As the morning sun peeked through the trees, Rodger Kram readied himself for the coming marathon. But not the kind he used to run.

Kram, a physiologist at the University of Colorado Boulder, stood next to undergrad James Wilson at the end of a rural dirt road. Each donned a strap of nylon webbing onto his head. Attached to the bottom of their straps — called tumplines — a log rested horizontally across the duo’s lower backs.
The pair was about to embark on a 25-kilometer trek to replicate how the ancient people of Chaco Canyon may have transported timber around 1,000 years ago (SN: 5/17/17). By the end of the day, their successful journey suggested that it would have taken just a few days for three people with tumplines to carry a full-size timber to Chaco, Kram, Wilson and colleagues reported on February 22 in the Journal of Archaeological Science: Reports.

Located in the northwest corner of New Mexico, Chaco Canyon is home to grand structures built between A.D. 850 and 1200. Multistoried stone buildings called great houses had roofs with timber beams about 5 meters long and 22 centimeters in diameter. The site contained at least 200,000 timbers of this size.
But the wood came from forests more than 75 kilometers away (SN: 9/26/01). Load-pulling animals and wheels weren’t there at the time, and the timbers don’t appear to have been dragged. Scientists are puzzled by how the ancient people, ancestors of modern-day Diné and Pueblo peoples, moved the large timbers.

A 1986 study suggested that each log used as a beam had a mass of 275 kilograms. But Kram suspected this number couldn’t be correct.

In 2016, he cut a section of a tree outside of his house — ponderosa pine, the same species used in Chaco — and weighed it on his bathroom scale. He then extrapolated that a 5-meter-long timber would be closer to 90 kilograms. This revelation led to a 2022 study recalculating the masses of the Chaco Canyon timbers as between 85 and 140 kilograms.

“As soon as we figured out that the weight was reasonable, I wanted to carry them,” Kram says.

He and Wilson proposed that tumplines could have been used to transport the timbers. These head straps have been found on every inhabited continent and are thought to have been used since at least around 2,000 years ago. They are still widely used to carry heavy loads, such as by professional porters in Nepal. A tumpline is placed on the crown of the head — to be in line with the cervical spine — with the attached cargo resting on the small of the back.
While there is no evidence that the people of Chaco used tumplines to haul timbers, there is proof that they used them to transport other items, like water vessels.

To see if tumpline timber transportation was humanly possible, Kram and Wilson trained for three months during the summer of 2020, gradually increasing their load weight and walk duration. Strangers who passed by couldn’t hide their confusion.

On the final day, the pair walked 25 kilometers while carrying a ponderosa pine that had been air-dried, which is how the people of Chaco may have prepared timbers. The 60-kilogram log was 2.5 meters long and 24 centimeters in diameter. The entire trek took almost 10 hours, and the weight of the full timber only slightly slowed the duo’s pace.

“I felt happy at the end that it was proved feasible, and that the 132-pound log we shared was off our necks,” says Wilson, now a medical student at the University of Colorado School of Medicine in Aurora. But “I never really doubted that we could do it.”

When you’re stressed and anxious, you might feel your heart race. Is your heart racing because you’re afraid? Or does your speeding heart itself contribute to your anxiety? Both could be true, a new study in mice suggests.

By artificially increasing the heart rates of mice, scientists were able to increase anxiety-like behaviors — ones that the team then calmed by turning off a particular part of the brain. The study, published in the March 9 Nature, shows that in high-risk contexts, a racing heart could go to your head and increase anxiety. The findings could offer a new angle for studying and, potentially, treating anxiety disorders.
The idea that body sensations might contribute to emotions in the brain goes back at least to one of the founders of psychology, William James, says Karl Deisseroth, a neuroscientist at Stanford University. In James’ 1890 book The Principles of Psychology, he put forward the idea that emotion follows what the body experiences. “We feel sorry because we cry, angry because we strike, afraid because we tremble,” James wrote.

The brain certainly can sense internal body signals, a phenomenon called interoception. But whether those sensations — like a racing heart — can contribute to emotion is difficult to prove, says Anna Beyeler, a neuroscientist at the French National Institute of Health and Medical Research in Bordeaux. She studies brain circuitry related to emotion and wrote a commentary on the new study but was not involved in the research. “I’m sure a lot of people have thought of doing these experiments, but no one really had the tools,” she says.

