New images of gas churning inside an ancient starburst galaxy help explain why this galactic firecracker underwent such frenzied star formation.

Using the Atacama Large Millimeter/submillimeter Array, or ALMA, researchers have taken the most detailed views of the disk of star-forming gas that permeated the galaxy COSMOS-AzTEC-1, which dates back to when the universe was less than 2 billion years old. The telescope observations, reported online August 29 in Nature, reveal an enormous reservoir of molecular gas that was highly susceptible to collapsing and forging new stars.
COSMOS-AzTEC-1 and its starburst contemporaries have long puzzled astronomers, because these galaxies cranked out new stars about 1,000 times as fast as the Milky Way does. According to standard theories of cosmology, galaxies shouldn’t have grown up fast enough to be such prolific star-formers so soon after the Big Bang.

Inside a normal galaxy, the outward pressure of radiation from stars helps counteract the inward pull of gas’s gravity, which pumps the brakes on star formation. But in COSMOS-AzTEC-1, the gas’s gravity was so intense that it overpowered the feeble radiation pressure from stars, leading to runaway star formation. The new ALMA pictures unveil two especially large clouds of collapsing gas in the disk, which were major hubs of star formation.
“It’s like a giant fuel depot that built up right after the Big Bang … and we’re catching it right in the process of the whole thing lighting up,” says study coauthor Min Yun, an astronomer at the University of Massachusetts Amherst.

Yun and colleagues still don’t know how COSMOS-AzTEC-1 stocked up such a massive supply of star-forming material. But future observations of the galaxy and its ilk using ALMA or the James Webb Space Telescope, set to launch in 2021, may help clarify the origins of these ancient cosmic monsters (SN Online: 6/11/14).

Obesity can affect brainpower, and a study in mice may help explain how.

In the brains of obese mice, rogue immune cells chomp nerve cell connections that are important for learning and memory, scientists report September 10 in the Journal of Neuroscience. Drugs that stop this synapse destruction may ultimately prove useful for protecting the brain against the immune cell assault.

Like people, mice that eat lots of fat quickly pack on pounds. After 12 weeks of a high-fat diet, mice weighed almost 40 percent more than mice fed standard chow. These obese mice showed signs of diminished brainpower, neuroscientist Elizabeth Gould of Princeton University and colleagues found. Obese mice were worse at escaping mazes and remembering an object’s location than mice of a normal weight.
On nerve cells, microscopic knobs called dendritic spines receive signals. Compared with normal-sized mice, obese mice had fewer dendritic spines in several parts of the mice’s hippocampi, brain structures important for learning and memory.

The dendritic spine destruction comes from immune cells called microglia, the results suggest. In obese mice, higher numbers of active microglia lurked among these sparser nerve cell connections compared with mice of normal weights. When the researchers interfered with microglia in obese mice, dendritic spines were protected and the mice’s performance on thinking tests improved.

Figuring out ways to stop microglia’s damage might one day prove to protect against obesity-related brain trouble, a concern relevant to the estimated 650 million obese adults worldwide. Obese people are also at a higher risk of dementias such as Alzheimer’s, and some researchers suspect microglia may be a culprit in those brain diseases more generally.

I’m relatively new to Oregon, but one of the ways I know I’m starting to settle in is my ability to recognize marijuana shops. Some are easy. But others, with names like The Agrestic and Mr. Nice Guy, are a little trickier to identify for someone who hasn’t spent much time in a state that has legalized marijuana.

A growing number of states have legalized both medical and recreational marijuana. At the same time, women who are pregnant or breastfeeding are using the drug in increasing numbers. A 2017 JAMA study described both survey results and urine tests of nearly 280,000 pregnant women in Northern California, where medical marijuana was legalized in 1996. The study showed that in 2009, about 4 percent of the women tested used marijuana. In 2016, about 7 percent of women did. Those California numbers may be even higher now, since recreational marijuana became legal there this year.
Some of those numbers may be due in part to women using marijuana to treat their morning sickness, a more recent study by some of the same researchers suggests. Their report, published August 20 in JAMA Internal Medicine, found that pregnant women with severe nausea and vomiting were 3.8 times more likely to use marijuana than pregnant women without morning sickness.

