evolution

The evolution of rationality: How chimps process conflicting evidence

Behavioral science, beliefs, Biology, chimps, evolution, Science / Beth Washington / 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 / Beth Washington / 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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Corals survived past climate changes by retreating to the deeps

Biology, climate change, corals, evolution, extinction, Florida, mass extinction, Science / DJ Henderson / November 12, 2025

A recent die-off in Florida puts the spotlight on corals’ survival strategies.

Scientists have found that the 2023 marine heat wave caused “functional extinction” of two Acropora reef-building coral species living in the Florida Reef, which stretches from the Dry Tortugas National Park to Miami.

“At this point, we do not think there’s much of a chance for natural recovery—their numbers are so low that successful reproduction is incredibly unlikely,” said Ross Cunning, a coral biologist at the John G. Shedd Aquarium.

This isn’t the first time corals have faced the borderline of extinction over the last 460 million years, and they have always managed to bounce back and recolonize habitats lost during severe climate changes. The problem is that we won’t live long enough to see them doing that again.

Killer heat waves

Marine heat waves kill corals by messing with the photosynthetic machinery of symbiotic microalgae that live in the corals’ tissues. When the temperature of water goes up too much, the microalgae start producing reactive oxygen species instead of nutritious sugars. The reactive oxygen is toxic to corals, which respond by expelling the microalgae. This solves the toxicity problem, but it also starves the corals and causes them to bleach (the algae are the source of their yellowish color).

The 2023 marine heat wave was not the first to hit the Florida Reef—it was the ninth on record. “Those eight previous heat waves also had major negative effects on coral reefs, causing widespread mortality,” Cunning told Ars. “But the 2023 heat wave blew all other heat waves out of the water. It was 2.2 to four times greater in magnitude than anything that came before it.”

Cunning’s team monitored two Acropora coral species: the staghorn and elkhorn. “They are both branching corals,” Cunning explained. “The staghorn has pointy branches that form dense thickets, whereas elkhorn produces arm-like branches that reach up and grow toward the surface, producing highly complex three dimensionality, like a canopy in the forest.”

He and his colleagues chose those two species because they essentially built the Florida Reef. They also grow the fastest among all Florida Reef corals, which means they are essential for its ability to recover from damage. “Acropora corals were the primary reef builders for the last ten thousand years,” Cunning said. Unfortunately, they also showed the highest levels of mortality due to heat waves.

Coral apocalypse

Cunning’s team found the mortality rate among Acropora corals reached 100 percent in the Dry Tortugas National Park, which is at the southernmost end of the Florida Reef. Moving north to Lower Keys, Middle Keys, and most of the Upper Keys, the mortality stayed at between 98 and 100 percent.

“Once you start moving a little bit further north, there’s the Biscayne National Park, where mortality rates were at 90 percent,” Cunning said. “It wasn’t until the furthest northern extent of the reef in Miami and Broward counties where mortality dropped to just 38 percent thanks to cooler temperatures that occurred there.”

Still, the mortality rate was exceptionally high throughout most of Acropora colonies across the Florida Reef. “What we’re facing is a functional extinction,” Cunning said.

But corals have been around for about 460 million years, and they have survived multiple mass extinction events, including the one that wiped out the dinosaurs. As vulnerable as they appear, corals seemingly have some get-out-of-death card they always pull when things turn really bad for them. This card, most likely, is buried deep in their genome.

Ancestral strength

“There have been studies looking into the evolutionary history of corals, but the difference between those and our work lies in technology,” said Claudia Francesca Vaga, a marine biologist at the Smithsonian Institution.

Her team looked at ultra conserved elements, stretches of DNA that are nearly identical across even distantly related species. These elements were used to build the most extensive phylogenetic tree of corals to date. Based on the genomic data and fossil evidence, Vaga’s team analyzed how 274 stony coral species are related to one another to retrace their common ancestor and reconstruct how they evolved from it.

“We managed to confirm that the first common ancestor of stony corals was most likely solitary—it didn’t live in colonies, and it didn’t have symbionts,” Vaga said.

