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‘Fourth strand’ of European ancestry discovered

The sequencing of genomes from this key region will have a major impact on human evolution

The genetic history of Europe is complicated due to the extensive and complex demographic history of the continent. Numerous migrations, population altering diseases, and sporadic periods of rapid population growth make studying Europe’s genetic history inherently complex.

Now, a previously unknown ‘fourth strand’ of ancient European ancestry has been discovered. Researchers performed the first sequencing of ancient genomes extracted from human remains that date back to the Late Upper Palaeolithic period over 13,000 years and found another, previously unknown ‘tribe’.

The Caucasus hunter-gatherer genome showed a continued mixture with the ancestors of the early farmers in the Levant area, which makes sense given the relative proximity. This ended, however, around 25,000 years ago, just before the time of the last glacial maximum, or peak Ice Age.

The research was conducted by an international team led by scientists from Cambridge University, Trinity College Dublin and University College Dublin. The findings are published today in the journal Nature Communications.

This new ancestry originates from populations of hunter-gatherers that became divided from western hunter-gatherers soon after the expansion. This ‘out of Africa’ expansion occurred about 45,000 years beforehand and resulted in the settling of the Caucasus area, where southern Russia merges Georgia today.

With the ice age coming to a close, these hunter-gatherers remained in the region for millennia. They weathered the ice age in the relative shelter of the Caucasus mountains but as the weather warmed, the “tribe” became more mobile and eventually came into contact with other populations, likely from further east.

These movements and changes led to a genetic mixture that resulted in the Yamnaya culture. The DNA of this is present in almost all populations from the European continent.

One of the lead senior authors Dr Andrea Manica, from Cambridge’s Department of Zoology, stated that “The question of where the Yamnaya come from has been a mystery up to now.”

The mystery now seems to be getting all relevant answers as researchers have found genetic make-up, which is a mix of Eastern European hunter-gatherers and a population from this pocket of Caucasus hunter-gatherers. The study states that this Caucasus pocket is the fourth major strand of ancient European ancestry and up until now researchers were not even aware of it.

Some hunter-gatherer populations migrated north-west following the ‘out of Africa’ expansion. These farmers colonized a majority of Europe from Spain to Hungary, while other populations settled around the eastern Mediterranean and Levant.

Finally, around 5,000 years ago, when Bronze Age started, the Yamnaya came into formation. Importantly, scientists have revealed that the Yamnaya owed half their ancestry to formerly unidentified and heritably dissimilar hunter-gatherer sources: the fourth strand.

This was concluded by the sequencing of ancient DNA that was recovered from two separate burials in Western.

Immediately after the expansion of anatomically modern humans into Europe from Africa, the lineage of this fourth Caucasus hunter-gatherer strand deviated from the western hunter-gatherers.

David Lordkipanidze, Director of the Georgian National Museum and co-author of the paper, stated that this is the initial sequence from Georgia. More palaeogenetic information from the rich collections of fossils is expected.

Photo: Eppie Jones