“The combination of shaping, wear, and resharpening indicates they were used to draw or mark on soft surfaces,” D’Errico told Ars in an email. “Although the material is too fragile to reveal the specific material on which they were used, such as hide, human skin, or stone, an experimental approach may, in the future, allow us at least to rule out their use on some materials.”
A 73,000-year-old drawing from Blombo Cave in South Africa looks like it was made with tools much like the ocher crayons from Crimea, which means that Neanderthals and Homo sapiens both invented crayons in their own little corners of the world at around the same time.
The surface of this flat piece of orange ocher was carved over 47,000 years ago, then worn smooth, perhaps by carrying in a bag. Credit: D’Errico et al. 2025
Sometimes you’re the crayon, sometimes you’re the canvas
A third item from Zaskalnaya V is a flat piece of orange ocher. One side is covered with a thin layer of hard, dark rock. But more than 47,000 years ago, someone carefully cut several deep lines, regularly spaced and almost parallel, into its surface. The area of stone between the lines has been worn and polished smooth, suggesting that someone carried it and handled it for years.
“The polish smoothing the engraved lines suggest that the piece was curated, perhaps transported in a bag,” D’Errico told Ars. Whoever carved the lines into the piece of ocher also appears to have been right-handed, based on the angle of the incisions’ walls.
“Traditionally viewed as lacking the cognitive flexibility and symbolic capacity of humans, the Neanderthals of Crimea demonstrate the opposite: They engaged in cultural practices that were not merely adaptive but deeply meaningful,” wrote D’Errico and his colleagues. “Their sophisticated use of ocher is one facet of their complex cultural life.”
The tip of this red ocher crayon was broken off. Credit: D’Errico et al. 2025
Coloring in some details of Neanderthal culture
It’s hard to say whether the rest of the ocher from the Zaskalnaya sites and other nearby rock shelters meant anything to the Neanderthals beyond the purely pragmatic. However, it’s unlikely that humans (of any stripe) could spend 70,000 years working with vividly colored pigment without developing a sense of aesthetics, assigning some meaning to the colors, or maybe doing both.
Europeans weren’t the first people to collect fossils in Australia.
Several species of short-faced kangaroos, like this one, once lived in Australia. Some stood two meters tall, while others were less than half a meter tall. Credit: By Ghedoghedo – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=8398432
Australia’s First Peoples may or may not have hunted the continent’s megafauna to extinction, but they definitely collected fossils.
A team of archaeologists examined the fossilized leg bone of an extinct kangaroo and realized that instead of evidence of butchery, cut marks on the bone reveal an ancient attempt at fossil collecting. That leaves Australia with little evidence of First Peoples hunting or butchering the continent’s extinct megafauna—and reopens the question of whether humans were responsible for the die-off of that continent’s giant Ice Age marsupials.
Fossil hunting in the Ice Age
In the unsolved case of whether humans hunted Australia’s Ice Age megafauna to extinction, the key piece of evidence so far is a tibia (one of the bones of the lower leg) from an extinct short-faced kangaroo. Instead of hopping like their modern relatives, these extinct kangaroos walked on their hind legs, probably placing all their weight on the tips of single hoofed toes. This particular kangaroo wasn’t quite fully grown when it died, which happened sometime between 44,500 and 55,200 years ago, based on uranium-series dating of the thin layer of rock covering most of the fossils in Mammoth Cave (in what’s now Western Australia).
There’s a shallow, angled chunk cut out of the bone near one end. When archaeologists first noticed the cut in 1970 after carefully chipping away the crust of calcium carbonate that had formed over the bone, it looked like evidence that Pleistocene hunters had carved up the kangaroo to eat it. But in their recent paper, University of New South Wales archaeologist Michael Archer and his colleagues say that’s probably not what happened. Instead, they have a stranger idea: “We suggest here that the purpose of this effort may have been the retrieval of the fossils from the bone-rich late-Pleistocene deposit in Mammoth Cave after its discovery by First Peoples,” they wrote in their recent paper.
This close-up image shows the cut kangaroo bone and a micro-CT image of the surfaces of the cut. Credit: Archer et al. 2025
The world used to be so much weirder
Based on the available archaeological evidence, it looks like people first set foot on Australia sometime around 65,000 years ago. At the time, the continent was home to a bizarre array of giant marsupials, as well as flightless birds even bigger and scarier than today’s emus and cassowaries. For the next 20,000 years, Australia’s First Peoples shared the landscape with short-faced kangaroos; Zygomaturus trilobus, a hulking 500-kilogram marsupial that looked a little like a rhinoceros; and Diprotodon optatum, the largest marsupial that ever lived: a 3,000-kilogram behemoth that roamed in huge herds (picture a bear about the size of a bison with a woodchuck’s face).
These species died out sometime around 45,000 or 40,000 years ago; today, they live on in ancient rock art and stories, some of which seem to describe people interacting with now-extinct species.
Since they had shared the continent with humans for at least 20,000 years at that point, it doesn’t seem that the sudden arrival of humans caused an immediate mass extinction. But it’s possible that by hunting or even setting controlled fires, people may have put just enough strain on these megafauna species to make them vulnerable enough for the next climate upheaval to finish them off.
In some parts of the world, there’s direct evidence that Pleistocene people hunted or scavenged meat from the remains of now-extinct megafauna. Elsewhere, archaeologists are still debating whether humans, the inexorable end of the last Ice Age, or some combination of the two killed off the world’s great Ice Age giants. The interaction between people and their local ecosystems looked (and still looks) different everywhere, depending on culture, environment, and a host of other factors.
The jury is still out on what killed the megafauna in Australia because the evidence we need either hasn’t survived the intervening millennia or still lies buried somewhere, waiting to be found and studied. For decades, the one clear bit of evidence has seemed to be the Mammoth Cave short-faced kangaroo tibia. But Archer and his colleagues argue that even that isn’t a smoking gun.
An archaeologist examines a fossil deposit in the wall of Mammoth Cave, in Western Australia. 50,000 years ago, one of the earliest people on the continent may also have stood here contemplating the fossils. Credit: Archer et al. 2025
Evidence of rock collecting, not butchery
For one thing, the researchers argue that the kangaroo had been dead for a very long time when the cut was made. Nine long, thin cracks run along the length of the tibia, formed when the bone dried and shrank. And in the cut section, there’s a short crack running across the width of the bone—but it stops at either end when it meets the long cracks from the bone’s drying. That suggests the bone had already dried and shrunk, leaving those long cracks before the cut was made. It may have just been a very old bone, or it may have already begun to fossilize, but the meat would have been long gone, leaving behind a bone sticking out of the cave wall.
Since there’s no mark or dent on the opposite side of the bone from the cut (which would have happened if it were lying on the ground being butchered), it was probably sticking out of the fossil bed in the cave wall when someone came along and tried to cut it free. And since a crust of calcium carbonate had time to form over the cut (it covers most of the fossils in Mammoth Cave like a rocky burial shroud), that must have happened at least 44,000 years ago.
That leaves us with an interesting mental image: a member of one of Australia’s First Peoples, 45,000 years ago, exploring a cave filled with the bones of fantastical, long-dead animals. This ancient caver finds a bone sticking out from the cave wall and tries to hack the protruding end free—twice, from different angles—before giving up and leaving it in place.
People have always collected cool rocks
We can’t know for sure why this long-ago person wanted the bone in the first place. (Did it have a religious purpose? Might it have made a good tool? Was it just a cool souvenir?) We also don’t know why they gave up their attempt. But if Archer and his colleagues are right, the bone leaves Australia without any clear evidence that ancient people hunted—or even scavenged food from the remains of—extinct Pleistocene megafauna like short-faced kangaroos.
“This is not to say that it did not happen, just that there is now no hard evidence to support that it did,” Archer and his colleagues wrote in their recent paper. We don’t yet know exactly how Australia’s First Peoples interacted with these species.
But whether Archer and his colleagues are correct in their analysis of this particular kangaroo bone or not, humans around the world have been picking up fossils for at least tens of thousands of years. There’s evidence that people in Australia have collected and traded the fossils of extinct animals for pretty much as long as people have been in Australia, including everything from trilobites to Zygomaturus teeth and the jawbones of other extinct marsupials.
“What we can conclude,” Archer and his colleagues wrote, “is that the first people in Australia who demonstrated a keen interest in and collected fossils were First Peoples, probably thousands of years before Europeans set foot on that continent.”
A recent study found lead in teeth from 2 million-year-old hominin fossils.
Our hominid ancestors faced a Pleistocene world full of dangers—and apparently one of those dangers was lead poisoning.
