Discovery of two-million-year-old teeth reveals secrets of ancient humans

The enamel that forms the outer layer of our teeth might seem like an unlikely place to find clues about evolution. But it tells us more than you'd think about the relationships between our fossil ancestors and relatives.
In our new study, published in the Journal of Human Evolution, we highlight a different aspect of enamel.
In fact, we highlight its absence.
Specifically, we show that tiny, shallow pits in fossil teeth may not be signs of malnutrition or disease. Instead, they may carry surprising evolutionary significance.
You might be wondering why this matters.
Well, for people like me who try to figure out how humans evolved and how all our ancestors and relatives were related to each other, teeth are very important. And having a new marker to look out for on fossil teeth could give us a new tool to help fit together our family tree.
Uniform, circular and shallow
These pits were first identified in the South African species Paranthropus robustus, a close relative of our own genus Homo. They are highly consistent in shape and size: uniform, circular and shallow.
Initially, we thought the pits might be unique to P. robustus. But our latest research shows this kind of pitting also occurs in other Paranthropus species in eastern Africa. We even found it in some Australopithecus individuals, a genus that may have given rise to both Homo and Paranthropus.
The enamel pits have commonly been assumed to be defects resulting from stresses such as illness or malnutrition during childhood. However, their remarkable consistency across species, time and geography suggests these enamel pits may be something more interesting.
The pitting is subtle, regularly spaced, and often clustered in specific regions of the tooth crown. It appears without any other signs of damage or abnormality.
Two million years of evolution
We looked at fossil teeth from hominins (humans and our closest extinct relatives) from the Omo Valley in Ethiopia, where we can see traces of more than two million years of human evolution, as well as comparisons with sites in southern Africa (Drimolen, Swartkrans and Kromdraai).
The Omo collection includes teeth attributed to Paranthropus, Australopithecus and Homo, the three most recent and well-known hominin genera. This allowed us to track the telltale pitting across different branches of our evolutionary tree.
What we found was unexpected. The uniform pitting appears regularly in both eastern and southern Africa Paranthropus, and also in the earliest eastern African Australopithecus teeth dating back around 3 million years. But among southern Africa Australopithecus and our own genus, Homo, the uniform pitting was notably absent.
A defect … or just a trait?
If the uniform pitting were caused by stress or disease, we might expect it to correlate with tooth size and enamel thickness, and to affect both front and back teeth. But it doesn't.
What's more, stress-related defects typically form horizontal bands. They usually affect all teeth developing at the time of the stress, but this is not what we see with this pitting.
We think this pitting probably has a developmental and genetic origin. It may have emerged as a byproduct of changes in how enamel was formed in these species. It might even have some unknown functional purpose.
In any case, we suggest these uniform, circular pits should be viewed as a trait rather than a defect.
A modern comparison
Further support for the idea of a genetic origin comes from comparisons with a rare condition in humans today called amelogenesis imperfecta, which affects enamel formation.
About one in 1,000 people today have amelogenesis imperfecta. By contrast, the uniform pitting we have seen appears in up to half of Paranthropus individuals.
Although it likely has a genetic basis, we argue the even pitting is too common to be considered a harmful disorder. What's more, it persisted at similar frequencies for millions of years.
A new evolutionary marker
If this uniform pitting really does have a genetic origin, we may be able to use it to trace evolutionary relationships.
We already use subtle tooth features such as enamel thickness, cusp shape, and wear patterns to help identify species. The uniform pitting may be an additional diagnostic tool.
For example, our findings support the idea that Paranthropus is a 'monophyletic group', meaning all its species descend from a (relatively) recent common ancestor, rather than evolving seperatly from different Australopithecus taxa.
And we did not find this pitting in the southern Africa species Australopithecus africanus, despite a large sample of more than 500 teeth. However, it does appear in the earliest Omo Australopithecus specimens.
So perhaps the pitting could also help pinpoint from where Paranthropus branched off on its own evolutionary path.
An intriguing case
One especially intriguing case is Homo floresiensis, the so-called 'hobbit' species from Indonesia. Based on published images, their teeth appear to show similar pitting.
If confirmed, this could suggest an evolutionary history more closely tied to earlier Australopithecus species than to Homo. However, H. floresiensis also shows potential skeletal and dental pathologies, so more research is needed before drawing such conclusions.
More research is also needed to fully understand the processes behind the uniform pitting before it can be used routinely in taxonomic work. But our research shows it is likely a heritable characteristic, one not found in any living primates studied to date, nor in our own genus Homo (rare cases of amelogenesis imperfecta aside).
As such, it offers an exciting new tool for exploring evolutionary relationships among fossil hominins.

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Daily Mail​

10 hours ago

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Scientists SOLVE the mystery of the ‘Dragon Man': Ancient skull is first ever found from lost group of ancient humans that lived 217,000 years ago

It has baffled scientists since it was first discovered back in 2018. But the mystery of the 'Dragon Man' skull has finally been solved - as a new study reveals its true identity. Using DNA samples from plaque on the fossil's teeth, researchers have proven that the Dragon Man belonged to a lost group of ancient humans called the Denisovans. This species emerged around 217,000 years ago and passed on traces of DNA to modern humans before being lost to time. Denisovans were first discovered in 2010 when palaeontologists found a single finger of a girl who lived 66,000 years ago in the Denisova Cave in Siberia. But with only tiny fragments of bones to work with, palaeontologists couldn't learn anything more about our long-lost ancestors. Now, as the first confirmed Denisovan skull, the Dragon Man can provide scientists with an idead of what these ancient humans might have looked like. Dr Bence Viola, a paleoanthropologist at the University of Toronto in Canada who was not involved in the study, told MailOnline: 'This is very exciting. Since their discovery in 2010, we knew that there is this other group of humans out there that our ancestors interacted with, but we had no idea how they looked except for some of their teeth.' Scientists have finally solved the mystery of the 'Dragon Man' skull which belonged to an ancient human who lived 146,000 years ago Scientists have now confirmed that the skull is that of a Denisovan (artist's impression), an ancient species of human which emerged around 217,000 years ago The Dragon Man skull is believed to have been found by a Chinese railway worker in 1933 while the country was under Japanese occupation. Not knowing what the fossilised skull could be but suspecting it might be important, the labourer hid the skull at the bottom of the well near Harbin City. He only revealed its location shortly before his death, and his surviving family found it in 2018 and donated it to the Hebei GEO University. Scientists dubbed the skull 'Homo Longi' or 'Dragon Man' after the Heilongjiang near where it was found, which translates to black dragon river. The researchers knew that this skull didn't belong to either homo sapiens or Neanderthals but couldn't prove which other species it might be part of. In two papers, published in Cell and Science, researchers have now managed to gather enough DNA evidence to prove that Dragon Man was a Denisovan. Lead researcher Dr Qiaomei Fu, of the Chinese Academy of Sciences, had previously tried to extract DNA from bones in the skull but had not been successful. To find DNA, Dr Fu had to take tiny samples of the plaque that had built up on Dragon Man's teeth. Previously, the only traces of Denisovans were small fragments of bone like these pieces found in Siberia which meant scientists didn't know what they might have looked like Who is Dragon Man? Dragon Man is the nickname for a skull found near Harbin City, China in 2018. Known officially as the Harbin Cranium, scientists determined that the skull did not belong to any known human ancestor species. Scientists gave it the titled Homo longi, meaning 'Dragon Man' after the Heilongjiang, or black dragon river, near where it was found. Scientists suspected that Dragon Man might have been a member of the Denisovan species of humans but could not confirm this. That was because the bones are so old that most traces of DNA have long since decayed. As plaque builds up it sometimes traps cells from the inside of the mouth, and so there could be traces of DNA left even after 146,000 years. When Dr Fu and her colleagues did manage to extract human DNA from the plaque, it was a match for samples of DNA taken from Denisovan fossils. For the first time, scientists now have a confirmed Denisovan skull which means they can work out what our lost ancestors actually looked like. The Dragon Man's skull has large eye sockets, a heavy brow and an exceptionally large and thick cranium. Scientists believe that Dragon Man, and therefore Denisovans, would have had a brain about seven per cent larger than a modern human. Reconstructions based on the skull show a face with heavy, flat cheeks, a wide mouth, and a large nose. However, the biggest implication of the Dragon Man skull's identification is that we now know Denisovans might have been much larger than modern humans. Dr Viola says: 'It emphasizes what we assumed from the teeth, that these are very large and robust people. This also confirms that Dragon Man was from an older lineage of Denisovans which dates back to the earliest records around 217,000 years ago, rather than from the late Denisovan line which branched off around 50,000 years ago 'Harbin [the Dragon Man skull] is one of, if not the largest human cranium we have anywhere in the fossil record.' However, scientists still have many questions about Denisovans that are yet to be answered. In particular, scientists don't yet know whether Dragon Man reflects the full range of diversity that could have existed within the Denisovan population. Dragon Man was probably a heavily-set, stocky hunter-gatherer built to survive the last Ice Age in northern China but Denisovan bones have been found in environments that weren't nearly as cold. Professor John Hawks, a paleoanthropologist from the University of Wisconsin–Madison, told MailOnline: 'Harbin gives us a strong indication that some of them are large, with large skulls. 'But we have some good reasons to suspect that Denisovans lived across quite a wide geographic range, from Siberia into Indonesia, and they may have been in many different environmental settings. 'I wouldn't be surprised if they are as variable in body size and shape as people living across the same range of geographies today.' THE DENISOVANS EXPLAINED Who were they? The Denisovans are an extinct species of human that appear to have lived in Siberia and even down as far as southeast Asia. The individuals belonged to a genetically distinct group of humans that were distantly related to Neanderthals but even more distantly related to us. Although remains of these mysterious early humans have mostly been discovered at the Denisova Cave in the Altai Mountains in Siberia, DNA analysis has shown the ancient people were widespread across Asia. Scientists were able to analyse DNA from a tooth and from a finger bone excavated in the Denisova cave in southern Siberia. The discovery was described as 'nothing short of sensational.' In 2020, scientists reported Denisovan DNA in the Baishiya Karst Cave in Tibet. This discovery marked the first time Denisovan DNA had been recovered from a location that is outside Denisova Cave. How widespread were they? Researchers are now beginning to find out just how big a part they played in our history. DNA from these early humans has been found in the genomes of modern humans over a wide area of Asia, suggesting they once covered a vast range. They are thought to have been a sister species of the Neanderthals, who lived in western Asia and Europe at around the same time. The two species appear to have separated from a common ancestor around 200,000 years ago, while they split from the modern human Homo sapien lineage around 600,000 years ago. Last year researchers even claimed they could have been the first to reach Australia. Aboriginal people in Australia contain both Neanderthal DNA, as do most humans, and Denisovan DNA. This latter genetic trace is present in Aboriginal people at the present day in much greater quantities than any other people around the world. How advanced were they? Bone and ivory beads found in the Denisova Cave were discovered in the same sediment layers as the Denisovan fossils, leading to suggestions they had sophisticated tools and jewellery. Professor Chris Stringer, an anthropologist at the Natural History Museum in London, said: 'Layer 11 in the cave contained a Denisovan girl's fingerbone near the bottom but worked bone and ivory artefacts higher up, suggesting that the Denisovans could have made the kind of tools normally associated with modern humans. 'However, direct dating work by the Oxford Radiocarbon Unit reported at the ESHE meeting suggests the Denisovan fossil is more than 50,000 years old, while the oldest 'advanced' artefacts are about 45,000 years old, a date which matches the appearance of modern humans elsewhere in Siberia.' Did they breed with other species? Yes. Today, around 5 per cent of the DNA of some Australasians – particularly people from Papua New Guinea – is Denisovans. Now, researchers have found two distinct modern human genomes - one from Oceania and another from East Asia - both have distinct Denisovan ancestry. The genomes are also completely different, suggesting there were at least two separate waves of prehistoric intermingling between 200,000 and 50,000 years ago. Researchers already knew people living today on islands in the South Pacific have Denisovan ancestry.

