The Kalash Genetic Isolate? The Evidence for Recent Admixture

To the editor: The recent paper “The Kalash Genetic Isolate: Ancient Divergence, Drift, and Selection,” by Ayub et al.1 suggests that the Kalash people of present-day Pakistan experienced “no detectable gene flow from their geographic neighbors in Pakistan or from other extant Eurasian populations” since their split from those populations over 8,000 years ago. They note that this finding of apparent genetic isolation contradicts the results of Hellenthal et al.,2 who inferred DNA introgression dated to 910–220 BCE in an overlapping sample of Kalash individuals. Hellenthal et al.2 inferred the (unknown) source of this DNA to have genetic similarities to a wide range of modern-day groups from West Asia and Europe, including Germany-Austria and Turkey, for example