The very first coral most likely did not rely on algae to produce its nutrients, which means it was immune to bleaching. It was also not attached to a substrate, so it could move from one habitat to another. Another advantage the first corals had was that they were not particularly picky—they could live just as well in the shallow waters as in the deep sea, since they didn’t get most of their nutrients from their photosynthetic symbionts.

Descending from these incredibly resilient ancestors, corals started to specialize. “We learned that symbiosis and coloniality can be acquired independently by stony coral linages and that it happened multiple times,” Vaga said.

Based on her team’s research, past mass extinction events usually wiped out 90 percent of the species living in shallow waters—the ones that were colonial and reliant on symbionts. “But each such extinction triggered a process of retaking the shallows by the more resilient deep-sea corals, which in time evolved symbiosis and coloniality again,” Vaga said.

Thanks to corals’ deep-sea cousins, even the most extreme environmental changes—global warming or sudden, severe variations in the oceans’ acidity or oxygen levels—could not kill them for good. Each mass extinction event they’ve been through just reverted them to factory settings and made them start over from scratch.

The only catch here is time. “We’re talking about four to five million years before coral populations recover,” Vaga said.

Long way back

According to Cunning, the consequence of Acropora corals’ extinction in the Florida Reef is a lower overall reef-building rate, which will lead to reduced biodiversity in the reef’s ecosystem. “There are going to be cascading effects, and humans will be impacted as well. Reefs protect our coastlines by buffering over 90 percent of wave energy,” Cunning said.

In Florida, where coastlines are heavily urbanized, this may translate into hundreds of millions of dollars per year in damages.

But Cunning said we still have means at our disposal to save Acropora corals. “We’re not going to give up on them,” he said.

One option for improving the resilience of corals could be to crossbreed them with species from outside of Florida Reef, ideally ones that live in warmer places and are better adapted to heat. “The first tests of this approach are underway right now in Florida; elkhorn corals were cross bred between Florida parents and Honduran parents,” Cunning said. He hopes this will help produce a new generation of corals that has a better shot at surviving the next heat wave.

Other interventions include manipulating corals’ algal symbionts. “There are many different species of algae with different levels of heat tolerance,” Cunning said. To him, a possible way forward would be to pair the Acropora corals with more heat-tolerant symbionts. “This should alter the bleaching threshold in these corals,” he explained.

Still, even interventions like these will take a very long time to make a difference. “But if four or five million years is the benchmark to beat, then yeah, it’s hopefully going to happen faster than that,” Cunning said.

The upside is that corals will likely pull off their de-extinction trick once again, even if we do absolutely nothing to help them. “In a few million years, they will redevelop coloniality, redevelop symbiosis, and rebuild something similar to the coral reefs we have today,” Vaga said. “This is good news for them. Not necessarily for us.”

Science, 2025. DOI: 10.1126/science.adx7825

Nature, 2025. DOI: 10.1038/s41586-025-09615-6

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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Dinosaurs may have flourished right up to when the asteroid hit

asteroid, Biology, dinosaurs, evolution, Impact, paleontology, Science / Mike M. / October 25, 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 / Beth Washington / 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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You can hold on to your butts thanks to DNA that evolved in fish

Biology, Development, evolution, how genes, limbs, Science / DJ Henderson / September 18, 2025

There were some indications that the same thing is true in fish, where the elimination of equivalent hox genes also interfered with the formation of the rays at the ends of fins. This would suggest that digits formed by elaborating on a genetic system that already existed in order to produce fins.

However, when a US-French team started looking at the regulation of one set of hox genes in the limbs, things turned out to be a bit more complicated. The hox gene clusters have two chunks of regulatory DNA that help set the activity of the genes within the cluster, one upstream of the genes, one downstream. (For the molecular biologists among us, that’s on the 5′ and 3′ sides of the gene cluster.) And we know that in vertebrates, some of the key regulatory DNA for one of the clusters is on the upstream side, since deleting it left all the genes in the cluster inactive in the region of the limb where digits form.

Same place, different reasons

So, the research team behind the new work deleted the equivalent region in a fish (the zebrafish) using the gene editing tool CRISPR. And, deleting the same area that wipes out hox gene activity in the digits in mice did… not very much. The hox gene activity was slightly reduced, but these genes were still active in the right place at the right time to make digits. So, while the activity looked the same, the reasons for the activity seem to be different in fish and mice. Which means that hox activity in the digits isn’t the ancestral state; instead, it seems to have evolved separately in the ray-finned fish and vertebrate lineages.

