Enlarge / A mammoth tusk thaws out of the ground in Siberia.

Ancient DNA has revolutionized how we understand human evolution, revealing how populations moved and interacted and introducing us to relatives like the Denisovans, a "ghost lineage" that we wouldn't realize existed if it weren't for discovering their DNA. But humans aren't the only ones who have left DNA behind in their bones, and the same analyses that worked for humans can work for any other group of species.

Today, the mammoths take their turn in the spotlight, helped by what appears to be the oldest DNA ever sequenced. DNA from three ancient molars, one likely to be over a million years old, has revealed that there is a ghost lineage of mammoths that interbred with distant relatives to produce the North American mammoth population.

Dating and the mammoth family tree

Mammoths share something with humans: like us, they started as an African population but spread across much of the planet. Having spread out much earlier, mammoth populations spent enough time separated from each other to form different species. After branching off from elephants, the mammoths first split into what are called southern and steppe species. Later still, adaptations to ice age climates produced the woolly mammoth and its close relative, the North American mammoth, called the Columbian mammoth. All of those species, however, are extinct, and the only living relatives are the elephants.

Enlarge / The structure of the SARS-CoV-2 spike protein. (credit: University of Arkansas )

Over the summer, you could almost hear a sigh of relief rising from the portion of the research community that was tracking the evolution of the SARS-CoV-2 virus. Viruses, especially those new to their hosts, often pick up mutations that help them adapt to their new habitat, or they evade drugs or immune attacks. But SARS-CoV-2 seemed to be picking up mutations at a relatively sedate pace, in part because its virus-copying enzymes had a feature that lets them correct some errors.

But suddenly, new variants appear to be everywhere , and a number of them appear to increase the threat posed by the virus. A new study helps explain the apparent difference: while new base changes in the virus' genetic material remain rare, some deletions of several bases appear to have evolved multiple times, indicating that evolution was selecting for them. The research team behind this new work found evidence that these changes alter how the immune system can respond to the virus.

This looks familiar

The researchers' interest in deletions started with their involvement with an immunocompromised cancer patient, who held off the infection for over two months without being able to clear the virus. Samples obtained from late in the infection revealed two different virus strains that each had a deletion in the gene encoding the spike protein that SARS-CoV-2 uses to attach to and enter cells.

Enlarge / This poor fossilized assassin bug's tiny penis is being closely scrutinized by paleontologists who consider the find "a rare treat"—because it has been so extraordinarily preserved. (credit: Daniel R. Swanson/Sam W. Heads)

A rare fossilized assassin bug is causing a bit of a stir in entomology circles, because it is so remarkably well-preserved that one can distinctly pick out its penis. The specimen dates back 50 million years to the Eocene epoch , meaning this particular taxonomic group may be twice as old as scientists previously assumed. The University of Illinois, Urbana-Champaign (UIUC) researchers who conducted the analysis described their unusual find in a new paper published in the Journal of Paleontology.

"Getting a complete fossilized insect is really rare, but getting a fossil of an insect from this long ago, that has this much detail, is pretty amazing and exciting," Gwen Pearson of UIUC's Department of Entomology, who is not a co-author on the paper, told Ars. Assassin bugs (part of the Reduviidae family, of the order Hemiptera ) are predators favored by gardeners because they eat pests. The mouth is distinctly shaped like a straw, the better to poke into the body of its prey, like a juice box, and slurp out the guts.

But of course, it's the preserved genitalia that make this fossilized specimen so exciting. The genitalia are contained within a shell—Ruth Schuster, writing at Haaretz , described the penis (technically its "pygophore") of the assassin bug as a "chitinous codpiece"—which is why it's difficult to tell whether a given insect specimen is male or female. In addition to the pygophore and the telltale stripes on the legs, the new fossil also distinctly shows the "basal plate," a structure shaped like a stirrup that supports the penis.

Enlarge / Picture of vials of Russia's Sputnik V vaccine against the novel coronavirus disease, COVID-19, seen at the Cotahuma Hospital in La Paz, Bolivia. (credit: Jorge Bernal/Getty Images )

Yesterday, the people behind Russia's leading vaccine, termed Sputnik V, issued a preliminary analysis of its function. The news was quite good: while the trial is ongoing and final results will have to wait, the interim data suggest that the vaccine could be over 90 percent effective.

Sputnik V is based on similar technology to the vaccines being developed by Johnson & Johnson and the Oxford/AstraZeneca collaborations. Strikingly, however, the preliminary efficiency is quite a bit higher than those vaccines are showing, and it's not clear how the Sputnik-specific features could possibly account for the difference.

Sounds great!

The results come out of a Phase III clinical trial involving roughly 21,000 participants being run in Moscow. Participants were all over the age of 18, hadn't received other vaccinations recently, weren't pregnant or drug users, and met a number of other criteria. PCR-based SARS-CoV-2 tests were performed at enrollment, and participants were also tested for the presence of antibodies against the virus.

Enlarge / Aerial view showing a tractor digging graves in a new area of the Nossa Senhora Aparecida, where COVID-19 victims are buried, in Manaus, Brazil. (credit: Marcio James / Getty Images )

While attention has been focused on the worrying new variants of SARS-CoV-2, there has been some good news: despite the evolution of a number of strains that appear to spread more readily, total COVID-19 cases have been dropping, both in the United States and globally. While there are a number of nations that are still seeing an increase in infections, a combination of reduced post-holiday spread and increased social interventions appear to be getting the surges seen in January under control.

