Prior to summer 2015, researchers believed that all Europeans had a shared ancestry stemming from three tribal populations: European hunter-gatherers, early European farmers, and ancient North Eurasians. According to an article published this week in the journal Nature Communications, by studying the genomes of ancient skeletons found in two caves in Western Georgia (Kotias Klde and Satsurblia), geneticists have discovered a fourth group, Caucasus hunter-gatherers, who also contributed DNA to the continent.

Satsurblia cave, where another sample was found. Image credit: Eppie Jones

The Caucasus hunter-gatherers are believed to have mixed with another group of hunter-gatherers around 25,000 years ago, "laying the genetic foundations of the Yamnaya people," according to the BBC. Yamnaya herders from the region, which includes present-day Russia and the Ukraine, entered Europe around 5000 years ago, possibly because of the spread of disease back home.

"The question of where the Yamnaya come from has been something of a mystery up to now," Andrea Manica, of the University of Cambridge, told the BBC. "We can now answer that as we've found that their genetic make-up is a mix of Eastern European hunter-gatherers and a population from this pocket of Caucasus hunter-gatherers who weathered much of the last Ice Age in apparent isolation." The group may have been responsible for introducing Indo-Aryan languages to the region, and are also believed to have influenced the cultures of central and south Asia.

To read more about the analysis of the skeleton genomes and of the Caucasus, head over to Nature Communications.