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A 36-million-year-old fossil skeleton is revealing a critical moment in the history of baleen whales: what happened when the ancestors of these modern-day filter feeders first began to distinguish themselves from their toothy, predatory predecessors. The fossil is the oldest known mysticete, a group that includes baleen whales, such as humpbacks, researchers report in the May 22 Current Biology.

Scientists have made predictions about what the first mysticetes might have looked like, but until now, haven’t had much fossil evidence to back up those ideas, says Nicholas Pyenson, a paleobiologist at the Smithsonian National Museum of Natural History in Washington, D.C. “Here, we have something we’ve been waiting for: a really old baleen whale ancestor.”
The earliest whales were predators with sharp teeth — a legacy carried on by today’s orcas, dolphins and other toothed whales. But at some point during whale history, the ancestors of modern mysticetes replaced teeth with baleen, fibrous plates that filter out small bits of food from seawater like a giant sieve. Such a huge lifestyle change didn’t happen overnight, though. And the new find, dubbed Mystacodon selenensis, shows the start of that transition, its discoverers say.

Mystacodon largely fits in well with what scientists have predicted from analyzing other whales, says Mark Uhen, a paleobiologist at George Mason University in Fairfax, Va. “It fleshes out this transition, rather than being something wacky and crazy we never thought of.”

Mystacodon was unearthed in a Peruvian desert by a team of European and Peruvian scientists. Like other early mysticetes, this one still had teeth — its name means “toothed mysticete.” The creature was probably close to 4 meters long, estimates study coauthor Olivier Lambert, a paleontologist at the Royal Belgian Institute of Natural Sciences in Brussels. That’s about the size of a pilot whale, and far smaller than today’s leviathan humpbacks.
The whale holds onto some features of primitive whales, Lambert says. For instance, it still had a bit of a protruding hip bone, suggesting the presence of tiny hind legs left over from when whales’ ancestors were four-legged, terrestrial creatures. “At this transition, scientists thought that this hind limb would be more or less gone,” Lambert says. But the new find suggests that completely losing those limbs took a little longer than previously believed. And the process probably happened independently in toothed whales, instead of one time in the common ancestor of baleen and toothed whales.
But Mystacodon also shows some more modern features. Its snout was flattened, just like in modern mysticetes. In the earliest whales, the joints in the front flippers — essentially elbows — could still be flexed, a relic of when those flippers were legs. Modern whales can’t move those joints, and neither could Mystacodon.
“This is the first indication of a locked elbow — the final step of the transition of the forelimbs into flippers,” Lambert says.

Wear patterns on Mystacodon’s teeth suggest that the whale was a suction feeder — vacuuming up its prey instead of chomping it. That could have been a step toward the filter-feeding strategies used by today’s baleen whales, Lambert suggests. (Other early mysticetes show similar wear, also suggesting suction-feeding tendencies.)

But the connection between suction feeding and filter feeding isn’t well-established, Pyenson says. Mysticetes didn’t become true filter feeders until millions of years later, he says. And scientists still don’t know what series of changes in the ocean environment and in mysticetes’ bodies led to the transformation. “I don’t think suction feeding alone is the primary step.”

Lambert and his colleagues will be looking for more ancient whales to further flesh out the story of early mysticetes. The region where the skeleton was found — the Pisco Basin on the southern coast of Peru — is a hot spot for evidence of ancient whales and dolphins that was overlooked for many years, Lambert says. “There is huge potential for the area where we excavated.”

Discoveries about the molecular ups and downs of fruit flies’ daily lives have won Jeffrey C. Hall, Michael Rosbash and Michael W. Young the Nobel Prize in physiology or medicine.

