Antarctica is losing ice at an increasingly rapid pace. In just the last five years, the frozen continent has shed ice nearly three times faster on average than it did over the previous 20 years.
An international team of scientists has combined data from two dozen satellite surveys in the most comprehensive assessment of Antarctica’s ice sheet mass yet. The conclusion: The frozen continent lost an estimated 2,720 billion metric tons of ice from 1992 to 2017, and much of that loss occurred in recent years, particularly in West Antarctica. Before 2012, the continent shed ice at a rate of 76 billion tons each year on average, but from 2012 to 2017, the rate increased to 219 billion tons annually. Combined, all that water raised the global sea level by an average of 7.6 millimeters, the researchers report in the June 14 Nature. About two-fifths of that rise occurred in the last five years, an increase in severity that is helping scientists understand how the ice sheet is responding to climate change.
“When we place that against the [Intergovernmental Panel on Climate Change’s] sea level projections, prior to this Antarctica was tracking the low end of sea-level-rise projections,” says study coauthor Andrew Shepherd, an earth scientist at the University of Leeds in England. “Now it’s tracking the upper end.”
Antarctica currently contains enough frozen water to raise the oceans by 58 meters. Melting ice from the continent is a major driver of the sea level rise that’s threatening coastal communities and ecosystems around the world with flooding as the climate changes (SN: 12/27/14, p. 29). A good estimate of Antarctica’s ice loss will help climate scientists better predict future sea level rise, Shepherd says, as the planet continues to warm. But in a place as big as Antarctica, it’s not easy to gauge the amount of ice and how it fluctuates. Satellites can collect different kinds of data to inform estimates, measuring the mass of the ice sheet or the depth of the ice or the speed at which glaciers flow into the ocean. But sorting out seasonal changes (such as the ice added annually from winter snowfall) from more meaningful long-term ones is hard. This group of researchers made their last big estimate of Antarctica’s shrinking ice sheet in 2012 and found that it had lost 1,320 billion tons of ice from 1992 to 2011 (SN: 12/29/12, p. 10). The new analysis paints a more dire picture. “In 2012, we concluded that over the 20-year period before that, Antarctica had been losing ice at a steady rate,” Shepherd says. But the new findings indicate that the rate of ice loss has now tripled, compared with the average rate from 1992 to 2011.
The new study combines data from three different ways of measuring ice via satellite to pinpoint a composite number. Researchers first computed the average mass change in ice suggested by each technique. Then they integrated those data, accounting for specific kinds of errors introduced by the different measurements.
West Antarctica dominates the melting, Shepherd and colleagues found. It was losing about 53 billion tons of ice each year, on average, in 1992. Now the rate has risen to about 159 billion tons per year.
That region probably loses ice more than other parts of the continent because the ice in West Antarctica is more sensitive to small temperature fluctuations. It sits on the seabed submerged in water, while other parts of the continent’s ice sheet, such as East Antarctica, sit higher, exposed to air. Even a small increase in ocean temperature (say, 0.5 degrees Celsius) transfers a lot more heat to that ice than a comparable increase in air temperature, Shepherd says. And when warm water starts to eat away at an ice shelf from underneath, it thins the shelf and hastens melting even further.
East Antarctica seems to be more stable. It appears to have even slightly gained mass in recent years, but those measurements are more uncertain. “I think it’s fair to say that the more work that gets done, the picture we get of Antarctica is that it’s more dynamic and more capable of rapid change than we used to think,” says Steve Rintoul, an oceanographer at CSIRO based in Hobart, Australia. Scientists had thought that such a large mass of ice was relatively resilient. Now its vulnerabilities are showing. Rintoul was not involved in the new analysis, but coauthored a perspective and a review on the future of Antarctica and the Southern Ocean in the same issue of Nature.
While ice cores can provide clues to Antarctica’s climate going back millennia, researchers have reliable satellite data on Antarctic ice going back only about 25 years. Getting a better handle on long-term trends for Antarctica — and for melting ice in Greenland and in glaciers around the world — requires more data. And that means keeping Earth-observing satellites, funded by governmental agencies such as NASA and the European Space Agency, in the air (SN Online: 2/9/18).
Narwhals are among the most elusive of whales. But for the first time, researchers have been able to eavesdrop on the creatures for days at a time as these unicorns of the sea dove, fed and socialized.
Biologist Susanna Blackwell and colleagues listened in on the clicks, buzzes and calls of the East Greenland narwhal (Monodon monoceros). The team’s findings, published June 13 in PLOS ONE, provide a peek into the daily behavior of the long-toothed whale. The research could help scientists determine how human-made noises may affect narwhals as the Arctic warms due to climate change and shipping lanes become more open.
Many whale sounds are recorded using hydrophones, underwater microphones that dangle in the water. But these acoustic devices have several drawbacks: They can’t sense the depth or direction from which noise comes, and they can’t detect which animal is making a sound.
Blackwell and colleagues skirted these issues by attaching an acoustic recording device to the narwhals themselves. “It is really like sitting on the back of a narwhal for a few days and experiencing the world,” Blackwell says. With the help of native Greenland hunters, the researchers tagged six of the skittish creatures from 2013 to 2016. The devices were attached with suction cups, and held in place for several days by a nylon string threaded through a ridge of cartilage on the narwhals’ backs. After three to eight days in the water, magnesium links to the string degraded and released the device, which the researchers retrieved using GPS. Tagging was stressful for the narwhals, says Blackwell, who works for Greeneridge Sciences, Inc., the Santa Barbara, Calif., company that manufactures the acoustic devices (SN Online: 12/7/17). But after a day of silence, the narwhals resumed their normal behavior. Like other species of toothed whales, narwhals use echolocation to hunt in the dark arctic waters. “They’re like wet bats,” says Kate Stafford, an oceanographer at the University of Washington in Seattle who did not participate in the study. The researchers found that the narwhals clicked while diving to locate their prey, often arctic and polar cod or squid. When closing in on a meal, the clicking sounds turned into a rapid buzzing noise. At the surface, the narwhals used whistle and trumpetlike calls to communicate with one another.
“We were very surprised that they actually have a very specialized way of using sound,” says study coauthor Mads Peter Heide-Jørgensen, a biologist at the Greenland Institute of Natural Resources based in Copenhagen. The narwhals’ sounds varied not only with each activity the animals did, but also with their depth. “Having some of this baseline data from an area that is relatively pristine is going to be really valuable going forward,” Stafford says.
Though the Scoresby Sound where the narwhal research took place is very remote, it won’t be for long. Human presence in the Arctic is increasing thanks to climate change, says Jens Koblitz, a bioacoustician at the University of Konstanz in Germany. Fishing boats, ships of oil prospectors and others are expected to spend more time in the Arctic as global warming reduces the extent of sea ice in the region (SN: 12/10/16, p. 15).
“This study is a great stepping-stone,” Koblitz says. If scientists discover that human sounds negatively affect the ways that the whales communicate, researchers might be able to protect some areas from human activity.
Making day-to-day activities more vigorous for a few minutes — such as briefly stepping up the pace of a walk — could offer people who don’t exercise some of the health benefits that exercisers enjoy.
That’s according to a new study of roughly 25,000 adults who reported no exercise in their free time. Those who incorporated three one- to two-minute bursts of intense activity per day saw a nearly a 40 percent drop in the risk of death from any cause compared with those whose days didn’t include such activity. The risk of death from cancer also fell by nearly 40 percent, and the risk of death from cardiovascular disease dropped almost 50 percent, researchers report online December 8 in Nature Medicine.
In a comparison with around 62,000 people who exercised regularly, including runners, gym-goers and recreational cyclists, the mortality risk reduction was similar.
“This study adds to other literature showing that even short amounts of activity are beneficial,” says Lisa Cadmus-Bertram, a physical activity epidemiologist at the University of Wisconsin–Madison, who was not involved in the research. “So many people are daunted by feeling that they don’t have the time, money, motivation, transportation, etc. to go to a gym regularly or work out for long periods of time,” she says. “The message we can take is that it is absolutely worth doing what you can.”
