Fossilized footprints from an iguana-like reptile provide what could be the earliest evidence of a lizard running on two legs.

The 29 exceptionally well-preserved lizard tracks, found in a slab of rock from an abandoned quarry in Hadong County, South Korea, include back feet with curved digits and front feet with a slightly longer third digit. The back footprints outnumber the front ones, and digit impressions are more pronounced than those of the balls of the feet. The lizard’s stride length also increases across the slab.
That’s what you’d expect to see in a transition from moseying along on four legs to scampering on two, says Yuong-Nam Lee, a paleontologist at Seoul National University who first came across the slab back in 2004. A closer examination two years ago revealed the telltale tracks.

Lee and his colleagues attribute the tracks to a previously unknown lizard ichnospecies, that is a species defined solely by trace evidence of its existence, rather than bones or tissue. Lee and his colleagues have dubbed the possible perpetrator Sauripes hadongensis and linked it to an order that includes today’s iguanas and chameleons in the Feb. 15 Scientific Reports.
Bipedal running certainly would have come in handy when escaping predatory pterosaurs some 110 million to 128 million years ago, the age of the rock slab. Lizard tracks are pretty rare in the fossil record, due to the reptiles’ lightweight bodies and penchant for habitats that don’t make great fossils. Though tracks appear in older fossils from the Triassic Epoch, 200 million to 250 million years ago, those prints belong to more primitive lizardlike reptiles. The new find edges out another set from the same region as the oldest true lizard tracks in the world by a few million years, the researchers say.
Plenty of modern lizards use two legs to scurry around. Some studies have linked similarities in ancient lizard bone structure to bipedal locomotion, but it is unclear exactly when lizards developed bipedalism. Lee’s team argues that these tracks represent the earliest and only direct evidence of bipedal running in an ancient lizard.

Martin Lockley, a paleontologist at the University of Colorado Denver who studies ancient animal tracks, points to alternative explanations. S. hadongensis might have trampled over front prints with its back feet, obscuring them and giving the appearance of two-legged running. Preservation can vary between back and front footprints. And the stride lengths aren’t quite as long as what Lockley says he’d expect to see in running. “Running or ‘leaping’ lizards make for a good story, but I am skeptical based on the evidence,” he adds.

So it may take the discovery of more fossilized lizard prints to determine whether S. hadongensis’ tracks truly represent running on two legs rather than simply scurrying on four.

When it comes to wild claims, hold your horses.

Free-roaming Przewalski’s horses of Central Asia are often called the last of the wild horses, the only living equines never domesticated. But a new genetic analysis of ancient horse bones suggests that these horses have a tamed ancestor after all, making them feral rather than wild.

The findings also debunk the idea that these domesticated ancestors — known as Botai horses —gave rise to all other modern horses. That leaves the progenitors of today’s domesticated horses a mystery, researchers report online February 22 in Science.

The earliest known domesticated horses were those of the ancient Botai people in northern Kazakhstan (SN: 3/28/09, p. 15). Botai sites dating to around 5,500 years ago are scattered with remnants of harnesses and pots with horse-milk residue, suggesting the animals provided both transportation and food.

To see how Botai horses relate to today’s steeds, evolutionary geneticist Ludovic Orlando of the Natural History Museum of Denmark in Copenhagen and colleagues analyzed DNA from 88 horses spanning the last 5,000 years or so across Europe and Asia. Horses from the last 4,000 years had less than 3 percent Botai ancestry, suggesting that different and unknown horses founded today’s populations. But Botai horses are direct ancestors of Przewalski’s horses, the study found.

Ask a classroom of children to draw a scientist, and you’ll see plenty of Crayola-colored lab coats, goggles and bubbling beakers. That image hasn’t changed much since the 1960s. But the person wearing the lab coat is shifting.

A new analysis finds that more female scientists have appeared in kids’ drawings in recent decades — going from nearly nonexistent in the 1960s to about a third in 2016.

