Modern humans and Neanderthals may have a shared, overlapping culture in Western Europe | Science

Modern humans and Neanderthals met and had sexor at least babies– at some point in prehistory. But how long and exactly where the two species intermingled is a mystery. Now a reassessment of radiocarbon dating at archaeological sites in France and northern Spain indicates that around 40,000 years ago our ancestors overlapped with Neanderthals in the region for up to 2 800 years old, sharing not only genes, but also potentially a culture.

“The duration is insignificant on a geological scale,” says Antonio Rodríguez-Hidalgo, an archaeologist at the Catalan Institute of Human Paleoecology and Social Evolution who was not involved in the study. “But on a human scale, there’s enough time for some very interesting things to happen.”

Other scientists, however, argue that the wide margins of error for many dates analyzed in the study undermine strong claims about the identity of the inhabitants and whether they indeed overlap. It’s “a good starting point,” but conclusions could change depending on more precise dating, says Sahra Talamo, a chemist who runs a radiocarbon lab at the University of Bologna.

Radiocarbon dating estimates the age of organic objects such as bones and charcoal based on the regular radioactive decay of their carbon-14 isotopes. Scientists have used the method for decades and have been improving it ever since. just as long.

A major overhaul came in 2020, when radiocarbon scientists announced that a brief reversal in the Earth’s magnetic field around 42,000 years ago, known as the Laschamp event, had temporarily boosted the amount of carbon-14 in the air. As a result, everything living at the time incorporated additional amounts of the isotope, dismissing modern efforts to radiocarbon date their remains.

“It pushed back dates that were about 40,000 years later in time and made things appear more than 43,000 or 44,000 years younger in time,” says Igor Djakovic, a doctor of archaeology. student at Leiden University.

This period coincides with a critical era in human history. A major type of stone tool technology in Europe known as the Châtelperronian industry – consisting of palm-sized scrapers and knives and traditionally associated with Neanderthals – was replaced by a set of tools more sophisticated called the proto-Aurignacian industry, which included smaller tools, plus precision-worked blades traditionally associated with modern humans. (There is some debate, however, over whether either industry was truly exclusive to humans or Neanderthals.) This period is also when Neanderthals began to disappear from their European strongholds of long standing and modern humans began to settle on the continent.

Hoping to clarify the dates of sites containing Châtelperronian and Proto-Aurignacian artifacts, Djakovic and his colleagues revived radiocarbon analyzes carried out by other teams representing 17 sites across France and northern Spain. They also recalculated the dates of 10 Neanderthal skeletons from the same range. But this time, they applied a recently developed calibration standard known as IntCal20, which accounts for the increase in carbon-14 caused by the Laschamp event. None of the dates have changed drastically, but overall the older dates have shifted a little younger while the younger dates have aged a little, compressing the estimated ranges.

Then they plotted these refined dates using a statistical approach called optimal linear estimation, which aims to predict when a particular technology may have started and ended based on intervals between the ages of known artifacts.

The researchers found that Proto-Aurignacian tools associated with modern humans appear in the region between 42,200 and 42,600 years ago, while Chatelperronian tools associated with Neanderthals disappear around 40,800 years ago. at 39,800 years old. This indicates that the two toolmaking industries overlapped in time and space for anywhere from 1400 to 2800 years ago, the team now concludes in Scientific reports. The dates – although based on a relatively small number of sites – also suggest that proto-Aurignacian tools spread from south to north over time, hinting at the possible route of modern humans across the continent, says Djakovic. .

This is not the first time researchers have proposed that modern humans and Neanderthals overlapped in Europe during this time. But the revised dates provide a narrower, more geographically limited window into such a possible event, Djakovic says.

This overlap would still have given time for generations of humans and Neanderthals to meet, cross paths, and share toolmaking tips. And that in turn could explain why later Châtelperronian tool caches seem to borrow proto-Aurignacian elements, such as small, precisely crafted blades, Djakovic says.

Still, he admits that such interpretations are speculative and controversial. Except for the small number of instances where modern human or Neanderthal remains have been found alongside these tools, no one knows for sure which species made which tools at most sites.

The study’s agnosticism about the species that made the tools is actually a strength, says Emmanuel Discamps, an archaeologist at CNRS, France’s national research agency. “Who knows if the Châtelperronian or the Proto-Aurignacian were made by Neanderthals, modern humans, hybrids, or a bit of all of these, depending on chronology and geography,” he says. By not assuming the identities of these toolmakers, he adds, researchers can envision more complex stories that might better match what really happened.

But the uncertainties in the radiocarbon file still make Shara Bailey, a paleoanthropologist at New York University, think. Radiocarbon dates are only reliable up to about 50,000 years ago. Dates measured towards the end of this range tend to have large margins of error, she said, making it difficult to draw firm conclusions about which objects are older than others. “I take the results of all these types of studies with a grain of salt.”

Katerina Douka, an archaeologist at the University of Vienna who helped collect some of the reanalyzed radiocarbon dates in the new study, says it’s great to see her team’s data reused to refine our understanding of when and where Neanderthals and modern humans were able to live side by side. side. “Western Europe is a dead end, and many have predicted that it could be a region where the two populations coexist and interact more intensely.”

But she suspects that in other parts of Europe, such overlaps between different human species and cultures may have been even more complex, and occurring at different times and paces, than the new paper suggests. . “There is much more to discover about this key period in human evolution.”

Helen D. Jessen