So some pregnant women are definitely using the drug, and exposing their fetuses to it, too. Ingredients in marijuana are known to make their way to fetuses by crossing the placenta during pregnancy (and by entering breast milk after the baby is born). But what actually happens when those marijuana compounds arrive?

That’s the question the American Academy of Pediatrics grapples with in a clinical report published in the August issue of Pediatrics. In an effort to provide guidance to caregivers and women, the AAP sums up the existing scientific literature on how marijuana affects mothers and babies.

While it seems like a bad idea to expose developing babies to marijuana, the science to back up that intuition is frustratingly slim. Some studies have turned up negative outcomes for babies, such as lower birth weight and a greater likelihood of needing the neonatal intensive care unit. And marijuana use during pregnancy has been tied to a greater risk of anemia in mothers. But other studies found no such effects.
This subject — and any topic that involves drugs and babies — is hard to study. Ethical reasons prevent scientists from assigning some pregnant women to use marijuana and others to abstain. Such randomization is a key feature of a solid study, and one that’s just not available in this case. That leaves scientists to study women who are already using marijuana while pregnant, and those women may have other characteristics that make a direct comparison difficult. That makes it harder to say whether it was marijuana, or something else, that is linked to a particular outcome.

Still, despite what the AAP calls “limited research,” there may be enough hints, from observational studies of women already using marijuana and from animal studies, to make pregnant women pause before using marijuana. Add to those red flags the fact that today’s marijuana is a lot more potent than it used to be, meaning that more of the active compound THC could reach the developing baby. And toxins such as pesticides might come along for the ride, perhaps causing other kinds of trouble.

These questions are more pressing as marijuana becomes easier to get legally, and as more pregnant women use it. Hopefully this shift will prompt scientists to figure out better ways to study the drug’s effects — or lack thereof.

NOORDWIJK, THE NETHERLANDS — Life might arise in the darkest of places: the moon of a planet wandering the galaxy without a star.

The gravitational tug-of-war between a moon and its planet can keep certain satellites toasty enough for liquid water to exist there — a condition widely considered crucial for life. Now computer simulations suggest that, given the right orbit and atmosphere, some moons orbiting rogue planets can stay warm for over a billion years, astrophysicist Giulia Roccetti reported March 23 at the PLANET-ESLAB 2023 Symposium. She and her colleagues also report their findings March 20 in the International Journal of Astrobiology.
“There might be many places in the universe where habitable conditions can be present,” says Roccetti, of the European Southern Observatory in Garching, Germany. But life presumably also needs long-term stability. “What we are looking for is places where these habitable conditions can be sustained for hundreds of millions, or billions, of years.”

Habitability and stability don’t necessarily need to come from a nearby sun. Astronomers have spotted about 100 starless planets, some possibly formed from gas and dust clouds the way stars form, others probably ejected from their home solar systems (SN: 7/24/17). Computer simulations suggest that there may be as many of these free-floating planets as there are stars in the galaxy.

Such orphaned planets might also have moons — and in 2021, researchers calculated that these moons need not be cold and barren places.

Unless a moon’s orbit is a perfect circle, the gravitational pull of its planet continually deforms it. Resulting friction inside the moon generates heat. In our own solar system, this process plays out on moons such as Saturn’s Enceladus and Jupiter’s Europa (SN: 11/6/17; SN: 8/6/20). A sufficiently thick, heat-trapping atmosphere, likely one dominated by carbon dioxide, might then keep the surface warm enough for water to remain liquid. That water could come from chemical reactions with the carbon dioxide and hydrogen in the atmosphere, initiated by the impact of high-speed charged particles from space.

But such a moon won’t stay warm forever. The same gravitational forces that heat it up also mold its orbit into a circle. Gradually, the ebb and flow of gravity felt by the moon deforms it less and less, and the supply of frictional heat dwindles.

