Humans

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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A collection of stone tools at the Milovice IV archaeological siteMartin Novák
A set of stone tools found in the Czech Republic appears to be the personal toolkit of a hunter-gatherer who lived about 30,000 years ago. The 29 artefacts, which include blades and points meant for hunting, skinning, basic butchering and cutting wood, offer a rare glimpse into the daily lives of ancient hunters, says Dominik Chlachula at the Czech Academy of Sciences in Brno.
In 2009, a village road collapsed in the Pavlovské vrchy mountains in the south-east of the country, opening up abandoned cellars that archaeologists began studying. In 2021, they found a deeper level of the site, called Milovice IV, containing charcoal dated to between 29,550 and 30,250 years ago. There, researchers found horse and reindeer bones, and – more recently – a bundle of stone tools, still positioned as if they had been wrapped in a leather pouch that had long since decayed.

The tools showed signs of significant use, says Chlachula. Most of the blades were worn down from cutting and scraping bones, wood and hides, and some bore marks of having been attached to a handle. Some of the points had fractures or microscopic traces of impact, and one had apparently been used as the tip of a spear or arrow.
Several of the pieces had been recycled from older, different tools, suggesting good stone was scarce or that the hunter was mindful of not wasting resources, he says.
Further analyses revealed that about two-thirds of the tools had been crafted from glacial deposit flint stones found at least 130 kilometres northward – and significantly farther if using winding footpaths to reach them. Most of the others appeared to come from western Slovakia, about 100 kilometres south-east. Whether the owner acquired the stones directly from deposits  or through a trade network remains unknown, says Chlachula.

Many pieces were too worn or broken to be used as is, he explains. But it is possible the hunter kept them in the hope of recycling them — or even for their sentimental value.

Neanderthals, ancient humans and cave art: France

Embark on a captivating journey through time as you explore key Neanderthal and Upper Palaeolithic sites of southern France, from Bordeaux to Montpellier, with New Scientist’s Kate Douglas.

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Left: The remains of a middle-aged woman at the Liyupo site in southern China, who was smoke-dried prior to burial about 8000 years ago. Right: A modern smoke-dried mummy of the Dani people in West Papua, IndonesiaZhen Li, Hirofumi Matsumura, Hsiao-chun Hung
Human bodies carefully preserved by smoking up to 14,000 years ago have been found at archaeological sites in South-East Asia, making them the oldest known mummies in the world.
A similar practice continues today among the Dani people in West Papua, Indonesia. The Dani mummify their deceased relatives by exposing the bodies to smoke, then keep and revere them as part of the household. Many of their mummies are tightly bound in crouching poses.
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Similar “hyper-flexed” ancient human remains have also been found in Australia, China, the Philippines, Laos, Thailand, Malaysia, South Korea and Japan.
Hsiao-chun Hung, at the Australian National University in Canberra, says that while she was working on ancient skeletons in Vietnam in 2017, she was struck by the similarity of the burial remains they were excavating to the Dani’s tradition.
Hung and her colleagues studied 54 hunter-gatherer burials from 11 archaeological sites located across South-East Asia, dating from 12,000 to 4000 years ago, to look for evidence of the skeletons having been slowly smoked. Most of the sites were in northern Vietnam and southern China.

Many of the remains showed clear signs of being partially burned, but not enough to have been cremated. The researchers then applied two analytical techniques – X-ray diffraction and infrared spectroscopy – to dozens of bone samples to reveal whether they were exposed to heat and how much.
Over 90 per cent of the 69 skeletal samples showed evidence of having been heated. The results showed that the human remains hadn’t been exposed to high heat but rather to low temperatures, indicating they had been smoked for possibly weeks or even months.
The oldest mummy tested by the team, from Hang Cho, Vietnam, was over 11,000 years old. But similarly singed, tightly bound skeletons were also found at another site in Hang Muoi, Vietnam, dated to over 14,000 years ago. “We did not test this one by X-ray or infrared because it was obviously partly burnt, and could be observed with the naked eye,” Hung says.
Until now, the oldest known mummified humans were from northern Chile, around 7000 years ago, and Ancient Egypt, from 4500 years ago.
Hung says all the evidence points to the likelihood that this type of burial practice was widespread across southern China and South-East Asia, stretching back at least 14,000 years or even earlier, and continuing until about 4000 to 3500 years ago, when farming populations became dominant in the region. The hyper-flexed bindings of the mummified bodies might have made them easier to transport, she says.

