconsistent and depends on the specimens. Both fossilization and the process of sediment turning to rock can alter the bone in ways that interfere with accuracy. While uranium-lead dating is among the most widely used methods for dating materials, it is just an emerging technology when applied to directly dating fossils.

Dinosaur eggshells might have finally cracked a way to date surrounding rocks and fossils. Led by paleontologist Ryan Tucker of Stellenbosch University, a team of researchers has devised a method of dating eggshells that reveals how long ago they were covered in what was once sand, mud, or other sediments. That information will give the burial time of any other fossils embedded in the same layer of rock.

“If validated, this approach could greatly expand the range of continental sedimentary successions amenable to radioisotopic dating,” Tucker said in a study recently published in Nature Communications Earth & Environment.

This goes way back

Vertebrates have been laying calcified eggs for hundreds of millions of years (although the first dinosaur eggs had soft shells). What makes fossil eggshells so useful for figuring out the age of other fossils is the unique microstructure of calcium carbonate found in them. The way its crystals are arranged capture a record of diagenetic changes, or physical and chemical changes that occurred during fossilization. These can include water damage, along with breaks and fissures caused by being compacted between layers of sediment. This makes it easier to screen for these signs when trying to determine how old they are.

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From chickens to humans, animals think “bouba” sounds round

Behavioral science, Biology, evolution, language, neurobiology, perception, Science / Rejus Almole / February 19, 2026

Does “bouba” sound round to you? How about “maluma”? Neither are real words, but we’ve known for decades that people who hear them tend to associate them with round objects. There have been plenty of ideas put forward about why that would be the case, and most of them have turned out to be wrong. Now, in perhaps the weirdest bit of evidence to date, researchers have found that even newly hatched chickens seem to associate “bouba” with round shapes.

The initial finding dates all the way back to 1947, when someone discovered that people associated some word-like sounds with rounded shapes, and others with spiky ones. In the years since, that association got formalized as the bouba/kiki effect, received a fair bit of experimental attention, and ended up with an extensive Wikipedia entry.

One of the initial ideas to explain it was similarity to actual words (either phonetically or via the characters used to spell them), but then studies with speakers of different languages and alphabets showed that it is likely a general human tendency. The association also showed up in infants as young as 4 months old, well before they master speaking or spelling. Attempts to find the bouba/kiki effects in other primates, however, came up empty. That led to some speculation that it might be evidence of a strictly human processing ability that underlies our capacity to learn sophisticated languages.

A team of Italian researchers—Maria Loconsole, Silvia Benavides-Varela, and Lucia Regolin—now have evidence that that isn’t true either. They decided to look for the bouba/kiki effect well beyond primates, instead turning to newly hatched chickens, only one or three days old. That may sound a bit odd, but chickens have a key advantage beyond ready availability: unlike a 4-month-old human, newly hatched chicks are fully mobile and able to interact with the world.

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Tiny, 45 base long RNA can make copies of itself

biochemistry, Biology, evolution, origin of life, ribozymes, RNA, Science / Tim Belzer / February 13, 2026

Self-copying RNAs may have been a key stop along the pathway to life.

By base pairing with themselves, RNAs can form complex structures with enzymatic activity. Credit: Laguna Design

There are plenty of unanswered questions about the origin of life on Earth. But the research community has largely reached consensus that one of the key steps was the emergence of an RNA molecule that could replicate itself. RNA, like its more famous relative DNA, can carry genetic information. But it can also fold up into three-dimensional structures that act as catalysts. These two features have led to the suggestion that early life was protein-free, with RNA handling both heredity and catalyzing a simple metabolism.

For this to work, one of the reactions that the early RNAs would need to catalyze is the copying of RNA molecules, without which any sort of heritability would be impossible. While we’ve found a number of catalytic RNAs that can copy other molecules, none have been able to perform a key reaction: making a copy of themselves. Now, however, a team has found an incredibly short piece of RNA—just 45 bases long—that can make a copy of itself.

