Philippa Kaur

A model of Homo heidelbergensis, which might have been the direct ancestor of Homo sapiensWHPics / Alamy
A timeline of genetic changes in millions of years of human evolution shows that variants linked to higher intelligence appeared most rapidly around 500,000 years ago, and were closely followed by mutations that made us more prone to mental illness.
The findings suggest a “trade-off” in brain evolution between intelligence and psychiatric issues, says Ilan Libedinsky at the Center for Neurogenomics and Cognitive Research in Amsterdam, the Netherlands.

“Mutations related to psychiatric disorders apparently involve part of the genome that also involves intelligence. So there’s an overlap there,” says Libedinsky. “[The advances in cognition] may have come at the price of making our brains more vulnerable to mental disorders.”
Humans split from our closest living relatives – chimpanzees and bonobos – more than 5 million years ago, and our brains have tripled in size since then, with the fastest growth over the past 2 million years.
While fossils allow scientists to study such changes in brain size and shape, they can’t reveal much about what those brains were capable of doing.

Recently, however, genome-wide association studies have examined many people’s DNA to determine which mutations are correlated with traits like intelligence, brain size, height and various kinds of illnesses. Meanwhile, other teams have been analysing specific aspects of mutations that hint at their age, providing estimates of when those variants first appeared.
Libedinsky and his colleagues pulled both methods together for the first time, to create an evolutionary timeline of humans’ brain-related genetics.
“We don’t have any trace of the cognition of our ancestors with regard to their behaviour and their mental issues – you can’t find those in the palaeontological records,” he says. “We wanted to see if we could build some sort of ‘time machine’ with our genome to figure this out.”
The team investigated the evolutionary origins of 33,000 genetic variants found in modern humans that have been linked to a wide variety of traits, including brain structure and various measures of cognition and psychiatric conditions, as well as physical and health-related features like eye shape and cancer. Most of these genetic mutations only show weak associations with a trait, says Libedinsky. “The links can be useful starting points, but they’re far from deterministic.”
They found that most of these genetic variants emerged between about 3 million and 4000 years ago, with an explosion of new ones in the past 60,000 years — around the time Homo sapiens made a major migration out of Africa.

Variants linked to more advanced cognitive abilities evolved relatively recently compared with those for other traits, says Libedinsky. For example, those related to fluid intelligence – essentially logical problem-solving in new situations – appeared about 500,000 years ago on average. That’s about 90,000 years later than variants associated with cancer, and nearly 300,000 years after those related to metabolic functions and disorders. Those intelligence-linked variants were closely followed by variants linked to psychiatric problems, around 475,000 years ago on average.
That trend repeated itself starting around 300,000 years ago, when many of the variants influencing the shape of the cortex – the brain’s outer layer responsible for higher-order cognition – appeared. In the past 50,000 years, numerous variants tied to language evolved, and these were closely followed by variants linked to alcohol addiction and depression.
“Mutations related to the very basic structure of the nervous system come a little bit before the mutations for cognition or intelligence, which makes sense, since you have to develop your brain first for higher intelligence to emerge,” says Libedinsky. “And then the mutation for intelligence comes before psychiatric disorders, which also makes sense. First you need to be intelligent and have language before you can have dysfunctions on these capabilities.”

The dates also line up with evidence suggesting that Homo sapiens acquired some of the variants linked to alcohol consumption and mood disorders from interbreeding events with Neanderthals, he adds.
Why evolution hasn’t weeded out the variants that predispose for psychiatric conditions isn’t clear, but it might be because the effects are modest and may confer advantages in some contexts, says Libedinsky.
“This kind of work is exciting because it allows scientists to revisit longstanding questions in human evolution, testing hypotheses in a concrete way using real-world data gleaned from our genomes,” says Simon Fisher at the Max Planck Institute for Psycholinguistics in Nijmegen, the Netherlands.
Even so, this kind of study can only examine genetic sites that still vary among living humans – meaning it misses older, now-universal changes that may have been key to our evolution, Fisher adds. Developing tools to probe “fixed” regions could offer deeper insight into what truly makes us human, he says.

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The skull of King Richard IIICarl Vivian/University of Leicester
The oral microbiome of King Richard III of England has been assembled by investigating the plaque on his teeth, and suggests he had a disease that can destroy the jaw.
In 2012, skeletal remains were discovered beneath a car park in Leicester, UK, on the grounds of the former Greyfriars church. The remains were suspected to belong to Richard III – who was killed in the battle of Bosworth Field in 1485 and brought to lie in state in Leicester – due to the head wounds matching accounts of his death and spine curvature matching that of his stance. Genetic analysis later confirmed it was him.