Deisseroth has spent his career developing those tools. He is one of the scientists who developed optogenetics — a technique that uses viruses to modify the genes of specific cells to respond to bursts of light (SN: 6/18/21; SN: 1/15/10). Scientists can use the flip of a light switch to activate or suppress the activity of those cells.
In the new study, Deisseroth and his colleagues used a light attached to a tiny vest over a mouse’s genetically engineered heart to change the animal’s heart rate. When the light was off, a mouse’s heart pumped at about 600 beats per minute. But when the team turned on a light that flashed at 900 beats per minutes, the mouse’s heartbeat followed suit. “It’s a nice reasonable acceleration, [one a mouse] would encounter in a time of stress or fear,” Deisseroth explains.

When the mice felt their hearts racing, they showed anxiety-like behavior. In risky scenarios — like open areas where a little mouse might be someone’s lunch — the rodents slunk along the walls and lurked in darker corners. When pressing a lever for water that could sometimes be coupled with a mild shock, mice with normal heart rates still pressed without hesitation. But mice with racing hearts decided they’d rather go thirsty.

“Everybody was expecting that, but it’s the first time that it has been clearly demonstrated,” Beyeler says.
The researchers also scanned the animals’ brains to find areas that might be processing the increased heart rate. One of the biggest signals, Deisseroth says, came from the posterior insula (SN: 4/25/16). “The insula was interesting because it’s highly connected with interoceptive circuitry,” he explains. “When we saw that signal, [our] interest was definitely piqued.”

Using more optogenetics, the team reduced activity in the posterior insula, which decreased the mice’s anxiety-like behaviors. The animals’ hearts still raced, but they behaved more normally, spending some time in open areas of mazes and pressing levers for water without fear.
A lot of people are very excited about the work, says Wen Chen, the branch chief of basic medicine research for complementary and integrative health at the National Center for Complementary and Integrative Health in Bethesda, Md. “No matter what kind of meetings I go into, in the last two days, everybody brought up this paper,” says Chen, who wasn’t involved in the research.

The next step, Deisseroth says, is to look at other parts of the body that might affect anxiety. “We can feel it in our gut sometimes, or we can feel it in our neck or shoulders,” he says. Using optogenetics to tense a mouse’s muscles, or give them tummy butterflies, might reveal other pathways that produce fearful or anxiety-like behaviors.

Understanding the link between heart and head could eventually factor into how doctors treat panic and anxiety, Beyeler says. But the path between the lab and the clinic, she notes, is much more convoluted than that of the heart to the head.

In the classic fairy tale, Hansel and Gretel dropped bread crumbs while walking through a treacherous forest so they wouldn’t lose their way. Rovers may one day use a similar trick to traverse other planets without losing their data.

Typically, if a rover permanently loses communication during a mission, all the information that it has gathered is lost. To avoid this, researchers suggest using a multi-rover system in which a smaller rover piggybacks on a larger “mother rover.” The smaller rover would then venture into any especially uncertain territory, such as a cave or lava tubes, deploying sensors the size of an AirPods case like bread crumbs as it goes.
The sensors could then communicate with each other via a wireless network and funnel any collected data back to the mother rover, theoretical physicist Wolfgang Fink and colleagues propose February 11 in Advances in Space Research. As proof of concept, the team built prototype sensors that communicate via Wi-Fi.

It’s not that the smaller rover would be following the “bread crumbs” back the way it came. Instead, “we use [the sensors] for the data to find its way communication-wise out of the cave to the mother rover,” says Fink, of the University of Arizona in Tucson.

The technology could also be useful here on Earth, especially after a natural disaster such as an earthquake. A rover could be sent with the deployable sensors into rubble where it’s too dangerous for people to perform search-and-rescue missions (SN: 12/3/14).

The bread crumb–like communication network could allow researchers to “cater to the essence of scientific exploration,” Fink says, by allowing rovers to overcome some of the constraints posed by tricky terrain. “To get to the real exciting science, you most of the time have to go to exotic places, hard-to-get-to places.”

An uncomfortable truth is that there is another influenza pandemic in humankind’s future. Whether it will be a relative of the lethal avian flu strain currently wreaking havoc in bird populations around the globe is anyone’s guess.

Because the virus, called H5N1, can be deadly to birds, mammals and people, researchers closely monitor reports of new cases. Worryingly, a new variant of H5N1 that emerged in 2020 has not only spread farther than ever before among birds, but has also spilled over into other animals, raising the specter of a human outbreak (SN: 12/12/22).

