title: Apparent variation in Neanderthal admixture among African populations is consistent with gene flow from Non-African populations.
abstract: Recent studies have found evidence of introgression from Neanderthals into modern humans outside of sub-Saharan Africa. Given the geographic range of Neanderthals, the findings have been interpreted as evidence of gene exchange between Neanderthals and modern humans descended from the Out-of-Africa (OOA) migration. Here, we examine an alternative interpretation in which the introgression occurred earlier within Africa, between ancestors or relatives of Neanderthals and a subset of African modern humans who were the ancestors of those involved in the OOA migration. Under the alternative model, if the population structure among present-day Africans predates the OOA migration, we might find some African populations show a signal of Neanderthal introgression whereas others do not. To test this alternative model, we compiled a whole-genome data set including 38 sub-Saharan Africans from eight populations and 25 non-African individuals from five populations. We assessed differences in the amount of Neanderthal-like single-nucleotide polymorphism alleles among these populations and observed up to 1.5% difference in the number of Neanderthal-like alleles among African populations. Further analyses suggest that these differences are likely due to recent non-African admixture in these populations. After accounting for recent non-African admixture, our results do not support the alternative model of older (e.g., >100 kya) admixture between modern humans and Neanderthal-like hominids within Africa.
authors.affiliation: Department of Genetics, Rutgers, The State University of New Jersey.
authors.forename: Shuoguo
authors.initials: S
authors.lastname: Wang
authors.forename: Joseph
authors.initials: J
authors.lastname: Lachance
authors.forename: Sarah A
authors.initials: SA
authors.lastname: Tishkoff
authors.forename: Jody
authors.initials: J
authors.lastname: Hey
authors.forename: Jinchuan
authors.initials: J
authors.lastname: Xing
mesh_terms: D017954:Africa South of the Sahara; D000818:Animals; D044383:Black People / Q000235:genetics*; D019143:Evolution, Molecular; D051456:Gene Flow; D006801:Humans; D059125:Neanderthals / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide
keywords: Neanderthal admixture; human evolution; whole-genome sequencing