economist on evolution: more blows to witzel et al

dec 20th

i'm afraid this link is premium content, but it clearly states that the evidence from genetics precludes an 'aryan' invasion of india in 1500 BCE. the first human migration to india is around 60,000 years ago, and europe was populated much later.

however, there are elements of 'conquest' still in the theories about india, see end of the excerpts below about female and male dna. this sounds like 'aryan tourist theory' (trademarked by me) warmed over, and i am sceptical about it. southerners ki jai :-)

TM 'aryan tourist theory': white guys go live in other countries on tourist visas, marry local women and settle down. thus their genes appear in the local population.

http://www.economist.com/surveys/displaystory.cfm?story_id=E1_VNJJNDJ

excerpts only, to protect the economist's copyright. it has a great chart too.

Detail, however is not the same as consensus, and there are two schools of thought about how people left Africa in the first place. Appropriately, some of their main protagonists are at the rival English universities of Oxford and Cambridge. The Oxford school, championed by Stephen Oppenheimer, believes that the descendants of a single emigration some 85,000 years ago, across the strait of Bab el Mandeb at the southern end of the Red Sea, are responsible for populating the rest of the world. The Cambridge school, championed by Robert Foley and Marta Mirazón Lahr, agrees that there was, indeed, a migration across this strait, though probably nearer to 60,000 years ago. However, it argues that many non-Africans are the descendants of at least one subsequent exodus.

Both schools agree that the Bab el Mandebites spread rapidly along the coast of southern Arabia and thence along the south coast of Asia to Australia, though Dr Oppenheimer has them turning inland, too, once they crossed the strait of Hormuz. But it is in describing what happened next that the two versions really part company, for it is here that the descendants of the Oxford migration run into the eruption of Toba.

That Toba devastated South and South-East Asia is not in doubt. Thick layers of ash from the eruption have been found as far afield as northern Pakistan. The question is whether there were people in Asia at the time. One of the most important pieces of evidence for Dr Oppenheimer's version of events is some stone tools in the ash layer in Malaysia, which he thinks were made by Homo sapiens. Molecular clocks have a regrettable margin of error, but radioactive dating is a lot more accurate. If he is right, modern humans must have left Africa before the eruption. The tools might, however, have been crafted by an earlier species of human that lived there before Homo sapiens.

For Dr Oppenheimer, the eruption was a crucial event, dividing the nascent human population of Asia into two disconnected parts, which then recolonised the intermediate ground. In the Cambridge version, Homo sapiens was still confined to Africa 74,000 years ago, and would merely have suffered the equivalent of a nuclear winter, not an ash-fall of up to five metres—though Dr Ambrose and his colleagues think even that would have done the population no good.

The Cambridge version is far more gentle. The descendants of its subsequent exodus expanded north-eastwards into central Asia, and thence scattered north, south, east and west—though in a spirit of open-mindedness, Sacha Jones, a research student in Dr Foley's department, is looking in the ash layer in India to see what she can find there.

Both also agree that Europe received two waves of migration. The ancestors of the bulk of modern Europeans came via central Asia about 35,000 years ago, though some people in the Balkans and other parts of southern Europe trace their lines back to an earlier migration from the Middle East. But the spread of agriculture from its Middle Eastern cradle into the farthest reaches of Europe does not, as some researchers once thought, seem to have been accompanied by a mass movement of Middle Eastern farmers.

The coming together of two groups of humans can be seen in modern India, too. In the south of the subcontinent, people have Y-chromosomes derived almost exclusively from what the Cambridge school would interpret as being northern folk (and the Oxford school as the western survivors of Toba). However, more than 20% of their mitochondria arrived in Asia with the first migration from Africa (or, according to taste, clung on along the south-eastern fringes of the ash plume).

That discovery speaks volumes about what happened when the two groups met. It suggests that many modern south Indians are descended from southern-fringe women, but few from southern-fringe men—implying a comprehensive conquest of the southerners by the northerners, who won extra southern wives.