Humans

Location of the Charco Verde II archaeological site in the Piedra river valley, SpainMULTIPALEOIBERIA project team
Excavations at a rock shelter have revealed that humans lived in high and remote regions of what is now Spain during the coldest part of the last glacial period, between 21,400 and 15,100 years ago.
High-altitude regions are colder and more challenging than low-lying zones, but even so, the Spanish plateau probably “hosted a relatively dense human settlement”, says Manuel Alcaraz-Castaño at the University of Alcalá in Spain.
Beginning 2.58 million years ago, Earth has been through alternating periods of cold “glacials”, in which the area covered by ice and snow expands, and warmer “interglacials” where the ice retreats. The last glacial period occurred from about 115,000 to 11,700 years ago. It was at its coldest between 26,500 and 19,000 years ago, a time called the last glacial maximum. This posed a significant challenge for modern humans, who had arrived in Europe about 20,000 years earlier.Advertisement
Conditions were particularly challenging on the meseta, a high-altitude plateau in what is now central Spain. Climate modelling by Ariane Burke at the University of Montréal in Canada and her colleagues concluded that as well as being cold and dry, the meseta was also highly unpredictable – making it harder to permanently settle there.
Nevertheless, people persisted. Since 2020, Alcaraz-Castaño and his colleagues have excavated a site called Charco Verde II in the Piedra river valley, Spain. Located around 1000 metres above sea level, Charco Verde II is a flat platform under an escarpment. Buried in the sediments, the team found fragments of charcoal from fires, animal bones with cut marks and signs of having been heated, and stone tools including blades and scrapers.
Radiocarbon dating suggests Charco Verde II was first inhabited between 21,400 and 20,800 years ago, and the residence ended between 16,600 and 15,100 years ago. It isn’t clear how continuous this was. “Occupations at the site were recurrent during 5000 years, but we still don’t know if there were prolonged periods where the site was not inhabited,” says Alcaraz-Castaño.
Preserved pollen and animal bones suggest the area was dominated by open grasslands, dotted with trees, such as juniper, and populated by herbivores like horses and ibex. Average annual temperatures were about 6 °C lower than today, says Alcaraz-Castaño, so in winter “ice and snow were probably everywhere around the site”. However, the summers were probably fairly mild.
“It’s nice to see people pushing the boundaries and finding new sites,” says Burke, who wasn’t involved in the new study. “In the early Upper Palaeolithic, people were perfectly capable of adapting to very cold environments.”
Her modelling studies identified the Charco Verde II region as relatively suitable for settlement because its climate was less variable than the central meseta. “It makes sense that the sites are where they say they are,” she says.
Burke adds that it is possible people did live even in the very harshest parts of the meseta, but such settlements may have been both scarce and short-lived. “Our chances of finding sites [there] are fairly small,” she says.

Such settlements were made possible by a host of behavioural skills. “Both fire and clothing were regular technologies of Upper Palaeolithic hunter-gatherers, as were some sorts of dwellings,” says Alcaraz-Castaño.
So far, Charco Verde II hasn’t yielded direct evidence of clothing. However, Burke notes that the team did find stone tools called burins that were often used to create the eyes in needles – “which means fine sewing skills and tight seams, so waterproof and windproof clothing”, she says.
Social networks were probably just as essential for survival, says Burke. Such networks “provide people with the means to exchange information over quite large territories”, she says, and to take shelter when conditions are harsh.
In line with this, the Charco Verde II dig revealed four perforated shell beads, one of them with traces of an ochre pigment. Such jewellery often served as a marker of identity, says Burke, and is a hint that, even in a sparsely populated region, people were still maintaining social relationships with other groups.