Emmanuel Stamatakis, an epidemiologist at the University of Sydney, and his colleagues analyzed a subset of records from the UK Biobank, a biomedical database containing health information on half a million people in the United Kingdom. The study’s non-exercising participants — more than half of whom were women and were 62 years old on average — had worn movement-tracking devices for a week.
Over an average seven years of follow-up, for those whose days included three to four bursts of activity, the mortality rate was 4.2 deaths from any cause per 1,000 people for one year. For those with no activity bursts, it was 10.4 deaths per 1,000 people for one year.
The researchers were looking for bursts of vigorous activity that met a definition determined in a laboratory study, including reaching at least 77 percent of maximum heart rate and at least 64 percent of maximum oxygen consumption. In real life, the signs that someone has reached the needed intensity level are “an increase in heart rate and feeling out of breath” in the first 15 to 30 seconds of an activity, Stamatakis says.
Regular daily activities offer several opportunities for these vigorous bursts, he says. “The simplest one is maximizing walking pace for a minute or two during any regular walk.” Other options, he says, include carrying grocery bags to the car or taking the stairs. “The largest population health gains will be realized by finding ways to get the least physically active people to move a little more.”
Look closely at a snowflake, and you’ll observe a one-of-a-kind gossamer lattice, its growth influenced by ambient conditions like temperature and humidity. Turns out, this sort of intricate self-assemblage can also occur in metals, researchers report in the Dec. 9 Science.
In pools of molten gallium, physicist Nicola Gaston and colleagues grew zinc nanostructures with symmetrical, hexagonal crystal frameworks. Such metal snowflakes could be useful for catalyzing chemical reactions and constructing electronics, says Gaston, of the MacDiarmid Institute for Advanced Materials and Nanotechnology at the University of Auckland in New Zealand.
“Self-assembly is the way nature makes nanostructures,” she says. “We’re trying to learn to do the same things.” Figuring out how to craft tiny, complex metal shapes in fewer steps and with less energy could be a boon for manufacturers.
The researchers chose gallium as a growth medium, due to its relatively low melting point, ability to dissolve many other metals and the tendency for its atoms to loosely organize while in a liquid state.
After mixing zinc into the gallium, the team subjected the alloy to elevated temperatures and different pressures, and then let the mixture cool to room temperature. The loose ordering of gallium atoms appeared to coax the crystallizing zinc to bloom into symmetrical, hexagonal structures resembling natural snowflakes and other shapes, the team found. It’s somewhat like how a fruit tray imparts order on the fruits stacked within, Gaston says.
The future may be bright for research into applications of gallium and other low-temperature liquid metals. “Not to take that snowflake metaphor too far, but [this work] really hints at new branches for scientific discovery,” Gaston says.
Meet the metric system’s newest prefixes: ronna-, quetta-, ronto- and quecto-.
Adopted November 18 at the 27th General Conference on Weights and Measures in Versailles, France, ronna- and quetta- describe exceedingly large numbers while ronto- and quecto- describe the exceedingly small. This is the first time that the International System of Units, or SI, has expanded since 1991, when the prefixes zetta-, yotta-, zepto and yocto- were added (SN: 1/16/93).
Numerically, ronna- is 1027 (that’s a digit followed by 27 zeroes) and quetta- is 1030 (30 zeroes). Their tiny counterparts ronto- and quecto- also refer to 27 and 30 zeroes, but those come after a decimal point. Until now, yotta- and yocto- (24 zeros) capped off the metric system’s range.
Science News spoke with Richard Brown, head of metrology at the National Physical Laboratory in Teddington, England, about what the latest SI expansion means for science. The following conversation has been edited for clarity and brevity.
SN: Why do we need the new prefixes?
Brown: The quantity of data in the world is increasing exponentially. And we expect that to continue to increase and probably accelerate because of quantum computing, digitalization and things like that. At the same time, this quantity of data is starting to get close to the top range of the prefixes we currently use. People start to ask what comes next?
SN: Where do the prefix names come from?
Brown: About five years ago, I heard a BBC podcast about these new names for quantities of data. And the two that they mentioned were brontobyte and hellabyte. Brontobyte, I think comes from brontosaurus being a big dinosaur and hellabyte comes from “‘hell of a big number.”
The problem with those from a metrology point of view, or measurement point of view, is they start with letters B and H, which already are in use for other units and prefixes. So we can’t have those as names. [It was clear] that we had to do something official because people were starting to need these prefixes. R and Q are not used for anything else, really, in terms of units or SI prefixes. [The prefix names themselves are] very, very loosely based on the Greek and Latin names for nine and 10. SN: How will the prefixes be used?
Brown: The whole point of the International System of Units is it’s an accepted global system, which if you use, you will be understood.
When you use a prefix with a unit, it means that the number associated with the unit changes. And people like small numbers that they can understand. So you can express the mass of the Earth in terms of ronnagrams; it’s six ronnagrams. And equally the mass of Jupiter is two quettagrams. Some good examples of [small numbers] are that the mass of an electron is about one rontogram, and the mass of one bit of data as stored on a mobile phone is around one quectogram.
I think the use of a suitable prefix makes things more understandable. And I think we shouldn’t forget that even if there’s not always a direct scientific usage immediately, they will gain traction over time.
Tyrannosaurus rex isn’t just a king to paleontologists — the dinosaur increasingly reigns over the world of art auctions. A nearly complete skeleton known as Stan the T. rex smashed records in October 2020 when a bidding war drove its price to $31.8 million, the highest ever paid for any fossil. Before that, Sue the T. rex held the top spot; it went for $8.3 million in 1997.
That kind of publicity — and cachet — means that T. rex’s value is sky-high, and the dinosaur continues to have its teeth firmly sunk into the auction world in 2022. In December, Maximus, a T. rex skull, will be the centerpiece of a Sotheby’s auction in New York City. It’s expected to sell for about $15 million.
Another T. rex fossil named Shen was anticipated to sell for between $15 million and $25 million at a Christie’s auction in Hong Kong in late November. However, the auction house pulled it over concerns about the number of replica bones used in the fossil. “These are astronomical sums of money, really surprising sums of money,” says Donna Yates, a criminologist at Maastricht University in the Netherlands who studies high-value collectibles.
Stan’s final price “was completely unexpected,” Yates says. The fossil was originally appraised at about $6 million — still a very large sum, though nothing like the final tally, which was the result of a three-way bidding war.
But the staggering amounts of money T. rex fossils now fetch at auction can mean a big loss for science. At those prices, the public institutions that might try to claim these glimpses into the deep past are unable to compete with deep-pocketed private buyers, researchers say.
One reason for the sky-high prices may be that T. rex fossils are increasingly being treated more like rare works of art than bits of scientific evidence, Yates says. The bones might once have been bought and sold at dusty “cowboy fossil” dealerships. But nowadays these fossils are on display in shiny gallery spaces and are being appraised and marketed as rare objets d’art. That’s appealing to collectors, she adds: “If you’re a high-value buyer, you’re a person who wants the finest things.”
But fossils’ true value is the information they hold, says Thomas Carr, a paleontologist at Carthage College in Kenosha, Wis. “They are our only means of understanding the biology and evolution of extinct animals.”
Keeping fossils of T. rex and other dinosaurs and animals in public repositories, such as museums, ensures that scientists have consistent access to study the objects, including being able to replicate or reevaluate previous findings. But a fossil sold into private or commercial hands is subject to the whim of its owner — which means anything could happen to it at any time, Carr says. “It doesn’t matter if [a T. rex fossil] is bought by some oligarch in Russia who says scientists can come and study it,” he says. “You might as well take a sledgehammer to it and destroy it.”
A desire for one’s own T. rex There are only about 120 known specimens of T. rex in the world. At least half of them are owned privately and aren’t available to the public. That loss is “wreaking havoc on our dataset. If we don’t have a good sample size, we can’t claim to know anything about [T. rex],” Carr says.
For example, to be able to tell all the ways that T. rex males differed from females, researchers need between 70 and 100 good specimens for statistically significant analyses, an amount scientists don’t currently have.
Similarly, scientists know little about how T. rex grew, and studying fossils of youngsters could help (SN: 1/6/20). But only a handful of juvenile T. rex specimens are publicly available to researchers. That number would double if private specimens were included.
Museums and academic institutions typically don’t have the kind of money it takes to compete with private bidders in auctions or any such competitive sales. That’s why, in the month before Stan went up for auction in 2020, the Society for Vertebrate Paleontology, or SVP, wrote a letter to Christie’s asking the auction house to consider restricting bidding to public institutions. The hope was that this would give scientists a fighting chance to obtain the specimens.
But the request was ignored — and unfortunately may have only increased publicity for the sale, says Stuart Sumida, a paleontologist at California State University in San Bernardino and SVP’s current vice president. That’s why SVP didn’t issue a public statement this time ahead of the auctions for Shen and Maximus, Sumida says, though the organization continues to strongly condemn fossil sales — whether of large, dramatic specimens or less well-known creatures. “All fossils are data. Our position is that selling fossils is not scientific and it damages science.”
Sumida is particularly appalled at statements made by auction houses that suggest the skeletons “have already been studied,” an attempt to reassure researchers that the data contained in that fossil won’t be lost, regardless of who purchases it. That’s deeply misleading, he says, because of the need for reproducibility, as well as the always-improving development of new analysis techniques. “When they make public statements like that, they are undermining not only paleontology, but the scientific process as well.”
And the high prices earned by Stan and Sue are helping to drive the market skyward, not only for other T. rex fossils but also for less famous species. “It creates this ripple effect that is incredibly damaging to science in general,” Sumida says. Sotheby’s, for example, auctioned off a Gorgosaurus, a T. rex relative, in July for $6.1 million. In May, a Deinonychus antirrhopus — the inspiration for Jurassic Park’s velociraptor — was sold by Christie’s for $12.4 million.
Protecting T. rex from collectors Compounding the problem is the fact that the United States has no protections in place for fossils unearthed from the backyards or dusty fields of private landowners. The U.S. is home to just about every T. rex skeleton ever found. Stan, Sue and Maximus hail from the Black Hills of South Dakota. Shen was found in Montana.
As of 2009, U.S. law prohibits collecting scientifically valuable fossils, particularly fossils of vertebrate species like T. rex, from public lands without permits. But fossils found on private lands are still considered the landowner’s personal property. And landowners can grant digging access to whomever they wish. Before the discovery of Sue the T. rex (SN: 9/6/14), private owners often gave scientific institutions free access to hunt for fossils on their land, says Bridget Roddy, currently a researcher at the legal news company Bloomberg Law in Washington, D.C. But in the wake of Sue’s sale in 1997, researchers began to have to compete for digging access with commercial fossil hunters.
These hunters can afford to pay landowners large sums for the right to dig, or even a share of the profits from fossil sales. And many of these commercial dealers sell their finds at auction houses, where the fossils can earn far more than most museums are able to pay.
Lack of federal protections for paleontological resources found on private land — combined with the large available supply of fossils — is a situation unique to the United States, Roddy says. Fossil-rich countries such as China, Canada, Italy and France consider any such finds to be under government protection, part of a national legacy.
In the United States, seizing such materials from private landowners — under an eminent domain argument — would require the government to pay “just compensation” to the landowners. But using eminent domain to generally protect such fossils wouldn’t be financially sustainable for the government, Roddy says, not least because most fossils dug up aren’t of great scientific value anyway.
There may be other, more grassroots ways to at least better regulate fossil sales, she says. While still a law student at DePaul University in Chicago, Roddy outlined some of those ideas in an article published in Texas A&M Journal of Property Law in May.
One option, she suggests, is for states to create a selective sales tax attached to fossil purchases, specifically for buyers who intend to keep their purchases in private collections that are not readily available to the public. It’s “similar to if you want to buy a pack of cigarettes, which is meant to offset the harm that buying cigarettes does to society in general,” Roddy says. That strategy could be particularly effective in states with large auction houses, like New York.
Another possibility is to model any new, expanded fossil preservation laws on existing U.S. antiquities laws, intended to preserve cultural heritage. After all, Roddy says, fossils aren’t just bones, but they’re also part of the human story. “Fossils have influenced our folklore; they’re a unifier of humanity and culture rather than a separate thing.”
Though fossils from private lands aren’t protected, many states do impose restrictions on searches for archaeological and cultural artifacts, by requiring those looking for antiquities to restore excavated land or by fining the excavation of certain antiquities without state permission. Expanding those restrictions to fossil hunting, perhaps by requiring state approval through permits, could also give states the opportunity to purchase any significant finds before they’re lost to private buyers.
Preserving fossils for science and the public Such protections could be a huge boon to paleontologists, who may not even know what’s being lost. “The problem is, we’ll never know” all the fossils that are being sold, Sumida says. “They’re shutting scientists out of the conversation.”
And when it comes to dinosaurs, “so many of the species we know about are represented by a single fossil,” says Stephen Brusatte, a paleontologist at the University of Edinburgh. “If that fossil was never found, or disappeared into the vault of a collector, then we wouldn’t know about that dinosaur.”
Or, he says, sometimes a particularly complete or beautifully preserved dinosaur skeleton is found, and without it, “we wouldn’t be able to study what that dinosaur looked like, how it moved, what it ate, how it sensed its world, how it grew.”
The point isn’t to put restrictions on collecting fossils so much as making sure they remain in public view, Brusatte adds. “There’s nothing as magical as finding your own fossils, being the first person ever to see something that lived millions of years ago.” But, he says, unique and scientifically invaluable fossils such as dinosaur skeletons should be placed in museums “where they can be conserved and studied and inspire the public, rather than in the basements or yachts of the oligarch class.”
After its record-breaking sale, Stan vanished for a year and a half, its new owners a mystery. Then in March 2022, news surfaced that the fossil had been bought by the United Arab Emirates, which stated it intends to place Stan in a new natural history museum.
Sue, too, is on public view. The fossil is housed at Chicago’s Field Museum of Natural History, thanks to the pooled financial resources of the Walt Disney Corporation, the McDonald Corporation, the California State University System and others. That’s the kind of money it took to get the highest bid on a T. rex 25 years ago.
And those prices only seem to be going up. Researchers got lucky with Sue, and possibly Stan.
As for Shen, the fossil’s fate remains in limbo: It was pulled from auction not due to outcry from paleontologists, but over concerns about intellectual property rights. The fossil, at 54 percent complete, may have been supplemented with a polyurethane cast of bones from Stan, according to representatives of the Black Hills Institute of Geological Research in Hill City, S.D. That organization, which discovered Stan, retains a copyright over the skeleton.
In response to those concerns, Christie’s pulled the lot, and now says that it intends to loan the fossil to a museum. But this move doesn’t reassure paleontologists. “A lot of people are pleased that the sale didn’t go through,” Sumida says. “But it sort of just kicks the can down the road.… It doesn’t mean they’re not going to try and sell it in another form, somewhere down the road.”
Ultimately, scientists simply can’t count on every important fossil finding its way to the public, Carr says. “Those fossils belong in a museum; it’s right out of Indiana Jones,” he says. “It’s not like they’re made in a factory somewhere. Fossils are nonrenewable resources. Once Shen is gone, it’s gone.”
The infant universe transforms from a featureless landscape to an intricate web in a new supercomputer simulation of the cosmos’s formative years.
An animation from the simulation shows our universe changing from a smooth, cold gas cloud to the lumpy scattering of galaxies and stars that we see today. It’s the most complete, detailed and accurate reproduction of the universe’s evolution yet produced, researchers report in the November Monthly Notices of the Royal Astronomical Society.
This virtual glimpse into the cosmos’s past is the result of CoDaIII, the third iteration of the Cosmic Dawn Project, which traces the history of the universe, beginning with the “cosmic dark ages” about 10 million years after the Big Bang. At that point, hot gas produced at the very beginning of time, about 13.8 billion years ago, had cooled to a featureless cloud devoid of light, says astronomer Paul Shapiro of the University of Texas at Austin. Roughly 100 million years later, tiny ripples in the gas left over from the Big Bang caused the gases to clump together (SN: 2/19/15). This led to long, threadlike strands that formed a web of matter where galaxies and stars were born.
As radiation from the early galaxies illuminated the universe, it ripped electrons from atoms in the once-cold gas clouds during a period called the epoch of reionization, which continued until about 700 million years after the Big Bang (SN: 2/6/17).