The variant was linked to a seal die-off in Maine last summer. In October, there was an H5N1 outbreak on a mink farm in Spain, researchers reported in January in Eurosurveillance. (It’s unclear how the mink were exposed, but the animals were fed poultry by-products.) Sea lions off the coast of Peru and wild bears, foxes and skunks, which prey upon or scavenge birds, in the United States and Europe have also tested positive for the virus.

Globally, hundreds of millions of domestic poultry have been culled or died from the new variant. It’s also likely that millions of wild birds have died, though few governmental agencies are counting, says Michelle Wille a viral ecologist at the University of Sydney who studies avian influenza. “This virus is catastrophic for bird populations.”

A handful of human cases have also been reported, though there’s no evidence that the virus is spreading among people. Of seven cases, six people recovered and one person from China died. In February, health officials in China reported an eighth case in a woman whose current condition is unknown.

What’s more, four of the reported human cases — including a U.S. case from Colorado and two workers linked to the Spanish mink farm — were in people who didn’t have any respiratory symptoms. That leaves open the possibility that those people were not truly infected. Instead, tests may have picked up viral contamination, say in the nose, that the people breathed in while handling infected birds.

The impossibility of predicting which avian influenza viruses might make the jump to people and spark an outbreak is in part related to knowledge gaps. These bird pathogens don’t typically easily infect or circulate among mammals including humans. And scientists don’t have a full grasp on how these viruses might need to change for human transmission to occur.

For now, it’s encouraging that so few people have gotten infected amid such a large outbreak among birds and other animals, says Marie Culhane, a food animal veterinarian at the University of Minnesota in St. Paul. Still, experts around the globe are diligently watching for any signs the virus may be evolving to spread more easily between people.

The good news is that flu drugs and vaccines that work against the virus already exist, Wille says. Compared with where the world was when the coronavirus behind the COVID-19 pandemic came on the scene, “we are already ahead of the game.”

How the virus would need to change to spread among people is a big unknown
This new iteration of bird flu is what’s called a highly pathogenic avian influenza, one that is particularly lethal for both domestic and wild birds. Aquatic birds such as ducks naturally carry avian flus with no or minor signs of infection. But when influenza viruses shuffle between poultry and waterfowl, variants with changes that make them lethal to birds can emerge and spread.

Avian viruses can be severe or even deadly for people. Since 2003, there have been 873 human cases of H5N1 infections reported to the World Health Organization. A little less than half of those people died. In February, an 11-year-old girl in Cambodia died after she developed severe pneumonia from an avian flu virus, the country’s first reported infection since 2014. Her father was also infected with the virus — a different variant than the one behind the widespread outbreak in birds —though he has not developed symptoms. It’s unknown how the two people were exposed.

Some of what scientists know about H5N1’s pandemic potential comes from controversial research on ferrets done more than a decade ago (SN: 6/21/13). Experiments showed that some changes to proteins that help the virus break into cells and make more copies of itself could help the virus travel through the air to infect ferrets, a common laboratory stand-in for humans in influenza research.

While researchers know these mutations are important in lab settings, it’s still unclear how crucial those changes are in the real world, says Jonathan Runstadler, a disease ecologist and virologist at Tufts University’s Cummings School of Veterinary Medicine in North Grafton, Mass.
Viruses change constantly, but not all genetic tweaks work together. A change may help one version of the virus transmit better, while also hurting another variant and making it less likely to spread.

“We’re not sure how critical or how big a difference or how much to worry about those mutations when they happen in the wild,” Runstadler says. “Or when they happen five years down the road when there are other changes in the virus’s genetic background that are impacting those [original] mutations.”

That doesn’t stop researchers from trying to pinpoint specific changes. Runstadler and his team look for viruses in nature that have jumped into new animals and work backward to figure out which mutations were crucial. And virologist Louise Moncla says her lab is trying to develop ways to scan entire genetic blueprints of viruses from past outbreaks to look for signatures of a virus that can jump between different animal species.

“There’s a ton that we don’t know about avian influenza viruses and host switching,” says Moncla, of the University of Pennsylvania.

Genetic analyses of H5N1 circulating on the mink farm in Spain, for instance, revealed a change known to help the virus infect mice and mammalian cells grown in the lab. Such a change could make it easier for the virus to spread among mammals, including people. There could have been mink-to-mink transmission on the farm, the researchers concluded, but it remains unclear how much of a role that specific mutation played in the outbreak.

It’s a numbers game for when influenza viruses with the ability to transmit among mammals might make the jump from birds, Runstadler says. “The more chances you give the virus to spill over and adapt, the higher the risk will be that one of those adaptations will be effective [at helping the virus spread among other animals] or take root and be a real problem.”

