There is a fascinating article in this morning’s Washington Post relating how scientists are discovering evidence that natural selection still plays a role in the evolution of the human genome:
The research offers a fascinating snapshot into how the human genome has continued to change as humans adapted to new circumstances over the past 10,000 years. As people went from hunter-gatherers to agricultural societies, for instance, there is evidence of genetic adaptations to new diseases and diets.
Europeans seem to be adapting to the increased availability of dairy products, with genetic changes that allow the enzyme lactase, which breaks down lactose in milk, to be available throughout life, not just in infancy. Similarly, East Asians show genetic changes that affect the metabolism of the sugar sucrose, while the Yoruba people in sub-Saharan Africa show genetic changes that alter how they metabolize the sugar mannose.
Where starvation was once widespread in humans’ evolutionary history, making it genetically advantageous to conserve calories as much as possible, the abundance of food in many countries today has led to the opposite problem — risk factors and diseases related to metabolic overload, including obesity and diabetes — suggesting these could be areas in which natural selection may currently be active, as genetic variations that help protect against such disorders gain selective advantage.
Several changes seem related to fertility and reproduction, areas of very high relevance to natural selection. The basic protein structure of sperm may have changed in East Asians and the Yoruba; East Asians also show genetic changes related to sperm motility; and Europeans show genetic changes related to egg viability, fertilization and the female immune response to sperm.
As we come to have a deeper understanding of the genome, its clear that findings like this will only continue to be uncovered. And the scientific evidence in favor of human evolution will continue to mount.