BBC News

a day ago

• BBC News

Why your fingers wrinkle in water (and what it can reveal about your health)

The skin on our fingertips and toes shrivels like prunes when soaked for a few minutes in water. But is this an adaptation that occurred to help us in our evolutionary past? And what can it reveal about your health today? Spend more than a few minutes soaking in a bath or paddling around a swimming pool and your fingers will undergo a dramatic transformation. Where there were once delicate whorls of lightly ridged epidermis, engorged folds of ugly pruned skin will now be found. And according to a recently published study, this striking change is worth a closer inspection – each time your fingertips pucker in this way, the wrinkles create the same pattern. It is the latest discovery about a phenomenon that has occupied the thoughts and work of scientists for decades. Bafflingly, only the skin on our fingers and toes wrinkles when immersed in water. Other body parts such as our forearms, torso, legs and face remain no more crinkled than they were before being submerged. Most researchers in the field have puzzled over what causes this puckering in the first place, but more recently the question of why and what purpose it may serve, has attracted their attention. Perhaps more intriguing still, however, is what our shrivelled fingers can reveal about our own health. Scientists have discovered changes in how our fingers wrinkle can point to diseases including type 2 diabetes, cystic fibrosis, nerve injuries and even cardiovascular problems. What causes our fingers to wrinkle It takes around 3.5 minutes in warm water – 40C (104F) is considered the optimal temperature – for your fingertips to begin wrinkling, while in cooler temperatures of about 20C (68F) it can take up to 10 minutes. Most studies have found it takes around 30 minutes of soaking time to reach maximum wrinklage, however. (Interestingly, recent research has shown that soaking your hands in warm vinegar can make your skin wrinkle far faster – in around just four minutes.) Fingertip wrinkling was commonly thought to be a passive response where the upper layers of the skin swelled as water flooded into the cells via a process known as osmosis – where water molecules move across a membrane to equalise the concentration of the solutions on either side. But as long ago as 1935, scientists have suspected there is more to the process than this. Doctors studying patients with injuries that had severed the median nerve – one of the main nerves that run down the arm to the hand – found that their fingers did not wrinkle. Among its many roles, the median nerve helps to control so-called sympathetic activities such as sweating and the constriction of blood vessels. Their discovery suggested that the water-induced wrinkling of fingertips was in fact controlled by the nervous system. Later studies by doctors in the 1970s provided further evidence of this, and they proposed using the immersion of the hands in water as a simple bedside test to assess nerve damage that might affect the regulation of unconscious processes such as blood flow. Then in 2003, neurologists Einar Wilder-Smith and Adeline Chow, who were working at the National University Hospital in Singapore at the time, took measurements of blood circulation in the hands of volunteers as they soaked them in water. They found that as the skin on the volunteers' fingertips began to wrinkle, there was a significant drop in blood flow in the fingers. When they applied a local anesthetic cream that caused the blood vessels in the fingers of healthy volunteers to temporarily constrict, they found it produced similar levels of wrinkling as water immersion. "It makes sense when you look at your fingers when they go wrinkly," says Nick Davis, a neuroscientist and psychologist at Manchester Metropolitan University, who has studied fingertip wrinkling. "The finger pads go pale and that is because the blood supply is being constricted away from the surface." Wilder-Smith and his colleagues proposed that when our hands are immersed in water, the sweat ducts in our fingers open up to allow water in, which leads to an imbalance in the salts in our skin. This change in the salt balance triggers the firing of nerve fibres in the fingers, leading to the blood vessels around the sweat ducts to constrict. This in turn causes a loss of volume in the fleshy area of the fingertip, which pulls the overlying skin downwards so that it distorts into wrinkles. The pattern of the wrinkles depends on the way the outermost layer of skin – the epidermis – is anchored to the layers beneath it. More like this: There have also been suggestions that the outer layers of skin may also swell a little to enhance the wrinkling. By osmosis alone, however, our skin would need to swell by 20% to achieve the wrinkles we see in our fingers, which would leave them hideously enlarged. But when the upper layers of skin swell slightly and the lower levels shrink at the same time, the wrinkling becomes pronounced far sooner, says Pablo Saez Viñas, a biomechanical engineer at the Technical University of Catalonia, who has used computer modelling to examine the mechanism. "You need both to have normal levels of wrinkles," he says. "If you don't have that neurological response, which happens in some individuals, wrinkles are inhibited." But if wrinkling is controlled by our nerves, it means our bodies are actively reacting to being in water. "That means it is happening for a reason," says Davis. "And that means it could be giving us an advantage." Why did our fingers evolve to wrinkle in water? It was a question from one of his children during a bath about why their fingers had gone wrinkly that recently led Davis to dig into what this advantage could be. With the help of 500 volunteers who visited the Science Museum in London during 2020, Davis measured how much force they needed to use to grip a plastic object. Perhaps unsurprisingly, those with dry, unwrinkled hands needed to use less force than people whose hands were wet – so their grip on the object was better. But when they submerged their hands in a water bath for a few minutes to turn their hands wrinkly, the grip force fell between the two even though their hands were still wet. "The results were amazingly clear," says Davis. "The wrinkling increased the amount of friction between the fingers and the object. What is particularly interesting is that our fingers are