The ongoing outbreak is still a big problem for birds
Irrespective of our inability to forecast human’s future with H5N1, it’s clear that many species of birds — and some other animals that eat them — are dying now. And more species of birds are dying in this outbreak than previous ones, Culhane and Wille say.

“We have seen huge outbreaks in raptors and seabirds, which were never really affected before,” Wille says. It’s possible that genetic changes have helped the virus to spread more efficiently among birds than previous versions of H5N1, but that’s unknown. “There are a number of studies underway to try and figure it out,” Wille says.
Historically, these deadly avian flus have not been a persistent problem in the Americas, Moncla says. Sporadic outbreaks of H5N1 variants are typically limited to places such as parts of Asia, where the virus has circulated in birds since its emergence in the late 1990s, and northern Africa.

North America’s last big avian flu outbreak was in 2015, when experts detected more than 200 cases of a different bird flu virus in commercial and backyard poultry across the United States. The poultry industry culled more than 45 million birds to stop that virus’s spread, Culhane says. “But it didn’t go away from the rest of the world.”

The latest version of H5N1 arrived on North American shores from Europe in late 2021, first popping up in Canada in Newfoundland and Labrador. From there, it spread south into the United States, where so far tens of millions of domestic poultry have been culled to prevent transmission on farms where the virus has been detected. By December 2022, the virus had made it to South America. In Peru, tens of thousands of pelicans and more than 700 sea lions have died since mid-January.

It’s important to understand exactly how nonbird animals are getting exposed, Culhane says. Highly pathogenic avian influenzas infect every organ of a bird’s body. So, a fox chowing down on an infected bird is exposing its own mouth, nose and stomach to a lot of virus as it eats its meal.

For now, experts are keeping an eye on infected animals to raise the alarm early if H5N1 starts transmitting among mammals.

“I do think that the mink outbreak, and then the sea lion outbreak, is a wake-up call,” Moncla says. “We should be doing our very best to implement all the science we can to try and understand what’s happening with these viruses so that if the situation does change, we are better prepared.”

An experimental treatment for endometriosis, a painful gynecological disease that affects some 190 million people worldwide, may one day offer new hope for easing symptoms.

Monthly antibody injections reversed telltale signs of endometriosis in monkeys, researchers report February 22 in Science Translational Medicine. The antibody targets IL-8, a molecule that whips up inflammation inside the scattered, sometimes bleeding lesions that mark the disease. After neutralizing IL-8, those hallmark lesions shrink, the team found.

The new treatment is “pretty potent,” says Philippa Saunders, a reproductive scientist at the University of Edinburgh who was not involved with work. The study’s authors haven’t reported a cure, she points out, but their antibody does seem to have an impact. “I think it’s really very promising,” she says.

Many scientists think endometriosis occurs when bits of the uterine lining — the endometrium — slough off during menstruation. Instead of exiting via the vagina, they voyage in the other direction: up through the fallopian tubes. Those bits of tissue then trespass through the body, sprouting lesions where they land. They’ll glom onto the ovaries, fallopian tubes, bladder and other spots outside of the uterus and take on a life of their own, Saunders says.
The lesions can grow nerve cells, form tough nubs of tissue and even bleed during menstrual cycles. They can also kick off chronic bouts of pelvic pain. If you have endometriosis, you can experience “pain when you urinate, pain when you defecate, pain when you have sex, pain when you move around,” Saunders says. People with the disease can also struggle with infertility and depression, she adds. “It’s really nasty.”
Once diagnosed, patients face a dearth of treatment options — there’s no cure, only therapies to alleviate symptoms. Surgery to remove lesions can help, but symptoms often come back.

The disease affects at least 10 percent of girls, women and transgender men in their reproductive years, Saunders says. And people typically suffer for years — about eight on average — before a diagnosis. “Doctors consider menstrual pelvic pain a very common thing,” says Ayako Nishimoto-Kakiuchi, a pharmacologist at Chugai Pharmaceutical Co. Ltd. in Tokyo. Endometriosis “is underestimated in the clinic,” she says. “I strongly believe that this disease has been understudied.”

Hormonal drugs that stop ovulation and menstruation can also offer relief, says Serdar Bulun, a reproductive endocrinologist at Northwestern University Feinberg School of Medicine in Chicago not involved with the new study. But those drugs come with side effects and aren’t ideal for people trying to become pregnant. “I see these patients day in and day out,” he says. “I see how much they suffer, and I feel like we are not doing enough.”

