The genetic revolution has changed all that. In this recent paper scientists have taken a close look at the entire primate family:
We conduct a phylogenetic analysis to determine the origin, evolution, patterns of speciation, and unique features in genome divergence among primate lineages. The resultant phylogenetic tree is remarkably robust and unambiguously resolves many long-standing issues in primate taxonomy. Our data provide a strong foundation for illuminating those genomic differences that are uniquely human and provide new insights on the breadth and richness of gene evolution across all primate lineages.
The story unfolds over a period of about 90 million years and covers many different creatures. Some, like the orangutang, are seriously endangered now. One of the stand out features of the primate group is their brains. Being remarkably cerebral they have a large brain:body size ratio, and of course of all the primates in all the world there is one whose brain is bigger than them all!