CoDaIII is the first simulation to fully account for the complicated interaction between radiation and the flow of matter in the universe, Shapiro says. It spans the time from the cosmic dark ages and through the next several billion years as the distribution of matter in the modern universe formed.
The animation from the simulation, Shapiro says, graphically shows how the structure of the early universe is “imprinted on the galaxies today, which remember their youth, or their birth or their ancestors from the epoch of reionization.”
An ancient hominid dubbed Homo naledi may have lit controlled fires in the pitch-dark chambers of an underground cave system, new discoveries hint.
Researchers have found remnants of small fireplaces and sooty wall and ceiling smudges in passages and chambers throughout South Africa’s Rising Star cave complex, paleoanthropologist Lee Berger announced in a December 1 lecture hosted by the Carnegie Institution of Science in Washington, D.C.
“Signs of fire use are everywhere in this cave system,” said Berger, of the University of the Witwatersrand, Johannesburg.
H. naledi presumably lit the blazes in the caves since remains of no other hominids have turned up there, the team says. But the researchers have yet to date the age of the fire remains. And researchers outside Berger’s group have yet to evaluate the new finds.
H. naledi fossils date to between 335,000 and 236,000 years ago (SN: 5/9/17), around the time Homo sapiens originated (SN: 6/7/17). Many researchers suspect that regular use of fire by hominids for light, warmth and cooking began roughly 400,000 years ago (SN: 4/2/12).
Such behavior has not been attributed to H. naledi before, largely because of its small brain. But it’s now clear that a brain roughly one-third the size of human brains today still enabled H. naledi to achieve control of fire, Berger contends.
Last August, Berger climbed down a narrow shaft and examined two underground chambers where H. naledi fossils had been found. He noticed stalactites and thin rock sheets that had partly grown over older ceiling surfaces. Those surfaces displayed blackened, burned areas and were also dotted by what appeared to be soot particles, Berger said.
Meanwhile, expedition codirector and Wits paleoanthropologist Keneiloe Molopyane led excavations of a nearby cave chamber. There, the researchers uncovered two small fireplaces containing charred bits of wood, and burned bones of antelopes and other animals. Remains of a fireplace and nearby burned animal bones were then discovered in a more remote cave chamber where H. naledi fossils have been found.
Still, the main challenge for investigators will be to date the burned wood and bones and other fire remains from the Rising Star chambers and demonstrate that the fireplaces there come from the same sediment layers as H. naledi fossils, says paleoanthropologist W. Andrew Barr of George Washington University in Washington, D.C., who wasn’t involved in the work.
“That’s an absolutely critical first step before it will be possible to speculate about who may have made fires for what reason,” Barr says.
Marsupials may have richer social lives than previously thought.
Generally considered loners, the pouched animals have a wide diversity of social relationships that have gone unrecognized, a new analysis published October 26 in Proceedings of the Royal Society B suggests. The findings could have implications for how scientists think about the lifestyles of early mammals.
“These findings are helpful to move us away from a linear thinking that used to exist in some parts of evolutionary theory, that species develop from supposedly simple into more complex forms,” says Dieter Lukas, an evolutionary ecologist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, who was not involved with the study.
Mammals run the gamut of social organization systems, ranging from loose, ephemeral interactions like aggregations of jaguars in the South American wetlands to the antlike subterranean societies of naked mole-rats (SN: 10/13/21; SN: 10/20/20).
But marsupials — a subgroup of mammals that give birth to relatively underdeveloped young reared in pouches — have traditionally been considered largely solitary. Some kangaroo species were known to form transient or permanent groups of dozens of individuals. But among marsupials, long-term bonds between males and females were thought rare and there were no known examples of group members cooperating to raise young. Previous work on patterns of mammalian social evolution regarded about 90 percent of examined marsupial species to be solitary.
“If you look at other [studies] about some specific species, you will see [the researchers] tend to assume that the marsupials are solitary,” says Jingyu Qiu, a behavioral ecologist at CNRS in Strasbourg, France.