Ethnographic records indicate that the tradition persisted in southern Australia into the late 19th and early 20th centuries, says Hung. “And our own ethnoarchaeological studies in the New Guinea Highlands reveal that, in some communities, this practice still continues today.”
“The results show that a unique combination of technique, tradition, culture, and above all, a deep belief and enduring love for the ancestors has persisted for an astonishing length of time and spread across a vast region, from the Palaeolithic era to the present,” she says.
Vito Hernandez at Flinders University in Adelaide, Australia, says the study challenges long-standing assumptions that early mummification practices arose only in arid areas like Atacama in South America or the Nile valley. “It emphasises the role tropical environments have played in fostering distinct mortuary traditions amongst early modern humans to have spread to the Far East and, potentially, the Pacific,” he says.
“By extending the timeline of mummification by at least 5000 years before Chinchorro culture [of South America], they highlight South-East Asia as an independent centre of cultural innovation and underscore the deep cultural continuities linking early Holocene hunter-gatherers in the region with present-day Indigenous groups in New Guinea and Australia,” says Hernandez.

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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Ibex can move nimbly across steep mountain slopesSerge Goujon/Shutterstock
Nearly 300,000 years ago, Neanderthals had already figured out how to hunt mountain goats along vertical cliffs and process them in well-organised camps.
Known for ambushing large animals in Western Europe’s flat meadows and forests, it seems Neanderthals adapted to the hills of Eastern Europe by adding nimble ibex to their hunting regime. The early humans skinned and butchered the animals in a nearby cave before roasting their bones for marrow and grease, showing impressive skill and knowledge far earlier than expected, says Stefan Milošević at the University of Belgrade in Serbia.

“The approach of hunting ibex is completely different, because it lives on a very rugged and steep, barren terrain,” he says. “We now see that early Neanderthals – who had barely differentiated themselves anthropologically as a species – were already exploiting ecological niches that no hominin had ever exploited before.”
Neanderthals evolved about 400,000 years ago, but most of what we know about them comes from sites in Western Europe that are younger than 150,000 years. So finding clues that fill in gaps in the Neanderthal timeline, habitat and culture is critical, says Marie-Hélène Moncel at France’s National Museum of Natural History in Paris, who wasn’t involved in the study.
In 2017, archaeologists found Neanderthal remains in an approximately 290,000-year-old layer of the Velika Balanica cave in Serbia, making them the oldest such remains found in Eastern Europe.

Since then, Milošević and his colleagues have discovered hundreds of stone tools and sifted through about 30,000 animal bone fragments in the cave. Nearly three-quarters of the fragments are slivers less than 2 centimetres long, and most of the identifiable ones are from ibex and red deer killed in spring and summer, suggesting the Neanderthals were seasonal cave dwellers.
Some bones – especially long deer legs – were burned and cracked open, meaning these early Neanderthals were probably heating bones to liquefy the marrow for easier extraction and leaving leftover fragments in the hearth so that bone grease would keep the fire burning. Others showed signs of tendon harvesting, possibly for rope or nets.
Deer skeletons represented older youngsters and adults, a sign of selective hunting that promotes herd survival, says Milošević. But the ibex were killed at all life stages – suggesting the Neanderthals were still “rookies” up against mountain goats, probably hunting with sharpened sticks and rudimentary traps. “They most likely had a lot of unsuccessful attempts,” he says.
In addition to these preferred food sources, the researchers also found a few processed remains from wild boar, cave bears, wolves, foxes, leopards and various birds.

