Jan Bartek – AncientPages.com – A recent study combining new DNA evidence with archaeological findings suggests that the last Neanderthals in Europe went through a profound population turnover, leaving them with very little genetic diversity in the millennia before their disappearance around 40,000 years ago.
Led by Professor Cosimo Posth at the Senckenberg Center for Human Evolution and Paleoenvironment at the University of Tübingen, an international research team reconstructed the complex genetic history of European Neanderthals. Earlier work had already hinted that the once widespread Neanderthal populations across Europe had largely vanished.
This new research points to a small, localized group that managed to endure severe climatic challenges by retreating to a refuge in what is now southwestern France about 75,000 years ago. The descendants of this resilient group appear to have spread across Europe after 65,000 years ago, with genetic evidence indicating that nearly all Late Neanderthals trace their ancestry back to this single lineage.
Excavations at the Tourtoirac rock shelter in France, where three Neanderthal remains analyzed in this study were found. Credit: Luc Doyon
Yet even this lineage was not spared from hardship. Posth and his colleagues found that these Neanderthals experienced a dramatic population decline around 45,000 years ago, with numbers dropping quickly and reaching a low point around 42,000 years ago—just before Neanderthals disappeared entirely.
Genetically, Neanderthals can be clearly distinguished from modern humans, Homo sapiens, who replaced Neanderthals by around 40,000 years ago. “We have evidence that Neanderthals inhabited Europe continuously between 400,000 and 40,000 years ago. However, we have only fragmentary details of their population history,” says Posth.
“So far, we know very little about the evolutionary developments that preceded their extinction.” He and his research team were therefore particularly interested in the Late Neanderthals, who lived between about 60,000 and 40,000 years ago.
10 Rare New Individuals
In their study, the researchers examined mitochondria in multiple Neanderthal tooth and bone samples recovered from caves and rockshelters. Mitochondria are small structures within cells that act like tiny organs and contain their own DNA. This mitochondrial DNA is inherited separately from the primary DNA located in the cell’s nucleus.
“Mitochondrial DNA does not contain nearly as much genetic information as the entire genome of a human being, but it usually survives longer and is easier to obtain,” says Charoula Fotiadou from Posth’s research group and first author of the study.
The research team sequenced the mitochondrial DNA of ten newly identified Neanderthal individuals from six archaeological sites located in Belgium, France, Germany, and Serbia. These new sequences were examined together with 49 previously published Neanderthal mitochondrial DNA samples to create a broader genetic dataset.
To place these genetic findings in a wider context, the results were integrated with archaeological evidence for Neanderthal presence across Europe. This archaeological information was sourced from ROAD, a large-scale database developed by the ROCEEH (The Role of Culture in Early Expansions of Humans) project, a collaboration involving the Heidelberg Academy of Sciences, the Senckenberg Research Institute and Natural History Museum Frankfurt, and the University of Tübingen.
“This allowed us to combine the two lines of evidence and reconstruct the demographic history of Neanderthals in terms of space and time,” said study co-author Jesper Borre Pedersen from the ROCEEH project.
Late Neanderthals All Of The Same Stock
The study shows that the severe climatic conditions of the Ice Age around 75,000 years ago had a major impact on European Neanderthals, significantly reducing their genetically diverse populations. According to the researchers, archaeological evidence from this period becomes scarcer, with fewer sites overall and a noticeable concentration of remaining sites in southwestern Europe.
Artist’s impression of the glacial landscape encountered by Neanderthals during the Ice Age. Credit: Direction de l’archéologie du Pas-de-Calais/Benoît Clarys
“Our data enabled us to reconstruct geographically that Neanderthals retreated to what is now southwestern France. There, around 65,000 years ago, a new population emerged and later spread across the whole of Europe,” says Posth.
“This explains why almost all Late Neanderthals sequenced so far—from the Iberian Peninsula to the Caucasus—belong to the same line of inherited mitochondrial DNA.” This demonstrates an enormous upheaval in the genetic history of European Neanderthals.
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In addition, the researchers used a statistical program to calculate whether the genetic changes in mitochondrial DNA diversity over time were consistent with the assumption of a population of constant size. This was not the case: according to the calculation, the number of Neanderthals declined rapidly and sharply between 45,000 and 42,000 years ago.
“Genetically speaking, the Late Neanderthals were a very homogeneous group,” says Posth. “So it may be that the low genetic diversity—and possibly also the subsequent isolation of small groups—contributed to the disappearance of the Neanderthals.”
The study was published in the journal Proceedings of the National Academy of Sciences
Written by Jan Bartek – AncientPages.com Staff Writer