Sorting social lives Qiu and her colleagues developed a database of field studies that illuminated marsupial social organization, taking into account how populations vary within a species and delving into the evolutionary history of marsupial social lives. The researchers compiled data from 120 studies on 149 populations of 65 marsupial species, categorizing each population as solitary, living in pairs — such as one male and one female — or falling into four kinds of group living, including one male and multiple females (or vice versa), multiple males and females, or single sex groups.
While 19 species, or 31 percent of those studied, appear to go strictly solo, nearly half of the species always live in pairs or groups. The team also found lots of variation within species; 27 of the 65 species — more than 40 percent — fell into multiple social organization classifications. When the researchers looked at this social variation against climatic conditions in Australia, they found that social variability was more common in drier environments with less predictable rainfall. It’s possible that being able to switch between solitary and group living acts as a buffer against resource unpredictability.
The researchers’ focus on social flexibility “highlights that there is nothing simple even about a supposedly solitary species,” Lukas says.
Implications for the earliest mammals Qiu and her colleagues also ran computer analyses comparing the evolutionary relationships of the marsupials with how they form social relationships. This let the team predict the social organization of the earliest marsupials, which split from placental mammals about 160 million years ago. Because modern marsupials have been considered solitary, the marsupial ancestors — and the earliest mammals on the whole — have generally been assumed to be solitary as well.
The team found that solitary was the most likely social category of the ancestral marsupials, a 35 percent probability. But Qiu points out that the varied combinations where pair and group living are possible options make up the other 65 percent. So “it is more likely that the ancestor was also non-solitary,” she says. The findings also give insights into the range of possible lifestyles experienced by the earliest mammals, she says.
But Robert Voss, a mammalogist at the American Museum of Natural History in New York City, questions the analyses’ insights about a potentially social ancestral marsupial. The uncertainty about the solitary alternative, he says, is largely due to the researchers’ benchmarks for what does and what doesn’t constitute social behavior — thresholds that Voss views as too permissive. For example, Voss disagrees with the team’s characterization of opossum social organization.
“Anecdotal observations of [members of the same species] occasionally denning together is not compelling evidence for social behavior,” says Voss. “None of the cited studies suggest that opossums are anything other than solitary.”
Future work, Qiu says, will involve gathering data on a larger subset of mammals outside of marsupials to get a clearer picture of how social traits have evolved among mammals.
A sacrificed spider monkey is shedding new light on an ancient Mesoamerican relationship.
The remains of a 1,700-year-old monkey found in the ancient city of Teotihuacan outside modern-day Mexico City suggest the primate was a diplomatic gift from the Maya. The find is the earliest evidence of a primate held in captivity in the Americas, researchers report November 21 in Proceedings of the National Academy of Sciences.
Unearthed in 2018 at the base of a pyramid in Teotihuacan, the monkey’s skeleton lay beside the corpses of other animals — including an eagle and several rattlesnakes — in an area of the city where visiting Maya elites may have resided.
Evidence of animal sacrifices, including of predators like jaguars, have been found in the city before. But “up to that point, we did not have any instances of sacrificed primates in Teotihuacan,” says Nawa Sugiyama, an anthropological archaeologist at the University of California, Riverside.
Chemical analysis of the spider monkey’s bones and teeth showed that the female had likely been captured in a humid environment at a young age sometime in the third century. The monkey then lived in captivity for a few years before meeting her end between the years 250 and 300.
The highlands around Mexico City are a long way from the natural habitat of spider monkeys (Ateles geoffroy), which require wet tropical forests to thrive. This fact, along with the presence of Maya murals and vessels, suggests to Sugiyama and her colleagues that the spider monkey was a gift from elite Mayas to the people of Teotihuacan.
The find is an example of diplomatic relations between two cultures that sometimes had violent interactions. Maya hieroglyphs indicated that military forces from Teotihuacan invaded the Maya city of Tikal in 378, marking the start of a roughly 70-year period in which Teotihuacan meddled in Maya politics (SN: 10/22/21).
The “striking” discovery of the monkey shows that relationship between these two cultures far predates the invasion, says David Stuart, an archaeologist and epigraphist at the University of Texas at Austin who was not involved in the study.
“The war of 378 had a long history leading up to it,” he says. “The monkey is a really compelling illustration of this long relationship.”