sensitive to this change in the surface friction and we use this information to apply less force to grip an object securely." The object that Davis' volunteers were gripping weighed less than a couple of coins, so the amount of grip required was small. But when performing more arduous tasks in a wet environment, this difference in friction could become more important. "If you don't have to squeeze as hard to grip something, the muscles in your hands get less tired and so you can do it for longer," he says. His findings match those by other researchers who have found that the wrinkling of our fingertips makes it easier for us to handle wet objects. In 2013, a team of neuroscientists at Newcastle University in the UK asked volunteers to transfer glass marbles of varying sizes and fishing weights from one container to another. In one case the objects were dry, and in the other they were at the bottom of a container filled with water. It took 17% longer for the participants to transfer the submerged objects with unwrinkled fingers than when they were dry. But when their fingers were wrinkled, they could transfer the submerged marbles and weights 12% quicker than when their fingers were wet and unwrinkled. Interestingly, there was no difference in transferring the dry objects with wrinkled or unwrinkled fingers. There are other baffling mysteries – women take longer to develop wrinkles than men do Some scientists have suggested that the wrinkles on our fingertips and toes may act like rain treads on tyres or the soles of shoes. The channels produced by the wrinkles help to squeeze water away from the point of contact between the fingers and an object. This suggests that humans may have evolved fingertip and toe wrinkling at some point in our past to help us grip wet objects and surfaces. "Since it seems to give better grip under water, I would assume that it has to do with either locomotion in very wet conditions or potentially with manipulating objects under water," says Tom Smulders, an evolutionary neuroscientist at Newcastle University who led the 2013 study. It could have given our ancestors a key advantage when it came to walking over wet rocks or gripping branches, for example. Alternatively, it could have helped us when catching or foraging for food such as shellfish. "The latter would imply it is unique to humans, whereas if it's the former, we would expect it to happen in other primates as well," says Smulders. Finger wrinkling has yet to be observed in our closest relatives in the primate world such as chimpanzees, but the fingers of Japanese macaque monkeys, which are known to bath for long periods in hot water, have been seen to also wrinkle after they have been submerged in water. But the lack of evidence in other primates does not mean it doesn't happen, it may simply be because no-one has looked closely enough yet, says Smulders. "We don't know the answer to this question yet." There are some other interesting clues about when this adaptation may have appeared in our species. Fingertip wrinkling is less pronounced in saltwater and takes longer than it does in freshwater. This is probably because the salt gradient between the skin and surrounding environment is lower in saltwater, and so the salt imbalance that triggers the nerve fibres is less dramatic. So, it could be an adaptation that helped our ancestors live in freshwater environments rather than along coastlines. But there are no firm answers, and some believe it could just be a coincidental physiological response with no adaptive function. What can we learn from the wrinkles? Strangely there are other baffling mysteries – women take longer to develop wrinkles than men do, for example. And why exactly does our skin return to its normal state – normally after 10-20 minutes – if there is no clear disadvantage to our grip on dry objects of having wrinkly fingertips? Surely if having wrinkly fingers can improve our grip in the wet, but not harm it when dry, why would our fingertips not be permanently wrinkly? One reason for that could be the change in sensation the wrinkling also causes. Our fingertips are packed with nerves, and the pruning of our skin changes the way we feel things we touch (although one study has shown it does not affect our ability to discriminate between objects based on touch). "Some people have a real aversion to it because picking something up with wrinkly fingers feels weird," says Davis. "It could be because the balance of skin receptors have changed position, but there could be a psychological dimension too. It would be fun to investigate why. There could be other things we can do less well with wrinkly fingers." But the wrinkling of our fingers and toes in water can reveal key information about our health in surprising ways too. Wrinkles take longer to form in people with skin conditions like psoriasis and vitiligo, for example. Patients with cystic fibrosis experience excessive wrinkling of their palms as well as their fingers, and this has even been noticed in people who are genetic carriers of the disease. Patients suffering from type 2 diabetes also sometimes show markedly decreased levels of skin wrinkling when their hands are placed in water. Similarly reduced wrinkling has been seen in people who have suffered heart failure, perhaps due to some disruption in the control of their cardiovascular system. Unsymmetrical wrinkling of the fingers – where one hand wrinkles less than the other despite the same immersion time – has even been suggested as an early sign of Parkinson's disease as it indicates the sympathetic nervous system is not functioning correctly on one side of the body. So, while the question of why our fingers and toes began wrinkling in water in the first place remains open, our pruney digits are proving useful to doctors in other surprising ways. * This article was originally published on 21 June 2022. It was updated on 19 June 2025 to include details of a new study on the repeatability of wrinkle patterns on wet fingers. -- If you liked this story, sign up for The Essential List newsletter – a handpicked selection of features, videos and can't-miss news, delivered to your inbox twice a week. For more science, technology, environment and health stories from the BBC, follow us on Facebook, X and Instagram.

Telegraph

a day ago

• Telegraph

US approves twice-yearly HIV jab in ‘breakthrough moment' for fight against Aids

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