The great primate evolutionary bottleneck did not occur out of Eurasia. The great primate evolutionary bottleneck occurred approximately 25 million years ago in Africa, when a period of intense cooling led to the extinction of the vast majority of ape species, reducing genetic diversity and leading to the emergence of the four extant lines of anthropoid - the platyrrhine (New World) monkeys, the catarrhine (Old World) monkeys, the lesser apes, and the great apes (including humans).