Lead exposure sounds like a modern problem, at least if you define “modern” the way a paleoanthropologist might: a time that started a few thousand years ago with ancient Roman silver smelting and lead pipes. According to a recent study, however, lead is a much more ancient nemesis, one that predates not just the Romans but the existence of our genus Homo. Paleoanthropologist Renaud Joannes-Boyau of Australia’s Southern Cross University and his colleagues found evidence of exposure to dangerous amounts of lead in the teeth of fossil apes and hominins dating back almost 2 million years. And somewhat controversially, they suggest that the toxic element’s pervasiveness may have helped shape our evolutionary history.
Joannes-Boyau and his colleagues took tiny samples of preserved enamel and dentin from the teeth of 51 fossils. In most of those teeth, the paleoanthropologists found evidence that these apes and hominins had been exposed to lead—sometimes in dangerous quantities—fairly often during their early years.
Tooth enamel forms in thin layers, a little like tree rings, during the first six or so years of a person’s life. The teeth in your mouth right now (and of which you are now uncomfortably aware; you’re welcome) are a chemical and physical record of your childhood health—including, perhaps, whether you liked to snack on lead paint chips. Bands of lead-tainted tooth enamel suggest that a person had a lot of lead in their bloodstream during the year that layer of enamel was forming (in this case, “a lot” means an amount measurable in parts per million).
In 71 percent of the hominin teeth that Joannes-Boyau and his colleagues sampled, dark bands of lead in the tooth enamel showed “clear signs of episodic lead exposure” during the crucial early childhood years. Those included teeth from 100,000-year-old members of our own species found in China and 250,000-year-old French Neanderthals. They also included much earlier hominins who lived between 1 and 2 million years ago in South Africa: early members of our genus Homo, along with our relatives Australopithecus africanus and Paranthropus robustus. Lead exposure, it turns out, is a very ancient problem.
Living in a dangerous world
This study isn’t the first evidence that ancient hominins dealt with lead in their environments. Two Neanderthals living 250,000 years ago in France experienced lead exposure as young children, according to a 2018 study. At the time, they were the oldest known examples of lead exposure (and they’re included in Joannes-Boyau and his colleagues’ recent study).
Until a few thousand years ago, no one was smelting silver, plumbing bathhouses, or releasing lead fumes in car exhaust. So how were our hominin ancestors exposed to the toxic element? Another study, published in 2015, showed that the Spanish caves occupied by other groups of Neanderthals contained enough heavy metals, including lead, to “meet the present-day standards of ‘contaminated soil.’”
Today, we mostly think of lead in terms of human-made pollution, so it’s easy to forget that it’s also found naturally in bedrock and soil. If that weren’t the case, archaeologists couldn’t use lead isotope ratios to tell where certain artifacts were made. And some places—and some types of rock—have higher lead concentrations than others. Several common minerals contain lead compounds, including galena or lead sulfide. And the kind of lead exposure documented in Joannes-Boyau and his colleagues’ study would have happened at an age when little hominins were very prone to putting rocks, cave dirt, and other random objects in their mouths.
Some of the fossils from the Queque cave system in China, which included a 1.8 million-year-old extinct gorilla-like ape called Gigantopithecus blacki, had lead levels higher than 50 parts per million, which Joannes-Boyau and his colleagues describe as “a substantial level of lead that could have triggered some developmental, health, and perhaps social impairments.”
Even for ancient hominins who weren’t living in caves full of lead-rich minerals, wildfires, or volcanic eruptions can also release lead particles into the air, and erosion or flooding can sweep buried lead-rich rock or sediment into water sources. If you’re an Australopithecine living upstream of a lead-rich mica outcropping, for example, erosion might sprinkle poison into your drinking water—or the drinking water of the gazelle you eat or the root system of the bush you get those tasty berries from… .
Our world is full of poisons. Modern humans may have made a habit of digging them up and pumping them into the air, but they’ve always been lying in wait for the unwary.
Cubic crystals of the lead-sulfide mineral galena.
Digging into the details
Joannes-Boyau and his colleagues sampled the teeth of several hominin species from South Africa, all unearthed from cave systems just a few kilometers apart. All of them walked the area known as Cradle of Humankind within a few hundred thousand years of each other (at most), and they would have shared a very similar environment. But they also would have had very different diets and ways of life, and that’s reflected in their wildly different exposures to lead.
A. africanus had the highest exposure levels, while P. robustus had signs of infrequent, very slight exposures (with Homo somewhere in between the two). Joannes-Boyau and his colleagues chalk the difference up to the species’ different diets and ecological niches.
“The different patterns of lead exposure could suggest that P. robustus lead bands were the result of acute exposure (e.g., wild forest fire),” Joannes-Boyau and his colleagues wrote, “while for the other two species, known to have a more varied diet, lead bands may be due to more frequent, seasonal, and higher lead concentration through bioaccumulation processes in the food chain.”
Did lead exposure affect our evolution?
Given their evidence that humans and their ancestors have regularly been exposed to lead, the team looked into whether this might have influenced human evolution. In doing so, they focused on a gene called NOVA1, which has been linked to both brain development and the response to lead exposure. The results were quite a bit short of decisive; you can think of things as remaining within the realm of a provocative hypothesis.
The NOVA1 gene encodes a protein that influences the processing of messenger RNAs, allowing it to control the production of closely related variants of a single gene. It’s notable for a number of reasons. One is its role in brain development; mice without a working copy of NOVA1die shortly after birth due to defects in muscle control. Its activity is also altered following exposure to lead.
But perhaps its most interesting feature is that modern humans have a version of the gene that differs by a single amino acid from the version found in all other primates, including our closest relatives, the Denisovans and Neanderthals. This raises the prospect that the difference is significant from an evolutionary perspective. Altering the mouse version so that it is identical to the one found in modern humans does alter the vocal behavior of these mice.
But work with human stem cells has produced mixed results. One group, led by one of the researchers involved in this work, suggested that stem cells carrying the ancestral form of the protein behaved differently from those carrying the modern human version. But others have been unable to replicate those results.
Regardless of that bit of confusion, the researchers used the same system, culturing stem cells with the modern human and ancestral versions of the protein. These clusters of cells (called organoids) were grown in media containing two different concentrations of lead, and changes in gene activity and protein production were examined. The researchers found changes, but the significance isn’t entirely clear. There were differences between the cells with the two versions of the gene, even without any lead present. Adding lead could produce additional changes, but some of those were partially reversed if more lead was added. And none of those changes were clearly related either to a response to lead or the developmental defects it can produce.
The relevance of these changes isn’t obvious, either, as stem cell cultures tend to reflect early neural development while the lead exposure found in the fossilized remains is due to exposure during the first few years of life.
So there isn’t any clear evidence that the variant found in modern humans protects individuals who are exposed to lead, much less that it was selected by evolution for that function. And given the widespread exposure seen in this work, it seems like all of our relatives—including some we know modern humans interbred with—would also have benefited from this variant if it was protective.
Workers with ropes could make the moai “walk” in zig-zag motion along roads tailor-made for the purpose.
Easter Island is famous for its giant monumental statues, called moai, built some 800 years ago and typically mounted on platforms called ahu. Scholars have puzzled over the moai on Easter Island for decades, pondering their cultural significance, as well as how a Stone Age culture managed to carve and transport statues weighing as much as 92 tons. One hypothesis, championed by archaeologist Carl Lipo of Binghamton University, among others, is that the statues were transported in a vertical position, with workers using ropes to essentially “walk” the moai onto their platforms.
The oral traditions of the people of Rapa Nui certainly include references to the moai “walking” from the quarry to their platforms, such as a song that tells of an early ancestor who made the statues walk. While there have been rudimentary field tests showing it might have been possible, the hypothesis has also generated a fair amount of criticism. So Lipo has co-authored a new paper published in the Journal of Archaeological Science offering fresh experimental evidence of “walking” moai, based on 3D modeling of the physics and new field tests to recreate that motion.
The first Europeans arrived in the 17th century and found only a few thousand inhabitants on the tiny island (just 14 by 7 miles across) thousands of miles away from any other land. In order to explain the presence of so many moai, the assumption has been that the island was once home to tens of thousands of people. But Lipo thought perhaps the feat could be accomplished with fewer workers. In 2012, Lipo and his colleague, Terry Hunt of the University of Arizona, showed that you could transport a 10-foot, 5-ton moai a few hundred yards with just 18 people and three strong ropes by employing a rocking motion.
In 2018, Lipo followed up with an intriguing hypothesis for how the islanders placed red hats on top of some moai; those can weigh up to 13 tons. He suggested the inhabitants used ropes to roll the hats up a ramp. Lipo and his team later concluded (based on quantitative spatial modeling) that the islanders likely chose the statues’ locations based on the availability of fresh water sources, per a 2019 paper in PLOS One.
The 2012 experiment demonstrated proof of principle, so why is Lipo revisiting it now? “I always felt that the [original] experiment was disconnected to some degree of theory—that we didn’t have particular expectations about numbers of people, rate of transport, road slope that could be walked, and so on,” Lipo told Ars. There were also time constraints because the attempt was being filmed for a NOVA documentary.