These three Americans were honored October 2 by the Nobel Assembly at the Karolinska Institute in Stockholm for their work in discovering important gears in the circadian clocks of animals. The trio will equally split the 9 million Swedish kronor prize — each taking home the equivalent of $367,000.
The researchers did their work in fruit flies. But “an awful lot of what was subsequently found out in the fruit flies turns out also to be true and of huge relevance to humans,” says John O’Neill, a circadian cell biologist at the MRC Laboratory of Molecular Biology in Cambridge, England. Mammals, humans included, have circadian clocks that work with the same logic and many of the same gears found in fruit flies, say Jennifer Loros and Jay Dunlap, geneticists at the Geisel School of Medicine at Dartmouth College.
Circadian clocks are networks of genes and proteins that govern daily rhythms and cycles such as sleep, the release of hormones, the rise and fall of body temperature and blood pressure, as well as other body processes. Circadian rhythms help organisms, including humans, anticipate and adapt to cyclic changes of light, dark and temperature caused by Earth’s rotation. When circadian rhythms are thrown out of whack, jet lag results. Shift workers and people with chronic sleep deprivation experience long-term jet lag that has been linked to serious health consequences including cancer, diabetes, heart disease, obesity and depression.
Before the laureates did their work, other scientists had established that plants and animals have circadian rhythms. In 1971, Seymour Benzer and Ronald Konopka (both now deceased and ineligible for the Nobel Prize) found that fruit flies with mutations in a single gene called period had disrupted circadian rhythms, which caused the flies to move around at different times of day than normal.

“But then people got stuck,” says chronobiologist Erik Herzog of Washington University in St. Louis. “We couldn’t figure out what that gene was or how that gene worked.”
At Brandeis University in Waltham, Mass., Hall, a geneticist, teamed up with molecular biologist Rosbash to identify the period gene at the molecular level in 1984. Young of the Rockefeller University in New York City simultaneously deciphered the gene’s DNA makeup. “In the beginning, we didn’t even know the other group was working on it, until we all showed up at a conference together and discovered we were working on the same thing,” says Young. “We said, ‘Well, let’s forge ahead. Best of luck.’”
It wasn’t immediately apparent how the gene regulated fruit fly activity. In 1990, Hall and Rosbash determined that levels of period’s messenger RNA — an intermediate step between DNA and protein — fell as levels of period’s protein, called PER, rose. That finding indicated that PER protein shuts down its own gene’s activity.

A clock, however, isn’t composed of just one gear, Young says. He discovered in 1994 another gene called timeless. That gene’s protein, called TIM, works with PER to drive the clock. Young also discovered other circadian clockworks, including doubletime and its protein DBT, which set the clock’s pace. Rosbash and Hall discovered yet more gears and the two groups competed and collaborated with each other. “This whole thing would not have turned out nearly as nicely if we’d been the only ones working on it, or they had,” Young says.

Since those discoveries, researchers have found that nearly every cell in the body contains a circadian clock, and almost every gene follows circadian rhythms in at least one type of cell. Some genes may have rhythm in the liver, but not the skin cells, for instance. “It’s normal to oscillate,” Herzog says.
Trouble arises when those clocks get out of sync with each other, says neuroscientist Joseph Takahashi at the University of Texas Southwestern Medical Center in Dallas. For instance, genes such as cMyc and p53 help control cell growth and division. Scientists now know they are governed, in part, by the circadian clock. Disrupting the circadian clock’s smooth running could lead to cancer-promoting mistakes.

But while bad timing might lead to diseases, there’s also a potential upside. Scientists have also realized that giving drugs at the right time might make them more effective, Herzog says.

Rosbash joked during a news conference that his own circadian rhythms had been disrupted by the Nobel committee’s early morning phone call. When he heard the news that he’d won the prize, “I was shocked, breathless really. Literally. My wife said, ‘Start breathing,’” he told an interviewer from the Nobel committee.

Young’s sleep was untroubled by the call from Sweden. His home phone is the kitchen, and he didn’t hear it ring, so the committee was unable to reach him before making the announcement. “The rest of the world knew, but I didn’t,” he says. Rockefeller University president Richard Lifton called him on his cell phone and shared the news, throwing Young’s timing off, too. “This really did take me surprise,” Young said during a news conference. “I had trouble even putting my shoes on this morning. I’d go pick up the shoes and realize I needed the socks. And then ‘I should put my pants on first.’”

When some bacteria manage to escape being killed by a virus, the microbes end up hamstringing themselves. And that could be useful in the fight to treat infections.

