The genetic origins of modern Europeans may be more complicated that previously thought.
Ancient people from Siberia who were related to the first humans to enter the Americas during the Ice Age also mingled with prehistoric populations in Europe and left their mark on the DNA of today's Europeans, scientists said on Wednesday.
Their study, published in the journal Nature, is the latest to use sophisticated genetic research to clarify the ancestry of modern populations.
Experts had thought today's Europeans descended from two other groups of people.
The first were primitive hunter-gatherers from western Europe who had lived on the continent since it was first colonized by our species more than 40,000 years ago. The second were farmers who migrated into Europe from a region spanning parts of Syria, Turkey and Iraq around 7,000 years ago.
The new study revealed the role of hunter-gatherers from the Siberian region who the scientists called “ancient north Eurasians.”
The scientists sequenced the genomes of a farmer who had lived in Germany about 7,000 years ago and eight hunter-gatherers who had lived in Luxembourg and Sweden about 8,000 years ago. They then compared those findings with the genomes of 2,345 people living today to decipher European ancestry.
“Our study does indeed show that European origins were more complex than previously imagined,” said Iosif Lazaridis, a postdoctoral research fellow at Harvard Medical School.
“It seems that Europeans -- who are often considered one group today -- actually have a complex history with at least three groups admixing in different proportions in their history,” Lazaridis added.
Almost all Europeans were found to have ancestry from all three of those ancient groups. The ancient north Eurasians contributed up to 20 percent of the genetics of Europeans, although this was the smallest proportion among the three ancestral groups.
People in northern Europe, especially the Baltic states, have the highest proportion of western European hunter-gatherer ancestry, with up to 50 percent of the DNA of Lithuanians coming from this group.
Southern Europeans had more of their genetic ancestry from the ancient farmers, with up to 90 percent of the DNA of Sardinians tracing back to these early European immigrants.
These farmers who came from the Near East brought new capabilities to Europe, domesticating animals including pigs and cows, growing crops including types of wheat, barley, peas and lentils, and using obsidian sickles for harvest.
Another of the researchers, Johannes Krause, a geneticist at the University of TJubingen and co-director of the Max Planck Institute for History and the Sciences in Germany, said the ancient north Eurasians “connect all modern Europeans and Native Americans.”
The findings show they not only mixed with prehistoric Europeans, but they also were related to the people who trekked more than 15,000 years ago across the frozen land bridge that once linked Siberia to Alaska and spread into the Americas.