“That experiment was basically a test to see if we could make it happen or not,” he explained. “Fortunately, we did, and our joy in doing so is pretty well represented by our hoots and hollers when it started to walk with such limited efforts. Some of the limitation of the work was driven by the nature of TV. [The film crew] just wanted us—in just a day and half—to give it a shot. It was 4: 30 on the last day when it finally worked so we really didn’t get a lot of time to explore variability. We also didn’t have any particular predictions to test.”
Example of a road moai that fell and was abandoned after an attempt to re-erect it by excavating under its base, leaving it partially buried at an angle. Credit: Carl Lipo
This time around, “We wanted to explore a bit of the physics: to show that what we did was pretty easily predicted by the physical properties of the moai—its shape, size, height, number of people on ropes, etc.—and that our success in terms of team size and rate of walking was consistent with predictions,” said Lipo. “This enables us to address one of the central critiques that always comes up: ‘Well, you did this with a 5-ton version that was 10 feet tall, but it would never work with a 30-ft-tall version that weighs 30 tons or more.'”
All about that base
You can have ahu (platforms) without moai (statues) and moai without ahu, usually along the roads leading to ahu; they were likely being transported and never got to their destination. Lipo and Hunt have amassed a database of 962 moai across the island, compiled through field surveys and photogrammetric documentation. They were particularly interested in 62 statues located along ancient transport roads that seemed to have been abandoned where they fell.
Their analysis revealed that these road moai had significantly wider bases relative to shoulder width, compared to statues mounted on platforms. This creates a stable foundation that lowers the center of mass so that the statue is more conducive to the side-to-side motion of walking transport without toppling over. Platform statues, by contrast, have shoulders wider than the base for a more top-heavy configuration.
The road moai also have a consistent and pronounced forward lean of between 6 degrees to 15 degrees from the vertical position, which moves the center of mass close to or just beyond the base’s front edge. Lipo and Hunt think this was due to careful engineering, not coincidence. It’s not conducive to stable vertical display but it is a boon during walking transport, because the forward lean causes the statue to fall forward when tilted laterally, with the rounded front base edge serving as a crucial pivot point. So every lateral rocking motion results in a forward “step.”
Per the authors, there is strong archaeological evidence that carvers modified the statues once they arrived at their platform destinations, modifying the base to eliminate the lean by removing material from the front. This shifted the center of mass over the base area for a stable upright position. The road moai even lack the carved eye sockets designed to hold white coral eyes with obsidian or red scoria for pupils—a final post-transport step once the statues had been mounted on their platforms.
Based on 3D modeling, Lipo and his team created a precisely scaled replica of one of the road moai, weighing 4.35 metric tons with the same proportions and mass distribution of the original statue. “Of course, we’d love to build a 30-foot-tall version, but the physical impossibility of doing so makes it a challenging task, nor is it entirely necessary,” said Lipo. “Through physics, we can now predict how many people it would take and how it would be done. That is key.”
Lipo’s team created 3D models of moai to determine the unique characteristics that made them able to be “walked” across Rapa Nui. Credit: Carl Lipo
The new field trials required 18 people, four on each lateral rope and 10 on a rear rope, to achieve the side-to-side walking motion, and they were efficient enough in coordinating their efforts to move the statue forward 100 meters in just 40 minutes. That’s because the method operates on basic pendulum dynamics, per the authors, which minimizes friction between the base and the ground. It’s also a technique that exploits the gradual build-up of amplitude, which “suggests a sophisticated understanding of resonance principles,” Lipo and Hunt wrote.
So the actual statues could have been moved several kilometers over the course of weeks with only modest-sized crews of between 20-50 people, i.e., roughly the size of an extended family or “small lineage group” on Easter Island. Once the crew gets the statue rocking side to side—which can require between 15 to 60 people, depending on the size and weight of the moai—the resulting oscillation only needs minimal energy input from a smaller team of rope handlers to maintain that motion. They mostly provide guidance.
Lipo was not the first to test the walking hypothesis. Earlier work includes that of Czech experimental archaeologist Pavel Pavel, who conducted similar practical experiments on Easter Island in the 1980s after being inspired by Thor Heyerdahl’s Kon Tiki. (Heyerdahl even participated in the experiments.) Pavel’s team was able to demonstrate a kind of “shuffling” motion, and he concluded that just 16 men and one leader were sufficient to transport the statues.
Per Lipo and Hunt, Pavel’s demonstration didn’t result in broad acceptance of the walking hypothesis because it still required a huge amount of effort to tilt the statue, producing more of a twisting motion rather than efficient forward movement. This would only have moved a large statue 100 meters a day under ideal conditions. The base was also likely to be damaged from friction with the ground. Lipo and Hunt maintain this is because Pavel (and others who later tried to reproduce his efforts) used the wrong form of moai for those earlier field tests: those erected on the platforms, already modified for vertical stability and permanent display, and not the road moai with shapes more conducive to vertical transport.
“Pavel deserves recognition for taking oral traditions seriously and challenging the dominant assumption of horizontal transport, a move that invited ridicule from established scholars,” Lipo and Hunt wrote. “His experiments suggested that vertical transport was feasible and consistent with cultural memory. Our contribution builds on this by showing that ancestral engineers intentionally designed statues for walking. Those statues were later modified to stand erect on ceremonial platforms, a transformation that effectively erased the morphological features essential for movement.”
The evidence of the roadways
Lipo and Hunt also analyzed the roadways, noting that these ancient roadbeds had concave cross sections that would have been problematic for moving the statues horizontally using wooden rollers or frames perpendicular to those roads. But that concave shape would help constrain rocking movement during vertical transport. And the moai roads were remarkably level with slopes of, on average, 2–3 percent. For the occasional steeper slopes, such as walking a moai up a ramp to the top of an ahu, Lipo and Hunt’s field experiments showed that these could be navigated successfully through controlled stepping.
Furthermore, the distribution pattern of the roadways is consistent with the road moai being left due to mechanical failure. “Arguments that the moai were placed ceremonially in preparation for quarrying have become more common,” said Lipo. “The algorithm there is to claim that positions are ritual, without presenting anything that is falsifiable. There is no reason why the places the statues fell due to mechanical reasons couldn’t later become ‘ritual,’ in the same way that everything on the island could be claimed to be ritual—a circular argument. But to argue that they were placed there purposefully for ritual purposes demands framing the explanation in a way that is falsifiable.”
Schematic representation of the moai transport method using coordinated rope pulling to achieve a “walking” motion. Credit: Carl Lipo and Terry Hunt, 2025
“The only line of evidence that is presented in this way is the presence of ‘platforms’ that were found beneath the base of one moai, which is indeed intriguing,” Lipo continued. “However, those platforms can be explained in other ways, given that the moai certainly weren’t moved from the quarry to the ahu in one single event. They were paused along the way, as is clear from the fact that the roads appear to have been constructed in segments with different features. Their construction appears to be part of the overall transport process.”
Lipo’s work has received a fair share of criticism from other scholars over the years, and his and Hunt’s paper includes a substantial section rebutting the most common of those critiques. “Archaeologists tend to reject (in practice) the idea that the discipline can construct cumulative knowledge,” said Lipo. “In the case of moai transport, we’ve strived to assemble as much empirical evidence as possible and have forwarded an explanation that best accounts for what we can observe. Challenges to these ideas, however, do not come from additional studies with new data but rather just new assertions.”
“This leads the public to believe that we (as a discipline) can never really figure anything out and are always going to be a speculative enterprise, spinning yarns and arguing with each other,” Lipo continued. “With the erosion of trust in science, this is fairly catastrophic to archaeology as a whole but also the whole scientific enterprise. Summarizing the results in the way we do here is an attempt to point out that we can build falsifiable accounts and can make contributions to cumulative knowledge that have empirical consequences—even with something as remarkable as the transport of moai.”
Experimental archaeology is a relatively new field that some believe could be the future of archaeology. “I think experimental archaeology has potential when it’s tied to physics and chemistry,” said Lipo. “It’s not just recreating something and then arguing it was done in the same way in the past. Physics and chemistry are our time machines, allowing us to explain why things are the way they are in the present in terms of the events that occurred in the past. The more we can link the theory needed to explain the present, the better we can explain the past.”
Jennifer is a senior writer at Ars Technica with a particular focus on where science meets culture, covering everything from physics and related interdisciplinary topics to her favorite films and TV series. Jennifer lives in Baltimore with her spouse, physicist Sean M. Carroll, and their two cats, Ariel and Caliban.
The ship wasn’t designed to withstand the powerful ice compression forces—and Shackleton knew it.
