Mammalian brains come in a variety of shapes, sizes, and organizations. Just how these neural disparities evolved remains mysterious.
Damon A. Clark of Princeton University and his colleagues are trying a new approach to this puzzle by comparing the proportions of nearly a dozen brain structures among many mammalian species. Like other related groups of species, mammals all share a basic arrangement of these structures. But in each species, these structures, as well as the overall brain, evolved to have specific sizes, the scientists report in the May 10 Nature.
About every 10 million years, the researchers propose, the brains composition undergoes sufficient remodeling to account for the arrival of dramatically new types of mammals.