The bacterium Shigella flexneri — one cause of the infectious disease shigellosis — can spread within cells that line the gut by propelling itself through the cells’ barriers. That causes tissue damage that can lead to symptoms like bloody diarrhea. But when S. flexneri in lab dishes evolved to elude a type of bacteria-killing virus, the bacteria couldn’t spread cell to cell anymore, making it less virulent, researchers report November 17 in Applied and Environmental Microbiology.

The research is a hopeful sign for what’s known as phage therapy (SN: 11/20/02). With antibiotic-resistant microbes on the rise, some researchers see viruses that infect and kill only bacteria, known as bacteriophages or just phages, as a potential option to treat antibiotic-resistant infections (SN: 11/13/19). With phage therapy, infected people are given doses of a particular phage, which kill off the problematic bacteria. The problem, though, is that over time those bacteria can evolve to be resistant against the phage, too.

“We’re kind of expecting phage therapy to fail, in a sense,” says Paul Turner, an evolutionary biologist and virologist at Yale University. “Bacteria are very good at evolving resistance to phages.”
But that doesn’t mean the bacteria emerge unscathed. Some phages attack and enter bacteria by latching onto bacterial proteins crucial for a microbe’s function. If phage therapy treatments relied on such a virus, that could push the bacteria to evolve in such a way that not only helps them escape the virus but also impairs their abilities and makes them less deadly. People infected with these altered bacteria might have less severe symptoms or may not show symptoms at all.

Previous studies with the bacteria Pseudomonas aeruginosa, for instance, have found that phage and bacteria can engage in evolutionary battles that drive the bacteria to be more sensitive to antibiotics. The new study hints that researchers could leverage the arms race between S. flexneri and the newly identified phage, which was dubbed A1-1 after being found in Mexican wastewater, to treat shigellosis.

S. flexneri in contaminated water is a huge problem in parts of the world where clean water isn’t always available, such as sub-Saharan Africa and southern Asia, says Kaitlyn Kortright, a microbiologist also at Yale University. Every year, approximately 1.3 million people die from shigellosis, which is caused by four Shigella species. More than half of those deaths are in children younger than 5 years old. What’s more, antibiotics to treat shigellosis can be expensive and hard to access in those places. And S. flexneri is becoming resistant to many antibiotics. Phage therapy could be a cheaper, more accessible option to treat the infection.

The blow to S. flexneri’s cellular spread comes because to enter cells, A1-1 targets a protein called OmpA, which is crucial for the bacteria to rupture host cell membranes. The researchers found two types of mutations that made S. flexneri resistant to A1-1. Some bacteria had mutations in the gene that produces OmpA, damaging the protein’s ability to help the microbes spread from cell to cell. Others had changes to a structural component of bacterial cells called lipopolysaccharide.

The mutations in lipopolysaccharide were surprising, Kortright says, because the relationship between that structural component and OmpA isn’t fully worked out. One possibility is that those mutations distort OmpA’s structure in a way that the phage no longer recognizes it and can’t enter bacterial cells.

One lingering question is whether S. flexneri evolves in the same way outside a lab dish, says Saima Aslam, an infectious diseases physician at the University of California, San Diego who was not involved in the work. Still, the findings show that it’s “not always a bad thing” when bacteria become phage-resistant, she says.

The twilight time between fully awake and sound asleep may be packed with creative potential.

People who recently drifted off into a light sleep later had problem-solving power, scientists report December 8 in Science Advances. The results help demystify the fleeting early moments of sleep and may even point out ways to boost creativity.

Prolific inventor and catnapper Thomas Edison was rumored to chase those twilight moments. He was said to fall asleep in a chair holding two steel ball bearings over metal pans. As he drifted off, the balls would fall. The ensuing clatter would wake him, and he could rescue his inventive ideas before they were lost to the depths of sleep.

Delphine Oudiette, a cognitive neuroscientist at the Paris Brain Institute, and colleagues took inspiration from Edison’s method of cultivating creativity. She and her colleagues brought 103 healthy people to their lab to solve a tricky number problem. The volunteers were asked to convert a string of numbers into a shorter sequence, following two simple rules. What the volunteers weren’t told was that there was an easy trick: The second number in the sequence would always be the correct final number, too. Once discovered, this cheat code dramatically cut the solving time.
After doing 60 of these trials on a computer, the volunteers earned a 20-minute break in a quiet, dark room. Reclined and holding an equivalent of Edison’s “alarm clock” (a light drinking bottle in one dangling hand), participants were asked to close their eyes and rest or sleep if they desired. All the while, electrodes monitored their brain waves.