The Endurance, frozen and keeled over in the ice of the Weddell Sea. Credit: BF/Frank Hurley
In 1915, intrepid British explorer Sir Ernest Shackleton and his crew were stranded for months in the Antarctic after their ship, Endurance, was trapped by pack ice, eventually sinking into the freezing depths of the Weddell Sea. Miraculously, the entire crew survived. The prevailing popular narrative surrounding the famous voyage features two key assumptions: that Endurance was the strongest polar ship of its time, and that the ship ultimately sank after ice tore away the rudder.
However, a fresh analysis reveals that Endurance would have sunk even with an intact rudder; it was crushed by the cumulative compressive forces of the Antarctic ice with no single cause for the sinking. Furthermore, the ship wasn’t designed to withstand those forces, and Shackleton was likely well aware of that fact, according to a new paper published in the journal Polar Record. Yet he chose to embark on the risky voyage anyway.
Author Jukka Tuhkuri of Aalto University is a polar explorer and one of the leading researchers on ice worldwide. He was among the scientists on the Endurance22 mission that discovered the Endurance shipwreck in 2022, documented in a 2024 National Geographic documentary. The ship was in pristine condition partly because of the lack of wood-eating microbes in those waters. In fact, the Endurance22 expedition’s exploration director, Mensun Bound, told The New York Times at the time that the shipwreck was the finest example he’s ever seen; Endurance was “in a brilliant state of preservation.”
As previously reported, Endurance set sail from Plymouth on August 6, 1914, with Shackleton joining his crew in Buenos Aires, Argentina. By the time they reached the Weddell Sea in January 1915, accumulating pack ice and strong gales slowed progress to a crawl. Endurance became completely icebound on January 24, and by mid-February, Shackleton ordered the boilers to be shut off so that the ship would drift with the ice until the weather warmed sufficiently for the pack to break up. It would be a long wait. For 10 months, the crew endured the freezing conditions. In August, ice floes pressed into the ship with such force that the ship’s decks buckled.
The ship’s structure nonetheless remained intact, but by October 25, Shackleton realized Endurance was doomed. He and his men opted to camp out on the ice some two miles (3.2 km) away, taking as many supplies as they could with them. Compacted ice and snow continued to fill the ship until a pressure wave hit on November 13, crushing the bow and splitting the main mast—all of which was captured on camera by crew photographer Frank Hurley. Another pressure wave hit in the late afternoon on November 21, lifting the ship’s stern. The ice floes parted just long enough for Endurance to finally sink into the ocean before closing again to erase any trace of the wreckage.
Once the wreck had been found, the team recorded as much as they could with high-resolution cameras and other instruments. Vasarhelyi, particularly, noted the technical challenge of deploying a remote digital 4K camera with lighting at 9,800 feet underwater, and the first deployment at that depth of photogrammetric and laser technology. This resulted in a millimeter-scale digital reconstruction of the entire shipwreck to enable close study of the finer details.
Challenging the narrative
The ice and wave tank at Aalto University. Credit: Aalto University
It was shortly after the Endurance22 mission found the shipwreck that Tuhkuri realized that there had never been a thorough structural analysis conducted of the vessel to confirm the popular narrative. Was Endurance truly the strongest polar ship of that time, and was a broken rudder the actual cause of the sinking? He set about conducting his own investigation to find out, analyzing Shackleton’s diaries and personal correspondence, as well as the diaries and correspondence of several Endurance crew members.
Tuhkuri also conducted a naval architectural analysis of the vessel under the conditions of compressive ice, which had never been done before. He then compared those results with the underwater images of the Endurance shipwreck. He also looked at comparable wooden polar expedition ships and steel icebreakers built in the late 1800s and early 1900s.
Endurance was originally named Polaris; Shackleton renamed it when he purchased the ship in 1914 for his doomed expedition. Per Tuhkuri, the ship had a lower (tween) deck, a main deck, and a short bridge deck above them that stopped at the machine room in order to make space for the steam engine and boiler. There were no beams in the machine room area, nor any reinforcing diagonal beams, which weakened this significant part of the ship’s hull.
This is because Endurance was originally built for polar tourism and for hunting polar bears and walruses in the Arctic; at the ice edge, ships only needed sufficiently strong planking and frames to withstand the occasional collision from ice floes. However, “In pack ice conditions, where compression from the ice needs to be taken into account, deck beams become of key importance,” Tuhkuri wrote. “It is the deck beams that keep the two ship sides apart and maintain the shape of a ship. Without strong enough deck beams, a vessel gets crushed by compressive ice, more or less irrespective of the thickness of planking and frames.”
The Endurance was nonetheless sturdy enough to withstand five serious ice compression events before her final sinking. On April 4, 1915, one of the scientists on board reported hearing loud rumbling noises from a 3-meter-high ice ridge that formed near the ship, causing the ship to vibrate. Tuhkuri believes this was due to a “compressive failure process” as ice crushed against the hull. On July 14, a violent snowstorm hit, and crew members could hear the ice breaking beneath the ship. The ice ridges that formed over the next few days were sufficiently concerning that Shackleton instituted four-hour watches on deck and insisted on having everything packed in case they had to abandon ship.
Crushed by the ice
Idealized cross sections of early Antarctic ships. Endurance was type (a); Deutschland was type (b). Credit: J. Tuhkuri, 2025
On August 1, an ice floe fractured and grinding noises were heard beneath the ship as the floe piled underneath it, lifting Endurance and causing her to first heel starboard and then heel to port, as several deck beams began to buckle. Similar compression events kept happening until there was a sudden escalation on September 30. The hull began vibrating hard enough to shake the whole rigging as even more ice crushed against the hull. Even the linoleum on the floors buckled; Harry McNish wrote in his diary that it looked like Endurance “was going to pieces.”
Yet another ice compression event occurred on October 17, pushing the vessel one meter into the air as the iron plates on the engine room’s floor buckled and slid over each other. Ship scientist Reginald James wrote that “for a time things were not good as the pressure was mostly along the region of the engine room where there are no beams of any strength,” while Captain Worsley described the engine room as “the weakest part of the ship.”
By the afternoon, Endurance was heeled almost 30 degrees to port, so much so that the keel was visible from the starboard side, per Tuhkuri, although the ice started to fracture in the evening so that the ship could shift upright again. The crew finally abandoned ship on October 27 after an even more severe compression event hit a few days before. Endurance finally sank below the ice on November 21.
Tuhkuri’s analysis of the structural damage to Endurance revealed that the rudder and the stern post were indeed torn off, confirmed by crew correspondence and diaries and by the underwater images taken of the wreck. The keel was also ripped off, with McNish noting in his diary that the ship broke into two halves as a result. The underwater images are less clear on this point, but Tuhkuri writes that there is something “some distance forward from the rudder, on the port side” that “could be the end of a displaced part of the keel sticking up from under the ship.”
All the diaries mentioned the buckling and breaking of deck beams, and there was much structural damage to the ship’s sides; for instance, Worsley writes of “great spikes of ice… forcing their way through the ship’s sides.” There are no visible holes in the wreck’s sides in the underwater images, but Tuhkuri posits that the damage is likely buried in the mud on the sea bed, given that by late October, Endurance “was heavily listed and the bottom was exposed.”
Jukka Tuhkuri on the ice. Credit: Aalto University
Based on his analysis, Tuhkuri concluded that the rudder wasn’t the sole or primary reason for the ship’s sinking. “Endurance would have sunk even if it did not have a rudder at all,” Tuhkuri wrote; it was crushed by the ice, with no single reason for its eventual sinking. Shackleton himself described the process as ice floes “simply annihilating the ship.”
Perhaps the most surprising finding is that Shackleton knew of Endurance‘s structural shortcomings even before undertaking the voyage. Per Tuhkuri, the devastating effects of compressive ice on ships were known to shipbuilders in the early 1900s. An early Swedish expedition was forced to abandon its ship Antarctic in February 1903 when it became trapped in the ice. Things progressed much like Endurance: the ice lifted Antarctic up so that the ship heeled over, with ice-crushed sides, buckling beams, broken planking, and a damaged rudder and stern post. The final sinking occurred when an advancing ice floe ripped off the keel.
Shackleton knew of Antarctic‘s fate and had even been involved in the rescue operation. He also helped Wilhelm Filchner make final preparations for Filchner’s 1911–1913 polar expedition with a ship named Deutschland; he even advised his colleague to strengthen the ship’s hull by adding diagonal beams, the better to withstand the Weddell Sea ice. Filchner did so, and as a result, Deutschland survived eight months of being trapped in compressive ice until the ship was finally able to break free and sail home. (It took a torpedo attack in 1917 to sink the good ship Deutschland.)
The same shipyard that modified Deutschland had also just signed a contract to build Endurance (then called Polaris). So both Shackleton and the shipbuilders knew how destructive compressive ice could be and how to bolster a ship against it. Yet Endurance was not outfitted with diagonal beams to strengthen its hull. And knowing this, Shackleton bought Endurance anyway for his 1914–1915 voyage. In a 1914 letter to his wife, he even compared the strength of its construction unfavorably with that of the Nimrod, the ship he used for his 1907–1909 expedition. So Shackleton had to know he was taking a big risk.
