American geneticist at Harvard University. Together with his colleague Ali Akbari, Reich developed a new statistical toolkit for analysing ancient DNA and applied it to the largest ancient-DNA dataset ever assembled: 15,836 ancient individuals of West Eurasian ancestry and 6,438 modern humans, spanning 18,000 years. The study, published in Nature on April 15th 2026, included new data for 10,016 ancient genomes, representing a doubling of the global pool of ancient DNA data and a 14-fold increase in sample size compared with previous studies of natural selection.
The results identified 479 gene variants as highly likely to have emerged through strong directional selection in the past 11,000 years—compared with just 21 previously known instances. The study suggested that a genetic signature found in roughly one in five modern-day samples, which helps the body identify pathogens but is also associated with an increased susceptibility to coeliac disease, was almost absent until around 4,000 years ago—later than the spread of agriculture. It also weakened the hypothesis that genes associated with cystic fibrosis were selected for because of resistance to cholera, finding no indication of selection during the period cholera is thought to have been endemic in West Eurasia.
The researchers identified 44 signatures of directional selection across groups of genes. Genes associated with type 2 diabetes in modern humans were selected against, as were those linked to schizophrenia and bipolar disorder. Strong directional selection appears to have intensified dramatically during the Holocene, beginning roughly 11,700 years ago. Pontus Skoglund of the Francis Crick Institute called the paper "an analytical tour de force".
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