About half of the participants stayed awake. Twenty-four fell asleep and stayed in the shallow, fleeting stage of sleep called N1. Fourteen people progressed to a deeper stage of sleep called N2.

After their rest, participants returned to their number problem. The researchers saw a stark difference between the groups: People who had fallen into a shallow, early sleep were 2.7 times as likely to spot the hidden trick as people who didn’t fall asleep, and 5.8 times as likely to spot it as people who had reached the deeper N2 stage.

Such drastic differences in these types of experiments are rare, Oudiette says. “We were quite astonished by the extent of the results.” The researchers also identified a “creative cocktail of brain waves,” as Oudiette puts it, that seemed to accompany this twilight stage — a mixture of alpha brain waves that usually mark relaxation mingled with the delta waves of deeper sleep.

The study doesn’t show that the time spent in N1 actually triggered the later realization, cautions John Kounios, a cognitive neuroscientist at Drexel University in Philadelphia who cowrote the 2015 book The Eureka Factor: Aha Moments, Creative Insight, and the Brain. “It could have been possible that grappling with the problem and initiating an incubation process caused both N1 and the subsequent insight,” he says, making N1 a “by-product of the processes that caused insight rather than the cause.”

More work is needed to untangle the connection between N1 and creativity, Oudiette says. But the results raise a tantalizing possibility, one that harkens to Edison’s self-optimizations: People might be able to learn to reach that twilight stage of sleep, or to produce the cocktail of brain waves associated with creativity on demand.

It seems Edison was onto something about the creative powers of nodding off. But don’t put too much stock in his habits. He is also said to have considered sleep “a criminal waste of time.”

Brains are like sponges, slurping up new information. But sponges may also be a little bit like brains.

Sponges, which are humans’ very distant evolutionary relatives, don’t have nervous systems. But a detailed analysis of sponge cells turns up what might just be an echo of our own brains: cells called neuroids that crawl around the animal’s digestive chambers and send out messages, researchers report in the Nov. 5 Science.

The finding not only gives clues about the early evolution of more complicated nervous systems, but also raises many questions, says evolutionary biologist Thibaut Brunet of the Pasteur Institute in Paris, who wasn’t involved in the study. “This is just the beginning,” he says. “There’s a lot more to explore.”

The cells were lurking in Spongilla lacustris, a freshwater sponge that grows in lakes in the Northern Hemisphere. “We jokingly call it the Godzilla of sponges” because of the rhyme with Spongilla, say Jacob Musser, an evolutionary biologist in Detlev Arendt’s group at the European Molecular Biology Laboratory in Heidelberg, Germany.

Simple as they are, these sponges have a surprising amount of complexity, says Musser, who helped pry the sponges off a metal ferry dock using paint scrapers. “They’re such fascinating creatures.”
With sponges procured, Arendt, Musser and colleagues looked for genes active in individual sponge cells, ultimately arriving at a list of 18 distinct kinds of cells, some known and some unknown. Some of these cells used genes that are essential to more evolutionarily sophisticated nerve cells in other organisms for sending or receiving messages in the form of small blobs of cellular material called vesicles.

One such cell, called a neuroid, caught the scientists’ attention. After seeing that this cell was using those genes involved in nerve cell signaling, the researchers took a closer look. A view through a confocal microscope turned up an unexpected locale for the cells, Musser says. “We realized, ‘My God, they’re in the digestive chambers.’”

Large, circular digestive structures called choanocyte chambers help move water and nutrients through sponges’ canals, in part by the beating of hairlike cilia appendages (SN: 3/9/15). Neuroids were hovering around some of these cilia, the researchers found, and some of the cilia near neuroids were bent at angles that suggested that they were no longer moving.
The team suspects that these neuroids were sending signals to the cells charged with keeping the sponge fed, perhaps using vesicles to stop the movement of usually undulating cilia. If so, that would be a sophisticated level of control for an animal without a nervous system.

