Bio-cultural adaptation: the example of lactose tolerance

María-Diolores Marrodán Serrano

With the development of the Neolithic culture, less than 10.000 years ago, our ancestors began to practice agriculture and to domesticate animals that provided them with milk. At the same time, the practice of the pottery allowed to manufacture containers to process and consume this drink, which is a nutritional supplement of great importance when its digestion is possible. The natural condition in our species and the rest of the mammals, is that our intestine ceases to produce lactase after the weaning period. However, in livestock societies the mutant allele that codifies for the persistence of enzymatic activity throughout life would produce an important selective advantage. Lactose tolerant individuals would see increased their availability of calories and nutrients, particularly calcium. Although certainly in those small human groups would act the genetic drift, the archaeological information and the current genetic analysis allow us to understand how the expansion of the allelic variants that confer persistence of lactase was carried out. The ability to digest milk diffused in parallel with pastoralist cultures and this phenomenon explains the great variability that lactose intolerance presents in the populations of the world.

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