“A lot has changed since the 1960s,” says David Miller, a Ph.D. candidate in psychology at Northwestern University who reports the findings with colleagues March 20 in Child Development.
The first of many “draw-a-scientist” studies asked nearly 5,000 children to draw a scientist between 1966 and 1977. “Of those 5,000 drawings,” Miller says, “only 28 … depicted a female scientist.” That’s just 0.6 percent.

Today, “more women are becoming scientists, and there’s some evidence that female scientists are being represented more in the media,” he says. For instance, in a content analysis of the magazine Highlights for Children, 13 percent of people pictured in science feature stories of the 1960s were women or girls, compared with 44 percent in the 2000s.
To look for changes in children’s perceptions over time, the researchers conducted a meta-analysis, combining data from 78 studies that included a total of more than 20,000 U.S. children in kindergarten through 12th grade.

On average, 28 percent of children drew female scientists in studies conducted from 1985 to 2016, the researchers found.

What hasn’t changed much: Kids pick up stereotypes by gender as they grow up. At age 6, girls in the more recent studies drew female scientists about 70 percent of the time. By age 16, 75 percent drew male scientists.

“This is a critical period in which kids are learning stereotypes,” Miller says. “It’s important that teachers and parents present diverse examples of both male and female scientists.”

Editors’ note: This story was corrected on March 21, 2018, to note that by age 16, girls drew only 25 percent of scientists as female.

Off the Kohala coast on the Big Island of Hawaii, Christine Gabriele spots whale 875. The familiar propeller scar on its left side and the shape of its dorsal fin are like a telltale fingerprint. Gabriele, a marine biologist with the Hawaii Marine Mammal Consortium, confirms the whale’s identity against her extensive photo catalog. Both Gabriele and this male humpback have migrated to this Pacific Island from Southeastern Alaska.

In those Alaska summer feeding grounds, Gabriele sees the same 300 or so whales “again and again.” But winter brings more than 10,000 whales to the waters of Hawaii from all over the North Pacific. Spotting 875 is like finding a needle in a haystack.
Gabriele is here today to focus on the slew of worrisome bumps on the familiar traveler’s flank. The bumps are separate from the usual ones bulging from the head of a humpback ( Megaptera novaeangliae ). Those iconic oversize hair follicles are thought to be part of the sensory system. The smaller body bumps look more like bad acne or an allergic reaction. Noted on rare occasions in the 1970s, the condition called nodular dermatitis has become much more prevalent. These days, Gabriele and colleagues see these skin lesions on over 75 percent of Hawaii’s humpback visitors.
The bumps coincide with other suggestions of declining health in the whales. In the nearly three decades that Gabriele has been studying whales, she would not describe the animals as skinny. Now, often “you can see their shoulder blades,” she says. “They look angular rather than round.”
Gabriele’s team is trying to figure out the cause of the bumps, comparing tissue samples from bumpy and nonbumpy whales. Several times per week, a small team sets out on the water, research permits in hand. Once a whale pod is spotted, Gabriele’s colleague Suzanne Yin zooms in with a camera and volunteer Kim New enlarges the image on her iPad, examining skin on the whale’s flanks and behind the blowhole to confirm if it’s bumpy or not. Gabriele carefully steers the boat so that Yin can shoot a biopsy dart from a crossbow.
The dart “takes a little plug of skin and blubber … about the size of a pencil eraser,” Gabriele says. The dart bounces off the whale and floats until the researchers can grab it. When darted, some whales dive; others show no reaction at all.

Collaborators from the National Institute of Standards and Technology’s Hollings Marine Laboratory in Charleston, S.C., are analyzing the skin for trace elements. National Marine Fisheries Service lab staff are studying the blubber for organic pollutants like PCBs and flame retardants. Preliminary results suggest that bumpy whales differ from nonbumpy in levels of manganese and a few other trace elements. Gabriele eagerly awaits the full analyses to make sense of what she’s seeing among the migratory creatures.

