Neanderthals, our closest extinct human relative, disappeared roughly 40,000 years ago. But before that, they overlapped with modern humans long enough to interbreed. For some people living today, around 2 percent of their DNA has been passed down by Neanderthals.
Now, a new paper indicates these two groups may have also shared some culture where they coexisted.
The research, published in Scientific Reports, suggests that modern humans and Neanderthals living in what’s now France and northern Spain overlapped for up to almost 3,000 years, even exchanging tools and ideas. To reach this conclusion, scientists recalculated the dates of approximately 40,000-year-old artifacts found in those regions, per Science’s Michael Price.
“This study confirms previous work that shows a considerable overlap of several thousand years between different human populations (Neanderthals and modern humans) in western Europe,” Thomas Higham, an archaeologist at the University of Vienna in Austria who was not involved with the study, tells the Guardian’s Hannah Devlin. Higham has conducted separate research showing a similar overlap between modern humans and Neanderthals.
Other scientists say the dates in this new paper have wide margins of error, calling into question whether or not the two species truly coexisted in this region. It’s “a good starting point,” but more accurate dating might come to another conclusion, Sahra Talamo, a chemist who studies human evolution at the University of Bologna in Italy and did not contribute to the research, tells Science.
Though it’s clear that modern humans and Neanderthals interacted in Europe, the researchers set out to find “in which specific regions this actually happened,” Igor Djakovic, lead author of the paper and an archaeologist at Leiden University in the Netherlands, tells the Agence France-Presse (AFP).
The new study used radiocarbon dating in an attempt to update previous estimates for the ages of 56 artifacts—half from modern humans and half from Neanderthals—found at 17 sites in France and northern Spain, according to the AFP. They also looked at ten Neanderthal specimens from the same area, per the Guardian.
Radiocarbon dating measures the amount of carbon-14, an isotope of carbon that decays into nitrogen over time. The rate at which carbon-14 decays is fixed, so if researchers know how much carbon-14 was in the environment historically, they can use the amount remaining in a specimen to work backward and figure out when it was from.
However, scientists realized in 2020 that Earth’s magnetic field briefly reversed around 42,000 years ago, which temporarily altered the amount of carbon-14 in the atmosphere. This led to inaccurate dating of artifacts from that time, per Science, so the new study redid dating for objects that other researchers had already examined.
Using modeling, the team then revealed that tools associated with humans appeared in the region between 42,200 and 42,600 years ago, and the tools connected with Neanderthals disappeared between 40,800 and 39,800 years ago. This suggests a period of overlap lasting 1,400 to 2,800 years, per the paper’s conclusion.
“In this region, there are a lot of similarities in the way that the two species were producing material culture and behaving,” Djakovic says to the Guardian. “It lends credence to the idea that there was some kind of interaction going on.”
But radiocarbon dating from so long ago has wide margins of error, so it can be challenging to determine the relative ages of different objects, as Shara Bailey, a paleoanthropologist at New York University who did not contribute to the study, tells Science. “I take the results of all these types of studies with a grain of salt.”