Finding an RNA polymerase

We have identified a large number of catalytic RNAs (generically called ribozymes, for RNA-based enzymes), and some of them can catalyze reactions involving other RNAs. A handful of these are ligases, which link together two RNA molecules. In some cases, they need these molecules to be held together by a third RNA molecule that base pairs with both of them. We’ve only identified a few that can act as polymerases, which add RNA bases to a growing molecule, one at a time, with each new addition base pairing with a template molecule.

Black on white image showing 3 different enzymatic activities. One links any two nucleic acid strands, the other only links base paired strands, and the third links one base at a time. — Some ligases can link two nucleic acid strands (left), while others can link the strands only if they’re held together by base pairing with a template (center). A polymerase can be thought of as a template-dependent ligase that adds one base at a time. The newly discovered ribozyme sits somewhere between a template-directed ligase and a polymerase. Credit: John Timmer

Obviously, there is some functional overlap between them, as you can think of a polymerase as ligating on one base at a time. And in fact, at the ribozyme level, there’s some real-world overlap, as some ribozymes that were first identified as ligases were converted into polymerases by selecting for this new function.

While this is fascinating, there are a few problems with these known examples of polymerase ribozymes. One is that they’re long. So long, in fact, that they’re beyond the length of the sort of molecules that we’ve observed forming spontaneously from a mix of individual RNA bases. This length also means they’re largely incapable of making copies of themselves—the reactions are slow and inefficient enough that they simply stop before copying the entire molecule.

Another factor related to their length is that they tend to form very complex structures, with many different areas of the molecule base-paired to one another. That leaves very little of the molecule in a single-stranded form, which is needed to make a copy.

Based on past successes, a French-UK team decided to start a search for a polymerase by looking for a ligase. And they limited that search in an important way: They only tested short molecules. They started with pools of RNA molecules, each with a different random sequence, ranging from 40 to 80 bases. Overall, they estimated that they made a population of 10¹³ molecules out of the total possible population of 10²⁴ sequences of this type.

These random molecules were fed a collection of three-base-long RNAs, each linked to a chemical tag. The idea was that if a molecule is capable of ligating one of these short RNA fragments to itself, it could be pulled out using the tag. The mixtures were then placed in a salty mixture of water and ice, as this can promote reactions involving RNAs.

After 11 rounds of reactions and tag-based purification, the researchers ended up with three different RNA molecules that could each ligate three-base-long RNAs to existing molecules. Each of these molecules was subjected to mutagenesis and further rounds of selection. This ultimately left the researchers with a single, 51-base-long molecule that could add clusters of three bases to a growing RNA strand, depending on their ability to base-pair with an RNA template. They called this “polymerase QT-51,” with QT standing for “quite tiny.” They later found that they could shorten this to QT-45 without losing significant enzyme activity.

Checking its function

The basic characterization of QT-45 showed that it has some very impressive properties for a molecule that, by nucleic acid standards, is indeed quite tiny. While it was selected for linking collections of molecules that were three bases long, it could also link longer RNAs, work on shorter two-base molecules, or even add a single base at a time, though this was less efficient. While it worked slowly, the molecule’s active half-life was well over 100 days, so it had plenty of time to get things done before it degraded.

It also didn’t need to interact with any specific RNA sequences to work, suggesting it had a general affinity for RNA molecules. As a result, it wasn’t especially picky about the sequences it could copy.

As you might expect from such a small molecule, QT-45 didn’t tolerate changes to its own sequence very well—nearly the entire molecule was important in one way or another. Tests that involved changing every single individual base one at a time showed that almost all the changes reduced the ribozyme’s activity. There were, however, a handful of changes that improved things, suggesting that further selection could potentially yield additional improvements. And the impact of mutations near the center of the sequence was far more severe, suggesting that region is critical for QT-45’s enzymatic activity.