A chicken eggshell has a tricky job: It must protect a developing chick, but then ultimately let the chick break free. The secret to its success lies in its complex nanostructure — and how that structure changes as the egg incubates.

Chicken eggshells are about 95 percent calcium carbonate by mass. But they also contain hundreds of different kinds of proteins that influence how that calcium carbonate crystalizes. The interaction between the mineral crystals and the proteins yields an eggshell that’s initially crack-resistant, while making nanoscale adjustments over time that ultimately let a chick peck its way out, researchers report online March 30 in Science Advances.
Researchers used a beam of ions to cut thin cross sections in chicken eggshells. They then analyzed the shells with electron microscopy and other high-resolution imaging techniques. The team found that proteins disrupt the crystallization of calcium carbonate, so that what seems at low resolution to be neatly aligned crystals is actually a more fragmented jumble. This misalignment can make materials more resilient: Instead of spreading unimpeded, a crack must zig and zag through scrambled crystals.
Lab tests back up that finding: The researchers added a key shell-building protein called osteopontin to calcium carbonate to yield crystals like those seen in the eggshells. The presence of that protein makes calcium carbonate crystals form in a nanostructured pattern, rather than smooth and even crystal, study coauthor Marc McKee, a biomineralization researcher at McGill University in Montreal, and colleagues found.

The team also found structural variation on a minute scale throughout the eggshell, though it’s only about a third of a millimeter thick. Inner layers have less osteopontin, leading to bigger nanostructures. That may make the inner shell less resilient than the outer shell, which makes sense, McKee says­­. The outer shell needs to be hard enough to protect the chick, while the inner shell nourishes the developing chick.

Over time, the inner layers of the shell dissolve through a chemical reaction, releasing calcium to build a chick’s developing bones. The eggshell undergoes structural changes to facilitate that process, McKee and his colleagues found.

The researchers compared fertilized eggs incubated for 15 days to nonfertilized eggs. Over time, the nanostructures toward the inner shell became smaller in fertilized eggs, but remained the same in the nonfertilized eggs. The change gives the inside of the eggshell a bumpier texture, and by extension, more surface area. That provides more space for that shell-dissolving chemical reaction to take place, the researchers propose. The reaction also thins the shell overall, making it easier for a chick to break through from the inside when it’s time to hatch.

Advances in imaging technology are helping scientists find new details like this even in objects as familiar as a chicken eggshell, says Lara Estroff, a materials scientist at Cornell University who wasn’t part of the research. In connecting the eggshell’s functionality with its fine-grain structure, the new study could provide inspiration for designing new kinds of materials with specific properties.

Your brain might make new nerve cells well into old age.

Healthy people in their 70s have just as many young nerve cells, or neurons, in a memory-related part of the brain as do teenagers and young adults, researchers report in the April 5 Cell Stem Cell. The discovery suggests that the hippocampus keeps generating new neurons throughout a person’s life.

The finding contradicts a study published in March, which suggested that neurogenesis in the hippocampus stops in childhood (SN Online: 3/8/18). But the new research fits with a larger pile of evidence showing that adult human brains can, to some extent, make new neurons. While those studies indicate that the process tapers off over time, the new study proposes almost no decline at all.
Understanding how healthy brains change over time is important for researchers untangling the ways that conditions like depression, stress and memory loss affect older brains.

When it comes to studying neurogenesis in humans, “the devil is in the details,” says Jonas Frisén, a neuroscientist at the Karolinska Institute in Stockholm who was not involved in the new research. Small differences in methodology — such as the way brains are preserved or how neurons are counted — can have a big impact on the results, which could explain the conflicting findings. The new paper “is the most rigorous study yet,” he says.

Researchers studied hippocampi from the autopsied brains of 17 men and 11 women ranging in age from 14 to 79. In contrast to past studies that have often relied on donations from patients without a detailed medical history, the researchers knew that none of the donors had a history of psychiatric illness or chronic illness. And none of the brains tested positive for drugs or alcohol, says Maura Boldrini, a psychiatrist at Columbia University. Boldrini and her colleagues also had access to whole hippocampi, rather than just a few slices, allowing the team to make more accurate estimates of the number of neurons, she says.
To look for signs of neurogenesis, the researchers hunted for specific proteins produced by neurons at particular stages of development. Proteins such as GFAP and SOX2, for example, are made in abundance by stem cells that eventually turn into neurons, while newborn neurons make more of proteins such as Ki-67. In all of the brains, the researchers found evidence of newborn neurons in the dentate gyrus, the part of the hippocampus where neurons are born.

Although the number of neural stem cells was a bit lower in people in their 70s compared with people in their 20s, the older brains still had thousands of these cells. The number of young neurons in intermediate to advanced stages of development was the same across people of all ages.

Still, the healthy older brains did show some signs of decline. Researchers found less evidence for the formation of new blood vessels and fewer protein markers that signal neuroplasticity, or the brain’s ability to make new connections between neurons. But it’s too soon to say what these findings mean for brain function, Boldrini says. Studies on autopsied brains can look at structure but not activity.

Not all neuroscientists are convinced by the findings. “We don’t think that what they are identifying as young neurons actually are,” says Arturo Alvarez-Buylla of the University of California, San Francisco, who coauthored the recent paper that found no signs of neurogenesis in adult brains. In his study, some of the cells his team initially flagged as young neurons turned out to be mature cells upon further investigation.

But others say the new findings are sound. “They use very sophisticated methodology,” Frisén says, and control for factors that Alvarez-Buylla’s study didn’t, such as the type of preservative used on the brains.

Composting waste is heralded as being good for the environment. But it turns out that compost collected from homes and grocery stores is a previously unknown source of microplastic pollution, a new study April 4 in Science Advances reports.

This plastic gets spread over fields, where it may be eaten by worms and enter the food web, make its way into waterways or perhaps break down further and become airborne, says Christian Laforsch, an ecologist at the University of Bayreuth in Germany. Once the plastic is spread across fields, “we don’t know its fate,” he says.
That fate and the effects of plastic pollution on land and in freshwater has received little research attention compared with marine plastic pollution, says ecologist Chelsea Rochman of the University of Toronto. Ocean microplastics have gained notoriety thanks in part to coverage of the floating hulk of debris called the great Pacific garbage patch (SN Online: 3/22/18).

But current evidence suggests that plastic pollution is as prevalent in land and freshwater ecosystems as it is in the oceans, where it’s found “from the equator to the poles,” says Rochman, author of a separate commentary on the state of plastic pollution research published in the April 6 Science. Plastic “is seen in the high Arctic, where we suspect it comes down in rain. We know it’s in drinking water, in our seafood and spread on our agricultural fields,” she says.

Laforsch and his colleagues looked at several different kinds of biowaste that’s composted and spread on farmland in Germany, including household compost and grass clippings, supermarket waste and grain silage leftover from biogas production.

Compost samples taken from supermarket waste contained the greatest amount of plastic particles, with 895 pieces larger than 1 millimeter found per kilogram of dry weight. Household compost in contrast contained 20 and 24 particles per kg of dry weight, depending on the size of the sieves used to sift the compost. The detritus included bits of polyester and a lot of styrene-based polymers, commonly used in food packaging. Almost no particles were found in samples of silage from biogas production.
“I never thought about plastic in compost ending up as fertilizer. But when you think about it, it makes sense,” says environmental scientist Ad Ragas of Radboud University in Nijmegen, The Netherlands, who wasn’t involved in the work. A crate of rotting cucumbers wrapped in plastic that gets chucked, those stickers on every tomato in a bunch — that packaging doesn’t disappear.

Ragas says compost probably doesn’t contribute as much plastic to the environment as other sources, such as sewage treatment plant sludge, which contains polyester debris from clothes washers, and runoff from streets, which can be loaded with particles of synthetic rubber used in tires. But the compost contribution deserves investigation, Ragas says. “This triggers a lot of questions we haven’t studied yet.”

