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The path taken out of Africa by early Homo sapiens may have had a scenic ocean view, a new genetic analysis suggests. The results, published today in the journal Science, indicate that our forebears followed a southern route along the coast and into Southeast Asia, instead of a northern route overland through the Middle East as previous theories held.
Researchers use mitochondrial DNA (mtDNA) from present-day humans to determine when populations diverged by considering the amount of variation as a measure of time. Greater variation is taken to mean that the populations have spent more time apart. Vincent Macaulay of the University of Glasgow and his colleagues analyzed mtDNA from 260 individuals from an isolated group in Malaysia known as the Orang Asil, which translates as "original people." Their findings indicate that there was a single migration of modern humans out of Africa, through India and into Southeast Asia and Australasia. This dispersal began more than 65,000 years ago and lasted only a few thousand years, the scientists say. An offshoot of these migrants later populated Europe and the Near East.
In a second related study, researchers led by Kumarasamy Thangaraj of the Center for Cellular and Molecular Biology in India studied the mtDNA from inhabitants of the Andaman and Nicobar Islands. Located between India and Myanmar, the islands are populated by six indigenous tribal groups. The scientists report that two lineages on the Andaman Islands evolved independently of other South and Southeast Asian populations and have most likely survived since the first out-of-Africa migration by anatomically modern humans. The Nicobarese, in contrast, are more closely related to other populations in Southeast Asia, which suggests that they arrived from the east within the past 18,000 years.