Philippa Kaur

An artefact made from a mammoth tusk is the oldest known boomerangTalamo et al., 2025, PLOS One, CC-BY 4.0
The world’s oldest known boomerang may be 22,000 years older than previously thought, suggesting it was crafted during a period when early humans displayed an increase in artistry.
In 1985, archaeologists unearthed a 72-centimetre-long ivory boomerang buried beneath six layers of sediment in Obłazowa cave in Poland. Later sediment sieving revealed a Homo sapiens thumb bone nearby, as well as antler tools, a bone bead and pendants made from fox teeth. In the 1990s, radiocarbon dating suggested the thumb was 31,000 years old – but surprisingly, the boomerang was dated to just 18,000 years old, several millennia younger than the artefacts in higher layers.
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Sahra Talamo at the University of Bologna in Italy suspected contamination. “Even a trace amount of modern carbon – from glue or conservation products – can throw off the radiocarbon date by tens of thousands of years,” she says. Analyses of the thumb’s carbon-nitrogen ratios showed signs of altered collagen, indicating that the preserved samples weren’t high enough quality for reliable radiocarbon dating.
Re-dating the contaminated boomerang would have been futile – and would have damaged the precious artefact needlessly, says Talamo. Instead, she and her colleagues dated 13 nearby animal bones, re-dated the human thumb bone and used statistical modelling to reconstruct the timeline. Their results showed that the entire sediment layer – and hence the boomerang and thumb as well – dates to between 39,000 and 42,000 years ago.
“In a way, this is an advertisement to museums that when you find something extraordinary, you should not cover it with glue or other restoration materials before completing all your analyses,” she says.
Its new age means the ivory boomerang predates the second-oldest known boomerangs – made from wood by Indigenous Australians – by 30,000 years. Unlike simpler throwing sticks, such as a 300,000-year-old wooden implement found in Schöningen, Germany, boomerangs are curved and aerodynamically shaped, even if they don’t always return to the thrower, says Talamo.
Indeed, although the ancient boomerang could most likely fly, its size and design probably made it unlikely to return to sender. Instead, it may have served a symbolic or ceremonial purpose, says Talamo, based on its decorative engravings, reddish pigment and smooth polish – combined with its placement beside a human thumb bone in a circle of imported stones.
The finding offers a glimpse into early humans’ cognitive abilities and craftsmanship during a burst of artistic expression that occurred during the Early Aurignacian period, starting around 40,000 years ago. During this time, symbolic artefacts such as mammoth ivory figurines, rock art and aesthetically crafted tools first appeared in Europe, says Talamo.

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My son is a wizard. He walks into the kitchen, looks at me and utters the magic words: “Can I have a cheese and tomato sandwich, please?” A few minutes later, just such a snack appears in front of him.
Other young animals can communicate their desire for food through grunts, tweets and growls. But only humans have the sophisticated system of grammar and vocabulary that allows us to communicate in precise terms.

This story is part of our Concepts Special, in which we reveal how experts think about some of the most mind-blowing ideas in science. Read more here

In fact, with studies of animals increasingly showing that they share many characteristics once thought to be the preserve of humans – from culture to emotions and even morality – language may seem like the one thing that truly sets us apart. “I think language makes us feel special as a species,” says Brian Lerch at the University of North Carolina at Chapel Hill.
Given all that, one of the key things researchers want to know about language is how it evolved, and why it only did so in our human lineage.
Psychologist Shimon Edelman at Cornell University in New York state thinks language’s magical power has a fairly straightforward evolutionary explanation. With his colleague Oren Kolodny, now at the Hebrew University of Jerusalem, he argues that it may have emerged 1.7 million years ago, when ancient humans began making stone hand-axes that are beyond the ability of non-human animals to produce.
The idea is that novice tool-makers would have required guidance from an expert to make their own hand-axes, so tool-making sites became classrooms. Proto-language might have emerged as a way for teachers to communicate to students – which could explain why both language and tool-making seem to require the brain to arrange and order thoughts into structured sequences.
But about a decade ago, a key experiment challenged that view. In 2014, Shelby Putt at Illinois State University and her colleagues tasked 24 volunteers with learning to make hand-axes from an expert who either talked them through the process or merely made the tools in the volunteers’ presence while occasionally pointing to direct their attention. Surprisingly, both methods were effective, suggesting verbal language isn’t necessary for complex tool-making.
This doesn’t mean Putt sees language and tool-making as completely unconnected. She thinks complex tool-making really did require humans to arrange and order their thoughts to stay on task. This, she argues, led to the expansion of the brain regions involved in working memory, which we use to briefly hold and manipulate ideas.
But Putt suspects it was only at some later date that humans used this ability to structure and order their thoughts to develop language – presumably because it helped them communicate better and boosted their chances of survival.

