Wednesday, February 5, 2014
When humans first left Africa some 60,000 years ago, they went on to leave their genetic footprints around the world, these same footprints have revealed that some humans decided to return to Africa, carrying genes from the rest of the world back to the continent
A new study of southern African genes reveals that a previously unknown migration took western Eurasian DNA back to continent 3,000 years ago. The study looked at the DNA of Khoisan tribes of southern Africa. The Khoisan tribes are thought to have lived in near-isolation from the rest of humanity for thousands of years. The study by Harvard University revealed that that some of their genes closely match people from modern-day southern Europe, including Spain and Italy. Researchers have now identified two migrations: One about 3,000 years ago, of non-Africans entering east Africa, and a second one 900–1,800 years ago. Dating methods suggest that the European DNA made their way into the Khoisan DNA sometime between 900 and 1800 years ago, before known European contact with the region. Meanwhile, archaeological studies of the region suggest that a subset of the Khoisan, known as the Khoe-Kwadi speakers, arrived in southern Africa from east Africa much earlier. Professor David Reich of Harvard University found that the proportion of Eurasian DNA was highest in Khoe-Kwadi tribes, who have up to 14% of western Eurasian ancestry. The recent research confirms a 2012 study by Luca Pagani of the Wellcome Trust Sanger Institute which found non-African genes in people living in Ethiopia. They found that the genomes of some Ethiopian populations bear striking similarities to those of populations in Israel and Syria, a potential genetic legacy of the Queen of Sheba and her companions. The team detected mixing between some Ethiopians and non-African populations dating to approximately 3,000 years ago.