“Even simple structural analysis shows that the ship was not designed for the compressive pack ice conditions that eventually sank it,” said Tuhkuri. “The danger of moving ice and compressive loads—and how to design a ship for such conditions—was well understood before the ship sailed south. So we really have to wonder why Shackleton chose a vessel that was not strengthened for compressive ice. We can speculate about financial pressures or time constraints, but the truth is, we may never know. At least we now have more concrete findings to flesh out the stories.”
Jennifer is a senior writer at Ars Technica with a particular focus on where science meets culture, covering everything from physics and related interdisciplinary topics to her favorite films and TV series. Jennifer lives in Baltimore with her spouse, physicist Sean M. Carroll, and their two cats, Ariel and Caliban.
And that makes perfect sense, because when you reduce hunters’ choices to simple math using what’s called the prey choice model (more on that below), these long-lost species offered bigger returns for the effort of hunting. In other words, giant sloths are extinct because they were delicious and made of meat.
Yup, it’s humanity’s fault—again
As the last Ice Age drew to a close, the large animals that had once dominated the world’s chilly Pleistocene landscapes started to vanish. Mammoths, saber-toothed tigers, and giant armadillos died out altogether. Other species went locally extinct; rhinoceroses no longer stomped around southern Europe, and horses disappeared from the Americas until European colonists brought new species with them thousands of years later.
Scientists have been arguing about how much of that was humanity’s fault for quite a while.
Most of the blame goes to the world’s changing climate; habitats shifted as the world mostly got warmer and wetter. But, at least in some places, humans may have sped the process along, either by hunting the last of the Pleistocene megafauna to extinction or just by shaking up the rest of the ecosystem so much that it was all too ready to collapse, taking the biggest species down with it.
It looks, at first glance, like South America’s late Ice Age hunters are safely not guilty. For one thing, the megafauna didn’t start dying out until thousands of years after humans first set foot in the region. Archaeologists also haven’t found many sites that contain both traces of human activity and the bones of extinct horses, giant armadillos, or other megafauna. And at those few sites, megafauna bones made up only a small percentage of the contents of ancient scrap piles. Not enough evidence places us at the crime scene, in other words—or so it seems.
On the other hand, the Ice Age megafauna began dying out in South America around 13,000 years ago, roughly the same time that a type of projectile point called the fishtail appeared. That may not be a coincidence, argued one study. And late last year, another study showed that farther north, in what’s now the United States, Clovis people’s diets contained mammoth amounts of… well, mammoth.
Now that we know what Denisovans looked like, they’re turning up everywhere.
This digital reconstruction makes Yunxian 2 look liess like a Homo erectus and more like a Denisovan (or Homo longi, according to the authors). Credit: Feng et al. 2025
A fossil skull from China that made headlines last week may or may not be a million years old, but it’s probably closely related to Denisovans.
The fossil skull, dubbed Yunxian 2, is one of three unearthed from a terrace alongside the Han River, in central China, in a layer of river sediment somewhere between 600,000 and 1 million years old. Archaeologists originally identified them as Homo erectus, but Hanjiang Normal University paleoanthropologist Xiaobo Feng and his colleagues’ recent digital reconstruction of Yunxian 2 suggests the skulls may actually have belonged to someone a lot more similar to us: a hominin group defined as a species called Homo longi or a Denisovan, depending on who’s doing the naming.
The recent paper adds fuel—and a new twist—to that debate. And the whole thing may hinge on a third skull from the same site, still waiting to be published.
This digital reconstruction makes Yunxian 2 look less like a Homo erectus and more like a Denisovan (or Homo longi, according to the authors). Credit: Feng et al. 2025
Denisovan or Homo longi?
The Yunxian skull was cracked and broken after hundreds of thousands of years under the crushing weight of all that river mud, but the authors used CT scans to digitally put the pieces back together. (They got some clues from a few intact bits of Yunxian 1, which lay buried in the same layer of mud just 3 meters away.) In the end, Feng and his colleagues found themselves looking at a familiar face; Yunxian 2 bears a striking resemblance to a 146,000-year-old Denisovan skull.
That skull, from Harbin in northeast China, made headlines in 2021 when a team of paleoanthropologists claimed it was part of an entirely new species, which they dubbed Homo longi. According to that first study, Homo longi was a distinct hominin species, separate from us, Neanderthals, and even Denisovans. That immediately became a point of contention because of features the skull shared with some other suspected Denisovan fossils.
Earlier this year, a team of researchers, which included one of the 2021 study’s authors, took samples of ancient proteins preserved in the Harbin skull; of the 95 proteins they found, three of them matched proteins only encoded in Denisovan DNA. While the June 2025 study suggested that Homo longi was a Denisovan all along, the new paper draws a different conclusion: Homo longi is a species that happens to include the population we’ve been calling Denisovans. As study coauthor Xijun Ni, of the Chinese Academy of Sciences, puts it in an email to Ars Technica, “Given their similar age range, distribution areas, and available morphological data, it is likely that Denisovans belong to the Homo longi species. However, little is known about Denisovan morphology.”
Of course, that statement—that we know little about Denisovan morphology (the shapes and features of their bones)—only applies if you don’t accept the results of the June 2025 study mentioned above, which clocked the Harbin skull as a Denisovan and therefore told us what one looks like.
And Feng and his colleagues, in fact, don’t accept those results. Instead, they consider Harbin part of some other group of Homo longi, and they question the earlier study’s methods and results. “The peptide sequences from Harbin, Penghu, and other fossils are too short and provide conflicting information,” Ni tells Ars Technica. Feng and his colleagues also question the results of another study, which used mitochondrial DNA to identify Harbin as a Denisovan.
In other words, Feng and his colleagues are pretty invested in defining Homo longi as a species and Denisovans as just one sub-group of that species. But that’s hard to square with DNA data.
Alas, poor Yunxian 2, I knew him well
Yunxian 2 has a wide face with high, flat cheekbones, a wide nasal opening, and heavy brows. Its cranium is higher and rounder than Homo erectus (and the original reconstruction, done in the 1990s), but it’s still longer and lower than is normal for our species. Overall, it could have held about 1,143 cubic centimeters of brain, which is in the ballpark of modern people. But its shape may have left less room for the frontal lobe (the area where a lot of social skills, logic, motor skills, and executive function happen) than you’d expect in a Neanderthal or a Homo sapiens skull.
Feng and his colleagues measured the distances between 533 specific points on the skull: anatomical landmarks like muscle attachment points or the joints between certain bones. They compared those measurements to ones from 26 fossil hominin skulls and several-dozen modern human skulls, using a computer program to calculate how similar each skull was to all of the others.
Yunxian 2 fits neatly into a lookalike group with the Harbin skull, along with two other skulls that paleoanthropologists have flagged as belonging to either Denisovans or Homo longi. Those two skulls are a 200,000- to 260,000-year-old skull found in Dali County in northwestern China and a 260,000-year-old skull from Jinniushi (sometimes spelled Jinniushan) Cave in China.
Those morphological differences suggest some things about how the individuals who once inhabited these skulls might have been related to each other, but that’s also where things get dicey.
An older reconstruction of the Yunxian 2 skull gives it a flatter look. Credit: government of Wuhan
Digging into the details
Most of what we know about how we’re related to our closest extinct hominin relatives (Neanderthals and Denisovans) comes from comparing our DNA to theirs and tracking how small changes in the genetic code build up over time. Based on DNA, our species last shared a common ancestor with Neanderthals and Denisovans sometime around 750,000 years ago in Africa. One branch of the family tree led to us; the other branch split again around 600,000 years ago, leading to Neanderthals and Denisovans (or Homo longi, if you prefer).
In other words, DNA tells us that Neanderthals and Denisovans are more closely related to each other than either is to us. (Unless you’re looking at mitochondrial DNA, which suggests that we’re more closely related to Neanderthals than to Denisovans; it’s complicated, and there’s a lot we still don’t understand.)
“Ancient mtDNA and genomic data show different phylogenetic relationships among Denisovans, Neanderthals and Homo sapiens,” says Ni. So depending on which set of data you use and where your hominin tree starts, it can be possible to get different answers about who is most closely related to whom. The fact that all of these groups interbred with each other can explain this complexity, but makes building family trees challenging.
It is very clear, however, that Feng and his colleagues’ picture of the relationships between us and our late hominin cousins, based on similarities among fossil skulls in their study, looks very different from what the genomes tell us. In their model, we’re more closely related to Denisovans, and the Neanderthals are off on their own branch of the family tree. Feng and his colleagues also say those splits happened much earlier, with Neanderthals branching off on their own around 1.38 million years ago; we last shared a common ancestor with Homo longi around 1 million years ago.