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“I want you to make a substitution in the course of our new IVF research partnership” … An extract from Sebastian Faulks’s new novel The Seventh SonScience Photo Library/ZEPHYR/Getty Images
“I have a proposition.” Parn leant forward and put his hand on Malik Wood’s knee.
“Oh yes?”
Parn sat back again. ‘Did you know I fund a palaeoanthropology research programme? It’s attached to the University of London. They do top genetic work. Looking at old bones. Sequencing the genome of Homo vannesiensis. That kind of thing. I know people there. In the labs. I have access.”Advertisement
“I bet.”
“You know all that work they did in Leipzig a few years back. The Max Planck people. Putting together genomes from scraps of forty-thousand-year-old bone. Brilliant stuff. But those PCR machines they used, they’re pretty old now. We have better kit.”
“And?”
Lukas Parn’s voice had lost all trace of the Outback. “I’m interested in hybrids. What they can tell us about ourselves. How we got to be the way we are. The inexplicable leap. The ‘saltation’, as you call it.”
“My God. You’re not a creationist, are you? You’re not going to try to prove that Homo sapiens was put together all in one go by God?”
“No.” Parn laughed. “No, I’m not a creationist. But I’m an exceptionalist. I believe that the superiority of Homo sapiens hasn’t yet been explained.”
“You’re saying Darwin was wrong?”
“Sure. He was wrong about a lot of things. Women. Genetics.”
“But by the standards of what was known at the time, he—”
“Exactly. ‘The time’ was 1850-something. Getting on for two hundred years ago. Anyway, it’s not about a Victorian with a beard. It’s about genetics, a word unknown to Darwin.”
“How am I involved in this?”
“Your lab. Your touch.”
Dr Wood drank some wine. “I’ll need to know more.”
“You will. In due course. But can I take it that you would be interested in having your salary increased. And a one-off bonus of, let’s say, five times salary on successful completion?”
“It depends on what I need to do.”
“Something well within your capabilities. I want you to make a substitution in the course of our new IVF research partnership with the NHS.”
“A substitution?”
“A simple switch. One guy’s sperm for another. Before it hits the egg.”
“That’s ethically—”
“Extremely important is what it is,” said Parn. “From a scientific point of view. We’re looking at a human hybrid.”
Extract taken from The Seventh Son by Sebastian Faulks (Hutchinson Heinemann, out now), the latest pick for the New Scientist Book Club. Sign up and read along with us here

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A Homo floresiensis skull, centre, found at Liang Bua cave on the Indonesian island of Flores.JIM WATSON/AFP via Getty Images
As a novelist, you write about what puzzles, inspires and keeps you awake at night. It feels like a one-off adventure and it’s only in retrospect, years later, that you can see a pattern or a link between different books.
My first half dozen novels look like an attempt to locate myself and my generation in history. I grew up in the 60s, when the world wobbled on the edge of mutually assured destruction, and as an adult, I was curious to know how we had come to that pass. After writing them, and in particular Birdsong (1993), I came to the conclusion that Homo sapiens is a very odd creature.
My next half dozen novels, I now think, were therefore concerned less with who we are  than what we are. In Human Traces (2005), I wrote about the early days of psychiatry and psychoanalysis, roughly from 1890 to 1920. The debate was between those who believe our mental frailties have a biological and/or genetic base and those who think they are shaped by the individual’s experience. This needed some research into genetics and the nature of human consciousness.Advertisement
Then, in about 2010, it emerged that we had bred with Neanderthals. My own genome, according to a commercial spit test, is 3.7 per cent that of another species. Then new humans were discovered, on Flores and in a Denisovan cave. It was intriguing to picture these different versions of the human strolling round the Earth together, even if their numbers were small and widely scattered. What made them human in taxonomic or philosophical terms? Are there other, even more interesting or closely related, species waiting to be unearthed?
It seemed such a shame that this fascinating diversity had been reduced to a single surviving expression: us. Suppose natural selection had worked differently and that if there had to be only one survivor of the genus Homo, it had a different admixture of genes, was less fecund, less driven, less destructive and better attuned to the planet.
Now imagine that with sapiens extinct, this last surviving human, similar but different from us, had stumbled one day on a pure sapiens archaeological site. Smaller brains, they’d note, physically a bit weak, but ferocious breeders. And hang on, what’s this? A hecatomb of bodies, millions of them, but killed neither for ritual nor sustenance. Why? And what’s this? A bit of matter rescued from a dead star a billion light years away. Cleverer than we thought, then. And here… The tall spire of a building. Did they hope to somehow climb into the sky to see their ever-absent gods?
The novel that emerged from all this, The Seventh Son, is set a little way into the future, though the science it relies on is all practicable now. It’s a serious book about what sort of creatures we are; I had never expected it to be so insistently comic or to end almost like a thriller in a chase across the barren wilds.
The Seventh Son by Sebastian Faulks (Hutchinson Heinemann, out now) is the latest pick for the New Scientist Book Club. Sign up and read along with us here