The organised positions of the bones in different sections of the cave point to distinct zones for specialised tasks. The hearth was in the centre, for example, with discarded bones piled up behind it, and the entrance appeared to be used as a tool workshop.
Overall, the findings point to “remarkable cognitive flexibility,” says José Carrión at the University of Murcia in Spain. “It’s a confirmation that Neanderthals were creative problem-solvers, managing complex habitats with ingenuity and skill. Neanderthals were humans – intelligent, social, and extraordinarily adaptive.”
“What emerges from Balanica is the picture of Neanderthals who were not only resilient but already experimenting with strategies and social organisation that we tend to associate with much later periods,” says Antonio Rodríguez-Hidalgo at the Archaeological Institute of Mérida in Spain. “It reminds us that Neanderthal sophistication was not a late spark, but a deep-rooted flame that ignited surprisingly early in human history.”

Neanderthals, ancient humans and cave art: France

Embark on a captivating journey through time as you explore key Neanderthal and Upper Palaeolithic sites of southern France, from Bordeaux to Montpellier, with New Scientist’s Kate Douglas.

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Archaeological excavations near Aldborough, UK, are helping us understand life after Roman occupationR Ferraby & M.J. Millet
When the Roman Empire withdrew from Britain, the result was not chaos and economic collapse. The metals industry in what is now northern England continued and even expanded in the subsequent centuries, according to an archaeological record of pollution from metalworking.
“The argument has been that, with the disappearance of state apparatus and linked state transport systems, the regional economies collapse totally,” says Christopher Loveluck at the University of Nottingham in the UK. But that isn’t what the archaeology revealed. “We’re seeing an increase in metal pollution products.”
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Loveluck is part of a team that has excavated Roman remains from Aldborough in North Yorkshire, England. Under Roman rule, this town was called Isurium Brigantum, where metals like iron and lead were mined and processed.
The team found aerosol pollution from these metalworking operations had become trapped in the silt accumulating in an ancient riverbed at the archaeological site. By digging through the layers of sediment, the team was able to reconstruct how pollution levels varied between 345 and 1779 AD.
“They get this long chronology, so you really can trace the ups and the downs,” says Jane Kershaw at the University of Oxford, who wasn’t involved in the research but who has studied early medieval metal mining.

In the late 300s and early 400s, the Roman Empire lost control of Britain and withdrew. “The government apparatus goes, the tax collection apparatus goes, no new coinage arrives in Britain, and they almost certainly withdraw all of the field army units as well,” Loveluck says. The subsequent centuries have few written records, and certain industries – notably wheel-thrown pottery – went into steep decline. This gave rise to a narrative of “the society of 5th century Britain just collapsing”, says Loveluck.
The riverbed record tells a different story. Lead pollution was low during Roman times, and fell only slightly in the late 300s and early 400s. It then rose steadily until the mid-500s. Likewise, pollution from ironworking rose during the first half of the 500s.
This, argues Loveluck, suggests continuity in the large-scale production of essential commodities.
The rise in metal production may have been due to internal fighting, suggests Kershaw. “It’s a period where the various Anglo-Saxon kingdoms are coalescing,” she says. “There’s a lot of fighting between those different kingdoms.” Many men were buried in graves with swords and knives.

Metal production then declined sharply in the mid-500s, and remained low for several decades. The team suggests this might be due to the Justinianic plague, which cut through the lands around the Mediterranean in 541-549 AD. Ancient DNA evidence from a graveyard in east England shows the plague did reach Britain. However, it is not clear how severe or widespread it was. “We don’t have grave pits full of plague victims, for instance, like we do with later plague events,” says Kershaw.
Anglo-Saxon coins dating from the 10th and 11th centuryAndrew Cowie/Alamy
The apparent resilience of Aldborough metal production in the face of the Roman withdrawal fits with other evidence of economic and political continuity. “Droitwich in Worcestershire [in western England] has an unbroken sequence of salt production from the Roman period to the modern period,” says Loveluck.
The period after the Roman withdrawal has been dubbed the Dark Ages, due to a lack of written records and supposed intellectual decline. However, historians say that is at best an oversimplification.
Some practices did cease, like wheel-thrown pottery and building using stone. But this period also saw the production of spectacular metalwork, often using copper. “If everything was so terrible and dark, how come they’re wearing these amazing brooches and they’ve got colourful bead necklaces,” says Kershaw.

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Acanceh in Mexico is home to many Maya peopleEducation Images/Universal Images Group via Getty Images
In the past, the quantity of zinc and other trace elements in human diets was determined largely by levels in local soils. Now it has been shown that our ancestors evolved to cope with local variations in micronutrient levels as they migrated around the world.
This might have led to some dramatic side effects – it is possible, for example, that the short stature of some peoples around the world is a byproduct of adaptation to low iodine levels. It is also possible that these past adaptations are causing some people today to get too much or too little of specific micronutrients.
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“For most of human evolution, the micronutrient composition of what you’re eating has been dependent on the underlying soil,” says Jasmin Rees at the University of Pennsylvania.
Her team has scanned nearly 900 genomes of people from all around the world to find evidence of adaptation to local levels of 13 trace elements, including iron, manganese and selenium. To do so, the team looked for signs of positive selection in 270 genes linked to uptake of these elements – that is, for gene variants that became more common in specific populations because they provided an advantage.
The strongest evidence was in iodine-linked genes in Maya peoples of Central America. Similar signatures were also found in the Mbuti and Biaka peoples in Central Africa, who have a shorter stature than most people.

In 2009, it was suggested that the Mbuti and Biaka peoples’ short stature could be due to adaptation to low iodine. This is because iodine-linked genes influence thyroid hormone activity, which has an effect on growth. These peoples are also known to be less prone to goitre – enlargement of the thyroid gland due to an iodine-deficient diet – than neighbouring groups.
Because the Maya population is also very short-statured, says Rees, her findings support the idea that adaptation to low iodine affects size. She and her colleagues also point out that the rainforest soils in the Maya region are known to be low in iodine.
“This is very speculative,” she says. “We can’t say exactly what is causing these short statures, but we’re seeing, at the very least, a coincidence where there seems to be selection on iodine-associated genes in these short-statured populations.”
In the Uyghur and Brahui peoples of Central and South Asia, where soil magnesium levels are especially high, there is strong selection affecting two genes related to magnesium uptake. Some of these gene variants have previously been linked to low levels of magnesium in the body, so the team suggests these changes reduce magnesium uptake to prevent toxicity from high levels in the environment.
These are just two examples – the team found signs of positive selection related to at least one micronutrient in just about every population around the world. “We see really widespread signatures of adaptation,” says Rees.

This study is just the beginning, she says. More work is needed to pin down the effects of the many gene variants the team identified. Now that food is traded globally, it could turn out that people with certain variants need more or less of specific micronutrients. Rees compares it to how in countries such as the UK, people with darker skin are advised to take vitamin D all year round rather than just in the winter.
“It would be important to know if individuals from particular populations are likely to be especially in need of particular micronutrient supplements,” says Mark Stoneking at the Max Planck Institute for Evolutionary Anthropology in Germany.
“When it comes to identifying signatures of selection from genomic data, they have done state-of-the-art work,” he says. “But a lot more work needs to be done to verify that these have been truly subject to selection – some of them will inevitably turn out to be false positives.”

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Has an asteroid impact influenced the course of human evolution?Anna Ivanova/Alamy
This is an extract from Our Human Story, our newsletter about the revolution in archaeology. Sign up to receive it in your inbox every month.
I am old enough to remember when the idea an asteroid impact wiped out the dinosaurs was new and exciting. When Luis Alvarez and his colleagues first suggested this in 1980 – the year before I was born – it was a big, dramatic claim. They didn’t even have an impact crater, just a layer of anomalous rock. It took decades, and the realisation in the 1990s that the Chicxulub impact crater in Mexico was the right age and size, to firm up the idea. Even now, palaeontologists are divided on whether the impact was the main cause of the mass extinction, or whether dinosaurs were already in decline before the big rock hit.

Obviously, nothing so earth-shattering happened during the period when humans evolved. The Chicxulub impactor was unusually large and exceptionally deadly.
However, life on Earth is subject to a whole host of other space-related threats. One idea doing the rounds is Earth’s magnetic field did something weird about 42,000 years ago. This supposedly caused a global ecological crisis, including possibly contributing to the extinction of the Neanderthals – paving the way for the global dominance of our species. The idea was first proposed in 2021 in Science, and my colleague Karina Shah wrote a news story about it.
What’s more, many other cosmic phenomena affect our planet. Meteorite impacts smaller than Chicxulub can still do a lot of damage to ecosystems in or near the impact zone. There are also risks from radiation from exploding stars or “supernovae”. These amount to an ongoing barrage of threats for life on our planet, including humans and our extinct relatives.

