GoKawiilSome gene variants became consistently more or less frequent over time in ancient human populations — a sign of natural selection. Credit: Denis-Art/Getty
The biggest ever study of ancient human DNA shows that human evolution has accelerated over the past 10,000 years.
Researchers identified hundreds of gene variants that evolved through natural selection in ancient people from western Eurasia — Europe and the Middle East — after the dawn of agriculture. Changes to these genes had widespread ramifications for the health of present-day populations.
“We are seeing dramatic changes,” says David Reich, a population geneticist at Harvard Medical School in Boston, Massachusetts, who co-led the 15 April Nature study1. However, some researchers remain unconvinced by the scale of the findings and results that show natural selection has affected gene variants underlying highly complex traits, such as mental illness and cognition.
Adapting to agriculture
Homo sapiens emerged in Africa around 200,000 to 300,000 years ago, before expanding to nearly every corner of the planet. The advent of farming introduced new foods, pathogens and other challenges, as people began living in larger groups and in closer proximity to animals.
Humans clearly adapted to these upheavals. But genomic studies of present-day and ancient people have uncovered only a smattering of genetic signs of natural selection, particularly for advantageous genes that have surged to high frequency, or ones that have proved to be harmful and become less common.
The best‑known example of such ‘directional selection’ is a genetic variant that maintains production of the lactose enzyme into adulthood, which enables many people of European ancestry to digest milk throughout their lives.
‘Truly gobsmacked’: Ancient-human genome count surpasses 10,000
To supercharge the search, Reich, Ali Akbari, a computational geneticist at Harvard Medical School, and their colleagues amassed the largest-ever collection of genomic data from ancient humans — from a total of 15,836 individuals from western Eurasia — including more than 10,000 newly sequenced genomes.
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