Thursday, January 30, 2020

Identifying and Interpreting Apparent Neanderthal Ancestry in African Individuals

Lu Chen, Aaron B. Wolf, Wenqing Fu, Liming Li, Joshua M. Akey
January 30, 2020


• IBDmix detects archaic ancestry without using a modern human reference population

• African individuals have a stronger Neanderthal ancestry signal than previously thought

• Evidence of back-to-Africa migrations contributing to Neanderthal ancestry in Africans

• Variation in non-African Neanderthal ancestry has been overestimated


Admixture has played a prominent role in shaping patterns of human genomic variation, including gene flow with now-extinct hominins like Neanderthals and Denisovans. Here, we describe a novel probabilistic method called IBDmix to identify introgressed hominin sequences, which, unlike existing approaches, does not use a modern reference population. We applied IBDmix to 2,504 individuals from geographically diverse populations to identify and analyze Neanderthal sequences segregating in modern humans. Strikingly, we find that African individuals carry a stronger signal of Neanderthal ancestry than previously thought. We show that this can be explained by genuine Neanderthal ancestry due to migrations back to Africa, predominately from ancestral Europeans, and gene flow into Neanderthals from an early dispersing group of humans out of Africa. Our results refine our understanding of Neanderthal ancestry in African and non-African populations and demonstrate that remnants of Neanderthal genomes survive in every modern human population studied to date.

No comments: