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Abstract

Genetic admixture is central to primate evolution. We combined 50 years of field observations of immigration and group demography with genomic data from ~9 generations of hybrid baboons to investigate the consequences of admixture in the wild. Despite no obvious fitness costs to hybrids, we found signatures of selection against admixture similar to those described for archaic hominins. These patterns were concentrated near genes where ancestry is strongly associated with gene expression. Our analyses also show that introgression is partially predictable across the genome. This study demonstrates the value of integrating genomic and field data for revealing how ?genomic signatures of selection? (e.g., reduced introgression in low-recombination regions) manifest in nature; moreover, it underscores the importance of other primates as living models for human evolution. Today, humans are the only extant members of our genus, Homo. This was not the case in the past, as we now know that our ancestors shared the planet with other Homo species. It has been suggested that selection against hybrid individuals would have acted against breeding across these species, but such a hypothesis is difficult to test today. To study this question, Vilgalys et al. took advantage of a decades-long dataset on two species of baboon from the Amboseli basin of Kenya. They found evidence of selection against hybrid, or admixed, ancestry similar to what has been predicted for ancestral hominids. Although evidence for selection against hybrids was clear, they also found that individual hybrids can thrive. ?SNV Coupled genomic and field data indicate selection against baboon hybrids despite no overt fitness costs in the wild.