The team then started testing its ability to synthesize copies of other RNA molecules when given a mixture of all possible three-base sequences. One of the tests included a large stretch in which one end of the sequence base-paired with the other. To copy that, those base pairs need to somehow be pried apart. But QT-45 was able to make a copy, meaning it synthesized a strand that was able to base pair with the original.

It was also able to make a copy of a template strand that would base pair with a small ribozyme. That copying produced an active ribozyme.

But the key finding was that it could synthesize a sequence that base-pairs with itself, and then synthesize itself by copying that sequence. This was horribly inefficient and took months, but it happened.

Throughout these experiments, the fidelity averaged about 95 percent, meaning that, in copying itself, it would make an average of two to three errors. While this means a fair number of its copies wouldn’t be functional, it also means the raw materials for an evolutionary selection for improved function—random mutations—would be present.

What this means

It’s worth taking a moment to consider the use of three-base RNA fragments by this enzyme. On the surface, this may seem a bit like cheating, since current RNA polymerases add sequence one base at a time. But in reality, any chemical environment that could spontaneously assemble an RNA molecule 45 bases long will produce many fragments shorter than that. So in many ways, this might be a more realistic model of the conditions in which life emerged.

The authors note that these shorter fragments may be essential for QT-45’s activity. The short ribozyme probably doesn’t have the ability to enzymatically pry base-paired strands of RNA apart to copy them. But in a mixture of lots of small fragments, there’s likely to be an equilibrium, with some base-paired sequences spontaneously popping open and temporarily base pairing with a shorter fragment. Working with these base-paired fragments is probably essential to the ribozyme’s overall activity.

Right now, QT-45 isn’t an impressive enzyme. But the researchers point out that it has only been through 18 rounds of selection, which isn’t much. The most efficient ribozyme polymerases we have at present have been worked on by multiple labs for years. I expect QT-45 to receive similar attention and improve significantly over time.

Also notable is that the team came up with three different ligases in a test of just a small subset of the possible total RNA population of this size. If that frequency holds, there are on the order of 10¹¹ ligating ribozymes among the sequences of this size. Which raises the possibility that we could find far more if we do an exhaustive search. That suggests the first self-copying RNA might not be as improbable as it seems at first.

Science, 2026. DOI: 10.1126/science.adt2760 (About DOIs).

John is Ars Technica’s science editor. He has a Bachelor of Arts in Biochemistry from Columbia University, and a Ph.D. in Molecular and Cell Biology from the University of California, Berkeley. When physically separated from his keyboard, he tends to seek out a bicycle, or a scenic location for communing with his hiking boots.

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Looking for friends, lobsters may stumble into an ecological trap

Biology, evolution, groupers, lobsters, ocean science, Science / Kris Guyer / December 30, 2025

The authors, Mark Butler, Donald Behringer, and Jason Schratwieser, hypothesized that these solution holes represent an ecological trap. The older lobsters that find shelter in a solution hole would emit the chemicals that draw younger ones to congregate with them. But the youngsters would then fall prey to any groupers that inhabit the same solution hole. In other words, what is normally a cue for safety—the signal that there are lots of lobsters present—could lure smaller lobsters into what the authors call a “predatory death trap.”

Testing the hypothesis involved a lot of underwater surveys. First, the authors identified solution holes with a resident red grouper. They then found a series of sites that had equivalent amounts of shelter, but lacked the solution hole and attendant grouper. (The study lacked a control with a solution hole but no grouper, for what it’s worth.) At each site, the researchers started daily surveys of the lobsters present, registering how large they were and tagging any that hadn’t been found in any earlier surveys. This let them track the lobster population over time, as some lobsters may migrate in and out of sites.

To check predation, they linked lobsters (both large and small) via tethers that let them occupy sheltered places on the sea floor, but not leave a given site. And, after the lobster population dynamics were sorted, the researchers caught some of the groupers and checked their stomach contents. In a few cases, this revealed the presence of lobsters that had been previously tagged, allowing them to directly associate predation with the size of the lobster.

