Sniff Sniff -- Smelling Leads to Smarter Mammals (8 of 8) (IMAGE)
Caption
In terrestrial vertebrates, large brains evolved, independently, twice. Relative brain size in living mammals and birds has increased by at least a factor of 10 over that in living reptiles. Pictured brains show the relative dimensions of the olfactory bulbs and cerebral hemispheres (red), the midbrain (yellow), the cerebellum (green), and the medulla (white). In birds, the midbrain lobes have been displaced laterally and ventrally by the expansion of the cerebral hemispheres, and the expansion of the cerebellum in both mammals and birds has resulted in pronounced foliation (folding) of the cerebellum. For more information, please see the related Perspective, "Evolving Large and Complex Brains," by R. Glenn Northcutt. This Perspective and image relates to an article that appeared in the May 20, 2011, issue of Science, published by AAAS. The study, by Dr. Timothy Rowe at University of Texas in Austin, and colleagues, was titled, "Fossil Evidence on Origin of the Mammalian Brain."
Credit
Image: N. Kevitiyagala/<i>Science</i> © 2011 AAAS
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