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:
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The researchers looked at fossil skulls of two ancient animals. The 205-million-year old Morganucodon was a proto-mammal: a reptile with some decidedly mammalian characteristics (it looked a bit mouse-like, researchers say), that is thought to be an ancestor of mammals today. The tiny mammal Hadrocodium---imagine a shrew the size of a paperclip---lived 195 million years ago.
Fossil skulls of these species are rare, and the researchers weren't about to bust them open to examine the brain cavity. Instead, they used high-resolution ...