Nishimoto-Kakiuchi’s team engineered an antibody that grabs onto the inflammatory factor IL-8, a protein that scientists have previously fingered as one potential culprit in the disease. The antibody acts like a garbage collector, Nishimoto-Kakiuchi says. It grabs IL-8, delivers it to the cell’s waste disposal machinery, and then heads out to snare more IL-8.

The team tested the antibody in cynomolgus monkeys that were surgically modified to have the disease. (Endometriosis rarely shows up spontaneously in these monkeys, the scientists discovered previously after screening more than 600 females.) The team treated 11 monkeys with the antibody injection once a month for six months. In these animals, lesions shriveled and the adhesive tissue that glues them to the body thinned out, too. Before this study, Nishimoto-Kakiuchi says, the team didn’t think such signs of endometriosis were reversible.
Her company has now started a Phase I clinical trial to test the safety of therapy in humans. The treatment is one of several endometriosis therapies scientists are testing (SN: 7/19/19) . Other trials will test new hormonal drugs, robot-assisted surgery and behavioral interventions.

Doctors need new options to help people with the disease, Saunders says. “There’s a huge unmet clinical need.”

LAS VEGAS — It’s a bold claim: The quest to create a superconductor that works under practical conditions is finally fulfilled, a team of researchers says. But controversy has dogged the team’s earlier claim of record-breaking superconductivity, and the new result is already facing extreme scrutiny.

The ultimate test will be whether the result can be confirmed by other researchers, says physicist Mikhail Eremets of the Max Planck Institute for Chemistry in Mainz, Germany. “I repeat it like [a] mantra: ‘Reproduce.’”
Many materials become superconductors, able to transmit electricity with no resistance, provided they’re cooled to very low temperatures. A few superconductors work under warmer conditions, but those must be squeezed to crushing pressures, so they’re impractical to use.

Now physicist Ranga Dias of the University of Rochester in New York and colleagues say they have created a superconductor that works at both room temperature and relatively low pressure. A superconductor that operates under such commonplace conditions could herald a new age of high-efficiency machines, supersensitive instrumentation and revolutionary electronics.

“This is the start of the new type of material that’s useful for practical applications,” Dias said March 7 at the American Physical Society meeting, where he reported the feat.

The superconductor is made of hydrogen mixed with nitrogen and a rare earth element called lutetium, Dias and colleagues report March 8 in Nature. The team combined the elements and squeezed them in a device known as a diamond anvil cell. The researchers then varied the pressure and temperature and measured the resistance to electrical flow in the compound.

At temperatures as high as 294 kelvins (about 21° Celsius or 70° Fahrenheit), the material seemed to lose any electrical resistance. It still required pressures of 10 kilobar, which is about 10,000 times the pressure of Earth’s atmosphere. But that’s far lower than the millions of atmospheres of pressure typically required for superconductors that operate near room temperature. If confirmed, that makes the material much more promising for real-world applications.

The material displayed several hallmarks of a superconductor, the team reports. Not only did the electrical resistance suddenly drop as it became superconducting, but the material also expelled magnetic fields and exhibited an abrupt change in its heat capacity, Dias says.

When the researchers put the squeeze on the material in the diamond anvil cell, it suddenly turned from a bluish hue to hot pink. “I had never seen a color change like this in a material,” Dias says. “It was like, wow.” That color change indicated a shift in the electrical properties of the material as it became a superconductor, Dias says.
This superconductor might be able to escape the confines of a diamond anvil cell, Dias says, opening it up to practical applications. A technique called strain engineering, for example, could mimic the required pressure. In such a process, researchers grow a material on a surface that constrains growth, putting a strain on the material that replicates the effects of externally applied squeezing.

Still, the research faces significant skepticism, in part because of the firestorm over the team’s earlier publication that claimed the discovery of superconductivity in a compound of carbon, sulfur and hydrogen at 15° C (SN: 10/14/20). Editors at Nature retracted that paper, over the objection of Dias and his coauthors, citing irregularities in the researchers’ data handling that undermined the editors’ confidence in the claims (SN: 10/3/22).

Several experts have expressed a lack of confidence in the new results presented by Dias’ group, based on that history. Not only was the previous result retracted, but other researchers were unable to reproduce it, says Eremets, including his own group at the Max Planck Institute. “The main test of validity — reproducibility — was failed, and from my point of view that’s the most important thing.”

The stakes are high. “If it’s true, it’s a great discovery,” says physicist Eugene Gregoryanz of the University of Edinburgh. But he views the researchers with suspicion. “Whether it’s true or not, I guess time will show.”

Others are more positive. “It’s an excellent study,” says materials chemist Russell Hemley of the University of Illinois Chicago. “The data as presented, in terms of evidence for superconductivity, is very strong.” Hemley was not involved with the study but has collaborated with Dias in the past, including on a follow-up to the retracted superconductor paper. Submitted February 16 at arXiv.org, that paper, which has not yet passed peer-review, reports that the previously claimed superconductor does function near room temperature.

The new superconductor is a hydrogen-rich type known as a hydride. Scientists predict that pure hydrogen should be a room-temperature superconductor, but only at extremely high pressures that make it difficult to produce. To lower the pressure, scientists have added in other elements, making hydride superconductors.

In 2015, Eremets and colleagues produced a compound of sulfur and hydrogen that was superconducting up to −70° C, a record high temperature at the time (SN: 12/15/15). A few years later, a compound of lanthanum and hydrogen was found to superconduct under still chilly conditions, but even closer to room temperature (SN: 9/10/18). Both materials require pressures too high for practical use.

It’s difficult to understand how the new superconductor fits in with other hydrides. Theoretical calculations of how similar hydrides behave wouldn’t suggest that such a material would be superconducting at the reported temperatures and pressures, says theoretical physicist Lilia Boeri of the Sapienza University of Rome. “For me, it looks very strange,” Boeri says. “It’s something completely unexpected…. If it’s true, it’s very different from the other hydrides.”

WASHINGTON — The tale of the first horseback riders may be written on the bones of the ancient Yamnaya people.

Five excavated skeletons dated to about 3000 to 2500 B.C. show clear signs of physical stress that hint these Yamnaya individuals may have frequently ridden horses, researchers reported March 3 at the American Association for the Advancement of Science Annual Meeting and in Science Advances. That makes the Yamnaya the earliest humans identified as likely horseback riders so far.
Five thousand years ago, the Yamnaya migrated widely, spreading Indo-European languages and altering the human gene pool across Europe and Asia (SN: 11/15/17; SN: 9/5/19). Their travels eventually stretched from modern-day Hungary to Mongolia, roughly 4,500 kilometers, and are thought to have taken place over only a couple of centuries.

“In many ways, [the Yamnaya] changed the history of Eurasia,” says archaeologist Volker Heyd of the University of Helsinki.

Horse domestication became widely established around 3500 B.C., probably for milk and meat (SN: 7/6/17). Some researchers have suggested the Botai people in modern-day Kazakhstan started riding horses during that time, but that’s debated (SN: 3/5/09). The Yamnaya had horses as well, and archaeologists have speculated that the people probably rode them, but evidence was lacking.

But the oldest known depictions of horseback riding are from about 2000 B.C. Complicating efforts to determine when the behavior emerged, possible riding gear would have been made of long-decayed natural materials, and scientists rarely, if ever, find complete horse skeletons from that time.
Heyd and colleagues weren’t seeking evidence of horsemanship. They were working on a massive project called the Yamnaya Impact on Prehistoric Europe to understand every aspect of the people’s lives.

While assessing over 200 human skeletons excavated from countries including Romania, Bulgaria and Hungary, bioanthropologist Martin Trautmann noticed that one individual’s bones carried distinct traits on the femur and elsewhere that he’d seen before. He immediately suspected horseback riding.

“It was just kind of a surprise,” says Trautmann, also of the University of Helsinki.

If it were a one-off case, he says he would have dismissed it. But as he continued analyzing skeletons, he noticed that several had the same traits.

Trautmann, Heyd and colleagues assessed all the skeletons for the presence of six physical signs of horseback riding that have been documented in previous research, a constellation of traits dubbed horsemanship syndrome. These signs included pelvis and femur marks that could have come from the biomechanical stress of sitting with spread legs while holding onto a horse, as well as healed vertebrae damage from injuries that could have come from falling off. The team also created a scoring system to account for the skeletal traits’ severity, preservation and relative importance.

“Bones are living tissue,” Trautmann says. “So they react to any type of environmental stimulus.”

The team deemed five Yamnaya male individuals as frequent horseback riders because they had four or more signs of horsemanship. Nine other Yamnaya males probably rode horses, but the researchers were less confident because the skeletons each displayed only three markers.
“Hypothetically speaking, it’s very logical,” says bioarchaeologist Maria Mednikova of the Russian Academy of Sciences in Moscow, who was not involved in the new study. The Yamnaya were very close to horses, she says, so at some point, they probably experimented with riding.

