Recent convergent evolution in humans

Tishkoff, et al. have found small genetic differences responsible for lactose persistence (the ability to digest milk as an adult) in some African populations. This ability is well known among some European populations. However, the mutations underlying lactose persistence among Europeans is different than those among Africans. Two populations struck upon two solutions to the same problem, known as convergent evolution.

What’s nice about this study is that the authors knew what they were looking for: other populations that domesticated milk-producing animals had adapted to take advantage of milk as a food source, so it was likely that these populations would have as well. In both cases, the selection of the alleles in question coincide with the introduction of milk-culture.

I like the methodology of this study, in contrast to other findings about recent selective sweeps in the human lineage, such as Microcephalin 1 and ASPM, which took a purely algorithmic approach to identifying gene candidates. Here, the authors were looking for genes that associated with a specific phenotypic function, rather than for any gene that had undergone recent selection.

Also, the ability to digest milk is a little more everyday; we know that not all adults can do it, so it is a nice story for talking about how evolutionary processes caused some of those small differences between us.