So, the researchers asked a simple question: If the regulatory DNA they deleted didn’t activate these genes in the limb, where was it needed? So, the researchers looked at where these hox genes were active in fish with and without the deletion. They found one region where it seems to matter: the developing cloaca. In fish, the cloaca is a single orifice that handles excretion (both urine and fecal material) as well as reproduction. So, it’s basically the fish equivalent of our rear ends.

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Genetically, Central American mammoths were weird

ancient DNA, Biology, evolution, mammoths, mexico, Science, woolly mammoth / DJ Henderson / August 29, 2025

This led a Mexican-European research collaboration to get interested in finding DNA from elsewhere in the Columbian mammoth’s range, which extended down into Central America. The researchers focused on the Basin of Mexico, which is well south of where any woolly mammoths were likely to be found. While the warmer terrain generally tends to degrade DNA more quickly, the team had a couple of things working in its favor. To begin with, there were a lot of bones. The Basin of Mexico has been heavily built up over the centuries, and a lot of mammoth remains have been discovered, including over 100 individuals during the construction of Mexico City’s international airport.

In addition, the team focused entirely on the mitochondrial genome. In contrast to the two sets of chromosomes in each cell, a typical cell might have hundreds of mitochondria, each of which could have dozens of copies of its genome. So, while the much smaller mitochondria don’t provide as much detail about ancestry, they’re at least likely to survive at high enough levels to provide something to work with.

And indeed they did. Altogether, the researchers obtained 61 new mitochondrial genomes from the mammoths of Mexico from the 83 samples they tested. Of these, 28 were considered high enough quality to perform an analysis.

Off on their own

By building a family tree using this genetic data, along with that from other Columbian and woolly mammoth samples, the researchers could potentially determine how different populations were related. And one thing became very clear almost immediately: They were in a very weird location on that tree.

To begin with, all of them clustered together in a single block, although there were three distinct groupings within that block. But the placement of that block within the larger family tree was notably strange. To begin with, there were woolly mammoths on either side of it, suggesting the lineage was an offshoot of woolly mammoths. That would make sense if all Columbian mammoths clustered together with the Mexican ones. But they don’t. Some Columbian mammoths from much farther north are actually more closely related to woolly mammoths than they are to the Mexican mammoths.

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New dinosaur species is the punk rock version of an ankylosaur

ankylosaurs, Biology, dinosaurs, evolution, paleontology, Science / Beth Washington / August 28, 2025

And we have known for sure that the armor was around back then, given that we’ve found the skin-derived osteoderms that comprise the armor in Jurassic deposits. But with little more than a rib and a handful of mouth parts to go on, it wasn’t really possible to say much more than that.

Until now, that is. Because the new Spicomellus remains show extremely clearly that the armor of ankylosaurs got less elaborate over time.

The small, solid-looking spikes found along the edges of later ankylosaurs? Forget those. Spicomellus had a back that was probably bristling with sharper spines, along with far larger ones along its outer edges. Each rib appears to have generated as many as six individual spikes. At a handful of locations, these spikes extended out to nearly a meter, looking more like lances than anything needed to ward off a close-in attack.

And the largest of these were along its neck. On the upper surface of its neck, several osteoderms fused to form a massive half-collar of bone and then extended out five or more individual spikes, each among the longest on the animal’s body. And there were three of these structures along the neck. “No known ankylosaur possesses any condition close to the extremely long pairs of spines on the cervical half-ring of Spicomellus,” its discoverers note.

As if its hedgehog-on-acid appearance weren’t enough, handles present on the tail vertebrae suggest that it also had a weaponized tail. All told, the researchers sum things up by saying, “The new specimen reveals extreme dermal armour modifications unlike those of any other vertebrate, extinct or extant, which fall far outside of the range of morphologies shown by other armoured dinosaurs.”