In the new study, Roccetti and her colleagues ran 8,000 computer simulations of a sunlike star with three Jupiter-sized planets. These simulations showed that planets that are ejected from their solar system will often sail off into space with their moons in tow.

The team then ran simulations of those moons, assumed to be the size of Earth, whizzing around their planets along the orbit they ended up with during the ejection. The goal was to see if gravitational heating occurred and if it lasted long enough for life to potentially originate there. Earth may have become habitable within a few hundred million years, although the earliest evidence of living organisms here date to about 1 billion years after the planet formed (SN: 1/26/18).
Because an atmosphere is crucial to heat retention, the team did their calculations with three alternatives. For moons with an atmosphere the same pressure as Earth’s, the period of potential habitability lasted at most about 50 million years, the team found. But it can last nearly 300 million years if the atmospheric pressure is 10 times that of Earth, and for about 1.6 billion years at pressures 10 times greater still. That amount of pressure may sound extreme, but it’s close to conditions on the similarly sized Venus.

Warmth and water might not be enough to let living organisms appear, though. Moons of free-floating planets “will not be the most favorable places for life to arise,” says astrophysicist Alex Teachey, of the Academia Sinica Institute of Astronomy & Astrophysics in Taipei, Taiwan.

“I think stars, due to their incredible power output and their longevity, are going to be far better sources of energy for life,” says Teachey, who studies the moons of exoplanets. “A big open question … is whether you can even start life in a place like Europa or Enceladus, even if the conditions are right to sustain life, because you don’t have, for example, solar radiation that can help along the process of mutation for evolution.”

But Roccetti — although not an astrobiologist herself — thinks moons of orphan planets have a few important advantages. They will have some, but not too much, water, which many astrobiologists think is a better starting point for life than, say, an ocean world. And not having a star nearby means there are no solar flares, which in many cases will destroy the atmosphere of an otherwise promising planet.

“There are many environments in our universe which are very different from what we have here on Earth,” she says, “and it is important to investigate all of them.”

Slow-motion large land snails made for easy catching and good eating as early as 170,000 years ago.

Until now, the oldest evidence of Homo sapiens eating land snails dated to roughly 49,000 years ago in Africa and 36,000 years ago in Europe. But tens of thousands of years earlier, people at a southern African rock-shelter roasted these slimy, chewy — and nutritious — creepers that can grow as big as an adult’s hand, researchers report in the April 15 Quaternary Science Reviews.
Analyses of shell fragments excavated at South Africa’s Border Cave indicate that hunter-gatherers who periodically occupied the site heated large African land snails on embers and then presumably ate them, say chemist Marine Wojcieszak and colleagues. Wojcieszak, of the Royal Institute for Cultural Heritage in Brussels, studies chemical properties of archaeological sites and artifacts.

The supersized delicacy became especially popular between about 160,000 and 70,000 years ago, the researchers say. Numbers of unearthed snail shell pieces were substantially larger in sediment layers dating to that time period.

New discoveries at Border Cave challenge an influential idea that human groups did not make land snails and other small game a big part of their diet until the last Ice Age waned around 15,000 to 10,000 years ago, Wojcieszak says.

Long before that, hunter-gatherer groups in southern Africa roamed the countryside collecting large land snails to bring back to Border Cave for themselves and to share with others, the team contends. Some of the group members who stayed behind on snail-gathering forays may have had limited mobility due to age or injury, the researchers suspect.

“The easy-to-eat, fatty protein of snails would have been an important food for the elderly and small children, who are less able to chew hard foods,” Wojcieszak says. “Food sharing [at Border Cave] shows that cooperative social behavior was in place from the dawn of our species.”

Border Cave’s ancient snail scarfers also push back the human consumption of mollusks by several thousand years, says archaeologist Antonieta Jerardino of the University of South Africa in Pretoria. Previous excavations at a cave on South Africa’s southern tip found evidence of humans eating mussels, limpets and other marine mollusks as early as around 164,000 years ago (SN: 7/29/11).

