As we all know, prior to the introduction of this study, admixture was only thought to be found in non-African ancestry with at least 2% of derived Neanderthal genes found in European populations while Oceanic populations having an additional 2%-4% of ancestry attributed to the Denisovans. Previous approaches, such as S*(Plagnol and Wall, 2006; Vernot and Akey, 2014), CRF (Sankar-araman et al., 2014), diCal-admix (Steinru ̈cken et al., 2018),and HMM (Skov et al., 2018), used an ‘‘unadmixed’’ modern reference panel of an African population as a c control for false positives resulting in masking the Neanderthal introgressed sequence in African populations. How this study differs is that the contributors applied a method called IBDmix (Identity by descent) to exclude the African reference panel used in prior studies from collected genotypes from Eurasia, African and American populations using only an Archaic reference genome to then calculate the amount of probability at a variant site in modern individuals.
Results show that samples from North African populations show an average of 17Mb of Neanderthal sequence and 1.2Mb Denisovan sequences in African individuals. With significant overlap of Neanderthal identified sequencing Africans populations show a sharing of more than 94% of the Neanderthal sequence between non-African populations. Two demographic models were tested to determine if a signal could be detected by an IBDmix, i.e. Neanderthal sequence via hybridity, migrating back to Africa or an early pre out of Africa dispersal. Yields show that both pre-OOA human-to-Neanderthal gene flow and elevated historic back migration contribute to the signal of Neanderthal ancestry detected in Africans.
Warrenkevin Henderson
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