Those questions include possible effects on different organisms, from plants to earthworms to birds to people, Rochman says. Those effects will likely differ depending on the kind of plastic, which varies depending on its starting polymer and the additives used to impart certain qualities such as flexibility, sturdiness or durability under ultraviolet light.

“We are not saying we should get rid of all plastics,” Rochman says. “But we do need to start thinking of plastics as a persistent global pollutant.”

A hellishly unprecedented scene — what anthropologists suspect is the largest known child sacrifice — has been unearthed on a bluff overlooking Peru’s northern shoreline.

Around 550 years ago, members of the Chimú empire ritually killed and buried at least 140 children, ages 5 to 14, and 200 young llamas, says a team led by Gabriel Prieto of the National University of Trujillo in Peru and John Verano of Tulane University in New Orleans.

“There are no other examples of child sacrifices anywhere in the world that compare to the magnitude of this Chimú event,” Verano says. The discovery was announced April 26 by National Geographic in Washington, D.C.
Except for a few incomplete skeletons, excavated children and llamas displayed cuts on their breast bones and dislocated ribs indicating that their chests had been sliced open. Three adults buried nearby on the bluff, including two women with violent head wounds, may have participated in the sacrifice.

Radiocarbon dating, mainly of ropes left around the llamas’ necks, puts the event at around 1450, shortly before the Inca conquered the Chimú in 1470.

A dried mud layer covering some of the sandy graves possibly resulted from flooding caused by massive rains. Agricultural crises triggered by repeated flooding might have led Chimú leaders to sacrifice children to their gods, Verano suggests.

For some neutron stars, the quickest way to cool off isn’t with a frosty beverage, but with lightweight, subatomic particles called neutrinos.

Scientists have spotted the first solid evidence that some neutron stars, the collapsed remnants of exploded stars, can rapidly cool their cores by emitting neutrinos. The result adds to evidence that scientists are gathering to understand the ultradense matter that is squished deep within a neutron star’s center.

The new evidence comes from a neutron star that repeatedly gobbled material from a neighboring star. The neutron star rapidly cooled off after its meals, scientists determined. X-rays emitted by the neutron star showed that the fast cooldown rate was consistent with a theorized effect called the direct Urca process, in which neutrinos quickly ferry energy away from a collapsed star, astrophysicist Edward Brown and colleagues report in the May 4 Physical Review Letters.
Neutron stars are known to emit neutrinos by a similar process that cools the star slowly. But previously, there wasn’t clear evidence for faster cooling. The team analyzed observations of the neutron star, located about 35,000 light-years from Earth, as it cooled during a 15-year interlude between feeding sessions. Neutrinos carried away energy about 10 times faster than the rate energy is radiated by the sun’s light — or about 100 million times quicker than the slow process, says Brown, of Michigan State University in East Lansing.

Although some other neutron stars have shown hints of such a quick chill, “this is basically the first object for which we can see the star actively cooling before our eyes,” says astrophysicist James Lattimer of Stony Brook University in New York, who was not involved with the research.

The direct Urca process, named by physicists George Gamow and Mário Schenberg in the 1940s, took its moniker from the now-defunct Urca casino in Rio de Janeiro. “The joke being that this process removes heat from the star the way the casino removes money from tourists’ pockets,” Brown says.
In the process, neutrons in the star’s core convert into protons and emit electrons and antineutrinos (the antimatter partners of neutrinos). Likewise, protons convert into neutrons and emit antielectrons and neutrinos. Because neutrinos and antineutrinos interact very rarely with matter, they can escape the core, taking energy with them. “The neutrino is a thief; it robs energy from the star,” says physicist Madappa Prakash of Ohio University in Athens, who was not involved with the research.

The observation may help scientists understand what goes on deep within neutron stars, the cores of which are squeezed to densities far beyond those achievable in laboratories. Although the simplest theory holds that the cores are crammed with neutrons and a smaller number of protons and electrons, scientists have also proposed that the collapsed stars may consist of weird states of matter, containing rare particles called hyperons or a sea of free-floating quarks, the particles that make up protons and neutrons (SN: 12/23/17, p. 7).