Given the nutritional value of large land snails, an earlier argument that it was eating fish and shellfish that energized human brain evolution may have been overstated, says Jerardino, who did not participate in the new study.
It’s not surprising that ancient H. sapiens recognized the nutritional value of land snails and occasionally cooked and ate them by 170,000 years ago, says Teresa Steele, an archaeologist at the University of California, Davis who was not part of the work. But intensive consumption of these snails starting around 160,000 years ago is unexpected and raises questions about whether climate and habitat changes may have reduced the availability of other foods, Steele says.

Researchers have already found evidence that ancient people at Border Cave cooked starchy plant stems, ate an array of fruits and hunted small and large animals. The oldest known grass bedding, from around 200,000 years ago, has also been unearthed at Border Cave (SN: 8/13/20).

Several excavations have been conducted at the site since 1934. Three archaeologists on the new study — Lucinda Backwell and Lyn Wadley of Wits University in Johannesburg and Francesco d’Errico of the University of Bordeaux in France — directed the latest Border Cave dig, which ran from 2015 through 2019.

Discoveries by that team inspired the new investigation. Excavations uncovered shell fragments of large land snails, many discolored from possible burning, in all but the oldest sediment layers containing remnants of campfires and other H. sapiens activity. The oldest layers date to at least 227,000 years ago.

Chemical and microscopic characteristics of 27 snail shell fragments from various sediment layers were compared with shell fragments of modern large African snails that were heated in a metal furnace. Experimental temperatures ranged from 200° to 550° Celsius. Heating times lasted from five minutes to 36 hours.

All but a few ancient shell pieces displayed signs of extended heat exposure consistent with having once been attached to snails that were cooked on hot embers. Heating clues on shell surfaces included microscopic cracks and a dull finish.

Only lower parts of large land snail shells would have rested against embers during cooking, possibly explaining the mix of burned and unburned shell fragments unearthed at Border Cave, the researchers say.

The battle over the heft of a hard-to-detect particle is heating up. What’s at stake? Only the leading theory describing all known matter in the universe.

A recalculation of the mass of an elementary particle, the W boson, has increased the tension between measurements from competing particle collider experiments. The ultimate outcome could bolster the standard model of particle physics, which describes the fundamental forces and quantum bits that make up everything we see in the cosmos. Or it could reveal signs of the standard model’s breakdown, depending on which lab’s answer prevails.
A reanalysis of old data from the Large Hadron Collider’s ATLAS experiment yields a W boson mass of about 80,360 million electron volts, or MeV. Researchers with the experiment, at CERN in Geneva, reported the measurement March 23 at the Rencontres de Moriond conference in La Thuile, Italy. The revised value is closely aligned with predictions from the standard model.

It also boasts reduced uncertainty from the researchers’ previous analysis of the data, which they reported in 2018, increasing their confidence that they got the mass right.

But the updated mass is at odds with that of another group. In 2022, scientists from the Collider Detector at Fermilab, or CDF, experiment shocked the physics community with a measurement of 80,434 MeV — about 100 MeV heavier than expected (SN: 4/7/22). If the CDF report is correct, it implies that something is off with the standard model that has persevered in the face of every experimental challenge thrown at it over the last 50 years.

The W boson is responsible for the weak force, one of three fundamental forces in the standard model (SN: 2/5/83). And “it’s the only mass of a particle in the standard model that can be calculated,” says theoretical physicist Sven Heinemeyer of the Karlsruhe Institute of Technology in Germany. That is, the standard model theory yields a specific mass for the W boson, whereas the masses of other particles such as electrons and quarks are inputs and can be — as far as the theory is concerned — any value. Finding a W boson mass that’s different from standard model predictions would show the current theory is wrong.

The ATLAS reanalysis offers a stronger counterpoint to the CDF claim than the earlier ATLAS analysis of the same data. “The new analysis is an important confirmation of our previous result,” says Andreas Hoecker, a physicist at CERN.

The latest ATLAS value widens the chasm that separates CDF’s mass measurement from the herd of other studies. But it shouldn’t be seen as erasing CDF’s standard model challenge, says Duke University physicist Ashutosh Kotwal, a member of the CDF collaboration.

