Washington (AFP)

When did Neanderthals disappear?

The question has stirred scientists for a long time.

Human remains from a cave in Belgium, analyzed using a new technique, are contributing to the debate today by turning out to be much older than previously considered.

According to previous radiocarbon dating, specimens from Spy Cave in Belgium, where many human remains have been found since the 19th century, date back only 24,000 years.

But according to a study published Monday in the scientific journal Pnas, they are in fact between 44,200 and 40,600 years old.

A multidisciplinary team from Belgium, Great Britain and Germany has developed a method to prepare the samples, allowing to avoid any external contamination, explained to AFP one of the co-authors of the study, Thibaut. Deviese, from the University of Oxford and Aix-Marseille.

The study thus concludes that the Neanderthals "disappeared from northern Europe (...) much earlier than previously suggested".

Getting a better idea of ​​when they died out is seen as an important first step in better understanding its nature, as well as why it eventually gave way to modern humans.

The method still relies on radiocarbon (radioactive variants of carbon, like carbon-14), which is considered the best dating method, but improves the way samples are processed.

All living things absorb carbon from the atmosphere or from food, including carbon-14, which decays over time.

Since plants and animals stop taking in when they die, what is left in matter helps determine when that being lived.

For bones, scientists extract the part made of collagen for analysis, because it is organic.

"What we have done goes further," explains Thibaut Deviese.

This is because the environment where the remains were found can contaminate the samples.

So the researchers focused on molecules called amino acids that they were absolutely certain were part of collagen.

- "Major role" -

The authors also dated the remains of two other sites in Belgium, Fonds-de-Foret and Engis, with comparable results.

"Almost two centuries after the discovery of Engis' Neanderthal child, we were able to give him a reliable age," said Thibaut Deviese.

“Dating all these specimens from Belgium was very exciting, as they played a major role in understanding and defining Neanderthals,” he said.

There is evidence that it may have survived longer in other regions than in Belgium, the study notes, however.

"Dating is crucial in archeology, because without a reliable framework of chronology, one cannot be sure of understanding the relations between the Neanderthals and Homo sapiens," he stressed.

Some stone tools have been attributed to the Neanderthals, which has been interpreted as a sign of their cognitive development, he for example detailed.

However, if it turns out that they did not exist as long as expected, then these objects must be re-examined to determine if they were really their work.

The disappearance of Neanderthals could be linked to climatic causes, too much inbreeding, or competition between species, recalls the study - but this is another burning question to which it do not answer.

© 2021 AFP