African Ancestry or Neanderthal-Human Genetic Admixture in Eurasians? African Diversity Matters.

Summary

Neanderthal and Denisovan genetic admixture with Eurasian modern humans, and a "signature" of Neanderthal admixture in African populations, are widely accepted "facts". Inferences of admixture are based mainly on the assumption that Yoruba, San and/or Pygmy populations contain all African genetic variation. Variants shared among Neanderthals and modern Eurasians, but not present in these Africans, are assumed to reflect 2-4% admixture. However, genetic diversity and geographic structure are greater in Africa than Eurasia, so small samples are inadequate. Non-African ancestry lies in northern and eastern Africa. Therefore, excluding northeast African genomes automatically identifies them as "admixed" rather than as descendants of the common ancestors of Eurasians and northern/eastern Africans. For example, the Maasai of Kenya appear to have 1-3% neanderthal admixture. How much would inferred archaic admixture with Eurasians be reduced by including Eastern and Northern Africans in admixture analyses? Adding Dinka from South Sudan to Yoruba and Pygmy data sets reduces Neanderthal admixture in modern French genomes from 2% to 1.3%. Conversely, using only Yoruba or Pygmy genomes increases estimates of Neanderthal admixture in Eurasians. Admixture should be considered unproven until more populations are used to ascertain African genomic diversity, and the alternative hypothesis of common ancestry is evaluated.

This Resource is Part of the Following Collections

• Society for American Archaeology 82nd Annual Meeting, Vancouver, BC (2017)

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Record Identifiers

Abstract Id(s): 16040