Although he reigned for just two years during the wars of the roses, Richard left a strong mark in English history, with rumours of him plotting the murder of his nephews after putting them in the Tower of London, and William Shakespeare portraying him as a ruthless villain in his eponymous play.
However, little is known about the king’s day-to-day life. To learn more, Turi King at the University of Bath, UK, and her colleagues scraped off samples of the dental calculus, or hardened plaque, on three of his well-preserved teeth.
They did this because plaque can work like a time capsule, preserving the DNA of microbes or food. “The amount of DNA recovered from the calculus of King Richard III is among the highest we have ever measured from an archaeological context,” they wrote in a paper where they reported detecting more than 400 million DNA sequences.

“No one has sequenced ancient DNA to 400 million sequences, that’s just astronomical,” says Laura Weyrich at Pennsylvania State University. “It shows to us that we can probably do things with ancient DNA that we didn’t think we could do before.”
King and her colleagues identified nearly 400 microbial species from the DNA. The number and types of species were similar to those detected in well-preserved dental calculus samples from England, Ireland, Germany and the Netherlands from the past 7000 years, spanning the Neolithic Period to the present. “It’s telling us that elite people have the sort of same microbial strains [as everyone else], despite this extravagant lifestyle, despite the travelling he would have done and the wars,” says Weyrich.
The team couldn’t recover enough plant or animal DNA to investigate Richard’s diet. However, a previous analysis of his bones revealed in the last two years of his life he consumed non-local wine and many game animals, fish and birds such as swans, herons and egrets.
However, Weyrich says the microbiome results might be different if the team were to zoom in on a sample from one part of one tooth and compare that against samples from the equivalent tooth in other populations, like those in Germany or the Netherlands. We also have different bacteria in the front of our mouth versus the back, and inside of teeth versus outside, so the team’s limited samples can’t tell us too much about Richard’s oral microbiome as a whole, she says.
The king’s well-preserved teeth meant they could be analysed to gauge his oral microbiomeCarl Vivian/University of Leicester
Nevertheless, one abundant bacterium was Tannerella forsythia. This has been linked to peridontal disease, a serious gum infection that destroys the bone that supports teeth. Oral hygiene in the 15th century was poor, and Richard had cavities when he died aged 32, but this doesn’t mean he necessarily had peridontal disease.
“One person can be colonised by potentially pathogenic bacteria and they will never cause any disease, whereas other people may have an infection,” says Pierre Stallforth at the Leibniz Institute for Natural Product Research and Infection Biology in Germany. Weyrich says an analysis that looks for bone loss in his jaw would be needed to tell whether Richard had periodontal disease.
“What I really like about this field is that it creates a link between social sciences, history and genetics,” says Stallforth. “Just having access to dental calculus from historical figures is amazing in terms of understanding more about their lives.”

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A life-sized camel engraving at Jebel Misma, Saudi ArabiaSahout Rock Art and Archaeology Project
Ancient inhabitants of the Arabian desert created monumental works of rock art on cliff faces, including life-sized images of camels, perhaps as a way to mark sources of water.
Michael Petraglia, at Griffith University in Brisbane, Australia, and his colleagues discovered 176 engravings on 62 panels in the Nefud desert in Saudi Arabia in 2023. There are 90 life-sized images of camels, another 15 smaller camel engravings and two camel footprints.

One of the rock art sites, featuring a 3-metre-tall dromedary, was more than 40 metres up the cliff and impossible for members of the team to safely reach and survey without deploying a drone.
“It would have been dangerous to make these engravings,” says Petraglia. “There’s no way I would go up there.”
Alongside the camels, and highlighting how much more benign the climate must have been, are other large animals including ibex, horses, gazelles and aurochs. The team also found engraved human figures and face masks.

“It’s not just doodling or marking the landscape,” says Petraglia. “These are engravings of things that would have been iconic for them culturally.”
The researchers say the images were possibly carved to warn any outsiders that the land was already occupied or to act as a signpost for ephemeral water sources. The new discoveries add to evidence of extensive past occupation of Saudi Arabia in prehistoric times.
Indicating the antiquity of the images, a natural varnish had formed over the engravings, a process that researchers know would have taken around 8000 years. However, it wasn’t possible to directly date the artwork, so the team excavated in the sediments under the rock art panels.
Excavation of a trench directly beneath a rock art panel at Jebel Arnaan, where engraving tools were discoveredSahout Rock Art and Archaeology Project
There, they found stone points, beads and ochres indicating links with Late Neolithic people in the Levant, as well as tools that would have been used to make the engravings. These objects were able to be dated and ranged in age from 12,800 to 11,400 years old.
Excavations were also undertaken in the small temporary lakes, called playas, near the engravings, which the ancient people would have relied on. Sediments and pollen records confirmed that the region would have been much wetter and greener.
But, even so, the environment was challenging and unlikely to be a place where people could settle and stay for long periods of time, says Petraglia.
“These were likely very mobile people and highly innovative,” he says. “These are sophisticated hunter-gatherers and definitely not people just sort of figuring it out.”