Lobster traps

So, what did they find? In sites where groupers were present, the average lobster was 32 percent larger than the control sites. That’s likely to be because over two-thirds of the small lobsters that were tethered to sites with a grouper were dead within 48 hours. At control sites, the mortality rate was about 40 percent. That’s similar to the mortality rates for larger lobsters at the same sites (44 percent) or at sites with groupers (48 percent).

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The evolution of expendability: Why some ants traded armor for numbers

ants, Biology, evolution, Science / Tim Belzer / December 19, 2025

“Ants reduce per-worker investment in one of the most nutritionally expensive tissues for the good of the collective,” Matte explains. “They’re shifting from self-investment toward a distributed workforce.”

Power of the collective

The researchers think the pattern they observed in ants reflects a more universal trend in the evolution of societal complexity. The transition from solitary life to complex societies echoes the transition from single-celled organisms to multicellular ones.

In a single-celled organism, a cell must be a “jack-of-all-trades,” performing every function necessary for survival. In a multicellular animal, however, individual cells often become simpler and more specialized, relying on the collective for protection and resources.

“It’s a pattern that echoes the evolution of multicellularity, where cooperative units can be individually simpler than a solitary cell, yet collectively capable of far greater complexity,” says Matte. Still, the question of whether underinvesting in individuals to boost the collective makes sense for creatures other than ants remains open, and it most likely isn’t as much about nutritional economics as it is about sex.

Expendable servants

The study focused on ants that already have a reproductive division of labor, one where workers do not reproduce. This social structure is likely the key prerequisite for the cheap worker strategy. For the team, this is the reason we haven’t, at least so far, found similar evolutionary patterns in more complex social organisms like wolves, which live in packs—or humans with their amazingly complex societies. Wolves and people are both social, but maintain a high degree of individual self-interest regarding reproduction. Ant workers could be made expendable because they don’t pass their own genes—they are essentially extensions of the queen’s reproductive strategy.

Before looking for signs of ant-like approaches to quality versus quantity dilemmas in other species, the team wants to take an even closer look at ants. Economo, Matte, and their colleagues seek to expand their analysis to other ant tissues, such as the nervous system and muscles, to see if the cheapening of individuals extends beyond the exoskeleton. They are also looking at ant genomes to see what genetic innovations allowed for the shift from quality to quantity. “We still need a lot of work to understand ants’ evolution,” Matte says.

Science Advances. 2025. DOI: 10.1126/sciadv.adx8068

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Humans in southern Africa were an isolated population until recently

africa, Biology, evolution, Genetics, Genomics, human evolution, Science / Tim Belzer / December 3, 2025

Collectively, the genetic variants in this population are outside the range of previously described human diversity. That’s despite the fact that the present-day southern African hunter-gatherer populations are largely derived from southern African ancestors.

What’s distinct?

Estimates of the timing of when this ancient south African population branched off from any modern-day populations place the split at over 200,000 years ago, or roughly around the origin of modern humans themselves. But this wasn’t some odd, isolated group; estimates of population size based on the frequency of genetic variation suggest it was substantial.

Instead, the researchers suggest that climate and geography kept the group separate from other African populations and that southern Africa may have served as a climate refuge, providing a safe area from which modern humans could expand out to the rest of the continent when conditions were favorable. That’s consistent with the finding that some of the ancient populations in eastern and western Africa contain some southern African variants by around 5,000 years ago.

As far as genetic traits are concerned, the population looked like pretty much everyone else present at the time: brown eyes, high skin pigmentation, and no lactose tolerance. None of the older individuals had genetic resistance to malaria or sleeping sickness that are found in modern populations. In terms of changes that affect proteins, the most common are found in genes involved in immune function, a pattern that’s seen in many other human populations. More unusually, genes that affect kidney function also show a lot of variation.