“The perspective on the CDF [announcement of a heavy W boson in 2022] does not change because of the ATLAS reanalysis,” Kotwal says. Because the reanalysis is based on data that ATLAS already released in 2017, he says, “the fact that ATLAS obtains a similar value as before is to be expected.”
Heinemeyer, who is not affiliated with ATLAS or CDF, sees a shift in the W boson mass landscape, but no sign of a resolution of the discrepancy.

“Having one new measurement is not enough,” Heinemeyer says. “If more and more measurements were to come out now from ATLAS and [other experiments], and they would all be in the same ballpark, at some point the community would decide CDF did something wrong.”

The next word on the W boson mass will probably come with pending studies from ATLAS and other experiments at CERN. The CDF experiment shut down in 2011, so it will not contribute further to the debate.

In the meantime, researchers hope to scrutinize each other’s analyses to search for clues that might help explain discrepancies in W boson mass measurements. “The CDF April 2022 paper provides a number of cross-checks of the CDF methodology and is transparent,” Kotwal says. “I look forward to detailed discussions of the ATLAS methodology.”

In the end, the conflict might reveal a new crack in the standard model. Or it could turn out to be another example of one of the most successful theories in history standing strong.

A 13-sided shape known as “the hat” has mathematicians tipping their caps.

It’s the first true example of an “einstein,” a single shape that forms a special tiling of a plane: Like bathroom floor tile, it can cover an entire surface with no gaps or overlaps but only with a pattern that never repeats.

“Everybody is astonished and is delighted, both,” says mathematician Marjorie Senechal of Smith College in Northampton, Mass., who was not involved with the discovery. Mathematicians had been searching for such a shape for half a century. “It wasn’t even clear that such a thing could exist,” Senechal says.

Although the name “einstein” conjures up the iconic physicist, it comes from the German ein Stein, meaning “one stone,” referring to the single tile. The einstein sits in a weird purgatory between order and disorder. Though the tiles fit neatly together and can cover an infinite plane, they are aperiodic, meaning they can’t form a pattern that repeats.

With a periodic pattern, it’s possible to shift the tiles over and have them match up perfectly with their previous arrangement. An infinite checkerboard, for example, looks just the same if you slide the rows over by two. While it’s possible to arrange other single tiles in patterns that are not periodic, the hat is special because there’s no way it can create a periodic pattern.
Identified by David Smith, a nonprofessional mathematician who describes himself as an “imaginative tinkerer of shapes,” and reported in a paper posted online March 20 at arXiv.org, the hat is a polykite — a bunch of smaller kite shapes stuck together. That’s a type of shape that hadn’t been studied closely in the search for einsteins, says Chaim Goodman-Strauss of the National Museum of Mathematics in New York City, one of a group of trained mathematicians and computer scientists Smith teamed up with to study the hat.

It’s a surprisingly simple polygon. Before this work, if you’d asked what an einstein would look like, Goodman-Strauss says, “I would’ve drawn some crazy, squiggly, nasty thing.”

Mathematicians previously knew of nonrepeating tilings that involved multiple tiles of different shapes. In the 1970s, mathematician Roger Penrose discovered that just two different shapes formed a tiling that isn’t periodic (SN: 3/1/07). From there, “It was natural to wonder, could there be a single tile that does this?” says mathematician Casey Mann of the University of Washington Bothell, who was not involved with the research. That one has finally been found, “it’s huge.”
Other shapes have come close. Taylor-Socolar tiles are aperiodic, but they are a jumble of multiple disconnected pieces — not what most people think of as a single tile. “This is the first solution without asterisks,” says mathematician Michaël Rao of CNRS and École Normale Supérieure de Lyon in France.

Smith and colleagues proved that the tile was an einstein in two ways. One came from noticing that the hats arrange themselves into larger clusters, called metatiles. Those metatiles then arrange into even larger supertiles, and so on indefinitely, in a type of hierarchical structure that is common for tilings that aren’t periodic. This approach revealed that the hat tiling could fill an entire infinite plane, and that its pattern would not repeat.