Scientific pioneers of the ancient world, Cairo and Alexandria: Egypt

Embark on an unforgettable journey through Egypt’s two most iconic cities, Cairo and Alexandria, where ancient history meets modern charm.

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The Yunxian 2 skull was squashed, but has now been reconstructed and appears to be an early DenisovanGary Todd (CC0)
The origins of our species may lie much further back in time than we thought, and the same may be true of our extinct Neanderthal and Denisovan cousins. According to a new analysis of fossil remains, the shared ancestor of the three groups lived over a million years ago – more than twice as old as previously believed.
“It does mean that we are missing a huge bit of the early story of these lineages, if we’re correct about these ancient branching points,” says Chris Stringer at the Natural History Museum in London.

The results could potentially help settle the search for Ancestor X: the population that gave rise to modern humans, Neanderthals and Denisovans. They could also mean that the Denisovans were our closest relatives – even closer than the Neanderthals, though not everyone is convinced on this last point.
Stringer and his colleagues, including Xijun Ni at the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, China, re-examined a fossil hominin from Yunxian in central China.
Two partial skulls were uncovered in a terrace above the Han River in 1989 and 1990, and described in 1992. Both skulls had been squashed during their time in the ground. However, the second, Yunxian 2, was less badly damaged.

Stringer, Ni and their colleagues used the latest methods to reconstruct Yunxian 2, including a technique that can use CT scans to digitally separate individual fragments of bone from the surrounding “matrix” of rock and sediment. “It’s long and low, with a big brow ridge,” says Stringer. It also has “a bit of a beaky nose”, and while the teeth are large, the third molars are small.
The Yunxian 2 cranium is 940,000 to 1.1 million years old. Hominins of that age are often thought to belong to Homo erectus, which emerged in Africa around 2 million years ago before spreading to southern Asia, including Indonesia, where it survived until perhaps 108,000 years ago. However, Stringer says it doesn’t fit the profile. Many of its features are typical of later groups, like the Neanderthals.
To figure out what Yunxian 2 is, the team compared it to 56 other hominin fossils. Based on the shapes of the remains, they drew a family tree, with similar fossils being closely related. On this basis, they identified three major groups, which include most of the fossils from the past million years.
The first was modern humans (Homo sapiens). The second was Neanderthals (Homo neanderthalensis), who lived in Europe and Asia during the past few hundred thousand years, vanishing around 40,000 years ago. The third was Denisovans, from eastern Asia.

Denisovans were originally discovered in 2010 using DNA from a bone fragment, and it has taken 15 years to identify larger fossils. Stringer was involved in the description of a skull from Harbin in China, dubbed Homo longi, which was identified as a Denisovan using molecular evidence in June. Yunxian 2 appears to be an early Denisovan, as do several other Asian fossils.
It is helpful to tie all these fossils into the Denisovan lineage, says geneticist Aylwyn Scally at the University of Cambridge. “We can get a better idea about where the Denisovans were, how they lived, and what kind of species they were.”
The finding that Yunxian 2 is Denisovan rewrites the story of recent human evolution in two ways. First, it appears to change how the three populations emerged. The conventional story, as revealed by genetics, is that an ancestral population – Ancestor X – split into two: one half became modern humans, and the other half became Neanderthals and Denisovans, who split from each other a bit later. However, in this reconstruction, it was the Neanderthals who broke away first, 1.38 million years ago, with modern humans and the Denisovans separating 1.32 million years ago.
If that is correct, Denisovans were our closest relatives, instead of being equally close to us as Neanderthals were, as the genetics indicates. However, Scally is dubious. That is partly because the history of these populations seems to be complex. “It isn’t actually well described by a simple tree,” which is the model the researchers used, but rather by a “tangled network”, he says. Furthermore, Scally says genetics is a better guide to such relationships than morphology – especially when you have only partial skeletons – and the genetics tells a clear story.
The second change is bigger: all three groups are much older than we thought. Genetics has suggested that the ancestors of modern humans split from the progenitors of Neanderthals and Denisovans around 500,000-700,000 years ago. But Yunxian 2 indicates that the Denisovan group was already separate over a million years ago.

