Researchers looking into human evolution have developed a new technique to study more intricately the movement of humans from Africa. The study, conducted by the Wellcome Trust Sanger Institute has found that African and non-African populations continued to to exchange genetic materical well after migration out of Africa 60,000 years ago. Four male genomes were sequenced and compared: one each from China, Europe, Korea and West Africa respectively.
     "Previous methods to explore these questions using genetic data have looked at a subset of the human genome. Our new approach uses the whole sequence of single individuals, and relies on fewer assumptions. Using such techniques we will be able to capitalize on the revolution in genome sequencing and analysis from projects such as The 1000 Genomes Project, and, as more people are sequenced, build a progressively finer detail picture of human genetic history," said Dr Richard Durbin, joint head of Human Genetics and leader of the Genome Informatics Group at the Sanger Institute.
     The researchers discovered that although African and non-African populations began to differentiate as early as 100,000-120,000 years ago, they remained largely as one population until 60-80,000 years ago. Following on from this time the population of European and East Asian ancestors dropped to one-tenth of its earlier size, overlapping the period during which modern human fossils and artefacts appear across Europe and Asia.
     "This elegant tool provides opportunities for further research to enable us to learn more about population history," says co-author Heng Li, from the Sanger Institute. "Each human genome contains information from the mother and the father, and the differences between these at any place in the genome carry information about its history. Since the genome sequence is so large, we can combine the information from tens of thousands of different places in the genome to build up a composite history of the ancestral contributions to the particular individual who was sequenced."

Edited from ScienceDaily (13 July 2011)