Enlarge / The fossil in question, oriented with its head to the left. (credit: Yang Jie / Zhang Xiguang)

Around half a billion years ago, in what is now the Yunnan Province of China, a tiny larva was trapped in mud. Hundreds of millions of years later, after the mud had long since become the black shales of the Yuan’shan formation, the larva surfaced again, a meticulously preserved time capsule that would unearth more about the evolution of arthropods.

Youti yuanshi is barely visible to the naked eye. Roughly the size of a poppy seed, it is preserved so well that its exoskeleton is almost completely intact, and even the outlines of what were once its internal organs can be seen through the lens of a microscope. Durham University researchers who examined it were able to see features of both ancient and modern arthropods. Some of these features told them how the simpler, more wormlike ancestors of living arthropods evolved into more complex organisms.

The research team also found that Y. yuanshi, which existed during the Cambrian Explosion (when most of the main animal groups started to appear on the fossil record), has certain features in common with extant arthropods, such as crabs, velvet worms, and tardigrades. “The deep evolutionary position of Youti yuanshi… illuminat[es] the internal anatomical changes that propelled the rise and diversification of [arthropods],” they said in a study recently published in Nature.

Enlarge / This is an intact phage. A tailocin looks like one of these with its head cut off. (credit: iLexx )

Long before humans became interested in killing bacteria, viruses were on the job. Viruses that attack bacteria, termed "phages" (short for bacteriophage), were first identified by their ability to create bare patches on the surface of culture plates that were otherwise covered by a lawn of bacteria. After playing critical roles in the early development of molecular biology, a number of phages have been developed as potential therapies to be used when antibiotic resistance limits the effectiveness of traditional medicines.

But we're relative latecomers in terms of turning phages into tools. Researchers have described a number of cases where bacteria have maintained pieces of disabled viruses in their genomes and converted them into weapons that can be used to kill other bacteria that might otherwise compete for resources. I only just became aware of that weaponization, thanks to a new study showing that this process has helped maintain diverse bacterial populations for centuries.

Evolving a killer

The new work started when researchers were studying the population of bacteria associated with a plant growing wild in Germany. The population included diverse members of the genus Pseudomonas , which can include plant pathogens. Normally, when bacteria infect a new victim, a single strain expands dramatically as it successfully exploits its host. In this case, though, the Pseudomonas population contained a variety of different strains that appeared to maintain a stable competition.

Enlarge / Transmission electron micrograph of a SARS-CoV-2 virus particle isolated from a patient sample and cultivated in cell culture. (credit: Getty | BSIP )

A remarkably mutated coronavirus variant classified as BA.2.86 seized scientists' attention last week as it popped up in four countries, including the US.

So far, the overall risk posed by the new subvariant is unclear. It's possible it could lead to a new wave of infection; it's also possible (perhaps most likely) it could fizzle out completely. Scientists simply don't have enough information to know. But, what is very clear is that the current precipitous decline in coronavirus variant monitoring is extremely risky.

In a single week, BA.2.86 was detected in four different countries, but there are only six genetic sequences of the variant overall —three from Denmark, and one each from Israel, the UK, and the US (Michigan). The six detections suggest established international distribution and swift spread. It's likely that more cases will be identified. But, with such scant data, little else can be said of the variant's transmission or possible distribution.

Enlarge / Artist's conception of the newly found species. (credit: Matheus Fernandes)

It was relatively small in comparison to the giants that would follow it later in Earth’s history. With a hip height of approximately 0.3 meters (about a foot) and a length of perhaps a meter (roughly three feet), this ancient reptile existed long before the evolution of the pterosaurs most of us recognize.

Its most striking features are its skull and hands, two body parts that rarely survive fossilization among similar animals this old. The skull consists of a raptorial-like beak without teeth, while its forelimbs end in long fingers with scimitar-like claws. These two surprising features are among many revelations in a paper published Wednesday in Nature.

Venetoraptor gassenae is the name of this new species of lagerpetid, a type of pterosaur precursor that lived about 230 million years ago in Brazil. Named for the district of Vale Vêneto in the same municipality in which the fossil was found—and for the plundering it might have done with its beak and claws ("raptor" is Latin for "plunderer")—it is also named to honor Valserina Maria Bulegon Gassen. Although not a paleontologist herself, the authors note that she is “one of the main people responsible for the CAPPA/UFSM ” (the Centro de Apoio à Pesquisa Paleontológica da Quarta Colônia, Universidade Federal de Santa Maria), a paleontological research support center).

Enlarge / It takes careful study and the right kind of bones to determine how something like this breathed. (credit: Tito Aureliano et. al. )

Somewhere in Earth’s past, some branches on the tree of life adopted a body plan that made breathing and cooling down considerably more efficient than how mammalian bodies like ours do it. This development might not seem like much on the surface, until you consider that it may have ultimately enabled some of the largest dinosaurs this planet has ever known. It was so successful that it was maintained by three different groups of extinct species and continues to exist today in the living descendants of dinosaurs.