The second proof relied on the fact that the hat is part of a continuum of shapes: By gradually changing the relative lengths of the sides of the hat, the mathematicians were able to form a family of tiles that can take on the same nonrepeating pattern. By considering the relative sizes and shapes of the tiles at the extremes of that family — one shaped like a chevron and the other reminiscent of a comet — the team was able to show that the hat couldn’t be arranged in a periodic pattern.
While the paper has yet to be peer-reviewed, the experts interviewed for this article agree that the result seems likely to hold up to detailed scrutiny.

Nonrepeating patterns can have real-world connections. Materials scientist Dan Shechtman won the 2011 Nobel Prize in chemistry for his discovery of quasicrystals, materials with atoms arranged in an orderly structure that never repeats, often described as analogs to Penrose’s tilings (SN: 10/5/11). The new aperiodic tile could spark further investigations in materials science, Senechal says.

Similar tilings have inspired artists, and the hat appears to be no exception. Already the tiling has been rendered artistically as smiling turtles and a jumble of shirts and hats. Presumably it’s only a matter of time before someone puts hat tiles on a hat.

The new aperiodic monotile discovered by Dave Smith, Joseph Myers, Craig Kaplan, and Chaim Goodman-Strauss, rendered as shirts and hats. The hat tiles are mirrored relative to the shirt tiles. pic.twitter.com/BwuLUPVT5a

— Robert Fathauer (@RobFathauerArt) March 21, 2023
And the hat isn’t the end. Researchers should continue the hunt for additional einsteins, says computer scientist Craig Kaplan of the University of Waterloo in Canada, a coauthor of the study. “Now that we’ve unlocked the door, hopefully other new shapes will come along.”

The ghost catfish transforms from glassy to glam when white light passes through its mostly transparent body. Now, scientists know why.

The fish’s iridescence comes from light bending as it travels through microscopic striped structures in the animal’s muscles, researchers report March 13 in the Proceedings of the National Academy of Sciences.

Many fishes with iridescent flair have tiny crystals in their skin or scales that reflect light (SN: 4/6/21). But the ghost catfish (Kryptopterus vitreolus) and other transparent aquatic species, like eel larvae and icefishes, lack such structures to explain their luster.

The ghost catfish’s see-through body caught the eye of physicist Qibin Zhao when he was in an aquarium store. The roughly 5-centimeter-long freshwater fish is a popular ornamental species. “I was standing in front of the tank and staring at the fish,” says Zhao, of Shanghai Jiao Tong University. “And then I saw the iridescence.”

To investigate the fish’s colorful properties, Zhao and colleagues first examined the fish under different lighting conditions. The researchers determined its iridescence arose from light passing through the fish rather than reflecting off it. By using a white light laser to illuminate the animal’s muscles and skin separately, the team found that the muscles generated the multicolored sheen.
The researchers then characterized the muscles’ properties by analyzing how X-rays scatter when traveling through the tissue and by looking at it with an electron microscope. The team identified sarcomeres — regularly spaced, banded structures, each roughly 2 micrometers long, that run along the length of muscle fibers — as the source of the iridescence.

The sarcomeres’ repeating bands, comprised of proteins that overlap by varying amounts, bend white light in a way that separates and enhances its different wavelengths. The collective diffraction of light produces an array of colors. When the fish contracts and relaxes its muscles to swim, the sarcomeres slightly change in length, causing a shifting rainbow effect.
The purpose of the ghost catfish’s iridescence is a little unclear, says Heok Hee Ng, an independent ichthyologist in Singapore who was not involved in the new study. Ghost catfish live in murky water and seldom rely on sight, he says. But the iridescence might help them visually coordinate movements when traveling in schools, or it could help them blend in with shimmering water to hide from land predators, like some birds, he adds.

Regardless of function, Ng is excited to see scientists exploring the ghost catfish’s unusual characteristics.

“Fishes actually have quite a number of these interesting structures that serve them in many ways,” he says. “And a lot of these structures are very poorly studied.”

DNA from a 9,000-year-old baby tooth from Alaska, the oldest natural mummy in North America and remains of ancient Brazilians is helping researchers trace the steps of ancient people as they settled the Americas. Two new studies give a more detailed and complicated picture of the peopling of the Americas than ever before presented.

