There's a popular theory that bird and mammal evolution kicked
into high gear after the dinosaurs went extinct. But now it
turns out lice were already diversifying long before the
dinosaurs died out. This is significant because lice would only
start to diversify when their various hosts - in other words,
birds and mammals - were themselves starting to diversify into
lots of different species. We know that, in the last hundred
million years, birds and mammals have spread into almost every
available ecological niche, and most researchers assumed that
this happened shortly after the dinosaurs went extinct 65
million years ago, thus opening up all this prime ecological
real estate. But now, new research by University of Illinois
ornithologist Kevin Johnson suggests that lice started
diversifying before the extinction event at the end of the
Cretaceous. This, as he explains, means big things for bird and
mammal evolution: This study lends support to the idea that
major groups of birds and mammals were around befor