Rowan Hooper

MODERN humans emerged just once out of Africa - and headed straight for the coast. That's the conclusion from genetic research suggesting that our love for the beach was evident early on

It is widely accepted that modem humans left Africa relatively recently, and most researchers thought that the route was northwards, overland into the Middle East and beyond. But by measuring genetic variation in an isolated population in south-east Asia, Vincent Macaulay at the University of Glasgow in the UK and his team conclude that the dispersal happened via a more southerly route.

"It looks likely that a founder population crossed the Red Sea and spread to Australia via India and south-east Asia, taking a southern route along the coast," says Macaulay (see Graphic). The team analysed mitochondrial DNA (mtDN A) from 260 members of the Orang Asli people, an isolated population who live in Malaysia and whose ancestors were the original inhabitants of the Malay peninsula.

By comparing their samples with mtDNA from people in Eurasia and Australasia Macaulay's team could work out when the migration out of Africa happened, based on the accumulation of mutations in the DNA. They calculate that the first humans arrived in Malaysia around 65,000 years ago. At this time the northern route out of Africa, over the Sinai peninsula and across northern Arabia, was covered by desert, which early humans would probably have found impossible to cross.

"The southern route has been seen as just another route taken by anatomically modem humans out of Africa," says Macaulay," but we are proposing that it is the only route to explain the mtDNA evidence." After reaching Malaysia, a group that would eventually settle Europe branched away, but the main dispersal group made a speedy onward journey to Australia, reaching it only a few thousand years later (Science, vol 308, p 1034).

The work clears up a question that has troubled anthropologists: how did modern humans from Africa populate distant Australia long before nearby Europe? The oldest human remains in

Australia were found at Lake Mungo, in the Willandra Lakes world heritage area in New South Wales. They date from 46,000 to 50,000 years ago, fitting neatly with the new genetic data.

Meanwhile, the oldest European human remains were reported this week from the Mladec caves in Moravia in the Czech Republic (Nature, vol 435, p 332). Eva Wild and colleagues at the Vienna Environmental Research Accelerator laboratory in Austria used radioactive carbon dating to date the remains at 31,000 years old.

If the migrants had looped northwards to Turkey to avoid the desert they should have left archaeological evidence there, says Peter Forster of the McDonald Institute for Archaeological Research at the University of Cambridge. "By default, the southern route makes more ecological sense."

The southern coastal route might have made nutritional sense, too. In 2000 evidence emerged that people living on the coast of the Red Sea in what is now Eritrea caught fish and shellfish. This may have made the coastal route attractive, says Macaulay. "It's even possible that the motivation for expanding eastwards was declining fish stocks in the Red Sea at the time of the glacial maximum, around 70,000 years ago." •

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