Out go the hypotheses

Because it’s so unusual, the skeleton’s characteristics are difficult to place within a neat family tree of the ankylosaurs. The researchers conclude that some details of its skeleton do suggest Spicomellus groups among the ankylosaurs and conclude that it’s probably an early branch from the main lineage. But without any other significant examples from the lineage at that time, it’s an extremely tentative conclusion. Still, the alternative is that this thing is unrelated to the only other organisms that share at least a few of its bizarre features, which is a difficult idea to swallow.

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Mammals that chose ants and termites as food almost never go back

ants, Biology, diet, evolution, mammals, Science, termintes / Kelly Newman / August 21, 2025

Insects are more influential than we realize

By showing that ant- and termite-based diets evolved repeatedly, the study highlights the overlooked role of social insects in shaping biodiversity. “This work gives us the first real roadmap, and what really stands out is just how powerful a selective force ants and termites have been over the last 50 million years, shaping environments and literally changing the face of entire species,” Barden said.

However, according to the study authors, we still do not have a clear picture of how much of an impact insects have had on the history of life on our planet. Lots of lineages have been reshaped by organisms with outsize biomass—and today, ants and termites have a combined biomass exceeding that of all living wild mammals, giving them a massive evolutionary influence.

However, there’s also a flip side. Eight of the 12 myrmecophagous origins are represented by just a single species, meaning most of these lineages could be vulnerable if their insect food sources decline. As Barden put it, “In some ways, specializing in ants and termites paints a species into a corner. But as long as social insects dominate the world’s biomass, these mammals may have an edge, especially as climate change seems to favor species with massive colonies, like fire ants and other invasive social insects.”

For now, the study authors plan to keep exploring how ants, termites, and other social insects have shaped life over millions of years, not through controlled lab experiments, but by continuing to use nature itself as the ultimate evolutionary archive. “Finding accurate dietary information for obscure mammals can be tedious, but each piece of data adds to our understanding of how these extraordinary diets came to be,” Vida argued.

Evolution, 2025. DOI: 10.1093/evolut/qpaf121 (About DOIs)

Rupendra Brahambhatt is an experienced journalist and filmmaker. He covers science and culture news, and for the last five years, he has been actively working with some of the most innovative news agencies, magazines, and media brands operating in different parts of the globe.

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Carnivorous crocodile-like monsters used to terrorize the Caribbean

Biology, crocodiles, evolution, migration, predators, Science / Kelly Newman / May 17, 2025

How did reptilian things that looked something like crocodiles get to the Caribbean islands from South America millions of years ago? They probably walked.

The existence of any prehistoric apex predators in the islands of the Caribbean used to be doubted. While their absence would have probably made it even more of a paradise for prey animals, fossils unearthed in Cuba, Puerto Rico, and the Dominican Republic have revealed that these islands were crawling with monster crocodyliform species called sebecids, ancient relatives of crocodiles.

While sebecids first emerged during the Cretaceous, this is the first evidence of them lurking outside South America during the Cenozoic epoch, which began 66 million years ago. An international team of researchers has found that these creatures would stalk and hunt in the Caribbean islands millions of years after similar predators went extinct on the South American mainland. Lower sea levels back then could have exposed enough land to walk across.

“Adaptations to a terrestrial lifestyle documented for sebecids and the chronology of West Indian fossils strongly suggest that they reached the islands in the Eocene-Oligocene through transient land connections with South America or island hopping,” researchers said in a study recently published in Proceedings of the Royal Society B.

Origin story

During the late Eocene to early Oligocene periods of the mid-Cenozoic, about 34 million years ago, many terrestrial carnivores already roamed South America. Along with crocodyliform sebecids, these included enormous snakes, terror birds, and metatherians, which were monster marsupials. At this time, the sea levels were low, and the islands of the Eastern Caribbean are thought to have been connected to South America via a land bridge called GAARlandia (Greater Antilles and Aves Ridge). This is not the first land bridge to potentially provide a migration opportunity.

Fragments of a single tooth unearthed in Seven Rivers, Jamaica, in 1999 are the oldest fossil evidence of a ziphodont crocodyliform (a group that includes sebecids) in the Caribbean. It was dated to about 47 million years ago, when Jamaica was connected to an extension of the North American continent known as the Nicaragua Rise. While the tooth from Seven Rivers is thought to have belonged to a ziphodont other than a sebacid, that and other vertebrate fossils found in Jamaica suggest parallels with ecosystems excavated from sites in the American South.

