Another useful metric is degree of surface convolution, with larger surface areas correlating with higher intelligence. Dolphins and whales have a degree of sur

Another useful metric is degree of surface convolution, with larger surface areas correlating with higher intelligence. Dolphins and whales have a degree of surface convolution similar to humans, although the thickness of their neocortex is about half that of humans. But the biggest factor is likely structure and organization of the cortex, not just size, density, or surface area. A good representation of structure is the homunculus [1], which emphasizes the mouth and hands. Undoubtedly, verbal and written communication have contributed enormously to the explosion of human intelligence. [1] http://www.rci.rutgers.edu/~uzwiak/AnatPhys/APFallLect19_files/image010.jpg http://www.rci.rutgers.edu/~uzwiak/AnatPhys/APFallLect19_fil...