Got Lactose Intolerance?

The New York Times has a nice, short, editorial about the complex dynamic between culture and evolution. The piece emphasizes a point in Monday’s story about a recent article in Nature analyzing lactose intolerance in Africans.

A team of scientists has now discovered that an important human genetic trait — a tolerance in adults for the milk sugar called lactose — might have developed in several East African ethnic groups 2,700 to 6,800 years ago. That is astonishingly recent.

It may also be the first genetic example of what researchers call convergent evolution in humans. In other words, lactose tolerance among African raisers of livestock arose independently of the same adaptive trait in northern European pastoralists. But there is something still more surprising about this discovery. The genetic change came about because of cultural change. The shift to cattle raising some 9,000 years ago gave an immediate survival advantage to adults who could digest milk, an ability infants usually lost as they aged.

We are used to the idea that species evolve because of changes in their natural environment. But part of the natural environment of humans is culture itself, and it is striking to think that genetic adaptation in humans has been driven, at least in part, by how humans have chosen to live.

2 thoughts on “Got Lactose Intolerance?

  1. The genetic change came about because of cultural change. You have to be careful about how to interpret this statement. The genetic mutation is just that, a mutation that occurs at random–ie. thalassemia mutations occur at random in populations outside of regions in which malaria is endemic. But while we look on lactose tolerance as a good thing, we must note that P. falciparum population explosion occured around the same time, and is likely linked to agriculture’s beginnings in the early Neolithic. Good outcomes and ill occur oftentimes under the same conditions.

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