Human Evolution Proceeding

Every so often, someone repeats the claim or assumption that human evolution has essentially stopped because human culture and technology have so reduced environmental pressures on human survival (for example, by helping infants survive who wouldn't have made it in the past). This claim is false, and demonstrably so.

The Economist reports studies of human genomes around the world:

The team identified several hundred genes that had undergone recent selection in at least one of the populations being studied. Some were not surprising. Genes involved in the generation of sex cells, and in fertilisation, are known from other work to have strong selective pressures on them, and those pressures clearly continue in modern humans. Nor was it much of a shock to discover selection, in Europeans, for changes in four skin-pigmentation genes known to be involved in reducing melanin content.

Perhaps the most intriguing results were those connected with food metabolism. The gene for alcohol dehydrogenase is undergoing selection in Asia, as is that for processing sucrose (table sugar). Meanwhile, the genes for processing two other sorts of sugar, lactose (found in milk) and mannose (found in some fruit) are changing in Europeans and Yoruba respectively. Fatty-acid metabolism, too, is changing in all three populations. And Europeans are having the toxin-disposal systems in their livers modified.

Some brain genes are also changing, including two that control the size of brains, and two involved in susceptibility to Alzheimer’s disease. And three genes that control bone growth have been modified in Europeans and East Asians, while the Yoruba have seen changes in genes that control hair growth.

Researchers don’t know what all of this means or where exactly human evolution is going, but it’s absolutely clear that human evolution is moving and that changes are occurring. Our technology and culture don’t prevent environmental pressures from acting on us, they just change what sorts of pressures exist and what direction in which they push us.

 

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