LONDON, May 12 - Like bank holiday trippers, the first modern humans who migrated from Africa probably headed for the seaside, new research suggests.
Genetic evidence points to a migration route from East Africa that followed the coast of the Indian Ocean.
Scientists had previously thought the exodus took place northward along the Nile and across the Sinai peninsula to Europe and Asia.
The new theory might explain why Europe appears to have been settled thousands of years later than Australia.
In Europe, indigenous Neanderthals were replaced by the ancestors of modern humans only about 30,000 to 40,000 years ago.
But southern Australia is known to have been inhabited by early modern humans 46,000 years ago, and northern Australia and south-East Asia even earlier.
Scientists plot early human migrations by studying mitochondrial DNA (mDNA) - a kind of DNA only inherited maternally - in people living today.
The degree of variation among the mDNA of different groups reflects the amount of time that has elapsed since they diverged from each other.
Two different teams writing in the journal Science use this approach to support the coastal route hypothesis.
One study, led by Vincent Macaulay, of the University of Glasgow, focused on the aboriginal Orang Asli people of Malaysia.
DNA analysis suggests they are descended from a founder'' population that arrived about 60,000 years ago, soon after their ancestors left Africa. Macaulay's team estimated that the dispersal of early humans along the 12,000km coast of the Indian Ocean took place very rapidly, at up to 4km per year. Population modelling suggested that several hundred founder’’ females joined the original migration out of Africa.
``The main dispersal from India to Australia (about) 65,000 years ago was rapid, most likely taking only a few thousand years,’’ the researchers wrote.
The other team led by Kumarasamy Thangaraj, of the Centre for Cellular and Molecular Biology in Hyderabad, India, looked at tribal populations on the Andaman and Nicobar islands.
The islands lie between India and Burma.
Two old populations of Andaman islanders were identified that are thought to have survived in genetic isolation since the out-of-Africa migration.
These people also appeared to have a history going back 60,000 years. In contrast, Nicobarese populations shared a genetic connection with other South-East Asian populations dating back just 15,000 years.