The direct Urca process can happen only if the fraction of protons in the center of the neutron star is larger than about 10 percent. So if the process happens, “that already tells us a lot,” says astrophysicist Wynn Ho of Haverford College in Pennsylvania, who was not involved in the research. Such observations could eliminate theories that would predict lower numbers of protons.

However, the scientists weren’t able to determine the mass of the neutron star, limiting the conclusions that can be drawn. But, says Prakash, if the mass of such a quickly cooling neutron star is measured, the neutron star’s interior makeup could be nailed down.

Far from their usual tropical waters, some 200 bottlenose dolphins and about 70 false killer whales have been spotted off the western coast of Canada’s Vancouver Island. Over on the Atlantic coast, bull sharks have turned a North Carolina estuary into a nursery — a sight more familiar in Florida, until now.

Two new studies highlight the unusual northern sightings of these three ocean predators.“Alone, these sightings could be seen as accidental, or vagrancies,” says marine ecologist Luke Halpin of Halpin Wildlife Research in Vancouver and part of the team tracking the dolphins sighting. “But we’re seeing a lot of warm-water species ranging into historically cold North Pacific waters.” Those include dwarf sperm whales (Kogia sima), pygmy sperm whales (Kogia breviceps) and short-finned pilot whales (Globicephala macrorhynchus) documented by other researchers.
The results suggest that these marine species will increasingly migrate outside of their typical range as climate change increases ocean temperatures, researchers say. In just the last century, average sea temperatures have risen every decade by 0.07 degrees Celsius, though temperature changes can vary widely by location.

The eastern North Pacific Ocean had experienced a three-year period of warming from 2013 to 2016, and by July 2017, water temperatures about 180 kilometers offshore of Vancouver Island hit 16.5° C. That’s smack in the middle of the range that common bottlenose dolphins (Tursiops truncatus) prefer and at the low end for false killer whales (Pseudorca crassidens).

Typically, bottlenose dolphins aren’t found in offshore waters above Eureka, Calif., and false killer whales don’t venture north of Pismo Beach, Calif. But during a routine seabird and marine mammal survey, Halpin spotted a large herd of the marine mammals off the boat’s stern. He watched for 40 minutes as the dolphins and false killer whales leaped through the water and paused to spyhop, popping their heads up vertically out of the water. At one point, some came within 400 meters of the boat. It was the first time either species had been seen in noncoastal waters of the Canadian Pacific, the researchers report online April 20 in Marine Biodiversity Records.

A similar trend is being seen in the Atlantic Ocean, with baby bull sharks appearing in increasing numbers every year since 2011 in Pamlico Sound in North Carolina, another research team reports online April 16 in Scientific Reports. Previously, the northernmost nursery for bull sharks (Carcharhinus leucas) had been Florida’s Indian River Lagoon.
But since 2008, water temperatures in early summer, when bull sharks give birth to live young, have exceeded 25° Celsius more than 60 percent of the time in the North Carolina estuary. Salinity also has slowly increased in the sound over the last few decades, from a range of 4.5 to 18.3 parts per thousand in 1971 to 9 to 17.4 parts per thousand since 2011. Young bull sharks are found only in salinities higher than 9 parts per thousand.

Changing conditions in the sound have created “the comfort zone that bull sharks will reproduce in,” says marine ecologist Charles Bangley of the Smithsonian Environmental Research Center in Edgewater, Md., lead author on the shark study.

Migration by these three top-level ocean predators could have consequences for predator-prey relationships, says marine ecologist Rebecca Selden at Rutgers University in New Brunswick, N.J., who was not involved in either of the studies. Dolphins and sharks eat a wide range of prey, so as they move into new areas, prey species there may encounter these larger predators for the first time. That could impact populations of prey species, which in turn could “cause some big ecosystem effects,” she says.