Among other things, I’m a primate. Whether I can call myself a fish or an ape is a matter of semantic dispute, as last month’s wide-ranging blog discussion showed, but there’s no real controversy in identifying myself as a member of the wider primate family. When primates originated, though, is a rather thorny problem.

The fossil record is the most direct way to track when lineages first evolved. By searching for the earliest members of a group, and comparing those organisms to those already known, paleontologists can get a handle on when that group originated. An archaic form with few specializations was probably close to when that lineage became established, but if the earliest known representative