These scenarios all assume that language is fundamentally a tool for communicating with others. But that might not be the case. A third way to think about the evolution of language focuses almost exclusively on the way it can help individuals “talk” to themselves and organise their thoughts to undertake complex tasks.
According to some, including the influential linguist Noam Chomsky, this is what drove the evolution of language, meaning it had nothing at all to do with tool-making. Instead, these researchers think language emerged as recently as 70,000 years ago, perhaps simply because of a random genetic mutation that prompted brain rewiring.
Truth be told, there is still little consensus about quite how language arose. But if Chomsky and his ilk are right, though it didn’t involve magic, it might at least have involved a little luck.

Read the other stories in this series using the links below:

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Exposure to hormones in utero could affect human brain growthPeter Dazeley/Getty Images
The human brain is one of the most complex objects in the universe – and that complexity may be due to a surge of hormones released by the placenta during pregnancy.
While numerous ideas have been proposed to explain human brain evolution, it remains one of our greatest scientific mysteries. One explanation, known as the social brain hypothesis, suggests that our large brains evolved to manage complex social relationships. It posits that navigating large group dynamics requires a certain degree of cognitive ability, pushing social species to develop bigger brains. For instance, other highly sociable animals, such as dolphins and elephants, have relatively large brains too. But the biological mechanism underlying this link has remained unclear.
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Now, Alex Tsompanidis at the University of Cambridge and his colleagues say the answer may be placental sex hormones. During pregnancy, the placenta – a temporary organ that acts as an intermediary between the fetus and the mother – produces hormones crucial for fetal development. These include sex hormones such as oestrogens and androgens.
“I know that seems like a jump – thinking about human evolution and then ending up on the placenta,” says Tsompanidis. “But the reason for that is because we’ve been looking at the fluctuations and variations in the levels of these hormones in the womb and seeing that they predict things like language development and social development.”
Emerging research also shows that these hormones influence the developing brain. For instance, a 2022 study found that administering androgens, such as testosterone, to brain organoids – simplified, miniature versions of the brain made from human stem cells – during a critical developmental period increased the number of cells in the cortex, a brain region crucial for memory, learning and thinking. Other studies in brain organoids have shown that oestrogens are important for forming and stabilising connections between neurons.
There is also some limited evidence that humans are exposed to higher levels of these hormones during pregnancy than non-human primates are. A 1983 study found that gorillas and chimpanzees have four to five times less oestrogen in their urine than humans during pregnancy. The placenta also has more activity in genes that produce aromatase – an enzyme that converts androgens into oestrogens – in humans than in macaque monkeys.
“These hormones have become very important for brain development, and if we look at it comparatively with other primates and other species, there seems to be evidence that these hormones are very high in humans [during pregnancy],” says Tsompanidis.
This influx could also help explain why humans form such large social groups. Some evolutionary biologists believe that we are able to build extensive social networks because the differences between the sexes are more subtle in humans than in other primates. For example, men and women are more similar in body size than male and female Neanderthals, says Tsompanidis. This is probably due to higher oestrogen levels in utero, he says.

“If you have a lot of oestrogen, not only are you a bit less masculinised, but you’re also more likely to have an interconnected brain,” says Tsompanidis. “So the push to increase oestrogen, the push to make everyone social and getting along, is actually what makes the human brain larger and more connected.”
“I agree that placental genes influence human brain development and likely hominin brain evolution,” says David Geary at the University of Missouri. “However, I think they are underestimating the influence of male-male competition on brain and cognitive evolution.”
While it is true that male humans within the same social group tend to be more cooperative and less aggressive towards one another than is seen in other primates, this may have evolved as a result of between-group conflicts, he says. After all, greater coordination and teamwork would be an advantage in a deadly confrontation, he points out.

