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ADAM lived tens of thousands of years after Eve, say geneticists. An extensive analysis of men鈥檚 Y chromosomes suggests that the 鈥渇ather鈥� of humankind is far younger than our mother.

Thanks to two genetic quirks, geneticists can trace our maternal and paternal lineages separately. The energy-producing structures in our cells, mitochondria, contain DNA and are inherited solely from our mother. In contrast, the Y chromosome, which contains the genes for 鈥渕aleness鈥�, is inherited only from fathers.

Genetic analysis of mitochondrial DNA sequences has revealed that all modern human mitochondria are derived from a single maternal ancestor-鈥渕itochondrial Eve鈥�-who lived around 140,000 years ago. This doesn鈥檛 mean that there was only one woman around at the time, just that all the descendants of other women with different mitochondria have died out.

Now Peter Oefner of Stanford University in California and a team of international researchers have traced humankind鈥檚 founding father. They analysed the Y chromosome of more than a thousand men from 21 different regions of the world with an unprecedented level of precision, looking at differences as small as one DNA letter at 167 sites on the chromosome.

Surprisingly, they found that 鈥淵-chromosome Adam鈥� lived much later than mitochondrial Eve-around 50,000 to 70,000 years ago. 鈥淚 expected that the mitochondria and Y would have had similar histories,鈥� says Oefner. 鈥淚t鈥檚 a striking difference.鈥�

What the finding doesn鈥檛 explain is why the modern Y chromosome lagged behind its mitochondrial mate in establishing dominance, or how it succeeded. Oefner says it is possible that some variation of the Y emerged that gave the men who had it an advantage, such as increased fertility or a larger size. Alternatively, he speculates that the victorious Y emerged in a family that made an important technological discovery.

The Y-chromosome analysis should greatly add to our understanding of how world populations have developed. The researchers have drawn up a human family tree based on the results (see below). Their findings support the 鈥淥ut of Africa鈥� theory, suggesting modern humans began migrating from Africa to Asia and beyond 44,000 years ago.

Oefner says the results emphasise the closeness of all humanity. 鈥淢ore than ever, this means we are all sitting in the same boat,鈥� he says.