The fossils found in areas like the US South that the ocean would otherwise separate suggest more than just related life forms. It’s possible that the Nicaragua Rise provided a pathway for migration similar to the one sebecids probably used when they arrived in the Caribbean islands.

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Some flies go insomniac to ward off parasites

Biology, circadian rhythm, Drosophila, evolution, fruit flies, parasites, Science / Mike M. / May 2, 2025

Those genes associated with metabolism were upregulated, meaning they showed an increase in activity. An observed loss of body fat and protein reserves was evidently a trade-off for resistance to mites. This suggests there was increased lipolysis, or the breakdown of fats, and proteolysis, the breakdown of proteins, in resistant lines of flies.

Parasite paranoia

The depletion of nutrients could make fruit flies less likely to survive even without mites feeding off them, but their tenaciousness when it comes to staying up through the night suggests that being parasitized by mites is still the greater risk. Because mite-resistant flies did not sleep, their oxygen consumption and activity also increased during the night to levels no different from those of control group flies during the day.

Keeping mites away involves moving around so the fly can buzz off if mites crawl too close. Knowing this, Benoit wanted to see what would happen if the resistant flies’ movement was restricted. It was doom. When the flies were restrained, the mite-resistant flies were as susceptible to mites as the controls. Activity alone was important for resisting mites.

Since mites are ectoparasites, or external parasites (as opposed to internal parasites like tapeworms), potential hosts like flies can benefit from hypervigilance. Sleep is typically beneficial to a host invaded by an internal parasite because it increases the immune response. Unfortunately for the flies, sleeping would only make them an easy meal for mites. Keeping both stereoscopic eyes out for an external parasite means there is no time left for sleep.

“The pattern of reduced sleep likely allows the flies to be more responsive during encounters with mites during the night,” the researchers said in their study, which was recently published in Biological Timing and Sleep. “There could be differences in sleep occurring during the day, but these differences may be less important as D. melanogaster sleeps much less during the day.”

Fruit flies aren’t the only creatures with sleep patterns that parasites disrupt. Evidence of shifts in sleep and rest in birds and bats has been shown to happen when there is a risk of parasitism after dark. For the flies, exhaustion has the upside of better fertility if they manage to avoid bites, so a mate must be worth all those sleepless nights.

Biological Timing and Sleep, 2025. DOI: 10.1038/s44323-025-00031-7

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Newly hatched hummingbird looks, acts like a toxic caterpillar

Biology, evolution, hummingbirds, mimicry, Science / DJ Henderson / April 6, 2025

Further observation of the nest revealed that the female hummingbird had added to its hatchling’s caterpillar camouflage by lining the nest with hairy-looking material from the seeds of balsa trees. The researchers also noticed that, whenever they approached the nest to film, the chick would move its head upward and start shaking it sideways while its feathers stood on end. It was trying to make itself look threatening.

When the research team backed off, the hummingbird chick went back to laying low in its nest. They wondered whether it behaved this way with actual predators, but eventually saw a wasp known to prey on young hummingbirds creep close to the nest. The chick displayed the same behavior it had with humans, which succeeded in scaring the wasp off.

Falk determined that the feathers, color, and head-shaking were eerily similar to the larvae of moths in the Megalopygidae and Saturniidae families, which are also endemic to the region. They might not be the mirror image of a particular species, but they appear close enough that predators would consider themselves warned.

“The behavior of the white-necked jacobin, when approached by humans and a predatory wasp, resembles the sudden ‘thrashing’ or ‘jerking’ behavior exhibited by many caterpillars in response to disturbance, including in the habitat where this bird was found,” he said regarding the same study.

…now you don’t

Could there be an alternate explanation for this hummingbird cosplaying as a caterpillar? Maybe. The researchers think it’s possible that the long feathers that appear to mimic spines may have evolved as a form of crypsis, or camouflage that helps an organism blend in with its background. The balsa tree material that’s similar to the feathers obviously helped with this.

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