Following DNA's footprints makes for a fascinating journey

Written history relates exactly how people of European ancestry came to be living in Australia or North America. But how did the Chinese come to be in China, the Indians in India, and the Australian Aborigines in Australia? This fascinating book, by deducing ancient human migration patterns from a study of the DNA of present populations, offers new answers to these old questions.

For over century, ethnographers seeking to understand the histories of different human groups relied on the evidence of old bones and pottery, together with what was shown by language. But for the last 20 years a molecular study of living people has provided a different kind of evidence. Central to such research are what are called "markers" in the Y-chromosomes carried by all males. These are mutations that have occurred at a particular point in time in a single male individual, and are subsequently passed down from father to son. They have been numbered, and a discussion of the significance of the M45, the M175 and so on, all nowadays very extensive, is at the heart of this intriguing book.

It was demonstrated a decade ago by the same means that, astonishing as it may seem, all human beings descend from a single woman, a primordial "Eve," who lived in Africa around 150,000 years ago. Now it is possible to trace the histories of the various human subgroups, and so piece together an understanding of when they migrated from Africa to where their core populations are still found today.

This line of research demonstrates, for instance, that Australia's Aborigines arrived in Australia along a route following the coast of southern Asia 60,000 years ago, long before the present inhabitants of most of Asia got to where they are.

The population of modern Europe, too, can be shown to have arrived, not by a seemingly direct route from Africa via the Middle East, but from Central Asia, and at a comparatively recent date.

The Chinese are shown to have almost certainly arrived in China in two streams, one north of the Himalayas, the other south. Chromosome marker differences can still be detected that separate many inhabitants of northern China from their southern counterparts.

As for the Native American populations, north and south of the equator, it's likely these arrived, crossing from Siberia to Alaska, in two waves. The first penetrated to the south, while the second was content to remain in the north. But neither population is likely to have been in the Americas longer than 15,000 years. And it is quite possible they all descend from a few dozen, or at most one or two hundred, founding individuals.

Many other things are demonstrated by this research. The successful extraction in 1997 of DNA sequences from Neanderthal remains, for instance, proves beyond doubt that this was a separate species from modern man. The claim that Europeans evolved separately, from part-Neanderthal ancestors, is here finally put to rest.

With regard to Europeans, the key marker here is the M137, dated as originating around 30,000 years ago. It is found with exceptional frequency in modern Irish and Basque populations, suggesting the earliest migrants moved, or were later pushed, furthest west.

Nineteenth century studies in language confirm this. Basque, for example, is unrelated to any other European language.