At the end of the Neanderthal era, there were apparently at least two genetically separate lines in Europe. This is suggested by DNA and isotope analyses of a Neanderthal discovered in the Mandrin Cave in France in 2015. The individual, whom the researchers nicknamed “Thorin,” lived around 42,000 to 50,000 years ago. Genetically, however, this early human was not similar to Neanderthals of this time, but to individuals who lived more than 100,000 years ago. Accordingly, Thorin belongs to a previously unknown line of Neanderthals that probably lived isolated from other populations for 50,000 years.
Until about 40,000 years ago, Neanderthals were widespread in Eurasia. Their range extended from southern and western Europe through the Middle East to Central Asia and Siberia. While the genetic makeup of the early human species changed over time, it was previously assumed that the late Neanderthals, who lived in the last millennia before their species became extinct, belonged to a single genetic line. This assumption is now being questioned by a new study.
Mysterious discovery
In 2015, a team led by Ludovic Slimak from the Paul Sabatier University in Toulouse discovered the remains of a Neanderthal in the Mandrin Cave near the French city of Montélimar, whom the researchers nicknamed “Thorin”. Based on the sediment layer in which the fossils were found, Slimak and his team estimated the age of their find to be around 42,000 to 50,000 years. This means that Thorin was a so-called late Neanderthal who lived shortly before the extinction of the early human species. To determine his relationship to other Neanderthals found so far, the team analyzed the ancient DNA from Thorin’s teeth and jaw and compared his genome sequence with previously sequenced Neanderthal genomes.
But the result did not match the age estimate. Thorin’s genome did not resemble that of the Neanderthals of his time, but rather that of Neanderthals who lived more than 100,000 years ago. “We worked for seven years to find out who was wrong – archaeologists or genomicists,” says Slimak. Using isotope analyses, which, among other things, provided information about the climatic conditions under which Thorin lived, the team confirmed the original age estimate. According to this, Thorin actually only lived 42,000 to 50,000 years ago – even if his genome seemed much more primitive.
Isolated despite spatial proximity
“This genome is a remnant of some of the earliest Neanderthal populations in Europe,” says co-author Martin Sikora of the University of Copenhagen. “The family tree that led to Thorin split from the family tree that led to the other late Neanderthals about 105,000 years ago.” This means that there were at least two genetically separate populations in the last millennia of Neanderthals. “The Thorin population spent 50,000 years without exchanging genes with other Neanderthal populations,” says Slimak.
This is particularly astonishing as the site is not far from other known Neanderthal settlements. “So we are dealing with 50 millennia in which two Neanderthal populations, living about ten days’ march apart, coexisted and completely ignored each other,” says Slimak. “That would be unimaginable for a Homo sapiens and shows that the Neanderthals must have perceived our world biologically very differently than we do.”
Extinction due to lack of exchange?
From the researchers’ point of view, this result could also provide an explanation for why the Neanderthals died out around 40,000 years ago, while Homo sapiens has survived to this day. “Classically, ecological factors, including climatic changes and volcanic eruptions, are often cited as the reason for the extinction of the Neanderthals,” explain the researchers. The new findings, however, suggest internal causes. “It is always good when a population is in contact with other populations,” says Sikora’s colleague Tharsika Vimala. “Isolation limits genetic diversity, which means that the population is less able to adapt to climate changes and pathogens. In social terms, a lack of knowledge exchange with others means that the population hardly develops any further.”
The socially and genetically isolated Neanderthals may have been at a disadvantage, particularly in contact with Homo sapiens, who already had extensive social networks at that time. “The extinction of the Neanderthals could therefore have been a complex process in which the history and ethology of these populations could have played a key role,” the researchers write.
Source: Ludovic Slimak (Université Paul Sabatier, Toulouse, France) et al., Cell Genomics, doi: 10.1016/j.xgen.2024.100593