People from North America moved into South America in at least three migration waves, researchers report online November 8 in Cell. The first migrants, who reached South America by at least 11,000 years ago, were genetically related to a 12,600-year-old toddler from Montana known as Anzick-1 (SN: 3/22/14, p. 6). The child’s skeleton was found with artifacts from the Clovis people, who researchers used to think were the first people in the Americas, although that idea has fallen out of favor. Scientists also previously thought these were the only ancient migrants to South America.
But DNA analysis of samples from 49 ancient people suggests a second wave of settlers replaced the Clovis group in South America about 9,000 years ago. And a third group related to ancient people from California’s Channel Islands spread over the Central Andes about 4,200 years ago, geneticist Nathan Nakatsuka of Harvard University and colleagues found.
People who settled the Americas were also much more genetically diverse than previously thought. At least one group of ancient Brazilians shared DNA with modern indigenous Australians, a different group of researchers reports online November 8 in Science.
Early Americans moved into prehistoric South America in at least three migratory waves, a study proposes. Ancestral people who crossed from Siberia into Alaska first gave rise to groups that settled North America (gray arrows). The first wave of North Americans (blue) were related to Clovis people, represented by a 12,600-year-old toddler from Montana called Anzick-1. They moved into South America at least 11,000 years ago, followed by a second wave (green) whose descendants contributed most of the indigenous ancestry among South Americans today. A third migration wave (yellow) from a group that lived near California’s Channel Island moved into the Central Andes about 4,200 years ago. Dotted areas indicate that people there today still have that genetic ancestry.
Genetically related, but distinct groups of people came into the Americas and spread quickly and unevenly across the continents, says Eske Willerslev, a geneticist at the Natural History Museum of Denmark in Copenhagen and a coauthor of the Science study. “People were spreading like a fire across the landscape and very quickly adapted to the different environments they were encountering.”

Both studies offer details that help fill out an oversimplified narrative of the prehistoric Americas, says Jennifer Raff, an anthropological geneticist at the University of Kansas in Lawrence who was not involved in the work. “We’re learning some interesting, surprising things,” she says.

For instance, Willerslev’s group did detailed DNA analysis of 15 ancient Americans different from those analyzed by Nakatsuka and colleagues. A tooth from Trail Creek in Alaska was from a baby related to a group called the ancient Beringians, who occupied the temporary land mass between Alaska and Siberia called Beringia. Sometimes called the Bering land bridge, the land mass was above water before the glaciers receded at the end of the last ice age. The ancient Beringians stayed on the land bridge and were genetically distinct from the people who later gave rise to Native Americans, Willerslev and colleagues found.

The link between Australia and ancient Amazonians also hints that several genetically distinct groups may have come across Beringia into the Americas.

The Australian signature was first found in modern-day indigenous South Americans by Pontus Skoglund and colleagues (SN: 8/22/15, p. 6). No one was sure why indigenous Australians and South Americans shared DNA since the groups didn’t have any recent contact. One possibility, says Skoglund, a geneticist at the Francis Crick Institute in London and a coauthor of the Cell paper, was that the signature was very old and inherited from long-lost ancestors of both groups.

So Skoglund, Nakatsuka and colleagues tested DNA from a group of ancient Brazilians, but didn’t find the signature. Willerslev’s group, however, examined DNA from 10,400-year-old remains from Lagoa Santa, Brazil, and found the signature, supporting the idea that modern people could have inherited it from much older groups. And Skoglund is thrilled. “It’s amazing to see it confirmed,” he says.

How that genetic signature got to Brazil in the first place is still a mystery, though. Researchers don’t think early Australians paddled across the Pacific Ocean to South America. “None of us really think there was some sort of Pacific migration going on here,” Skoglund says.

That leaves an overland route through Beringia. There’s only one problem: Researchers didn’t find the Australian signature in any of the ancient remains tested from North or Central America. And no modern-day indigenous North or Central Americans tested have the signature either.