That said, there are worrying signs that, at least in the US, a number of states are making the same mistakes that ensured that the virus never really went away after the first surge in cases. And the spread of many new variants drives home the need to avoid complacency.

Going down

The general fall in cases came up at a recent press briefing from the World Health Organization. "For the third week in a row, the number of new cases of COVID-19 reported globally fell last week," said WHO Director-General Tedros Adhanom Ghebreyesus. "There are still many countries with increasing numbers of cases, but at the global level, this is encouraging news."

Enlarge / Look at this lovely cube-shaped piece of poo, courtesy of the Australian bare-nosed wombat. (credit: Patricia J. Yang et al., 2021)

Scientists have been puzzling for decades over how the Australian bare-nosed wombat poops out neat little cubes of feces instead of tapered cylinders like pretty much all other animals. According to a new paper published in the journal Soft Matter, the secret lies in their intestines, which have varying stiff and soft regions that serve to shape the poo during the digestive process. Earlier preliminary findings by the same group won the 2019 Ig Nobel Physics Prize.

"Bare-nosed wombats are renowned for producing distinctive, cube-shaped poos. This ability to form relatively uniform, clean cut feces is unique in the animal kingdom," said University of Tasmania wildlife ecologist Scott Carver , a co-author on the paper. "They place these feces at prominent points in their home range, such as around a rock or a log, to communicate with each other. Our research found that these cubes are formed within the last sections of the intestine—and finally proves that you really can fit a square peg through a round hole."

Zoologist Eric Guiler first noted the unusual shape of wombat droppings in 1960, and to date, wombats are the only known animals to produce six-sided cube-shaped poo. It's one of several examples of naturally occurring pattern formation, such as the columns of Ireland's Giant's Causeway (formed by cooling lava), or how vibrating membranes can make grains of sand form " Chladni figures ." But naturally occurring cube shapes are extremely rare. The Australian bare-nosed wombat ( Vombatus ursinus ) can pump out as many as 100 cube-shaped droppings a day.

A rotational deceleration experiment with egg yolk, using an egg scrambler and measuring the soft matter deformation, to find possible answers about concussions. (video link)

A growing number of professional football players have been diagnosed with a neurodegenerative disease called chronic traumatic encephalopathy (CTE), likely the result of suffering repeated concussions or similar repetitive brain trauma over the course of their careers. It's also common in other high-contact sports like boxing, Muay Thai, kickboxing, and ice hockey. We might find clues about the underlying physics by studying the deformation of egg yolks, according to a new paper published in The Physics of Fluids. This in turn could one day lead to better prevention of such trauma.

Egg yolk submerged in liquid egg white encased in a hard shell is an example of what physicists call "soft matter in a liquid environment." Other examples include the red blood cells that flow through our circulatory systems and our brains, surrounded by cerebrospinal fluid (CBR) inside a hard skull.  How much a type of soft matter deforms in response to external impacts is a key feature, according to Villanova University physicist Qianhong Wu and his co-authors on this latest study. They point to red blood cells as an example. It's the ability of red blood cells to change shape under stress (" erythrocyte deformability " ) that lets them squeeze through tiny capillaries, for instance, and also triggers the spleen to remove red blood cells whose size, shape, and overall deformability have been too greatly altered.

Electric eels were long believed to be solitary predators, preferring to hunt and kill their prey alone by sneaking up on unsuspecting sleeping fish at night and shocking them into submission. But according to a recent paper published in the journal Ecology and Evolution, there are rare circumstances in which eels employ a social hunting strategy instead. Specifically, researchers have observed more than 100 electric eels in a small lake in the Brazilian Amazon River basin forming cooperative hunting parties to capture small fish called tetras.

"This is an extraordinary discovery," co-author C. David de Santana , of the Smithsonian National Museum of Natural History, said. "Nothing like this has ever been documented in electric eels. Hunting in groups is pretty common among mammals, but it's actually quite rare in fishes. There are only nine other species of fishes known to do this, which makes this finding really special."

Electric eels are technically knife fish. The eel produces its signature electric discharges—both low and high voltages, depending on the purpose for discharging—via three pairs of abdominal organs comprised of electrocytes, located symmetrically along both sides of the eel. The brain sends a signal to the electrocytes, opening ion channels and briefly reversing the polarity. The difference in electric potential then generates a current, much like a battery with stacked plates.

Enlarge (credit: Rizlan Bencheikh and Bruce Arey, PNNL )

In recent years, researchers have used DNA to encode everything from an operating system to malware . Rather than being a technological curiosity, these efforts were serious attempts to take advantage of DNA's properties for long-term storage of data. DNA can remain chemically stable for hundreds of thousands of years, and we're unlikely to lose the technology to read it, something you can't say about things like ZIP drives and MO disks.

But so far, writing data to DNA has involved converting the data to a sequence of bases on a computer, and then ordering that sequence from someplace that operates a chemical synthesizer—living things don't actually enter into the picture. But separately, a group of researchers had been figuring out how to record biological events by modifying a cell's DNA, allowing them to read out the cell's history. A group at Columbia University has now figured out how to merge the two efforts and write data to DNA using voltage differences applied to living bacteria.

CRISPR and data storage

The CRISPR system has been developed as a way of editing genes or cutting them out of DNA entirely. But the system first came to the attention of biologists because it inserted new sequences into DNA. For all the details, see our Nobel coverage , but for now, just know that part of the CRISPR system involves identifying DNA from viruses and inserting copies of it into the bacterial genome in order to recognize it should the virus ever appear again.