Yes, we are still evolving. And one of the strongest examples of recent evolution in people has been found on the Cape Verde islands in the Atlantic, where a gene variant conferring a form of malaria resistance has become more common.
Portuguese voyagers settled the uninhabited islands in 1462, bringing slaves from Africa with them. Most of the archipelago鈥檚 half a million inhabitants are descended from these peoples.
Most people of West African origin have a variant in a gene called DARC that protects against malaria. This gene codes for a receptor that malaria parasites exploit to get inside cells; the variant reduces receptor levels.
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Amy Goldberg at Duke University in North Carolina and her colleagues analysed data on gene variants in 564 Cape Verdeans collected by another team. They found that around half the people on the outer islands have the protective DARC variant.
However, on the more densely populated main island of Santiago, where there have been many malaria outbreaks over the centuries, about 80 per cent of people have the variant. Here, the protective variant is more common than other variants of West African origin, showing there has been strong selection for it.
Read more: How to think about鈥� Evolution
The local population鈥檚 resistance to malaria has long been noticed, the researchers point out. After visiting the islands in 1721, reported that, during the rainy season, a disease in Santiago is 鈥渄angerous to strangers鈥�.
The strength of selection for a particular gene variant 鈥� how fast a beneficial gene variant spreads per generation 鈥� can be calculated, and is called the selection coefficient. 鈥淲e estimate the selection coefficient is approximately 0.08, one of the highest inferred in humans,鈥� the researchers write.
鈥淚f correct, a selection coefficient of 0.08 would be among the highest identified,鈥� says Sharon Grossman at the Broad Institute in Massachusetts, who wasn鈥檛 involved in the research.
By comparison, selection coefficients are estimated to be between 0.02 and 0.14 for the lactase tolerance variants that allows adults to digest milk, says Grossman. For the sickle cell variants that also convey malaria resistance, they are between 0.05 and 0.18.
Researchers have found many other examples of recent human evolution. For instance, we also appear to be evolving to drink less alcohol.
Goldberg declined to discuss the findings until the paper has been peer reviewed and accepted for publication in a scientific journal.
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