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9500-year-old Mesolithic baskets from the Cueva de los Murciélagos in SpainMUTERMUR project
Intricate baskets and shoes found in a Spanish cave show that people living in Europe thousands of years ago were skilled at weaving objects from plant fibres.
Cueva de los Murciélagos, or the Cave of the Bats, is a cave system in south-west Spain that was discovered during mining activities in the 19th century. Excavations of the cave have since revealed several mummified corpses alongside objects including baskets, sandals and a wooden hammer.
Francisco Martínez Sevilla at the University of Alcalá in Spain and his colleagues have now analysed 76 of these artefacts. They are considered among the best-preserved plant-based objects from prehistoric Europe, thanks to the low humidity inside the cave.Advertisement
Around 65 of the items were found to be made from a fibre called esparto grass. This includes a set of baskets, with either a flat or a more cylindrical shape, as well as sandals that were made by crushing and twisting the esparto.
A wooden mallet and esparto sandals dated to around 6000 years agoMUTERMUR project
The other artefacts are made of wood and include tools such as a hammer and digging sticks.
The team carbon-dated 14 of these objects and found that they belonged to one of two time periods: 7950 to 7360 BC or 4370 to 3740 BC. The older objects were created by hunter-gatherers during the Mesolithic age, says Martínez Sevilla, while the later ones were probably used by Neolithic farmers.
The oldest dated sandal was found to be around 6000 years old, which makes it the oldest shoe ever found in Europe, says Martínez Sevilla.
“The use of vegetal fibres in Europe is older than we expected,” says team member Maria Herrero-Otal at the Autonomous University of Barcelona in Spain. “We imagine the Mesolithic populations as simpler, but it seems that they were much more complex than we thought.” More

A human bone from up to about 5900 years ago found inside the Cueva de los Marmoles cave in Granada, SpainJ.C. Vera Rodríguez, CC-BY 4.0
Prehistoric farmers and herders in southern Spain buried their dead in a large cave – but may have later cut them up to make tools and possibly eat their bone marrow.
Since 1934, scientists, amateur archaeologists and even tomb raiders have been exploring human skeletal remains left in a Granada cave, called Cueva de los Marmoles.
Within the 2500-square-metre cave – which has harboured multiple generations of bodies across three millennia – people have previously found a carefully carved human skull cup, a well-crafted tibia tool and dozens of other bone fragments. New evidence suggests that some remains may have been intentionally broken and scraped up to a year after the individuals died.Advertisement
The findings indicate that people may have been manipulating the deceased’s bones, after the cadavers had decayed slowly for some time in the cave’s cool, humid environment, says researcher Marco Milella at the University of Bern in Switzerland.
Milella, his co-lead researcher Rafael Martínez Sánchez at the University of Córdoba, Spain, and their colleagues went to the cave to collect further artefacts and investigate them using modern methods, such as advanced carbon dating, and hi-tech microscopic and scanning equipment.
They examined 411 bone fragments and 57 teeth that were unearthed in various zones of the cave, some of which they borrowed from a museum. They found that the remains were from at least a dozen human adults and children living in prehistoric agricultural societies. The findings suggest that people used the cave as a burial site during three distinct periods: 3900 to 3750 BC, 2600 to 2300 BC and 1400 to 1200 BC.
The team also found that while 3 per cent of the fragments had been gnawed by animals, nearly a third had been intentionally broken or cut with human tools. These fractures, scrapes and slices occurred when the bones were still “fresh” – probably up to a year after death, according to the researchers.

But the bones show no signs of having been forcefully separated from muscles or tendons. “This suggests that the human remains were already partially decomposed when manipulated, but with the bone still being relatively elastic,” says Millela. “This, in turn, points to action not performed shortly after the death of the individuals, but at least some months after death.”
Notable specimens include a skull – probably from a middle-aged man – that had been scraped with stone tools and fashioned into a bowl or cup, and a teenager’s shinbone that had been broken, polished and rounded into a sort of spatula, possibly for scraping other materials, such as leather. Several long bones had also been fractured and their insides scraped out, suggesting the marrow had been extracted for consumption, or possibly as part of a cultural practice of “cleaning the remains”, says Milella.
Lacking any evidence of violence, the remains are probably not the result of power struggles between different populations, he says. His team is planning to carry out DNA research that will compare the relationships among the individuals buried in the cave.