So there’s nothing especially distinctive or modern apparent in this population, especially not in comparison to any other populations we know of in Africa at the same time. But they are unusual in that they suggest there was a large, stable, and isolated group from other populations present in Africa at the time. Over time, we’ll probably get additional evidence that fits this population into a coherent picture of human evolution. But for now, its presence is a bit of an enigma, given how often other populations intermingled in our past.

Nature, 2025. DOI: 10.1038/s41586-025-09811-4 (About DOIs).

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AI trained on bacterial genomes produces never-before-seen proteins

AI, bacteria, Biology, Computer science, evolution, Genomics, large language model, Science / Kris Guyer / November 21, 2025

The researchers argue that this setup lets Evo “link nucleotide-level patterns to kilobase-scale genomic context.” In other words, if you prompt it with a large chunk of genomic DNA, Evo can interpret that as an LLM would interpret a query and produce an output that, in a genomic sense, is appropriate for that interpretation.

The researchers reasoned that, given the training on bacterial genomes, they could use a known gene as a prompt, and Evo should produce an output that includes regions that encode proteins with related functions. The key question is whether it would simply output the sequences for proteins we know about already, or whether it would come up with output that’s less predictable.

Novel proteins

To start testing the system, the researchers prompted it with fragments of the genes for known proteins and determined whether Evo could complete them. In one example, if given 30 percent of the sequence of a gene for a known protein, Evo was able to output 85 percent of the rest. When prompted with 80 percent of the sequence, it could return all of the missing sequence. When a single gene was deleted from a functional cluster, Evo could also correctly identify and restore the missing gene.

The large amount of training data also ensured that Evo correctly identified the most important regions of the protein. If it made changes to the sequence, they typically resided in the areas of the protein where variability is tolerated. In other words, its training had enabled the system to incorporate the rules of evolutionary limits on changes in known genes.

So, the researchers decided to test what happened when Evo was asked to output something new. To do so, they used bacterial toxins, which are typically encoded along with an anti-toxin that keeps the cell from killing itself whenever it activates the genes. There are a lot of examples of these out there, and they tend to evolve rapidly as part of an arms race between bacteria and their competitors. So, the team developed a toxin that was only mildly related to known ones, and had no known antitoxin, and fed its sequence to Evo as a prompt. And this time, they filtered out any responses that looked similar to known antitoxin genes.

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The evolution of rationality: How chimps process conflicting evidence

Behavioral science, beliefs, Biology, chimps, evolution, Science / Tim Belzer / November 16, 2025

In the first step, the chimps got the auditory evidence, the same rattling sound coming from the first container. Then, they received indirect visual evidence: a trail of peanuts leading to the second container. At this point, the chimpanzees picked the first container, presumably because they viewed the auditory evidence as stronger. But then the team would remove a rock from the first container. The piece of rock suggested that it was not food that was making the rattling sound. “At this point, a rational agent should conclude, ‘The evidence I followed is now defeated and I should go for the other option,’” Engelmann told Ars. “And that’s exactly what the chimpanzees did.”

The team had 20 chimpanzees participating in all five experiments, and they followed the evidence significantly above chance level—in about 80 percent of the cases. “At the individual level, about 18 out of 20 chimpanzees followed this expected pattern,” Engelmann claims.

He views this study as one of the first steps to learn how rationality evolved and when the first sparks of rational thought appeared in nature. “We’re doing a lot of research to answer exactly this question,” Engelmann says.

The team thinks rationality is not an on/off switch; instead, different animals have different levels of rationality. “The first two experiments demonstrate a rudimentary form of rationality,” Engelmann says. “But experiments four and five are quite difficult and show a more advanced form of reflective rationality I expect only chimps and maybe bonobos to have.”

In his view, though, humans are still at least one level above the chimps. “Many people say reflective rationality is the final stage, but I think you can go even further. What humans have is something I would call social rationality,” Engelmann claims. “We can discuss and comment on each other’s thinking and in that process make each other even more rational.”

