Thursday, August 27, 2009

Computing the spread of lactase persistence   posted by Razib @ 8/27/2009 08:08:00 PM

As most readers of this weblog know most humans as adults cannot digest lactose. The ability to digest lactose via the persistence of the enzyme lactase is differentially distributed. Both inferential methods and a small number of ancient genetic extractions suggest that this ability arose within the last 10,000 years. A new paper, The Origins of Lactase Persistence in Europe:
Most adults worldwide do not produce the enzyme lactase and so are unable to digest the milk sugar lactose. However, most people in Europe and many from other populations continue to produce lactase throughout their life (lactase persistence). In Europe, a single genetic variant, −13,910*T, is strongly associated with lactase persistence and appears to have been favoured by natural selection in the last 10,000 years. Since adult consumption of fresh milk was only possible after the domestication of animals, it is likely that lactase persistence coevolved with the cultural practice of dairying, although it is not known when lactase persistence first arose in Europe or what factors drove its rapid spread. To address these questions, we have developed a simulation model of the spread of lactase persistence, dairying, and farmers in Europe, and have integrated genetic and archaeological data using newly developed statistical approaches. We infer that lactase persistence/dairying coevolution began around 7,500 years ago between the central Balkans and central Europe, probably among people of the Linearbandkeramik culture. We also find that lactase persistence was not more favoured in northern latitudes through an increased requirement for dietary vitamin D. Our results illustrate the possibility of integrating genetic and archaeological data to address important questions on human evolution.

Here's a graphical illustration of their conclusion:

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