She now plans to check for the horse-riding traits in the Yamnaya skeletons she has access to. “The human skeletal system is like a book — if you have some knowledge, you can read it,” Mednikova says.

Archaeologist Ursula Brosseder, who also was not involved in the work, warns not to interpret this finding as equestrianism reaching its full bloom within the Yamnaya culture. Brosseder, formerly of the University of Bonn in Germany, sees the paper’s discovery as humans still figuring out what they could do with horses as part of early domestication.

As for Heyd, he says he has long suspected that the Yamnaya rode horses, considering that they had the animals and expanded so rapidly across such a large area. “Now, we have proof.”

SpaceX’s rapidly growing fleet of Starlink internet satellites now make up half of all active satellites in Earth orbit.

On February 27, the aerospace company launched 21 new satellites to join its broadband internet Starlink fleet. That brought the total number of active Starlink satellites to 3,660, or about 50 percent of the nearly 7,300 active satellites in orbit, according to analysis by astronomer Jonathan McDowell using data from SpaceX and the U.S. Space Force.
“These big low-orbit internet constellations have come from nowhere in 2019, to dominating the space environment in 2023,” says McDowell, of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. “It really is a massive shift and a massive industrialization of low orbit.”

SpaceX has been launching Starlink satellites since 2019 with the goal of bringing broadband internet to remote parts of the globe. And for just as long, astronomers have been warning that the bright satellites could mess up their view of the cosmos by leaving streaks on telescope images as they glide past (SN: 3/12/20).

Even the Hubble Space Telescope, which orbits more than 500 kilometers above the Earth’s surface, is vulnerable to these satellite streaks, as well as those from other satellite constellations. From 2002 to 2021, the percentage of Hubble images affected by light from low-orbit satellites increased by about 50 percent, astronomer Sandor Kruk of the Max-Planck Institute for Extraterrestrial Physics in Garching, Germany, and colleagues report March 2 in Nature Astronomy.

The number of images partially blocked by satellites is still small, the team found, rising from nearly 3 percent of images taken between 2002 and 2005 to just over 4 percent between 2018 and 2021 for one of Hubble’s cameras. But there are already thousands more Starlink satellites now than there were in 2021.

“The fraction of [Hubble] images crossed by satellites is currently small with a negligible impact on science,” Kruk and colleagues write. “However, the number of satellites and space debris will only increase in the future.” The team predicts that by the 2030s, the probability of a satellite crossing Hubble’s field of view any time it takes an image will be between 20 and 50 percent.
The sudden jump in Starlink satellites also poses a problem for space traffic, says astronomer Samantha Lawler of the University of Regina in Canada. Starlink satellites all orbit at a similar distance from Earth, just above 500 kilometers.

“Starlink is the densest patch of space that has ever existed,” Lawler says. The satellites are constantly navigating out of each other’s way to avoid collisions (SN: 2/12/09). And it’s a popular orbital altitude — Hubble is there, and so is the International Space Station and the Chinese space station.
“If there is some kind of collision [between Starlinks], some kind of mishap, it could immediately affect human lives,” Lawler says.

SpaceX launches Starlink satellites roughly once per week — it launched 51 more on March 3. And they’re not the only company launching constellations of internet satellites. By the 2030s, there could be 100,000 satellites crowding low Earth orbit.

So far, there are no international regulations to curb the number of satellites a private company can launch or to limit which orbits they can occupy.

“The speed of commercial development is much faster than the speed of regulation change,” McDowell says. “There needs to be an overhaul of space traffic management and space regulation generally to cope with these massive commercial projects.”

The oldest known fossils of pollen-laden insects are of earwig-like ground-dwellers that lived in what is now Russia about 280 million years ago, researchers report. Their finding pushes back the fossil record of insects transporting pollen from one plant to another, a key aspect of modern-day pollination, by about 120 million years.

The insects — from a pollen-eating genus named Tillyardembia first described in 1937 — were typically about 1.5 centimeters long, says Alexander Khramov, a paleoentomologist at the Borissiak Paleontological Institute in Moscow. Flimsy wings probably kept the creatures mostly on the forest floor, he says, leaving them to climb trees to find and consume their pollen.

