Response to Hellenthal et al.:

To the editor: In our paper “The Kalash Genetic Isolate: Ancient Divergence, Drift, and Selection,” we reported that the Kalash people of present-day Pakistan experienced no detectable gene flow from their geographic neighbors in Pakistan, or from the other extant western Eurasian populations tested, since their split from a common ancestor.1 It is probably true that no human population is completely cut off from all others, but populations with limited gene flow to and from the outside, especially when combined with a small effective population size and increased genetic drift, endogamous practices, and a different admixture history from neighboring populations, are commonly described as “isolates.” All these features are observed in the Kalash.

Source: The American Journal of Human Genetics - February 4, 2016 Category: Genetics & Stem Cells Authors: Qasim Ayub, Massimo Mezzavilla, Luca Pagani, Marc Haber, Aisha Mohyuddin, Shagufta Khaliq, Syed Qasim Mehdi, Chris Tyler-Smith Tags: Letters to the Editor Source Type: research