Decoded: The Mystery of Human Migration

A new study aims to analyse modern DNA to track how man spread across the globe.

Saturday 31 December 2011


It is the greatest journey in history, and now the story of how the first members of our species walked out of their African homeland to colonise almost every corner of the world is being told by reading the DNA of their living descendents.

Half a million people from around the globe are participating in an ambitious project to reconstruct some of the ancient migratory routes that took Homo sapiens from their ancient African homelands to the relatively new territories of Asia, Europe, Oceania and America.

Hidden within the genetic makeup of people alive today is the encoded story of how their ancient ancestors made this epic journey, which covered many thousands of miles over many tens of thousands of years to complete.

The Genographic Project, a landmark study into ancient human migrations, aims to decode these hidden signposts within our DNA. By doing so, the project hopes to unravel the complex movements of the earliest men and women who were driven through necessity or curiosity to explore new territories and establish fresh roots in strange lands.

Human palaeontology, the study of ancient remains, suggests that the species Homo sapiens originated in Africa, probably East Africa, about 200,000 years ago, but it was only about 60,000 years ago that anatomically modern humans began their long and arduous journey out of Africa.

In recent years, with the ability to decode the human genome quickly and cheaply, it has been possible to compare the palaentological record with historical information on human movements stored within our DNA.

Over time, human DNA has amassed a bewildering variety of mutations that scientists can now exploit to build a picture of how men and women today are descended from the first people who moved along these ancient migratory routes.

One of the first big surprises of the Genographic Project, for instance, is the discovery that the initial journey out of Africa may not have been through the "northern route" of the Sinai Peninsula and Middle East, as initially proposed. Instead, they seem to have moved out of Africa by a "southern route" at the Bab-el-Mandeb straits at the mouth of the Red Sea separating East Africa from southern Arabia.

This migration may have required boats to traverse the shallow waters that would have existed there 60,000 years ago. But even with this apparent physical obstacle, scientists believe that the DNA analysis of the female X chromosome of present-day humans suggests it is still the most likely route taken out of Africa. "This was really the first study that had used that kind of genetic information to look at global patterns of human variability," said Spencer Wells, director of the Genographic Project and explorer-in-residence at National Geographic, one of the project's sponsors.

"What it confirmed was that the earliest migration out of Africa, and probably the major migration, had gone out through the Bab-el-Mandeb Strait to India. There could have been subsequent migrations out via the Middle East but certainly the majority of people trace back to that original migration event, and we're still tracing out the details of exactly what happened."

The DNA evidence shows clearly and unequivocally that Africa was the homeland of anatomically modern humans, neat, independent confirmation of the palaeontology. The genetic variation within people living in Africa, which is related to the length of time spent on the continent, is greater than all the variation in the rest of the world put together. "We see more variation in Africa than in any other group so that tells us we've been accumulating variation for longer than in any other group," Dr Wells added.

"Outside of Africa, we see more variation in India than anywhere else which tells use we've been living in India for longer than any other place outside Africa. The question is, how many waves of migration out of Africa were there, and what were the timings of those events?"

The information being gathered by the Genographic Project is starting to put dates to the key crossroads in the greatest journey of human history.

Decoded: The Mystery of Human Migration - Science - News - The Independent

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So, this should really ber titled "popular theory confirmed", but what the hell. Interesting that the southern route out of Africa now looks strong, as that does change things somewhat, and goes a long way to explaining the presence of Australian Aborigines and south-Indian Dalits. This also reinforces the idea that that however implausible it seems, humans MUST have had boats tens of thousands of years ago.