Mammals' Big Brains Started with Better Sense of Smell

Mammals' increased brain size may have come from long-ago natural selection for a better sense of smell, suggests a new study published today in Science. By reconstructing in 3D the skulls of two animals far back on the mammal family tree, the researchers saw that growth of smell-related brain regions accounted for much of the early increase in brain size as mammals developed. How the Heck: