Study Shows Mixing Between Prehistoric Populations of Europe and Africa

Study presents solid genetic evidence of gene flow between prehistoric Africa and Europe that occurred more than 11,000 years ago.
Scientists already know from genetic evidence that human populations of Africa and Europe mixed in ancient times, from the days of the Roman Empire through to the slave trade of the colonial period. But evidence of any mixing prior to that has been comparatively less abundant. Now, researchers conclude from a recently completed study (published online on March 27, 2012 in Genome Research) that genetic material was exchanged between Europe and Africa as far back as 11,000 years ago, or more.

"It was very surprising to find that more than 35 percent of the sub-Saharan lineages in Europe arrived during a period that ranged from more than 11,000 years ago to the Roman Empire times," said senior study author Dr. Antonio Salas of the University of Santiago de Compostela. The other 65% of European lineages showing African lineage represent population groups that arrived more recently.

The researchers analyzed and compared mtDNA genome sequences from different regions of Europe with that of other groups around the world. During this process they analyzed the mtDNA genomes of "haplogroup L", (a lineage of sub-Saharan African origin) in Europe. Because small changes occur over long periods of time in the mtDNA sequence of different populations, geneticists can use the changes as "markers" that hint at movements and migrations of human groups in the past, classifying them into distinct "haplogroups." For the first time, researchers were able to identify abundant traces from prehistoric times indicating contact and exchange between European and African populations long before the advent of the civilizations of recorded history.

How and why, then, did this occur?

The authors infer that these contacts were likely made via movements to and from North Africa over both land connections and coastal routes, possibly as groups in Europe migrated south because of expanding glaciation of the Ice Age, producing southward pressure on populations, and returning northward as glaciation receded. The mixing thus may have occurred in tandem with the ebb and flow of the Ice Age glacial movements.
The researchers also anticipate that their genetics studies will help individuals who want to learn more about their own ancestry. "There is a growing interest in direct-to-consumer genetic testing, including those aimed to serve a public interested in reconstructing their ancestry," says Salas. "Studies like the one presented here will help to unravel inferences made in these studies."

Scientists from the University of Santiago de Compostela (Galicia, Spain), the University of Perugia (Perugia, Italy), the University of Pavia (Pavia, Italy), the Sorenson Molecular Genealogy Foundation (Salt Lake City, UT), the University of Oxford (Oxford, UK), and the National Institute of Toxicology and Forensic Science (Sevilla, Spain) contributed to this study.

The study is published in Genome Research as: Cerezo M, Achilli A, Olivieri A, Perego UA, Gómez-Carballa A, Brisighelli F, Lancioni H, Woodward SR, López-Soto M, Carracedo Á, Capelli C, Torroni A, Salas A. Reconstructing ancient mitochondrial DNA links between Africa and Europe. Genome Res doi: 10.1101/gr.134452.111.
http://popular-archaeology.com/issue/march-2012/article/study-shows-mixing-between-prehistoric-populations-of-europe-and-africa
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