Fig. 7

Hypothesized gorilla population dynamics over the course of the last 50,000 years. Ranges and geographical locations in panels A-C are rough approximations, whereas D is based on present-day IUCN species ranges, same as Fig. 1A. A Western and eastern gorillas split prior to the Last Glacial Maximum (LGM). B Global cooling during LGM led to forest contractions and reduction of population sizes of both western and eastern gorillas. Bwindi becomes separated from other eastern gorillas. C During the African humid period, eastern populations expand westwards and separate into Grauer’s gorillas and the Virunga mountain gorilla population. Gene flow occurs between Cross River ancestors and Grauer’s gorillas. D Aridification in east Africa, leading to reduction in population size