Sometimes, at least in humans, social interactions can also increase our irrationality instead. But chimps don’t seem to have this problem. Engelmann’s team is currently running a study focused on whether the choices chimps make are influenced by the choices of their fellow chimps. “The chimps only followed the other chimp’s decision when the other chimp had better evidence,” Engelmann says. “In this sense, chimps seem to be more rational than humans.”

Science, 2025. DOI: 10.1126/science.aeb7565

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World’s oldest RNA extracted from Ice Age woolly mammoth

ancient DNA, ancient RNA, Biology, evolution, Genomics, mammoths, paleontology, Science / Rejus Almole / November 14, 2025

A young woolly mammoth now known as Yuka was frozen in the Siberian permafrost for about 40,000 years before it was discovered by local tusk hunters in 2010. The hunters soon handed it over to scientists, who were excited to see its exquisite level of preservation, with skin, muscle tissue, and even reddish hair intact. Later research showed that, while full cloning was impossible, Yuka’s DNA was in such good condition that some cell nuclei could even begin limited activity when placed inside mouse eggs.

Now, a team has successfully sequenced Yuka’s RNA—a feat many researchers once thought impossible. Researchers at Stockholm University carefully ground up bits of muscle and other tissue from Yuka and nine other woolly mammoths, then used special chemical treatments to pull out any remaining RNA fragments, which are normally thought to be much too fragile to survive even a few hours after an organism has died. Scientists go to great lengths to extract RNA even from fresh samples, and most previous attempts with very old specimens have either failed or been contaminated.

A different view

The team used RNA-handling methods adapted for ancient, fragmented molecules. Their scientific séance allowed them to explore information that had never been accessible before, including which genes were active when Yuka died. In the creature’s final panicked moments, its muscles were tensing and its cells were signaling distress—perhaps unsurprising since Yuka is thought to have died as a result of a cave lion attack.

It’s an exquisite level of detail, and one that scientists can’t get from just analyzing DNA. “With RNA, you can access the actual biology of the cell or tissue happening in real time within the last moments of life of the organism,” said Emilio Mármol, a researcher who led the study. “In simple terms, studying DNA alone can give you lots of information about the whole evolutionary history and ancestry of the organism under study. “Obtaining this fragile and mostly forgotten layer of the cell biology in old tissues/specimens, you can get for the first time a full picture of the whole pipeline of life (from DNA to proteins, with RNA as an intermediate messenger).”

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Dinosaurs may have flourished right up to when the asteroid hit

asteroid, Biology, dinosaurs, evolution, Impact, paleontology, Science / Kris Guyer / October 23, 2025

That seemingly changes as of now, with new argon dating of strata from the Naashoibito Member in the San Juan Basin of present-day New Mexico. Many dinosaur fossils have been obtained from this region, and we know the site differs from the sort of ecosystem found at Hell Creek. But it was previously thought to date back closer to a million years before the mass extinction. The new dates, plus the alignment of magnetic field reversals, tell us that the ecosystem was a contemporary of the one in Hell Creek, and dates to the last few hundred thousand years prior to the mass extinction.

Diverse ecosystems

The fossils at Naashoibito have revealed an ecosystem we now label the “Alamo Wash local fauna.” And they’re fairly distinct from the ones found in Wyoming, despite being just 1,500 kilometers further south. Analyzing the species present using ecological measures, the researchers found that dinosaurs formed two “bioprovinces” in the late Cretaceous—essentially, there were distinct ecosystems present in the northern and southern areas.

This doesn’t seem to be an artifact of the sites, as mammalian fossils seem to reflect a single community across both areas near the mass extinction, but had distinct ecologies both earlier and after. The researchers propose that temperature differences were the key drivers of the distinction, something that may have had less of an impact on mammals, which are generally better at controlling their own temperatures.

Overall, the researchers conclude that, rather than being dominated by a small number of major species, “dinosaurs were thriving in New Mexico until the end of the Cretaceous.”