That’s a big difference from DNA results, especially when it comes to timing. And the timing is likely to be the biggest controversy here. In a recent commentary on Feng and his colleagues’ study, University of Wisconsin paleoanthropologist John Hawks argues that you can’t just leave genetic evidence out of the picture.
“What this research should have done is to put the anatomical comparisons into context with the previous results from DNA, especially the genomes that enable us to understand the relationships of Denisovan, Neanderthal, and modern human groups,” Hawks writes.
(It’s worth a side note that most news stories describe Yunxian 2 as being a million years old, and so do Feng and his colleagues. But electron spin resonance dating of fossil animal bones from the same sediment layer suggests the skull could be as young as 600,000 years old or as old as 1.1 million. That still needs to be narrowed down to everyone’s satisfaction.)
What’s in a name?
Of course, DNA also tells us that even after all this branching and migrating, the three species were still similar enough to reproduce, which they did several times. Many groups of modern people still carry traces of Neanderthal and Denisovan DNA in their genomes, courtesy of those exchanges. And some ancient Neanderthal populations were carrying around even older chunks of human DNA in the same way. That arguably makes species definitions a little fuzzy at best—and maybe even irrelevant.
“I think all these groups, including Neanderthals, should be recognized within our own species, Homo sapiens,” writes Hawks. Hawks contends that the differences among these hominin groups “were the kind that evolve among the populations of a single species over time, not starkly different groups that tread the landscape in mutually unrecognizeable ways.”
But humans love to classify things (a trait we may have shared with Neanderthals and Denisovans), so those species distinctions are likely to persist even if the lines between them aren’t so solid. As long as that’s the case, names and classifications will be fodder for often heated debate. And Feng’s team is staking out a position that’s very different from Hawks’. “‘Denisovan’ is a label for genetic samples taken from the Denisova Cave. It should not be used everywhere. Homo longi is a formally named species,” says Ni.
Technically, Denisovans don’t have a formal species name, a Latinized moniker like Homo erectus that comes with a clear(ish) spot on the family tree. Homo longi would be a more formal species name, but only if scientists can agree on whether they’re actually a species.
An archaeologist comes face to face with the Yunxian 3 skull Credit: government of Wuhan
The third Yunxian skull
Paleoanthropologists unearthed a third skull from the Yunxian site in 2022. It bears a strong resemblance to the other two from the area (and is apparently in better shape than either of them), and it dates to about the same timeframe. A 2022 press release describes it as “the most complete Homo erectus skull found in Eurasia so far,” but if Feng and his colleagues are right, it may actually be a remarkably complete Homo longi (and/or Denisovan) skull. And it could hold the answers to many of the questions anthropologists like Feng and Hawks are currently debating.
“It remains pretty obvious that Yunxian 3 is going to be central to testing the relationships of this sample [of fossil hominins in Feng and colleagues’ paper],” writes Hawks.
The problem is that Yunxian 3 is still being cleaned and prepared. Preparing a fossil is a painstaking, time-consuming process that involves very carefully excavating it from the rocky matrix it’s embedded in, using everything from air-chisels to paintbrushes. And until that’s done and a scientific report on the skull is published, other paleoanthropologists don’t have access to any information about its features—which would be super useful for figuring out how to define whatever group we eventually decide it belongs to.
For the foreseeable future, the relationships between us and our extinct cousins (or at least our ideas about those relationships) will keep changing as we get more data. Eventually, we may have enough data from enough fossils and ancient DNA samples to form a clearer picture of our past. But in the meantime, if you’re drawing a hominin family tree, use a pencil.
A local Neolithic community in northeastern France may have clashed with foreign invaders, cutting off limbs as war trophies and otherwise brutalizing their prisoners of war, according to a new paper published in the journal Science Advances. The findings challenge conventional interpretations of prehistoric violence as bring indiscriminate or committed for pragmatic reasons.
Neolithic Europe was no stranger to collective violence of many forms, such as the odd execution and massacres of small communities, as well as armed conflicts. For instance, we recently reported on an analysis of human remains from 11 individuals recovered from El Mirador Cave in Spain, showing evidence of cannibalism—likely the result of a violent episode between competing Late Neolithic herding communities about 5,700 years ago. Microscopy analysis revealed telltale slice marks, scrape marks, and chop marks, as well as evidence of cremation, peeling, fractures, and human tooth marks.
This indicates the victims were skinned, the flesh removed, the bodies disarticulated, and then cooked and eaten. Isotope analysis indicated the individuals were local and were probably eaten over the course of just a few days. There have been similar Neolithic massacres in Germany and Spain, but the El Mirador remains provide evidence of a rare systematic consumption of victims.
Per the authors of this latest study, during the late Middle Neolithic, the Upper Rhine Valley was the likely site of both armed conflict and rapid cultural upheaval, as groups from the Paris Basin infiltrated the region between 4295 and 4165 BCE. In addition to fortifications and evidence of large aggregated settlements, many skeletal remains from this period show signs of violence.
Friends or foes?
Overhead views of late Middle Neolithic violence-related human mass deposits in Pit 124 of the Alsace region, France. Credit: Philippe Lefranc, INRAP
Archaeologist Teresa Fernandez-Crespo of Spain’s Valladolid University and co-authors focused their analysis on human remains excavated from two circular pits at the Achenheim and Bergheim sites in Alsace in northwestern France. Fernandez-Crespo et al. examined the bones and found that many of the remains showed signs of unhealed trauma—such as skull fractures—as well as the use of excessive violence (overkill), not to mention quite a few severed left upper limbs. Other skeletons did not show signs of trauma and appeared to have been given a traditional burial.
In the late 1500s, a few decades after the khipu in this recent study was made, an Indigenous chronicler named Guaman Poma de Ayala described how older women used khipu to “keep track of everything” in aqllawasai: places that basically functioned as finishing schools for Inca girls. Teenage girls, chosen by local nobles, were sent away to live in seclusion at the aqllawasai to weave cloth, brew chicha, and prepare food for ritual feasts.
What happened to the girls after aqllawasai graduation was a mixed bag. Some of them were married (or given as concubines) to Inca nobles, others became priestesses, and some ended up as human sacrifices. But some of them actually got to go home again, and they probably took their knowledge of khipu with them.
“I think this is the likely way in which khipu literacy made it into the countryside and the villages,” said Hyland. “These women, who were not necessarily elite, taught it to their children, etc.” That may be where the maker of KH0631 learned their skills: either in an aqllawasai or from a graduate of one (we still don’t know this particular khipu-maker’s gender).
“Science confirming what they already knew”
The finely crafted khipu turning out to be the work of a commoner shows that numeracy was widespread and surprisingly egalitarian in the Inca empire, but it also reveals a centuries-long thread connecting the Inca and their descendants.
Modern people—the descendants of the Inca—still use khipu today in some parts of Peru and Chile. Some scholars (mostly non-Indigenous ones) have argued that these modern khipu weren’t really based on knowledge passed down for centuries but were instead just a clumsy attempt to copy the Inca technology. But if commoners were using khipu in the Inca empire, it makes sense for that knowledge to have been passed down to modern villagers.
“It points to a continuity between Inka and modern khipus,” said Hyland. “In the few modern villages with living khipu traditions, they already believe in this continuity, so it would be the case of science confirming what they already know.”
Some stone tools found near a river on the Indonesian island of Sulawesi suggest that the first hominins had reached the islands by at least 1.04 million years ago. That’s around the same time that the ancestors of the infamously diminutive “Hobbits” may have reached the island of Flores.
Archaeologist Budianto Hakim of Indonesia’s National Research and Innovation Agency and his colleagues were the ones who recently unearthed the tools from a site on Sulawesi. Although a handful of stone flakes from that island don’t tell us who the ancestors of the small species were or how they reached remote islands like Flores and Luzon, the tools are one more piece in the puzzle. And this handful of stone flakes may eventually play a role in helping us understand how other hominin species conquered most of the world long before we came along.
Crossing the ocean a million years ago
Sometimes the deep past leaves the smallest traces. At the Calio site, a sandstone outcrop in what’s now a cornfield outside the village of Ujung in southern Sulawesi, people left behind just a handful of sharp stone flakes roughly a million years ago. There are seven of them, ranging from 22 to 60 millimeters long, and they’re scratched, worn, and chipped from tumbling around at the bottom of a river. But it’s still clear that they were once shaped by skilled human—or at least human-like—hands that used hard stones as hammers to make sharp-edged chert flakes for cutting and scraping.
The oldest of these tools is likely to be between 1.04 and 1.48 million years old. Hakim and his colleagues dated teeth from a wild pig to around 1.26 million years ago. They were part of a jawbone archaeologists unearthed from a layer just above the oldest flake. Throw in some statistical modeling, and you get the range of likely dates for the stone flake buried in the deepest layer of soil.