Still, Raff thinks it likely that an ancestral group of people from Asia split off into two groups, with one heading to Australia and the other crossing the land bridge into the Americas. The group that entered the Americas didn’t leave living descendants in the north. Or, because not many ancient remains have been studied, it’s possible that scientists have just missed finding evidence of this particular migration.

If Raff is right, that could mean that multiple groups of genetically distinct people made the Berigian crossing, or that one group crossed but was far more genetically diverse than researchers have realized.

The studies may also finally help lay to rest a persistent idea that some ancient remains in the Americas are not related to Native Americans today.

The Lagoa Santans from Brazil and a 10,700-year-old mummy from a place called Spirit Cave in Nevada had been grouped as “Paleoamericans” because they both had narrow skulls with low faces and protruding jaw lines, different from other Native American skull shapes. Some researchers have suggested that Paleoamericans — including the so-called Kennewick Man, whose 8,500-year-old remains were found in the state of Washington (SN: 12/26/15, p. 30) — weren’t Native Americans, but a separate group that didn’t have modern descendants.

But previous studies of Paleoamericans and Willerslev’s analysis of the Spirit Cave mummy’s DNA provide evidence that, despite their skull shapes, the Paleoamericans were not different from other Native Americans of their time. And the ancient people are more closely related to present-day Native Americans than any other group.

Willerslev presented the results about the Spirit Cave mummy to the Fallon Paiute-Shoshone tribe when the data became available. Based on the genetic results, the tribe was able to claim the mummy as an ancestor and rebury the remains.

What do you get when you flip a fossilized “jellyfish” upside down? The answer, it turns out, might be an anemone.

Fossil blobs once thought to be ancient jellyfish were actually a type of burrowing sea anemone, scientists propose March 8 in Papers in Palaeontology.

From a certain angle, the fossils’ features include what appears to be a smooth bell shape, perhaps with tentacles hanging beneath — like a jellyfish. And for more than 50 years, that’s what many scientists thought the animals were.
But for paleontologist Roy Plotnick, something about the fossils’ supposed identity seemed fishy. “It’s always kind of bothered me,” says Plotnick, of the University of Illinois Chicago. Previous scientists had interpreted one fossil feature as a curtain that hung around the jellies’ tentacles. But that didn’t make much sense, Plotnick says. “No jellyfish has that,” he says. “How would it swim?”

One day, looking over specimens at the Field Museum in Chicago, something in Plotnick’s mind clicked. What if the bell belonged on the bottom, not the top? He turned to a colleague and said, “I think this is an anemone.”

Rotated 180 degrees, Plotnick realized, the fossils’ shape — which looks kind of like an elongated pineapple with a stumpy crown — resembles some modern anemones. “It was one of those aha moments,” he says. The “jellyfish” bell might be the anemone’s lower body. And the purported tentacles? Perhaps the anemone’s upper section, a tough, textured barrel protruding from the seafloor.

Plotnick and his colleagues examined thousands of the fossilized animals, dubbed Essexella asherae, unearthing more clues. Bands running through the fossils match the shape of some modern anemones’ musculature. And some specimens’ pointy protrusions resemble an anemone’s contracted tentacles.
“It’s totally possible that these are anemones,” says Estefanía Rodríguez, an anemone expert at the American Museum of Natural History in New York City who was not involved with the work. The shape of the fossils, the comparison with modern-day anemones — it all lines up, she says, though it’s not easy to know for sure.

Paleontologist Thomas Clements agrees. Specimens like Essexella “are some of the most notoriously difficult fossils to identify,” he says. “Jellyfish and anemones are like bags of water. There’s hardly any tissue to them,” meaning there’s little left to fossilize.
Still, it’s plausible that the blobs are indeed fossilized anemones, says Clements, of Friedrich-Alexander-Universität Erlangen-Nürnberg in Germany. He was not part of the new study but has spent several field seasons at Mazon Creek, the Illinois site where Essexella lived some 310 million years ago. Back then, the area was near the shoreline, Clements says, with nearby rivers dumping sediment into the environment – just the kind of place ancient burrowing anemones may have once called home.