Recently, Khramov and his colleagues scrutinized 425 fossils of Tillyardembia in the institute’s collection. Six had clumps of pollen grains trapped on their heads, legs, thoraxes or abdomens, the team reports February 28 in Biology Letters. A proportion that small isn’t surprising, Khramov says, because the fossils were preserved in what started out as fine-grained sediments. The early stages of fossilization in such material would tend to wash away pollen from the insects’ remains.
The pollen-laden insects had only a couple of types of pollen trapped on them, the team found, suggesting that the critters were very selective in the tree species they visited. “That sort of specialization is in line with potential pollinators,” says Michael Engel, a paleoentomologist at the University of Kansas in Lawrence who was not involved in the study. “There’s probably vast amounts of such specialization that occurred even before Tillyardembia, we just don’t have evidence of it yet.”

Further study of these fossils might reveal if Tillyardembia had evolved special pollen-trapping hairs or other such structures on their bodies or heads, says Conrad Labandeira, a paleoecologist at the National Museum of Natural History in Washington, D.C., also not part of the study. It would also be interesting, he says, to see if something about the pollen helped it stick to the insects. If the pollen grains had structures that enabled them to clump more readily, for example, then those same features may have helped them grab Velcro-like onto any hairlike structures on the insects’ bodies.

A form of lightning with a knack for sparking wildfires may surge under climate change.

An analysis of satellite data suggests “hot lightning” — strikes that channel electrical charge for an extended period — may be more likely to set landscapes ablaze than more ephemeral flashes, researchers report February 10 in Nature Communications. Each 1 degree Celsius of warming could spur a 10 percent increase in the most incendiary of these Promethean bolts, boosting their flash rate to about four times per second by 2090 — up from nearly three times per second in 2011.
That’s dangerous, warns physicist Francisco Javier Pérez-Invernón of the Institute of Astrophysics of Andalusia in Granada, Spain. “There will be more risk of lightning-ignited wildfires.”

Among all the forces of nature, lightning sets off the most blazes. Flashes that touch down amid minimal or no rainfall — known as dry lightning — are especially effective fire starters. These bolts have initiated some of the most destructive wildfires in recent years, such as the 2020 blazes in California (SN: 12/21/20).

But more than parched circumstances can influence a blast’s ability to spark flames. Field observations and laboratory experiments have suggested the most enduring form of hot lightning — “long continuing current lightning”— may be especially combustible. These strikes channel current for more than 40 milliseconds. Some last longer than one-third of a second — the typical duration of a human eye blink.

“This type of lightning can transport a huge amount of electrical discharge from clouds to the ground or to vegetation,” Pérez-Invernón says. Hot lightning’s flair for fire is analogous to lighting a candle; the more time a wick or vegetation is exposed to incendiary energy, the easier it kindles.

Previous research has proposed lightning may surge under climate change (SN: 11/13/14). But it has remained less clear how hot lightning — and its ability to spark wildfires — might evolve.

Pérez-Invernón and his colleagues examined the relationship between hot lightning and U.S. wildfires, using lightning data collected by a weather satellite and wildfire data from 1992 to 2018.

Long continuing current lightning could have sparked up to 90 percent of the roughly 5,600 blazes encompassed in the analysis, the team found. Since less than 10 percent of all lightning strikes during the summer in the western United States have long continuing current, the relatively high ignition count led the researchers to infer that flashes of hot lightning were more prone to sparking fire than typical bolts.
The researchers also probed the repercussions of climate change. They ran computer simulations of the global activity of lightning during 2009 to 2011 and from 2090 to 2095, under a future scenario in which annual greenhouse gas emissions peak in 2080 and then decline.

The team found that in the later period, climate change may boost updraft within thunderstorms, causing hot lightning flashes to increase in frequency to about 4 strikes per second globally — about a 40 percent increase from 2011. Meanwhile, the rate of all cloud-to-ground strikes might increase to nearly 8 flashes per second, a 28 percent increase.

After accounting for changes in precipitation, humidity and temperature, the researchers predicted wildfire risk will significantly increase in Southeast Asia, South America, Africa and Australia, and risk will go up most dramatically in North America and Europe. However, risk may decrease in many polar regions, where rainfall is projected to increase while hot lightning rates remain constant.

It’s valuable to show that risk may evolve differently in different places, says Earth systems scientist Yang Chen of the University of California, Irvine, who was not involved in the study. But, he notes, the analysis uses sparse data from polar regions, so there is a lot of uncertainty. Harnessing additional data from ground-based lightning detectors and other data sources could help, he says. “That [region is] important, because a lot of carbon can be released from permafrost.”

Pérez-Invernón agrees more data will help improve projections of rates of lightning-induced wildfire, not just in the polar regions, but also in Africa, where blazes are common but fire reports are lacking.