Population Genetics of the Ashkenazim


The Ashkenazim are a well‐studied population with a dynamic and unique history. The spread of Jewish populations from the Middle East to locations in the Diaspora in the past 2000 years represents a microcosm of the evolutionary processes affecting modern humans as they dispersed out of Africa (e.g. founder effects, migrations, admixture and adaptation). Ashkenazim – Jews who trace their ancestry to founders who moved to the Rhine Valley in the fourth century – are no exception. Recent studies both support and refute long‐standing hypotheses of Ashkenazi origins. Together, the results Strengthen the inferences that Ashkenazi Jews trace their ancestry to a genetically diverse population in the Middle East that underwent a series of founder events – reducing genetic diversity relative to the ancestral population – and that subsequently experienced significant gene flow during the period of Ashkenazi residency in Europe.

Key Concepts

  • Ashkenazi Jews are genetically more similar to each other than to individuals from other populations.
  • Ashkenazi Jews are most closely related to other Jewish populations.
  • The Ashkenazim likely arose from a genetically diverse population in the Middle East.
  • Ashkenazi Jews appear equally close to both Middle Eastern and European populations.
  • Ashkenazi Jews are not closely related to modern populations that best represent the Khazars.
  • Ashkenazi Jews likely received 30–60% gene flow from Europeans.
  • Ashkenazi Jews likely underwent multiple extreme events of population size reduction and expansion.
  • About half of the genomic regions under putative selection in the Ashkenazim are not found to be under selection in Europeans.
  • Most Ashkenazi disease loci are not under strong positive selection.

Keywords: Ashkenazim; population genetics; genomics; demography; SNP array; admixture; founder effect; selection

Figure 1. Four possible models of AJ origins. Model (a) depicts a complete Middle Eastern origin with no gene flow from Europeans, with multiple population reductions and expansions. Model (b) depicts a partial Middle Eastern origin with gene flow from Europeans, and multiple population reductions and expansions. Model (c) model depicts a complete European or Turkic origin, with no ancestry from the Middle East. The time points a, b and c indicate the Out of Middle East (100–80 generations ago), out of Rome (70–50 generations ago) and eastern expansion (40–20 generations ago) events, respectively.
Figure 2. Population structure inferred by ADMIXTURE analysis. ADMIXTURE plots at K = 10. Each individual is represented by a vertical stacked column of genetic membership proportions. The Jewish groups are highlighted in red. Western Ashkenazi Jews: France, Germany and the Netherlands; Central and Eastern Ashkenazi Jews: Austria, Belorussia, Hungary, Latvia, Lithuania, Poland, Romania and Russia. Reproduced from Behar et al. © Digital Commons @Wayne State University.
Figure 3. PCA of common variants in Ashkenazim (AJ), non‐AJ Jewish, European and Middle Eastern populations. Reproduced with permission from Carmi et al. © Nature Publishing Group.
Figure 4. A diagram of a two‐population demographic model with Ashkenazim and Flemish. The diagram shows the reconstruction of the ancient history by fitting the joint allele frequency spectrum using dadi and using a mutation rate of 1.44 × 10−8 per generation per bp, and recent AJ history by fitting the IBD length decay pattern. The wide arrow represents an admixture event; all effective population sizes (horizontal arrows) are in number of diploid individuals; all times were computed assuming 25 years per generation. Adapted and reproduced with permission from Carmi et al. © Nature Publishing Group.
Figure 5. The distribution, over all pairs of individuals, of the fraction of the genome shared IBD (segment lengths >3 cM) within AJ, within Flemish (FL) or between AJ and FL. Adapted and reproduced with permission from Carmi et al. © Nature Publishing Group.


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Further Reading

Entine J (2007) Abraham's Children: Race, Identity, and the DNA of the Chosen People. New York: Grand Central Publishing.

Jacobs NA (2005) Yiddish: A Linguistic Introduction. New York: Cambridge University Press.

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Ostrer H (2012b) Legacy: A Genetic History of the Jewish People. New York: Oxford University Press, Inc.

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Gladstein, Ariella, and Hammer, Michael F(Mar 2016) Population Genetics of the Ashkenazim. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0020818.pub2]