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A flint used to shape a log identified at the archaeological site Kalambo Falls in ZambiaLarry Barham, University of Liverpool
Ancient humans were building large wooden structures – possibly houses – almost half a million years ago. The discovery, the earliest evidence of wooden construction, suggests that some ancient communities were far less nomadic than we have assumed.
“These people were behaving in ways I hadn’t expected,” says Larry Barham at the University of Liverpool, UK. “It’s a disruptive discovery.”
Barham and his colleagues uncovered the evidence at Kalambo Falls, an archaeological site in Zambia. In 2019, they spent a month excavating a sandbar some 300 metres upstream of the falls.Advertisement
One of the first artefacts they found was a wooden tool, probably a digging stick. “The number of sites where wood is preserved is small,” says researcher Geoff Duller at Aberystwyth University, UK.
As they continued to dig, they made another discovery: a 1.4-metre-long log overlying an even larger log that was too big to fully excavate during their month-long project. They saw that the overlying log had been worked with tools to fashion a deep notch midway along its length. This allowed it to interlock with the underlying log at a 75-degree angle, creating a relatively sturdy joint. The researchers speculate that the two interlocking logs were once part of a larger wooden structure.
Duller then dated the artefacts using a technique called post-infrared infrared stimulated luminescence. This involves measuring the time since the mineral grains in the sand that surrounded the wood were last exposed to light prior to their burial. The mineral grains – and the artefacts they surround – were buried about 476,000 years ago, which implies that the wooden structure was built before our species evolved. The engineers therefore belonged to an earlier human species, possibly Homo heidelbergensis.
We already knew that ancient humans made use of wood. For instance, researchers have discovered 300,000-year-old wooden spears at a site in Germany, possibly made by H. heidelbergensis. “But those wooden implements are portable,” says Barham, which fits with the prevailing idea that early humans were always on the move. The large wooden structure at Kalambo Falls suggests to Barham that at least some early humans were staying put and choosing to enhance their environment. “They were investing in this place.”
“There’s something really exciting about this discovery that they were constructing and [they] had a real sense of the importance of place,” says Penny Bickle at the University of York, UK.
The ability to modify the local environment – sometimes called niche construction – isn’t uniquely human. Plenty of other species, such as beavers, do this too, but their techniques are far less sophisticated than those used at Kalambo Falls. “To my knowledge, [non-human] animals do not use tools to modify materials to create structures,” says Annemieke Milks at the University of Reading, UK.
The engineers at Kalambo Falls needed to produce sharp-edged stone tools from rocks, recognise they could use those tools to cut through wood and then work in groups to transport and modify that wood to produce a large structure. “It involved a lot of planning and I do think language was involved” says Barham.
However, it is difficult to say exactly what sort of wooden structure the logs once belonged to. Barham speculates it might have been a dwelling or maybe a wooden walkway raised above the wet floodplain designed to keep early humans, and their food, dry. Manuel Domínguez-Rodrigo at Rice University in Texas says that, while it may have been a structure or shelter, we can’t read too much into the function of just two pieces of wood.

In an accompanying opinion article, Milks says that the finding shows “when people started to structurally alter the planet for their own benefit”, arguably drawing a line between Kalambo Falls and today’s highly modified human environments.
But Barham thinks the story is more complicated. He says there were periods after the Kalambo Falls structure was built when humans were typically more mobile – meaning there isn’t a direct link between the apparently sedentary behaviour on show at Kalambo Falls and the sedentary human lifestyles of recent millennia.
Either way, the discovery should shift perceptions, says Barham, because it gives us a rare insight into just how important wood must have been to ancient humans. “We might need to rethink our labelling of the Stone Age,” he says. “Maybe it was more of a wood age.”

Journal references: Nature DOI: 10.1038/s41586-023-06557-9 and DOI: 10.1038/d41586-023-02858-1

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Rock art in Twyfelfontein, NamibiaAndreas Pastoors, CC-BY 4.0
Expert trackers have been able to identify the species depicted in around 400 animal footprints carved on rocks in Namibia during the Stone Age. In most cases, they were also able to identify the animal’s sex, the exact leg that made the print and whether the animal was an adult or not.
Numerous rock engravings thought to be up to  5000 years old have been found in sites around an area called Twyfelfontein in north-west Namibia. Many depict animal or human footprints, so Andreas Pastoors at the University of Erlangen-Nuremberg in Germany asked three trackers from Namibia, Tsamgao Ciqae, /Ui Kxunta and Thui Thao, to help his team study them. The three usually work for commercial hunters.
The trio identified the engraved animal tracks as depicting more than 40 species, ranging from rhinos and giraffes to aardvarks and porcupines. Around 60 of the tracks are those of birds, such as the secretary bird and the marabou stork.Advertisement

Most species depicted are still found in the area, but some – including blue wildebeest, buffalo, bushbucks and vervet monkeys – are found only in areas with more water, hundreds of kilometres away. Pastoors says there is no evidence the climate has changed in the region, so he thinks those who did the engravings must have travelled to where these animals lived.
The trackers also identified the sex depicted in around 100 engraved human footprints at the same sites, along with whether the footprints were meant to be those of an adult or child. The trackers identified the vast majority as depicting the footprints of children, with just 15 out of 106 being attributed to adults and three being unclear.
There is no way to check if the identifications made by the trackers definitely correspond with what the artists intended to depict. However, to experienced trackers the footprints of animals are just as distinct and recognisable as the animal itself, says Pastoors. Just as few people doubt that ancient carvings that look like lions really are of lions, so the trackers are confident in their identifications. “They always work together and make consensus decisions,” says Pastoors.
The team has considered numerous different possibilities for why the carvings of tracks were made, including that they were for teaching. But there is no clear evidence supporting any of the ideas. “We cannot understand what the depictions were made for, there’s no clue,” says Pastoors.
Similar carved tracks are found at many sites around the world, says Pastoors, who has also previously enlisted the same trackers to help analyse preserved human footprints on the floors of caves in Europe.

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From its origins on the Tibetan plateau, humans have transported cannabis across the planetAlexis Wnuk
Cannabis is everywhere: today, the plant grows on every continent except Antarctica. But that wasn’t always the case. So how did this “weed” come to take over the world?
Its success is due in large part to us. The evidence suggests that cannabis first evolved nearly 28 million years ago on the Tibetan plateau, after splitting off from the last common ancestor it shared with the hop plant. At first, early humans may have unwittingly spread it. By clearing vegetation for settlements and heaping food scraps in waste dumps, they gave cannabis what it needed to thrive: open, sunny areas with fertile soil. That is why some scientists refer to the plant as a weedy “camp follower”.
In time, humans came to appreciate the many uses of the cannabis plant, and it is believed to be one of the first plants we cultivated when we began farming around 12,000 years ago. The stalks could be dried to create fibres, the seeds could be eaten or used to make oil and the resin-coated bracts could have been used for their medicinal and mind-altering purposes (though evidence for the latter is much more recent).Advertisement
The plant’s utility enabled its spread and humans became the most important agent for its dispersal. Its seeds aren’t encased in tasty fruit, making them less attractive to animals, and they are round and heavy and lack wings that would let them hitch a ride on the wind.

From the Tibetan plateau, the plant spread across central and East Asia, with nomadic groups later carrying it into the Indian subcontinent, eastern Europe and the Middle East by about 2000 BC. As people began to cultivate cannabis for a broader range of uses, including its psychoactive effects, different varieties of the plant emerged. This gave rise to the two major types we know today – Cannabis sativa and Cannabis indica – though there is still debate over whether these are actually separate species or just different types of the same species.
By the Middle Ages, cannabis was grown across Europe, and Arab and Indian traders carried it into Africa and South-East Asia. Finally, colonial empires brought the plant to the Americas beginning in the 16th century.

The science of cannabis

As the use of marijuana and its compounds rises around the world, New Scientist explores the latest research on the medical potential of cannabis, how it is grown and its environmental impact, the way cannabis affects our bodies and minds and what the marijuana of the future will look like.

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