The complex evolutionary history of gorillas: insights from genomic data

Relatively little is known about the evolutionary and demographichistories of gorillas, one of our closest living relatives.In this study, we used samples from both western (Gorilla gorilla)and eastern (Gorilla beringei) gorillas to infer the timingof the split between these geographically disjunct populationsand to elaborate the demographic history of gorillas. Here wepresent DNA sequences from 16 noncoding autosomal loci from15 western gorillas and 3 eastern gorillas, including 2 noninvasivelysampled free-ranging individuals. We find that the genetic diversityof gorillas is similar to that of chimpanzees but almost twiceas high as that of bonobos and humans. A significantly positiveFu & Li's D was observed for western gorillas, suggestinga complex demographic history with a constant, long-term populationsize and ancestral population structure. Among different population-splitscenarios, our data suggest a complex history of western andeastern gorillas including an initial population split at around0.9–1.6 MYA and subsequent, primarily male-mediated geneflow until approximately 80,000–200,000 years ago. Furthermore,simulations revealed that more gene flow took place from easternto western gorilla populations than vice versa.