Our knowledge of placental differences between primates is also limited. Many non-human primates, such as chimpanzees, eat the placenta after giving birth, making it difficult to study, says Tsompanidis.
Identifying which factors shaped human brain evolution is more than just an intellectual pursuit: it could also shed light on neurodiversity.
“Not all humans are social or have incredible language skills – and that is fine. That doesn’t make them any less human,” says Tsompanidis. Understanding how the brain evolved could provide insight on whether certain cognitive traits come with trade-offs, he says.

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Exposure to hormones in utero could affect human brain growthPeter Dazeley/Getty Images
The human brain is one of the most complex objects in the universe – and that complexity may be due to a surge of hormones released by the placenta during pregnancy.
While numerous ideas have been proposed to explain human brain evolution, it remains one of our greatest scientific mysteries. One explanation, known as the social brain hypothesis, suggests that our large brains evolved to manage complex social relationships. It posits that navigating large group dynamics requires a certain degree of cognitive ability, pushing social species to develop bigger brains. For instance, other highly sociable animals, such as dolphins and elephants, have relatively large brains too. But the biological mechanism underlying this link has remained unclear.
Advertisement
Now, Alex Tsompanidis at the University of Cambridge and his colleagues say the answer may be placental sex hormones. During pregnancy, the placenta – a temporary organ that acts as an intermediary between the fetus and the mother – produces hormones crucial for fetal development. These include sex hormones such as oestrogens and androgens.
“I know that seems like a jump – thinking about human evolution and then ending up on the placenta,” says Tsompanidis. “But the reason for that is because we’ve been looking at the fluctuations and variations in the levels of these hormones in the womb and seeing that they predict things like language development and social development.”
Emerging research also shows that these hormones influence the developing brain. For instance, a 2022 study found that administering androgens, such as testosterone, to brain organoids – simplified, miniature versions of the brain made from human stem cells – during a critical developmental period increased the number of cells in the cortex, a brain region crucial for memory, learning and thinking. Other studies in brain organoids have shown that oestrogens are important for forming and stabilising connections between neurons.
There is also some limited evidence that humans are exposed to higher levels of these hormones during pregnancy than non-human primates are. A 1983 study found that gorillas and chimpanzees have four to five times less oestrogen in their urine than humans during pregnancy. The placenta also has more activity in genes that produce aromatase – an enzyme that converts androgens into oestrogens – in humans than in macaque monkeys.
“These hormones have become very important for brain development, and if we look at it comparatively with other primates and other species, there seems to be evidence that these hormones are very high in humans [during pregnancy],” says Tsompanidis.
This influx could also help explain why humans form such large social groups. Some evolutionary biologists believe that we are able to build extensive social networks because the differences between the sexes are more subtle in humans than in other primates. For example, men and women are more similar in body size than male and female Neanderthals, says Tsompanidis. This is probably due to higher oestrogen levels in utero, he says.

“If you have a lot of oestrogen, not only are you a bit less masculinised, but you’re also more likely to have an interconnected brain,” says Tsompanidis. “So the push to increase oestrogen, the push to make everyone social and getting along, is actually what makes the human brain larger and more connected.”
“I agree that placental genes influence human brain development and likely hominin brain evolution,” says David Geary at the University of Missouri. “However, I think they are underestimating the influence of male-male competition on brain and cognitive evolution.”
While it is true that male humans within the same social group tend to be more cooperative and less aggressive towards one another than is seen in other primates, this may have evolved as a result of between-group conflicts, he says. After all, greater coordination and teamwork would be an advantage in a deadly confrontation, he points out.

Our knowledge of placental differences between primates is also limited. Many non-human primates, such as chimpanzees, eat the placenta after giving birth, making it difficult to study, says Tsompanidis.
Identifying which factors shaped human brain evolution is more than just an intellectual pursuit: it could also shed light on neurodiversity.
“Not all humans are social or have incredible language skills – and that is fine. That doesn’t make them any less human,” says Tsompanidis. Understanding how the brain evolved could provide insight on whether certain cognitive traits come with trade-offs, he says.

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Hominin cranium from Harbin, China, now identified as a DenisovanHebei GEO University
The Denisovans, a mysterious group of ancient humans originally identified purely from DNA, finally have a face.
Using molecular evidence, Qiaomei Fu at the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing and her colleagues have confirmed what many researchers suspected: that a skull from China known as “dragon man” belonged to a Denisovan.

This fits with other evidence suggesting that the Denisovans were large and stocky. “I think we’re looking at individuals that are all [around] 100 kilos [of] lean body mass: enormous, enormous individuals,” says Bence Viola at the University of Toronto in Canada, who was not involved in the study.
The Denisovans were first identified in 2010. In Denisova cave in the Altai mountains of Siberia, researchers found a sliver of finger bone from an unidentified ancient human. Preserved DNA revealed that it wasn’t a modern human (Homo sapiens), nor a Neanderthal (Homo neanderthalensis), but something hitherto unknown.
Genetic evidence also revealed that Denisovans had interbred with modern humans. Today, populations in South-East Asia and Melanesia carry up to 5 per cent Denisovan DNA, which implies that Denisovans were once widespread in Asia.
After these discoveries, researchers began looking for Denisovan fossils, both in the field and in museum collections. Several have been found, notably a lower jawbone from Baishiya Karst cave on the Tibetan plateau, which was confirmed using proteins from the fossil and DNA from surrounding sediments. In April, a jawbone dredged from the Penghu Channel off the coast of Taiwan was confirmed to be Denisovan, based on preserved proteins.
However, there was still a frustrating disconnect. The fossils confirmed as Denisovans using molecular evidence were all small, so they weren’t very informative. Meanwhile, there were many more complete fossils from Asia that were suspected to be Denisovan, but none had yielded molecular evidence.
Fu and her colleagues set out to obtain preserved DNA or protein from a hominin cranium found in Harbin in north-east China. First described in 2021 after having been kept secret for decades, the cranium is unusually large and bulky, with thick brow ridges and capacity for a brain of a similar size to ours. It was named Homo longi – or dragon man – by its discoverers.
“My impression was, this is the right kind of thing in the right place at the right time to be a Denisovan,” says Viola.
Fu says it was extremely difficult to get preserved molecules from the Harbin cranium. Her team’s attempts to obtain DNA from the bone proved fruitless. However, they did manage to get 95 proteins, which included three variants that are unique to Denisovans.
Feeling that this wasn’t enough to be certain, Fu began testing dental calculus, the hard plaque that forms on teeth. This yielded mitochondrial DNA, which is inherited from the mother. It was a “tiny amount”, she says, but enough to confirm that the remains were Denisovan.
“That’s an incredible result, and fantastic that they even tried,” says Samantha Brown at the National Research Center for Human Evolution in Burgos, Spain. “I think most researchers would overlook dental calculus for genetic studies.”

Now that the bulky Harbin skull has been identified as Denisovan, it confirms something long suspected: Denisovans were big.
“There were clues [to] that right from the beginning with their teeth,” says Brown: the handful of molars that were found were unusually large. Known jawbones were also big. “We thought Neanderthals were the stocky ancestor, but actually it might be Denisovans that really were the big boys of the palaeontological record.”
It isn’t clear why this was the case. Neanderthals’ size and build have been linked to the cold climates in Europe and western Asia where they lived. Some Denisovan sites, including Denisova cave and the Tibetan plateau, were also cold – but others were tropical. “I think we’ll have to think about what this really means,” says Viola.
It may be that the Denisovans changed over time. Fragments from Denisova cave reveal two groups: one from 217,000 to 106,000 years ago, and the other from 84,000 to 52,000 years ago. The Harbin cranium is at least 146,000 years old, and Fu found that its proteins and mitochondrial DNA matched the older group. But we don’t have confirmed large fossils of the more recent Denisovans, so we don’t know what they were like.
“There’s just lots of different groups of these guys who are moving around the landscape, kind of independently, that are often separated from each other for probably tens of thousands of years,” says Viola. We shouldn’t expect them to all look alike, he says.

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