ABSTRACT
After the nuclear winter of the extinction event, the surviving mammals found themselves in a world that would, over the next ten million years, get slowly warmer. The fossilised skulls of early primates provide several tantalising clues about what this different "way of living" might have been. For over a century, the dominant story of how primates evolved was the "arboreal hypothesis": it was simply the move to a tree-dwelling life that drove change. Primates are intensely social creatures and they live together in groups ranging up to eight hundred in size. As with the joining together of cells into multicellular forms, being part of a bunch offers some obvious protection. Evolved increases in brain size were much more significant for primates because each time the primate brain expanded, it did so in a way that resulted in many more neurons than if it were any other species.
