Neanderthals existed for hundreds of thousands of years but we know little about their early ancestry. Now DNA analysis of 120,000-year-old bones from Germany and Belgium sheds light on their mysterious past.
The study reveals a remarkable continuity of European Neanderthal ancestry and a migration to the east that seems to have ousted their Siberian relatives. It also shows that some European Neanderthals hold clues about other ancient hominins in their DNA, as a result of interbreeding.
Neanderthals first arose around 430,000 years ago, living in Europe and central Asia until their demise some 40,000 years ago. Few details are known about their population history, not least because the DNA in their ancient bones is hard to analyse due to degradation. Contamination with modern DNA can also be a problem whenever people handle the remains – something that has happened a lot with some Neanderthal bones that were excavated decades ago.
Thighs and faces
Stéphane Peyrégne at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, and his colleagues retrieved gene sequences from two different European Neanderthals from 120,000 years ago. One was obtained from a thigh bone found in the Hohlenstein-Stadel cave in Germany. The other was from a face bone from Scladina cave in Belgium.
The researchers compared these DNA profiles with genetic profiles of two Neanderthals who lived in the Denisova cave in Siberia 90,000 and 120,000 years ago. They also looked at Neanderthal DNA from individuals who lived in Europe about 40,000 years ago.
“It’s the first time we can look at Neanderthals in Europe across a long period of time,” says Peyrégne. “It’s very exciting because we don’t know about the early history of Neanderthals. We can start asking questions about the relationships of the different Neanderthals that occupied Europe.”
Importantly, the team managed to obtain gene sequences from DNA found in the nucleus of cells of the Neanderthal bones. This reveals far more detailed information about ancestry than DNA from mitochondria of cells, which only tells us about the maternal lineage.
The team found that the 90,000-year-old Neanderthal from the Denisova cave was more closely related to the 120,000-year-old European Neanderthals than to the individual who had lived in the same cave 30,000 years previously. This suggests that the European population migrated eastwards and replaced the Neanderthals already living there.
The researchers also found that the Neanderthals living in Europe around 40,000 years ago were closely related to those who had lived there 80,000 years previously, suggesting long-term stability of this population.
“The continuity of the Neanderthal lineage in Europe suggests that Europe was the core area of Neanderthals, from which they repeatedly dispersed to the east, possibly in reaction to climatic cycles,” says Katerina Harvati at the University of Tübingen, Germany, who wasn’t involved in this study.
But things weren’t always so straightforward for the European Neanderthal ancestry. Peyrégne’s study also found that the mitochondrial genome of the Hohlenstein-Stadel Neanderthal was from a different lineage to that found in all other known Neanderthal genomes, as a result of breeding with a genetically distant hominin.
This confirms an earlier genetic analysis of the Hohlenstein-Stadel Neanderthal, which proposed that this mitochondrial genome originated when Neanderthals mated more than 219,000 years ago with an early human who had migrated from Africa. However, the new analysis by Peyrégne’s team suggests an alternative origin: that this unexpected maternal lineage could be the result of interbreeding with a mystery Neanderthal population.
“It is possible that there was this isolated Neanderthal population that we haven’t discovered yet that could have contributed the mitochondrial genome to the Hohlenstein-Stadel Neanderthal,” says Peyrégne.” Europe was heavily glaciated between 130,000 and 190,000 years ago and it is possible that some populations became cut-off during this time, he says.
Journal reference: Science Advances, DOI: 10.1126/sciadv.aaw5873
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