So: have cosmic phenomena influenced the course of human evolution?
Flip flop
Earth’s magnetic field protects us from intense solar radiation and cosmic raysMilos Kojadinovic/Alamy
Let’s first consider Earth’s magnetic field. The field is generated by the movement of molten metal in the planet’s core, which powers vast electrical currents and thus a magnetic field. It extends far out into space and protects us from intense solar radiation and cosmic rays.
However, the magnetic field is not entirely stable. Every few hundred thousand years, it flips direction: the north magnetic pole switches to the south and vice versa. During these reversals, the field weakens and more radiation reaches the surface.
Less dramatically but more frequently, the field undergoes an “excursion”. During an excursion, the field’s strength dramatically weakens, perhaps for thousands of years, and its direction may change – but not fully reverse – before returning to its original state.
42,000 years ago, the magnetic field underwent a particularly big excursion, dubbed the Laschamps event after the village in France where it was first detected. During the event, the magnetic field was almost entirely reversed. The 2021 study suggested it occurred between 41,560 and 41,050 years ago, and lasted a few hundred years.
In that study, researchers found evidence of changes in atmospheric ozone levels during the period when the magnetic field was weakening. This, they said, should have driven “synchronous global climate shifts that caused major environmental changes, extinction events, and transformations in the archaeological record”.
This year we got an update on that idea. In April, a separate group published a follow-up study in Science. They modelled the field excursion in more detail and found the aurora borealis would have been visible further south, including over Europe and northern Africa. This, they argued, would have exposed hominins to more harmful ultraviolet radiation.
The authors go on to suggest modern humans in western Eurasia may have used red pigments called ochre at this time – perhaps as a sunscreen. Those same people also seem to have had better techniques for making clothing, enabling them to make more tailored garments. These two factors, they say, may have helped modern humans to protect themselves from the radiation – while Neanderthals failed to do so.

It’s certainly a neat coincidence that the Laschamps event occurred so soon, barely 1000 years, before the last documented appearance of the Neanderthals. That does seem suspicious.
But we should also step back and look at the full 7-million-year history of humans and hominins. How many times has the magnetic field flipped out during that period, and did all those excursions and reversals cause havoc?
The answer is, it flipped out a lot. The most recent full reversal was the Brunhes-Matuyama reversal 795,000 to 773,000 years ago. That’s before the Neanderthals, but perhaps around the time of the common ancestor they shared with us. There have been several other reversals during the last 7 million years.
Excursions, which are smaller, are more common but also harder to pin down. A 2008 study looked at the last 2 million years and found 14 well-evidenced excursions (including Laschamps), plus an additional six with weaker support.
The upshot of all this is Neanderthals lived through at least three excursions before the Laschamps event, and possibly more. So why would the Laschamps event take them down after they’d survived all the other ones?
Likewise, if the Laschamps event was so dangerous it took out the Neanderthals, we would expect to see extinctions among other species too. In fact, large animals or “megafauna” were going extinct in Australia as early as 50,000 years ago, but survived in the Americas until much more recently, perhaps 13,000 years ago. There isn’t an obvious extinction spike around 42,000 years ago.
All of which makes me very wary of the Laschamps Event Neanderthal Extinction Hypothesis, as nobody is calling it. I don’t want to be too definitive – maybe it was a contributing factor – but I don’t believe it was the main cause.
The other claims of cosmic events influencing human evolution have similar problems.
Big boom
Take meteorite impacts. If you want to lose an afternoon down an internet rabbit hole, like I just did, go have a look at Impact Earth: a database of impact craters on Earth, presented as an interactive map. There you can learn about, for instance, the Zhamanshin hypervelocity impact crater in Kazakhstan, which is 13 kilometres across and 910,000 years old, or the 14-kilometre-wide Pantasma crater in Nicaragua from 804,000 years ago. Both dwarf the famous Barringer crater in Arizona, which is not quite 1.2 kilometres across and perhaps 61,000 years old.
Impact Earth lists 48 impact craters and deposits from the last 2.6 million years. If we go back to 7 million years ago, the approximate time of the first hominins, there are a few more. In chronological order:

Shunak, Kazakhstan, 7 to17 million years ago, 2.8 km across
Bigach, Kazakhstan, maybe 6 million years ago, 8 km across
Karla, Russia, 4 to 6 million years ago, 12 km across
Tsenkher, Mongolia, 4.9 million years ago, 7 km across
Roter Kamm, Namibia, 3.8 million years ago, 2.5 km across
El’gygytgyn, Russia, 3.65 million years ago, about 15 km across
Aouelloul, Mauritania, 3.1 million years ago, 0.39 km across

Bear in mind, these are just the ones we know about. Now, none of these compares to the Chicxulub crater, which is perhaps 200 kilometres across. The largest ones are between one-tenth and one-twentieth of that. Nevertheless, such impacts would still have significant consequences.
Of course, timing and location matter. Big impacts in Kazakhstan 6 or 7 million years ago probably didn’t disturb humans, because at that time hominins were confined to Africa. But I do wonder what hominins made of the Roter Kamm and Aouelloul impacts, both of which struck Africa when Australopithecus lived there. I couldn’t find any studies describing ecological consequences from either impact.
One more impact occurred around 790,000 years ago. It left distinctive melted rocks called tektites scattered over South-East Asia and Australia. A 2019 study linked it to a possible buried crater in Laos, which is about 15 kilometres in diameter. I suspect that might be too far east, and too early anyway, to have affected the Neanderthals. However, it must have been a significant event for the Homo erectus living in the area. But not too significant, given H. erectus survived as a species until between 117,000 and 108,000 years ago.
Dying stars
Supernovae emit huge pulses of matter and radiationNASA/DOE/Fermi LAT Collaboration, CXC/SAO/JPL-Caltech/Stew​ard/O. Krause et al., NRAO/AUI
What about even more distant events, like exploding stars? When massive stars go supernova, they emit huge pulses of matter and radiation that expand out across the galaxy. We have known for years nearby supernovae can leave traces on the rock record, in the form of unusual isotopes of iron.
Actually nailing this down is quite tricky, but there do seem to have been a few within the last 4 million years. One reading of the data suggested two – 2.3 and 1.5 million years ago, respectively. Another study also found two, but 1.5 to 3.2 million and 6.5 to 8.7 million years ago. These days, researchers seem to be zeroing in on 2 to 3 million years ago as a period when Earth got hit by supernova radiation.
Naturally, researchers have speculated about possible effects. One suggestion, published in May, is extra cosmic rays from the supernova led to more global cloud cover and thus cooler temperatures, and this could have affected the australopithecines living in Africa at the time. Well, maybe.
Physicist Adrian Melott at the University of Kansas has spent the last 20 years on what he calls “astrobiophysics”: basically, investigating ways that events in space such as supernovae could have affected life on Earth. Most of it is about events long before the first hominins, but not all.

Melott has highlighted 2.6 million years ago, when the Pliocene Period ended and the Pleistocene began. At this time, large marine animals suffered an extinction event. Maybe a supernova was the root cause. Melott has suggested the supernova would have dosed the planet with muon particles, leading to climatic changes like more frequent wildfires and direct impacts such as higher cancer rates. However, the palaeontologists who identified the extinction instead linked it to a loss of productive coastal habitats.
That’s enough listing of threats from outer space. My point is simply there have been a lot of these seemingly-dangerous events over the course of human evolution. Yet there is a near-total lack of evidence that any of these events caused extinctions, either of hominins or of other species.
Consequently, I tend to think asteroid impacts, exploding stars and reversals of the planet’s magnetic field have only played small roles in the story of human evolution. Some of those meteorite impacts surely had significant local impacts – how could they not? But that’s not the same as wiping out a hominin species, or driving a new adaptation.
The next time you see an excitable headline about some cosmic event killing off the Neanderthals or the like, remember this – and take it with a big pinch of salt.

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