Even the younger end of that estimate would make these tools the oldest evidence yet of hominins (of any species) in the islands of Indonesia and the Philippines. This area, sometimes called Wallacea, lies between the continents of Asia and Australia, separated from both by wide channels of deep ocean.
“But the Calio site has yet to yield any hominin fossils,” said Brumm, “so while we now know there were tool-makers on Sulawesi a million years ago, their identity remains a mystery.” But they may be related to the Hobbits, a short-statured group of hominins who lived hundreds of kilometers away on the island of Flores until around 50,000 years ago.
“The discovery of Early Pleistocene artifacts at Calio suggests that Sulawesi was populated by hominins at around the same time as Flores, if not earlier,” wrote Hakim and his colleagues in their recent paper.
The Flores connection
The islands that now make up Indonesia and the Philippines have been a hominin hotspot for at least a million years. Our species wandered onto the scene sometime between 63,000 and 73,000 years ago, but at least one other hominin species had already been there for at least a million years. We’re just not sure exactly who they were, when they arrived, or how.
“Precisely when hominins first crossed to Sulawesi remains an open question, as does the taxonomic affinity of the colonizing population,” the authors note.
This map shows the islands of Wallacea. The large one just east of Java is Sulawesi. Credit: Darren O’Connell
That’s why the handful of stone tools the team recently unearthed at Calio matter: They’re another piece of that puzzle, albeit a small one. Every slightly older date is one step closer to the first hominin tools, bones, or footprints in these islands, and another pin on the map of who was where and when.
And that map is accumulating quite a lot of pins, representing an ever-increasing number of species. Once the first hominins made it across the Makassar Strait, they found themselves in isolated groups on islands cut off from the mainland—and each other—so the hominin family tree started branching very quickly. On at least two islands, Flores and Luzon, those original hominin settlers eventually gave rise to local species, Homo floresiensis and Homo luzonensis. And University of Wollongong paleoanthropologist Richard Roberts, a co-discoverer of Homo floresiensis, thinks there are probably more isolated island hominin species.
In 2019, when Homoluzonensis was first described, Roberts told Ars, “These new fossils, and the assignation of them to a new species (Homo luzonensis), fulfills one of the predictions Mike Morwood and others (myself included) made when we first reported (15 years ago!) the discovery of Homo floresiensis: that other unknown species of hominins would be found in the islands of Southeast Asia.”
Both Homo floresiensis (the original “Hobbits”) and Homo luzonensis were short, clocking in at just over a meter tall. Their bones and teeth are different enough from each other to set them apart as a unique species, but they have enough in common that they probably share a common ancestor—one they don’t share with us. They’re more like our distant cousins, and the islands of Wallacea may have been home to many other such cousins, if Roberts and his colleagues are correct.
Complicated family history
But who was the common ancestor of all these hominin cousins? That’s where things get complicated (as if they weren’t already). Most paleoanthropologists lean toward Homo erectus, but there’s a chance—along with some tantalizing hints, and no direct evidence—that much more ancient human relatives called Australopithecines may have made the journey a million (or two) years before Homo erectus.
Finger and toe bones from Homo luzonensis are curved, as if they spent as much of their lives climbing trees as walking. That’s more like Australopithecines than any member of our genus Homo. But their teeth are smaller and shaped more like ours. Anthropologists call this mix of features a mosaic, and it can make it tough to figure out how hominin species are related. That’s part of why the question of when the ancestors of the Hobbits arrived on their respective islands is so important.
Compare the teeth and phalanx of Homo luzonensis to those of Homo sapiens (right) and Australopithecus afarensis (left). Credit: Tocheri 2019
We don’t know the answer yet, but we do know that someone was making stone tools on Flores by 1.02 million years ago. Those toolmakers may have been Homo erectus, Australopithecines, or something already recognizable as tiny Homo floresiensis. The Hobbits (or their ancestors) were distinctly “Hobbity” by around 700,000 years ago; fossil teeth and bones from a handful of hominins at a site called Mata Menge make that clear. The Hobbits discovered at Liang Bua Cave on Flores date to somewhere between 50,000 and 100,000 years ago.
Meanwhile, 2,800 kilometers away on the island of Luzon, the oldest stone tools, along with their obvious cut marks left behind on animal bones, date back to 700,000 years ago. That’s as old as the Mata Menge Hobbits on Flores. The oldest Homo luzonensis fossils are between 50,000 and 67,000 years old. It’s entirely possible that older evidence, of the island’s original settlers and of Homo luzonensis, may eventually be found, but until then, we’re left with a lot of blank space and a lot of questions.
And now we know that the oldest traces of hominin presence on Sulawesi is at least 1.04 million years old. But might Sulawesi have its own diminutive hominins?
So are there more Hobbits out there?
“Sulawesi is a wild card—it’s like a mini-continent in itself,” said Brumm. “If hominins were cut off on this huge and ecologically rich island for a million years, would they have undergone the same evolutionary changes as the Flores hobbits? Or would something totally different have happened?”
Reconstruction of Homo floresiensis by Atelier Elisabeth Daynes. Credit: Kinez Riza
A phenomenon called island dwarfism played a role in Homo floresiensis‘ evolution; species that live in relative isolation on small islands tend to evolve into either much larger or much smaller versions of their ancestors (which is why the Hobbits shared their island home with pygmy elephants and giant moas). But how small does an island need to be before island dwarfism kicks in? Sulawesi is about 12 times as large as Flores, for example. So what might the descendants of the Calio toolmakers have looked like by 100,000 years ago?
That’s something that we’ll only know if archaeologists on Sulawesi, like Hakim and his team, find fossil remains of those hominins.
Seafarers or tsunami survivors?
Understanding exactly when hominins first set foot on the island of Sulawesi might eventually help us figure out how they got there. These islands are thousands of kilometers from the Southeast Asian mainland and from each other, so getting there would have meant crossing vast stretches of deep, open ocean.
Archaeologists haven’t found any evidence that anyone who came before our species built boats or rafts, although those watercraft would have been made of materials that tend to decay pretty quickly, so even scraps of ancient wood and rope are extremely rare and lucky finds. But some ancient hominins did have a decent grasp of all the basic skills they’d need for at least a simple raft: woodworking and rope-making.
Another possibility is that hominins living on the coast of mainland Southeast Asia could have been swept out to sea by a tsunami, and some of them could have been lucky enough to survive the misadventure and wash ashore someplace like Sulawesi, Flores, or Luzon (RIP to any others). But for that scenario to work, enough hominins would have had to reach each island to create a lasting population, and it probably had to happen more than once to end up with hominin groups on at least three distant islands.
Either way, it’s no small feat, even for a Hobbit with small feet.
Other July stories: Solving a 150-year-old fossil mystery and the physics of tacking a sailboat.
150-year-old fossil of Palaeocampa anthrax isn’t a sea worm after all. Credit: Christian McCall
It’s a regrettable reality that there is never enough time to cover all the interesting scientific stories we come across each month. In the past, we’ve featured year-end roundups of cool science stories we (almost) missed. This year, we’re experimenting with a monthly collection. July’s list includes the discovery of the tomb of the first Maya king of Caracol in Belize, the fluid dynamics of tacking a sailboat, how to determine how fast blood was traveling when it stained cotton fabric, and how the structure of elephant ears could lead to more efficient indoor temperature control in future building designs, among other fun stories.
Tomb of first king of Caracol found
Credit: Caracol Archeological Project/University of Houston
Archaeologists Arlen and Diane Chase are the foremost experts on the ancient Maya city of Caracol in Belize and are helping to pioneer the use of airborne LiDAR to locate hidden structures in dense jungle, including a web of interconnected roadways and a cremation site in the center of the city’s Northeast Acropolis plaza. They have been painstakingly excavating the site since the mid-1980s. Their latest discovery is the tomb of Te K’ab Chaak, Caracol’s first ruler, who took the throne in 331 CE and founded a dynasty that lasted more than 460 years.
This is the first royal tomb the husband-and-wife team has found in their 40+ years of excavating the Caracol site. Te K’ab Chaak’s tomb (containing his skeleton) was found at the base of a royal family shrine, along with pottery vessels, carved bone artifacts, jadeite jewelry, and a mosaic jadeite death mask. The Chases estimate that the ruler likely stood about 5’7″ tall and was probably quite old when he died, given his lack of teeth. The Chases are in the process of reconstructing the death mask and conducting DNA and stable isotope analysis of the skeleton.
How blood splatters on clothing
Credit: Jimmy Brown/CC BY 2.0
Analyzing blood splatter patterns is a key focus in forensic science, and physicists have been offering their expertise for several years now, including in two 2019 studies on splatter patterns from gunshot wounds. The latest insights gleaned from physics concern the distinct ways in which blood stains cotton fabrics, according to a paper published in Forensic Science International.