The finding suggests that sponges are using bits and bobs of communications systems that ultimately came together to work as brains of other animals. Understanding the details might provide clues to how nervous systems evolved. “What did animals have, before they had a nervous system?” Musser asks. “There aren’t many organisms that can tell us that. Sponges are one of them.”

As the chill of autumn encroaches on Siberia’s grasslands, Richard’s pipits usually begin their southward trek to warmer latitudes. But a growing number of the slender, larklike songbirds seem to be heading west instead, possibly establishing a new migratory route for the species.

This would be the first new route known to emerge on an east-west axis in a long-distance migratory bird, researchers report October 22 in Current Biology. The finding could have implications for how scientists understand the evolution of bird migration routes over time and how the animals adapt to a shifting climate.

Richard’s pipits (Anthus richardi) typically breed in Siberia during the summer and travel south for the winter to southern Asia. Occasionally, “vagrant” birds get lost and show up far from this range, including in Europe. But as a Ph.D. student at the Université Grenoble Alpes in France, evolutionary biologist Paul Dufour noticed, along with colleagues, that described sightings and photo records of the pipits wintering in southern France had increased from a handful of birds annually in the 1980s and 1990s to many dozens in recent years.

So, Dufour, now at the University of Gothenburg in Sweden, and his team started monitoring the pipits in France and Spain to see where the birds were coming from, and if the birds were visiting Europe on purpose or just getting lost.

The researchers captured seven pipits in France during the winter of 2019–2020, tagging them with a sensor that estimates the birds’ geographic positions based on light levels and length of day. The team then released the birds. The next winter, the team successfully recaptured three of them. Those sensors showed that the birds had all flown back to the same part of southwestern Siberia for the summer before returning to France.

The researchers also examined images in citizen-science databases of 331 Richard’s pipits that were photographed in Europe and North Africa, categorizing the birds by apparent age. Among songbirds, Dufour says, vagrants are always young birds. Songbirds tend to follow a route based on instincts written into their DNA, replicating the trip their ancestors took. But storms or mutations that create faulty wayfinding abilities can send young songbirds off target.
Wherever it arrives, the songbird’s first migration creates a mental map for every migration after, so any adult birds in Europe have made the trip more than once. Since more than half of the birds in southern Europe and nearby northwestern Africa documented in the winter were adults, Dufour and his colleagues think that many of these pipits are seasonal migrants.

Contemporary shifts in migration routes are more common in species that travel via the cues of a traveling group, like geese or cranes. Songbirds usually migrate alone, following their instinctual route when young, Dufour says, so changes to migration patterns are rarer.

What’s more, east-west migration is unusual in birds. Most species that travel this way are ones that migrate short distances within the tropics, says Jessie Williamson, an ornithologist at the University of New Mexico in Albuquerque who was not involved with the research. “It’s exciting that an understudied migratory behavior like east-west migration is in the spotlight,” she says.

If the pipits’ European trek is in fact now an established route, it’s possible that the detour was facilitated by climate change, which may also be meddling with birds’ migrations in other ways (SN: 12/17/19). Dufour and his team used computer models that estimate climate suitability for the pipits in Europe based on variables like temperature and precipitation. The researchers compared two periods — 1961 to 1990 and 1990 to 2018 — and found that warmer temperatures in the latter period have made most parts of southern Europe a better wintering location for the birds than they were before.
The selection of European wintering grounds may also involve the deterioration of ancestral, southern Asian sites, but the researchers haven’t investigated that yet. Climate change could be affecting that too, Dufour says. But “we suspect that habitat modification in Southeast Asia — increasing urbanization, less open areas — may also be part of the equation.”

Ginny Chan, an ecologist at the Swiss Ornithological Institute in Sempach who was not involved with the research, says that the types of environmental changes that could be hurting bird populations “are happening very quickly in the traditional wintering range [for Richard’s pipits] in South and East Asia.” In India, the Richard’s pipit population has declined by more than 90 percent over the last couple of decades, Chan says.