While this speaks directly to the idea that limited diversity may have primed the dinosaurs for extinction, it also may have implications for the impact of the contemporaneous eruptions in the Deccan Traps. If these were having a major global impact, then it’s a bit unlikely that dinosaurs would be thriving anywhere.

Even with the new data, however, our picture is still limited to the ecosystems present on the North American continent. We do have fossils from elsewhere, but they’re not exactly dated. There are some indications of dinosaurs in the late Cretaceous in Europe and South America, but we don’t have a clear picture of the ecosystems in which they were found. So, while these findings help clarify the diversity of dinosaurs in the time leading up to their extinction, there’s still a lot left to learn.

Science, 2025. DOI: 10.1126/science.adw3282 (About DOIs).

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Fiji’s ants might be the canary in the coal mine for the insect apocalypse

ants, Biology, evolution, Fiji, insects, Science, speciation / Tim Belzer / September 26, 2025

A new genetic technique lets museum samples track population dynamics.

In late 2017, a study by Krefeld Entomological Society looked at protected areas across Germany and discovered that two-thirds of the insect populations living in there had vanished over the last 25 years. The results spurred the media to declare we’re living through an “insect apocalypse,” but the reasons behind their absence were unclear. Now, a joint team of Japanese and Australian scientists have completed a new, multi-year study designed to get us some answers.

Insect microcosm

“In our work, we focused on ants because we have systematic ways for collecting them,” says Alexander Mikheyev, an evolutionary biologist at the Australian National University. “They are also a group with the right level of diversity, where you have enough species to do comparative studies.” Choosing the right location, he explained, was just as important. “We did it in Fiji, because Fiji had the right balance between isolation—which gave us a discrete group of animals to study—but at the same time was diverse enough to make comparisons,” Mikheyev adds.

Thus, the Fijian archipelago, with its 330 islands, became the model the team used to get some insights into insect population dynamics. A key difference from the earlier study was that Mikheyev and his colleagues could look at those populations across thousands of years, not just the last 25.

“Most of the previous studies looked at actual observational data—things we could come in and measure,” Mikheyev explains. The issue with those studies was that they could only account for the last hundred years or so, because that’s how long we have been systematically collecting insect samples. “We really wanted to understand what happened in the longer time frame,” Mikheyev says.

To do this, his team focused on community genomics—studying the collective genetic material of entire groups of organisms. The challenge is that this would normally require collecting thousands of ants belonging to hundreds of species across the entire Fijian archipelago. Given that only a little over 100 out of 330 islands in Fiji are permanently inhabited, this seemed like an insurmountable challenge.

To go around it, the team figured they could run its tests on ants already collected in Fijian museums. But that came with its own set of difficulties.

DNA pieces

Unfortunately, the quality of DNA that could be obtained from museum collections was really bad. From the perspective of DNA preservation, the ants were obtained and stored in horrific conditions, since the idea was to showcase them for visitors, not run genetic studies. “People were catching them in malaise traps,” Mikheyev says. “A malaise trap is basically a bottle of alcohol that sits somewhere in Fiji for a month. Those samples had horribly fragmented, degraded DNA.”

To work with this degraded genetic material, the team employed a technique they called high-throughput museumomics, a relatively new technique that looks at genetic differences across a genome without sequencing the whole thing. DNA sampled from multiple individuals was cut and marked with unique tags at the same repeated locations, a bit like using bookmarks to pinpoint the same page or passage in different issues of the same book. Then, the team sequenced short DNA fragments following the tag to look for differences between them, allowing them to evaluate the genetic diversity within a population. “We developed a series of methods that actually allowed us to harness these museum-grade specimens for population genetics,” Mikheyev explains.

