Genetic Map of Europe

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Biologists have constructed a genetic map of Europe showing the degree of relatedness between its various populations.
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The genetic map of Europe bears a clear structural similarity to the geographic map. The major genetic differences are between populations of the north and south (the vertical axis of the map shows north-south differences, the horizontal axis those of east-west).
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Data for the map were generated by gene chips programmed to test and analyze 500,000 sites of common variation on the human genome, although only the 300,000 most reliable sites were used for the map.
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lactose tolerance, an adaptation that arose among a cattle herding culture in northern Europe some 5,000 years ago. Most people switch off the lactose digesting gene after weaning, but the cattle herders evidently gained a great survival advantage by keeping the gene switched on through adulthood.
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