Other Siberian bird species that typically migrate south but have recently shown up in Europe in growing numbers, like the yellow-browed warbler and Siberian chiffchaff, may also be making their own westward routes, Dufour suspects.

If other Siberian songbird species are also establishing new western migration routes, this could mean that migratory songbirds are more flexible travelers than scientists previously thought, Dufour says.

That could have hopeful implications for some birds as species worldwide deal with a changing climate. But the new research, he adds, shouldn’t overshadow other studies of migratory birds — like barnacle geese and the European pied flycatcher — which show that some of these species are not as able to cope with climate change.

In a remote corner of Brazil’s Amazon rainforest, researchers have spent decades catching and measuring birds in a large swath of forest unmarred by roads or deforestation. An exemplar of the Amazon’s dazzling diversity, the experimental plot was to act as a baseline that would reveal how habitat fragmentation, from logging or roads, can hollow out rainforests’ wild menagerie.

But in this pristine pocket of wilderness, a more subtle shift is happening: The birds are shrinking.

Over 40 years, dozens of Amazonian bird species have declined in mass. Many species have lost nearly 2 percent of their average body weight each decade, researchers report November 12 in Science Advances. What’s more, some species have grown longer wings. The changes coincide with a hotter, more variable climate, which could put a premium on leaner, more efficient bodies that help birds stay cool, the researchers say.

“Climate change isn’t something of the future. It’s happening now and has been happening and has effects we haven’t thought of,” says Ben Winger, an ornithologist at the University of Michigan in Ann Arbor who wasn’t involved in the research but has documented similar shrinkage in migratory birds. Seeing the same patterns in so many bird species across widely different contexts “speaks to a more universal phenomenon,” he says.

Biologists have long linked body size and temperature. In colder climates, it pays to be big because having a smaller surface area relative to one’s volume reduces heat loss through the skin and keeps the body warmer. As the climate warms, “you’d expect shrinking body sizes to help organisms off-load heat better,” says Vitek Jirinec, an ecologist at the Integral Ecology Research Center in Blue Lake, Calif.

Many species of North American migratory birds are getting smaller, Winger and colleagues reported in 2020 in Ecology Letters. Climate change is the likely culprit, Winger says, but since migrators experience a wide range of conditions while globe-trotting, other factors such as degraded habitats that birds may encounter can’t be ruled out.

To see if birds that stay put have also been shrinking, Jirinec and colleagues analyzed data on nonmigratory birds collected from 1979 to 2019 in an intact region of the Amazon that spans 43 kilometers. The dataset includes measurements such as mass and wing length for over 11,000 individual birds of 77 species. The researchers also examined climate data for the region.
All species declined in mass over this period, the researchers found, including birds as different as the Rufous-capped antthrush (Formicarius colma), which snatches insects off the forest floor, and the Amazonian motmot (Momotus momota), which scarfs down fruit up in trees. Species lost from about 0.1 percent to nearly 2 percent of their average body weight each decade. The motmot, for example, shrunk from 133 grams to about 127 grams over the study period.

These changes coincided with an overall increase in the average temperature of 1 degree Celsius in the wet season and 1.65 degrees C in the dry season. Temperature and precipitation also became more variable over the time period, and these short-term fluctuations, such as an especially hot or dry season, better explained the size trends than the steady increase in temperature.

“The dry season is really stressful for birds,” Jirinec says. Birds’ mass decreased the most in the year or two after especially hot and dry spells, which tracks with the idea that birds are getting smaller to deal with heat stress.

Other factors, like decreased food availability, could also lead to smaller sizes. But since birds with widely different diets all declined in mass, a more pervasive force like climate change is the likely cause, Jirinec says.

Wing length also grew for 61 species, with a maximum increase of about 1 percent per decade. Jirinec thinks that longer wings make for more efficient, and thus cooler, fliers. For instance, a fighter jet, with its heavy body and compact wings, takes enormous power to maneuver. A light and long-winged glider, by contrast, can cruise along much more efficiently.

“Longer wings may be helping [birds] fly more efficiently and produce less metabolic heat,” which can be beneficial in hotter conditions, he says. “But that’s just a hypothesis.” This body change was most pronounced in birds that spend their time higher up in the canopy, where conditions are hotter and drier than the forest floor.