But the trouble didn’t end there. Differences among Fijian ant taxa are based on their appearance, not genetic analysis. For years, researchers were collecting various ants and determining their species by looking at them. This led to 144 species belonging to 40 genera. For Mikheyev’s team, the first step was to look at the genomes in the samples and see if these species divisions were right. It turned out that they were mostly correct, but some species had to be split, while others were lumped together. At the end, the team confirmed that 127 species were represented among their samples.

Overall, the team analyzed more than 4,000 specimens of ants collected over the past decade or so. And gradually, a turbulent history of Fijian ants started to emerge from the data.

The first colonists

The art of reconstructing the history of entire populations from individual genetic sequences relies on comparing them to each other thoroughly and running a whole lot of computer simulations. “We had multiple individuals per population,” Mikheyev explains. “Let’s say we look at this population and find it has essentially no diversity. It suggests that it very recently descended from a small number of individuals.” When the contrary was true and the diversity was high, the team assumed it indicated the population had been stable for a long time.

With the DNA data in hand, the team simulated how populations of ants would evolve over thousands of years under various conditions, and picked scenarios that best matched the genetic diversity results it obtained from real ants. “We identified multiple instances of colonization—broadscale evolutionary events that gave rise to the Fijian fauna that happened in different timeframes,” Mikheyev says. There was a total of at least 65 colonization events.

The first ants, according to Mikheyev, arrived at Fiji millions of years ago and gave rise to 88 endemic Fijian ant species we have today. These ants most likely evolved from a single ancestor and then diverged from their mainland relatives. Then, a further 23 colonization events introduced ants that were native to a broader Pacific region. These ants, the team found, were a mixture of species that colonized Fiji naturally and ones that were brought by the first human settlers, the Lapita people, who arrived around 3,000 years ago.

The arrival of humans also matched the first declines in endemic Fijian ant species.

Slash and burn

“In retrospect, these declines are not really surprising,” Mikheyev says. The first Fijian human colonists didn’t have the same population density as we have now, but they did practice things like slash-and-burn agriculture, where forests were cut down, left to dry, and burned to make space for farms and fertilize the soil. “And you know, not every ant likes to live in a field, especially the ones that evolved to live in a forest,” Mikheyev adds. But the declines in Fijian endemic ant species really accelerated after the first contact with the Europeans.

The first explorers in the 17th and 18th centuries, like Abel Tasman and James Cook, charted some of the Fijian islands but did not land there. The real apocalypse for Fijian ants began in the 19th century, when European sandalwood traders started visiting the archipelago on a regular basis and ultimately connected it to the global trade networks.

Besides the firearms they often traded for sandalwood with local chiefs, the traders also brought fire ants. “Fire ants are native to Latin America, and it’s a common invasive species extremely well adapted to habitats we create: lawns or clear-cut fields,” Mikheyev says. Over the past couple of centuries, his team saw a massive increase in fire ant populations, combined with accelerating declines in 79 percent of endemic Fijian ant species.

Signs of apocalypse

To Mikheyev, Fiji was just a proving ground to test the methods of working with museum-grade samples. “Now we know this approach works and we can start leveraging collections found in museums around the world—all of them can tell us stories about places where they were collected,” Mikheyev says. His ultimate goal is to look for the signs of the insect apocalypse, or any other apocalypse of a similar kind, worldwide.

But the question is whether what’s happening is really that bad? After all, not all ants seem to be in decline. Perhaps what we see is just a case of a better-adapted species taking over—natural selection happening before our eyes?

“Sure, we can just live with fire ants all along without worrying about the kind of beautiful biodiversity that evolution has created on Fiji,” Mikheyev says. “But I feel like if we just go with that philosophy, we’re really going to be irreparably losing important and interesting parts of our ecology.” If the current trends persist, he argues, we might lose endemic Fijian ants forever. “And this would make our world worse, in many ways,” Mikheyev says.

Science, 2025. DOI: 10.1126/science.ads3004

Jacek Krywko is a freelance science and technology writer who covers space exploration, artificial intelligence research, computer science, and all sorts of engineering wizardry.

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