Movin' On Up

Up out of Africa, that is, according to this study:

By studying the DNA of an ancient people in Malaysia, a team of geneticists says it has illuminated many aspects of how modern humans migrated from Africa.

The geneticists say there was only one migration of modern humans out of Africa; that it took a southern route to India, Southeast Asia and Australia; and that it consisted of a single band of hunter-gatherers, probably just a few hundred people strong.

Because these events occurred in the last Ice Age, when Europe was at first too cold for human habitation, the researchers say, it was populated only later, not directly from Africa but as an offshoot of the southern migration. The people of this offshoot would presumably have trekked back through the lands that are now India and Iran to reach the Near East and Europe.

The findings depend on analysis of mitochondrial DNA, a type of genetic material inherited solely through the female line. They are reported today in Science by a team of geneticists led by Dr. Vincent Macaulay of the University of Glasgow.

Everyone in the world can be placed on a single family tree, in terms of their mitochondrial DNA, because everyone has inherited that piece of DNA from a single woman, the mitochondrial Eve, who lived some 200,000 years ago.

There were, of course, many other women in that ancient population. But over the generations, one mitochondrial DNA replaced all the others through the process known as genetic drift.

With the help of mutations that have built up on the one surviving copy, geneticists can arrange people in lineages and estimate the time of origin of each lineage.

With this approach, Dr. Macaulay's team calculates that the emigration from Africa occurred 65,000 years ago, pushed along the coasts of India and Southeast Asia and reached Australia by 50,000 years ago, the date of the earliest known archaeological site there.

The Malaysian people whom the geneticists studied are the Orang Asli. The term means "original men" in Malay.

They are probably descended from this first migration, because they have several ancient mitochondrial DNA lineages that are found nowhere else.

These lineages are 42,000 to 63,000 years old, the geneticists say. Subgroups of the Orang Asli, like the Semang, have probably been able to remain intact because they adapted to the harsh existence of living in forests, said Dr. Stephen Oppenheimer, the member of the geneticists' team who collected blood samples in Malaysia.

Is it me, or is there a flaw in this approach?

The likelihood that a tiny band of several hundred could wander over thousands of miles of harsh terrain, engaging in dangerous hunting with primitive weapons, subject to the whims of their environment, just strikes me as off.

Moreover, haven't these geneticists made a basic error in assuming that just because a certain lineage of mitochondrial DNA doesn't exist today it never existed at all? Wouldn't lineages die out all the time, especially those of isolated groups making the first exoduses out of Africa?