It took 7 years and 16,000 ancient genomes to rewrite this theory

Pulling off a study this size took years of groundwork. The Reich Lab at Harvard Medical School spent roughly seven years building a large collection of ancient DNA sequences from people who once lived across West Eurasia, covering what is now Europe and parts of the Middle East.

Getting to this scale required essentially industrialising the process of ancient DNA research, using automated systems to extract genetic material from old bone fragments, clean it and prepare it for sequencing on a scale that simply was not possible before. The resulting dataset of nearly 16,000 ancient human genomes is said to double the size of existing ancient human DNA research.

The effort paid off. Published in the journal Nature under the title ‘Ancient DNA reveals pervasive directional selection across West Eurasia,’ the study found that natural selection did not slow down once humans invented medicine, built cities and started farming, as long believed. Instead, it sped up, reshaping 479 gene variants tied to everything from disease risk to basic survival.

According to lead researcher David Reich, this research essentially allows scientists to assign a specific place and time to the evolutionary forces that have shaped modern humans, something that was largely out of reach before this scale of ancient genomic data became available.

Image: Wikimedia Commons/by Biswarup Ganguly