Genetic evidence of an early exit of Homo sapiens sapiens from Africa through eastern Africa

The out-of-Africa scenario(1) has hitherto provided little evidence for the precise route by which modern humans left Africa. Two major routes of disp ersal have been hypothesized: one through North Africa into the Levant, doc umented by fossil remains(2), and one through Ethiopia along South Asia, fo r which little, if any, evidence exists(3). Mitochondrial DNA (mtDNA) can b e used to trace maternal ancestry, The geographic distribution and variatio n of mtDNAs can be highly informative in defining potential range expansion s and migration routes in the distant past. The mitochondrial haplogroup M, first regarded as an ancient marker of East-Asian origin(4,5), has been fo und at high frequency in India(6) and Ethiopia(7), raising the question of its origin. (A haplogroup is a group of haplotypes that share some sequence variations.) Its variation and geographical distribution suggest that Asia n haplogroup M separated from eastern-African haplogroup M more than 50.000 years ago. Two other variants (489C and 10873C) also support a single orig in of haplogroup M in Africa. These findings, together with the virtual abs ence of haplogroup M in the Levant and its high frequency in the South-Arab ian peninsula, render Rn the first genetic indicator for the hypothesized e xit route from Africa through eastern Africa/western India. This was possib ly the only successful early dispersal event of modern humans out of Africa .