A team of researchers from Ireland and the United Kingdom discovered genetic evidence from 13,000-year-old human remains that could very well reveal more information regarding the ancestry of early Europeans.
In a study featured in the journal Nature Communications, scientists from the University College Dublin, Trinity College Dublin and Cambridge University have found what is regarded as the "fourth strand" after sequencing prehistoric genomes retrieved from the remains of a human that lived during the Late Upper Paleolithic period.
The research team believes that the newly discovered genetic strand point to the lineage of hunter-gatherer populations that separated from hunter-gatherers from the west a short period after they migrated from the African continent approximately 45,000 years ago.
These ancient people then went on to establish settlements in Europe's Caucasus region, which corresponds to the modern-day territories of Georgia and southern Russia.
The new group of hunter-gathers stayed in this region for thousands of years, where they became increasingly isolated from the rest of the prehistoric world as the Ice Age entered its final "Glacial Maximum" around 25,000 years ago.
The Caucasus Mountains provided them with relative shelter during this period until they were finally able to move again after the frozen environment began to thaw. This is when they made their first contact with other human populations that likely came from the east.
The resulting mixture of genes between the two groups of ancient peoples led to the creation of the Yamnaya culture, which consisted of Steppe herders accustomed to horseback riding that migrated into Western Europe approximately 5,000 years ago.
This event is considered to be the starting point of the Bronze Age when the Yamnaya people brought their knowledge of animal herding and metallurgy into the continent. They also brought their ancestral DNA derived from the Caucasus hunter-gatherers that is now believed to be present in virtually all European people.
"The question of where the Yamnaya come from has been something of a mystery up to now," Dr. Andrea Manica, a researcher from Cambridge's zoology department and one of the authors of the study, said.
The researchers believe the discovery of the fourth major strand of ancient European ancestry can now help them unlock the secret to the Yamnaya people's origins.
Other Ancestral Groups of European Populations
Earlier studies on prehistoric Eurasian genomes suggest that there were three other ancestral groups that likely have contributed to the creation of present-day Europeans in different degrees.
In 2014, scientists carried out a genome sequencing of DNA samples retrieved from close to a dozen ancient inhabitants of Europe and found that modern-day Europeans trace their lineage to three populations in varying combinations.
These are the hunter-gatherers, which were blue-eyed individuals who migrated into the European continent from Africa around 40,000 years ago; the Middle Eastern farmers, which were brown-eyed individuals who arrived much more recently; and a mysterious group of ancient people who likely came from northern Europe and parts of Siberia.
The genomes samples the researchers used were derived from 8,000-year-old male hunter-gatherers from Sweden and Luxembourg, as well as those from a 7,500-year-old female from Germany.
Sequencing for these genomes was conducted by researchers from the University of Tübingen in Germany and the Harvard Medical School in the United States.
A team from the University Pompea Fabra in Spain also sequenced DNA samples taken from the remains of a 7,000-year-old hunter-gatherer found in northwest Spain.