Whether these changes in shape and size represent an evolutionary adaptation to climate change, or simply a physiological response to warmer temperatures, remains unclear (SN: 5/8/20). Whichever is the case, Jirinec suggests that the change shows the pernicious power of human activity (SN: 10/26/21).

“The Amazon rainforest is mysterious, remote and teeming with biodiversity,” he says. “This study suggests that even in places like this, far removed from civilization, you can see signatures of climate change.”

Regenerating body parts is never easy. For instance, some lizards can grow back their tails, but these new appendages are pale imitations of the original. Now, genetically modified stem cells are helping geckos grow back better tails.

Tweaking and implanting embryonic stem cells on the tail stumps of mourning geckos (Lepidodactylus lugubris) allowed the reptiles to grow tails that are more like the original than ever before, researchers report October 14 in Nature Communications. These findings are a stepping-stone to developing regenerative therapies in humans that may one day treat hard-to-heal wounds.

A gecko’s tail is an extension of its spine — with the vertebrae to prove it. Regenerated tails, however, are simpler affairs. “It’s just a bunch of concentric tubes of fat, muscle and skin,” says Thomas Lozito, a biologist at the University of Southern California in Los Angeles.

That’s because stem cells in adult geckos produce a molecular signal that encourages the formation of cartilage in new tails, but not bone or nervous tissues (SN: 8/17/18). Lozito and his colleagues used embryonic stem cells, which can develop into a wider range of tissues than adult stem cells, modified them to ignore this signal and then implanted them on the tail stumps of geckos that had their tails surgically removed. The tails that grew from these modified stem cells had bonelike grooves in the cartilage and generated new neural tissue at the top of the tail.

These modified tails still lack a spinal cord, making them a far cry from the original. “We fixed one problem, but there are still many imperfections,” Lozito says. “We’re still on the hunt for the perfect tail.”

Mystery mummies from Central Asia have a surprising ancestry. These people, who displayed facial characteristics suggesting a European heritage, belonged to a local population with ancient Asian roots, a new study finds. Until now, researchers had pegged the mummified Bronze Age bunch as newcomers and debated about where in West Asia they originally came from.

Desert heat naturally mummified hundreds of bodies buried in western China’s Tarim Basin from roughly 4,000 to 1,800 years ago. Preserved remains of these people have been excavated since the 1990s (SN: 2/25/95). Those interred around 4,000 years ago belonged to the Xiaohe culture, a population that mixed animal herding with plant cultivation. Their boat-shaped coffins were unlike any others in the region. And preserved cheese, wheat, millet and clothes made from western Eurasian wool found in Xiaohe graves pointed to distant contacts or origins.

Archaeogeneticist Yinqiu Cui of Jilin University in Changchun, China, and an international team analyzed DNA from 13 Tarim Basin mummies from roughly 4,100 to 3,700 years ago and five other human mummies from the nearby Dzungarian Basin from around 5,000 to 4,800 years ago.
Tarim people displayed Asian ancestry mainly traceable to hunter-gatherers who inhabited much of northern Eurasia more than 9,000 years ago. That finding suggests that the mummies belonged to a population that did not mate with outsiders for many millennia, the researchers report October 27 in Nature. No DNA links were found to western Eurasian herders from the Afanasievo culture (SN: 11/15/17), who some researchers have regarded as precursors of Xiaohe people.

A predominantly Afanasievo ancestry did appear in the Dzungarian individuals. Milk proteins found in dental tartar from seven Tarim mummies indicated that those people regularly consumed dairy products, a practice possibly learned from Afanasievo descendants in the Dzungarian Basin, the researchers say.

Concerns abound about what’s gone wrong in modern societies. Many scholars explain growing gaps between the haves and the have-nots as partly a by-product of living in dense, urban populations. The bigger the crowd, from this perspective, the more we need power brokers to run the show. Societies have scaled up for thousands of years, which has magnified the distance between the wealthy and those left wanting.

In The Dawn of Everything, anthropologist David Graeber and archaeologist David Wengrow challenge the assumption that bigger societies inevitably produce a range of inequalities. Using examples from past societies, the pair also rejects the popular idea that social evolution occurred in stages.

