Genetic Map of Europe Features the Lactase Mutation

All regular readers of this blog should know by know that the ability to continue drinking milk as an adult is the result of a mutation. The mutated gene never sends the signal to turn off lactase production at about the age of weaning. Humans have probably always occasionally had this mutation, but it didn't start to spread through the population until dairying started, a known 8000 years ago and probably earlier than that.

The mutation spread from the Middle East up into and across Europe. Since historically, the majority of white Americans had ancestors from northern and western Europe, the areas where the mutation was most prevalent, Americans inherited the European's dairy culture.

Huge amounts of investigation of DNA have more precisely traced those pathways, and the spread of the lactose tolerance gene is one of the best studied subjects in modern genetics.

Genomic sites that carry the strongest signal of variation among populations may be those influenced by evolutionary change, Dr. Kayser said. Of the 100 strongest sites, 17 are found in the region of the genome that confers lactose tolerance, an adaptation that arose among a cattle herding culture in northern Europe some 5,000 years ago.

That's from an article by Nicholas Wade in The New York Times, which has a very cool map in it.



The map comes from an article that will appear in next week's Current Biology, "Correlation between Genetic and Geographic Structure in Europe," by Oscar Lao, et al.

Wade wrote:

The map also identifies the existence of two genetic barriers within Europe. One is between the Finns (light blue, upper right) and other Europeans. It arose because the Finnish population was at one time very small and then expanded, bearing the atypical genetics of its few founders.

The other is between Italians (yellow, bottom center) and the rest. This may reflect the role of the Alps in impeding free flow of people between Italy and the rest of Europe.