Blood is a surprisingly complicated fluid, in part because the red blood cells in human blood can form long chains, giving it the consistency of sludge. And blood starts to coagulate immediately once it leaves the body. Blood is also viscoelastic: not only does it deform slowly when exposed to an external force, but once that force has been removed, it will return to its original configuration. Add in coagulation and the type of surface on which it lands, and correctly interpreting the resulting spatter patterns becomes incredibly difficult.
The co-authors of the July study splashed five different fabric surfaces with pig’s blood at varying velocities, capturing the action with high-speed cameras. They found that when a blood stain has “fingers” spreading out from the center, the more fingers there are, the faster the blood was traveling when it struck the fabric. And the faster the blood was moving, the more “satellite droplets” there will be—tiny stains surrounding the central stain. Finally, it’s much easier to estimate the velocity of blood splatter on plain-woven cotton than on other fabrics like twill. The researchers plan to extend future work to include a wider variety of fabrics, weaves, and yarns.
The uber-rich aren’t like the rest of us in so many ways, including their canny exploitation of highly secretive offshore financial systems to conceal their assets and/or identities. Researchers at Dartmouth have used machine learning to analyze two public databases and identified distinct patterns in the strategies oligarchs and billionaires in 65 different countries employ when squirreling away offshore assets, according to a paper published in the journal PLoS ONE.
One database tracks offshore finance, while the other rates different countries on their “rule of law.” This enabled the team to study key metrics like how much of their assets elites move offshore, how much they diversify, and how much they make use of “blacklisted” offshore centers that are not part of the mainstream financial system. The researchers found three distinct patterns, all tied to where an oligarch comes from.
Billionaires from authoritarian countries are more likely to diversify their hidden assets across many different centers—a “confetti strategy”—perhaps because these are countries likely to exact political retribution. Others, from countries with effective government regulations—or where there is a pronounced lack of civil rights—are more likely to employ a “concealment strategy” that includes more blacklisted jurisdictions, relying more on bearer shares that protect their anonymity. Those elites most concerned about corruption and/or having their assets seized typically employ a hybrid strategy.
The work builds on an earlier 2023 study concluding that issuing sanctions on individual oligarchs in Russia, China, the US, and Hong Kong is less effective than targeting the small, secretive network of financial experts who manage that wealth on behalf of the oligarchs. That’s because sanctioning just one wealth manager effectively takes out several oligarchs at once, per the authors.
The Middle Ages are stereotypically described as the “Dark Ages,” with a culture driven by superstition—including its medical practices. But a perusal of the hundreds of medical manuscripts collected in the online Corpus of Early Medieval Latin Medicine (CEMLM) reveals that in many respects, medical practices were much more sophisticated; some of the remedies are not much different from alternative medicine remedies touted by TikTok influencers today. That certainly doesn’t make them medically sound, but it does suggest we should perhaps not be too hasty in who we choose to call backward and superstitious.
Per Binghamton University historian Meg Leja, medievalists were not “anti-science.” In fact, they were often quite keen on learning from the natural world. And their health practices, however dubious they might appear to us—lizard shampoo, anyone?—were largely based on the best knowledge available at the time. There are detox cleanses and topical ointments, such as crushing the stone of a peach, mixing it with rose oil, and smearing it on one’s forehead to relieve migraine pain. (Rose oil may actually be an effective migraine pain reliever.) The collection is well worth perusing; pair it with the Wellcome-funded Curious Cures in Cambridge Libraries to learn even more about medieval medical recipes.
Physics of tacking a sailboat
Credit: Jonathan King/NYU
Possibly the most challenging basic move for beginner sailors is learning how to tack to sail upwind. Done correctly, the sail will flip around into a mirror image of its previous shape. And in competitive sailboat racing, a bad tack can lose the race. So physicists at the University of Michigan decided to investigate the complex fluid dynamics at play to shed more light on the tricky maneuver, according to a paper published in the journal Physical Review Fluids.
After modeling the maneuver and conducting numerical simulations, the physicists concluded that there are three primary factors that determine a successful tack: the stiffness of the sail, its tension before the wind hits, and the final sail angle in relation to the direction of the wind. Ideally, one wants a less flexible, less curved sail with high tension prior to hitting the wind and to end up with a 20-degree final sail angle. Other findings: It’s harder to flip a slack sail when tacking, and how fast one manages to flip the sail depends on the sail’s mass and the speed and acceleration of the turn.
Maintaining a comfortable indoor temperature constitutes the largest fraction of energy usage for most buildings, with the surfaces of walls, windows, and ceilings contributing to roughly 63 percent of energy loss. Engineers at Drexel University have figured out how to make surfaces that help rather than hamper efforts to maintain indoor temperatures: using so-called phase-change materials that can absorb and release thermal energy as needed as they shift between liquid and solid states. They described the breakthrough in a paper published in the Journal of Building Engineering.
The Drexel group previously developed a self-warming concrete using a paraffin-based material, similar to the stuff used to make candles. The trick this time around, they found, was to create the equivalent of a vascular network within cement-based building materials. They used a printed polymer matrix to create a grid of channels in the surface of concrete and filled those channels with the same paraffin-based material. When temperatures drop, the material turns into a solid and releases heat energy; as temperatures rise, it shifts its phase to a liquid and absorbs heat energy.
The group tested several different configurations and found that the most effective combination of strength and thermal regulation was realized with a diamond-shaped grid, which boasted the most vasculature surface area. This configuration successfully slowed the cooling and heating of its surface to between 1 and 1.2 degrees Celsius per hour, while holding up against stretching and compression tests. The structure is similar to that of jackrabbit and elephant ears, which have extensive vascular networks to help regulate body temperature.
Natural history museums have lots of old specimens in storage, and revisiting those specimens can sometimes lead to new discoveries. That’s what happened to University of Michigan evolutionary biologist Richard J. Knecht as he was poring over a collection at Harvard’s Museum of Comparative Zoology while a grad student there. One of the fossils, originally discovered in 1865, was labeled a millipede. But Knecht immediately recognized it as a type of lobopod, according to a paper published in the journal Communications Biology. It’s the earliest lobopod yet found, and this particular species also marks an evolutionary leap since it’s the first known lobopod to be non-marine.
Lobopods are the evolutionary ancestors to arthropods (insects, spiders, and crustaceans), and their fossils are common along Paleozoic sea beds. Apart from tardigrades and velvet worms, however, they were thought to be confined to oceans. But Palaeocampa anthrax has legs on every trunk, as well as almost 1,000 bristly spines covering its body with orange halos at their tips. Infrared spectroscopy revealed traces of fossilized molecules—likely a chemical that emanated from the spinal tips. Since any chemical defense would just disperse in water, limiting its effectiveness, Knecht concluded that Palaeocampa anthrax was most likely amphibious rather than being solely aquatic.
Jennifer is a senior writer at Ars Technica with a particular focus on where science meets culture, covering everything from physics and related interdisciplinary topics to her favorite films and TV series. Jennifer lives in Baltimore with her spouse, physicist Sean M. Carroll, and their two cats, Ariel and Caliban.
Neanderthals at Kebara had pretty broad tastes in meat. The butchered bones found in the cave were mostly an even mix of small ungulates (largely gazelle) and medium-sized ones (red deer, fallow deer, wild goats, and boar), with just a few larger game animals thrown in. And it looks like the Kebara Neanderthals were “use the whole deer” sorts of hunters because the bones came from all parts of the animals’ bodies.
On the other hand (or hoof), at Amud, archaeologists found that the butchered bones were almost entirely long bone shafts—legs, in other words—from gazelle. Apparently, the Neanderthal hunters at Amud focused more on gazelle than on larger prey like red deer or boar, and they seemingly preferred meat from the legs.
And not too fresh, apparently—the bones at Kebara showed fewer cut marks, and the marks that were there tended to be straighter. Meanwhile, at Amud, the bones were practically cluttered with cut marks, which crisscrossed over each other and were often curved, not straight. According to Jallon and her colleagues, the difference probably wasn’t a skill issue. Instead, it may be a clue that Neanderthals at Amud liked their meat dried, boiled, or even slightly rotten.
That’s based on comparisons to what bones look like when modern hunter-gatherers butcher their game, along with archaeologists’ experiments with stone tool butchery. First, differences in skill between newbie butchers and advanced ones don’t produce the same pattern of cut marks Jallon and her colleagues saw at Amud. But “it has been shown that decaying carcasses tend to be more difficult to process, often resulting in the production of haphazard, deep, and sinuous cut marks,” as Jallon and her colleagues wrote in their recent paper.
So apparently, for reasons unknown to modern archaeologists, the meat on the menu at Amud was, shall we say, a bit less fresh than that at Kebara. Said menu was also considerably less varied. All of that meant that if you were a Neanderthal from Amud and stopped by Kebara for dinner (or vice versa) your meal might seem surprisingly foreign.