Because lungs don’t usually survive fossilization, one might wonder how scientists are able to ascertain anything about the breathing capabilities of extinct species. The answer lies within their bones.

In a suite of papers published in late 2022 and early 2023 , paleontologists examined fossil microstructure within some of the earliest known dinosaurs to determine just how early parts of this system evolved.

Enlarge (credit: Raymond Gehman / Getty Images )

People in the US transmitted the pandemic coronavirus to white-tailed deer at least 109 times, and the animals widely spread the virus among themselves, with a third of the deer tested in a large government-led study showing signs of prior infection. The work also suggests that the ubiquitous ruminants returned the virus to people in kind at least three times.

The findings, announced this week by the US Department of Agriculture, are in line with previous research, which suggested that white-tailed deer can readily pick up SARS-CoV-2 from humans, spread it to each other , and, based on at least one instance in Canada, transmit the virus back to humans .

But the new study , led by the USDA's Animal and Plant Health Inspection Service (APHIS), provides a broader picture of deer transmission dynamics in the US and ultimately bolsters concern that white-tailed deer have the potential to be a virus reservoir. That is, populations of deer can acquire and harbor SARS-CoV-2 viral lineages, which can adapt to their new hosts and spill back over to humans, causing new waves of infection. It's conceivable that viruses moving from deer to humans could at some point qualify as new variants, potentially with the ability to dodge our immune protections built up from past infection and vaccination.

Enlarge / Artist's reconstruction of the shark as it once lived. (credit: Klug et. al. )

Sharks are largely cartilaginous, a body structure that often doesn’t survive fossilization. But in a paper published in the Swiss Journal of Paleontology, scientists describe an entirely new species of primitive shark from the Late Devonian period, a time when they were just beginning to proliferate in ancient oceans.

The team found several exceptionally well-preserved fossils that include soft tissues such as scales, musculature, digestive tract, liver, and blood vessel imprints. Also preserved: the species’ most distinct feature, widely separated nasal organs, somewhat akin to those on today’s hammerhead sharks. The find suggests that sharks’ finely tuned sense of smell, the subject of urban legends, was already being selected for just as these predators were becoming established.

A key time and a rare find

Christian Klug is the lead author and curator of the Paleontological Institute and Museum at Zurich University. He explained the significance of the Devonian period in the oceans’ history, when life was flourishing and an evolutionary arms race was in full swing. “With increasing competition among predators inhabiting the water column, the entire organism was selected for more efficiency,” he explained. “This affected swimming abilities, feeding apparatus, but also the sensory systems, which are essential to detect prey, to orient themselves in space, and to escape from even larger predators such as the huge placoderm Dunkleosteus and the equally large shark Ctenacanthus .”

Enlarge / All steroids past and present share the complex ringed structure but differ in terms of the atoms attached to those rings. (credit: KATERYNA KON/SCIENCE PHOTO LIBRARY )

All of the organisms we can see around us—the plants, animals, and fungi—are eukaryotes composed of complex cells. Their cells have many internal structures enclosed in membranes, which keep things like energy production separated from genetic material, and so on. Even the single-celled organisms on this branch of the tree of life often have membrane-covered structures that they move and rearrange for feeding.

Some of that membrane flexibility comes courtesy of steroids. In multicellular eukaryotes, steroids perform various functions; among other things, they’re used as signaling molecules, like estrogen and testosterone. But all eukaryotes insert various steroids into their membranes, increasing their fluidity and altering their curvature. So the evolution of an elaborate steroid metabolism may have been critical to enabling complex life.

Now, researchers have traced the origin of eukaryotic steroids almost a billion years further back in time. The results suggest that many branches of the eukaryotic family tree once made early versions of steroids. But our branch evolved the ability to produce more elaborate ones—which may have helped us outcompete our relatives.

Enlarge (credit: Beth Zaiken)

An international team of scientists has published the results of their research into 23 woolly mammoth genomes in Current Biology . As of today, we have even more tantalizing insights into their evolution, including indications that, while the woolly mammoth was already predisposed to life in a cold environment, it continued to make further adaptations throughout its existence.

Years of research, as well as multiple woolly mammoth specimens, enabled the team to build a better picture of how this species adapted to the cold tundra it called home. Perhaps most significantly, they included a genome they had previously sequenced from a woolly mammoth that lived 700,000 years ago, around the time its species initially branched off from other types of mammoth. Ultimately, the team compared that to a remarkable 51 genomes—16 of which are new woolly mammoth genomes: the aforementioned genome from Chukochya, 22 woolly mammoth genomes from the Late Quaternary, one genome of an American mastodon (a relative of mammoths), and 28 genomes from extant Asian and African elephants.

From that dataset, they were able to find more than 3,000 genes specific to the woolly mammoth. And from there, they focused on genes where all the woolly mammoths carried sequences that altered the protein compared to the version found in their relatives. In other words, genes where changes appear to have been naturally selected.