After the extinction of the dinosaurs, mammals took over and had room to evolve larger bodies, but their brains remained small to begin with
Life
31 March 2022
A reconstruction of the brains (purple) inside the skulls of the mammals Arctocyon primaevus (left), which lived about 59 million years ago, and Hyrachyus modestus (right), which lived about 45 million years ago Ornella Bertrand and Sarah Shelley
In the wake of the mass extinction 66 million years ago that wiped out all of the dinosaurs apart from the birds, mammals underwent an evolutionary explosion. The small species that survived the consequences of the asteroid-triggered “end-Cretaceous” event diversified and began to evolve into new niches, filling forests that sprung up from the ashes of the …