It may be that there isn’t a single date for any of these splits, says Scally. They could have been protracted, with groups sometimes separating and sometimes coming together. In that case, Stringer and his colleagues could be correct that the divergence began over a million years ago, but it took hundreds of thousands of years to play out.
This longer timeline opens new questions. The oldest known fossils of our species are about 300,000 years old. So, where are all the older ancestors dating back a million years ago? “Either we don’t have them, or they’re there and they haven’t been recognised,” says Stringer.
We also don’t know what Ancestor X was like, or where it lived. “Ten years ago, I would have said probably Africa is the ancestry of most of these groups,” says Stringer. “It looks more likely that the ancestor was outside of Africa, perhaps in Western Asia,” he says. “That would imply that the ancient sapiens ancestor must have gone into Africa and then evolved in Africa for most of the rest of that 1 million years.”
Stringer points out that there are few known fossils from western Asia dating to a million years ago, and India has yielded only one hominin fossil. “There’s many, many places where we really don’t have the evidence,” he says.
One source of data may be the Yunxian site. In 2022, a third skull was found there, apparently in better condition, but it hasn’t yet been described.

Neanderthals, ancient humans and cave art: France

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Ludovic Slimak helped uncover the remains of Thorin, a NeanderthalLaure Metz
The Last NeanderthalLudovic Slimak (translated by Andrew Brown) (Polity Press (UK, 26 September; US, 24 November))
A Neanderthal skeleton spotted by chance under some leaves, calcified soot and a trove of remarkably tiny arrowheads. These assorted finds from Grotte Mandrin in France have not only transformed our understanding of Neanderthals, but also of the first waves of our species, Homo sapiens, to have reached Europe.
Even more remarkably, the cave has revealed secrets about when the two groups first encountered each other, and why one species subsequently thrived, while the other went extinct. That is the question tackled in The Last Neanderthal: Understanding how humans die, a new book by palaeoanthropologist Ludovic Slimak at the University of Toulouse, France, who led the excavations at Grotte Mandrin.
Central to this story is Thorin, a Neanderthal fossil discovered in 2015 just outside the cave entrance, when the sweep of a brush revealed five of his teeth, visible on the soil surface. To preserve every bit of information from this rare find, the bones were painstakingly excavated using tweezers to remove one grain of sand at a time. It took seven years just to recover the remains of his skull and left hand.
The discovery opened up a mystery that took years to solve: different dating techniques produced wildly conflicting results about when Thorin had lived. Eventually, it was confirmed that the fossil was between 42,000 and 50,000 years old, making Thorin one of the last Neanderthals (the species died out entirely around 40,000 years ago). Remarkably, his genome could be sequenced, revealing he was part of a previously unknown lineage that diverged from the main Neanderthal population at least 50,000 years earlier, then existed in extreme isolation.
The Last Neanderthal is a deeply personal and philosophical book that conjures a vivid sense of what it is like to investigate Thorin’s existence and that of the different groups that occupied the cave over millennia. The distinctive smell at Grotte Mandrin, Slimak realises, is from the soot of ancient fires preserved in calcite layers on the walls, forming a black-and-white “bar code”. The bar code can be precisely dated, so bits that have fallen to the floor provide dates for different occupations, revealing that H. sapiens occupied the cave just six months after Neanderthals left. The book conveys Slimak’s astonishment at discovering Thorin hiding in plain sight. “You don’t find a Neanderthal body by taking a stroll through the forest, just like that, lying on the side of the path,” he writes. “It’s crazy.”
The jaw of Thorin, a Neanderthal fossil discovered in 2015Xavier Muth
Which brings us to the question of why the Neanderthals died out. This is much debated, with the finger typically pointed at extermination by the incoming H. sapiens, or climatic upheaval resulting from a volcanic eruption or a flipping of Earth’s magnetic field. But Slimak has a different view, drawing on evidence found at Grotte Mandrin, in particular a layer of tiny, triangular stone points that were probably used as arrowheads by one of the first waves of H. sapiens to reach the region about 55,000 years ago.
These points are almost identical to artefacts made by H. sapiens in roughly the same time period at a site called Ksar Akil in Lebanon, nearly 4000 kilometres away. This indicates that these people were remarkably efficient at preserving and standardising their traditions across vastly distant social networks, leading Slimak to conclude that they had far more efficient “ways of being in the world” than Neanderthals, who lived in small, isolated groups without such standardisation.
We might like to imagine a dramatic face-off between H. sapiens and Neanderthals, but the reality was totally different, he writes. Drawing on accounts of the collapses of numerous Indigenous groups in Africa, Australia and the Americas after colonisation, Slimak argues that Neanderthal groups slowly fell apart when confronted with others who had a much more efficient way of existing. “It is in the collapse of their views on the reality of the world that humans die… not with a bang but a whimper,” he writes.

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The bones were painstakingly excavated using tweezers to remove a grain of sand at a time
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It is a desperately sad eventuality to contemplate, yet immersing yourself in the world of these lost people in The Last Neanderthal is a rare treat.

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