Such stages, according to conventional wisdom, began with humans living in small hunter-gatherer bands where everyone was on equal footing. Then an agricultural revolution about 12,000 years ago fueled population growth and the emergence of tribes, then chiefdoms and eventually bureaucratic states. Or perhaps murderous alpha males dominated ancient hunter-gatherer groups. If so, early states may have represented attempts to corral our selfish, violent natures.

Neither scenario makes sense to Graeber and Wengrow. Their research synthesis — which extends for 526 pages — paints a more hopeful picture of social life over the last 30,000 to 40,000 years. For most of that time, the authors argue, humans have tactically alternated between small and large social setups. Some social systems featured ruling elites, working stiffs and enslaved people. Others emphasized decentralized, collective decision making. Some were run by men, others by women. The big question — one the authors can’t yet answer — is why, after tens of thousands of years of social flexibility, many people today can’t conceive of how society might effectively be reorganized.
Hunter-gatherers have a long history of revamping social systems from one season to the next, the authors write. About a century ago, researchers observed that Indigenous populations in North America and elsewhere often operated in small, mobile groups for part of the year and crystallized into large, sedentary communities the rest of the year. For example, each winter, Canada’s Northwest Coast Kwakiutl hunter-gatherers built wooden structures where nobles ruled over designated commoners and enslaved people, and held banquets called potlatch. In summers, aristocratic courts disbanded, and clans with less formal social ranks fished along the coast.

Many Late Stone Age hunter-gatherers similarly assembled and dismantled social systems on a seasonal basis, evidence gathered over the last few decades suggests. Scattered discoveries of elaborate graves for apparently esteemed individuals (SN: 10/5/17) and huge structures made of stone (SN: 2/11/21), mammoth bones and other material dot Eurasian landscapes. The graves may hold individuals who were accorded special status, at least at times of the year when mobile groups formed large communities and built large structures, the authors speculate. Seasonal gatherings to conduct rituals and feasts probably occurred at the monumental sites. No signs of centralized power, such as palaces or storehouses, accompany those sites.

Social flexibility and experimentation, rather than a revolutionary shift, also characterized ancient transitions to agriculture, Graeber and Wengrow write. Middle Eastern village excavations now indicate that the domestication of cereals and other crops occurred in fits and starts from around 12,000 to 9,000 years ago. Ancient Fertile Crescent communities periodically gave farming a go while still hunting, foraging, fishing and trading. Early cultivators were in no rush to treat tracts of land as private property or to form political systems headed by kings, the authors conclude.

Even in early cities of Mesopotamia and Eurasia around 6,000 years ago (SN: 2/19/20), absolute rule by monarchs did not exist. Collective decisions were made by district councils and citizen assemblies, archaeological evidence suggests. In contrast, authoritarian, violent political systems appeared in the region’s mobile, nonagricultural populations at that time.

Early states formed in piecemeal fashion, the authors argue. These political systems incorporated one or more of three basic elements of domination: violent control of the masses by authorities, bureaucratic management of special knowledge and information, and public demonstrations of rulers’ power and charisma. Egypt’s early rulers more than 4,000 years ago fused violent coercion of their subjects with extensive bureaucratic controls over daily affairs. Classic Maya rulers in Central America 1,100 years ago or more relied on administrators to monitor cosmic events while grounding earthly power in violent control and alliances with other kings.

States can take many forms, though. Graeber and Wengrow point to Bronze Age Minoan society on Crete as an example of a political system run by priestesses who called on citizens to transcend individuality via ecstatic experiences that bound the population together.

What seems to have changed today is that basic social liberties have receded, the authors contend. The freedom to relocate to new kinds of communities, to disobey commands issued by others and to create new social systems or alternate between different ones has become a scarce commodity. Finding ways to reclaim that freedom is a major challenge.

These examples give just a taste of the geographic and historical ground covered by the authors. Shortly after finishing writing the book, Graeber, who died in 2020, tweeted: “My brain feels bruised with numb surprise.” That sense of revelation animates this provocative take on humankind’s social journey.