Meanwhile, in the Old World, the catarrhines had also diverged into three major families. The cercopithecoids, including all the Asian and African monkeys, branched away 32 million years ago and started truly diversifying around 18 million years ago. The remaining catarrhines split into two groups just 20 million years ago – the hylobatids, including all the gibbons; and the hominids, including ourselves and the other great apes.
The history of the cercopithecoids is a convoluted puzzle, not least because the genetic differences within the group are lower than expected. As they evolved, it seems that many subspecies and species mated with one another to produce hybrid lineages. They turned a neat forking tree into a tangled bush.
Image by Mark Laidre