Pitfalls of the geographic population structure (GPS) approach applied to human genetic history: A case study of ashkenazi jews

Abstract

In a recent interdisciplinary study,Das et al. have attempted to trace the homeland ofAshkenazi Jews and of their historical language, Yiddish (Das et al. 2016. LocalizingAshkenazic Jews to Primeval Villages in the Ancient Iranian Lands ofAshkenaz.Genome Biol Evol. 8:1132-1149). Das et al. applied the geographic population structure (GPS) method to autosomal genotyping data and inferred geographic coordinates of populations supposedly ancestral to Ashkenazi Jews, placing themin Eastern Turkey. They argued that this unexpected genetic result goes against the widely acceptednotion ofAshkenazi origin in the Levant, and speculated that Yiddishwas originally a Slavic language strongly influenced by Iranian and Turkic languages, and later remodeled completely under Germanic influence. In our view, there aremajor conceptual problems with both the genetic and linguistic parts of thework.Weargue that GPS is a provenancing tool suited to inferring the geographic region where a modern and recently unadmixed genome is most likely to arise, but is hardly suitable for admixed populations and for tracing ancestry up to 1,000 years before present, as its authors have previously claimed. Moreover, all methods of historical linguistics concur that Yiddish is a Germanic language, with no reliable evidence for Slavic, Iranian, or Turkic substrata.