No. 77: Sep-Oct 1991
When anthropologist D. Falk discovered that an automobile's engine was limited in power by its radiator's capacity to cool it, he applied this thinking to the human brain.
The human brain, like the automobile engine, must be kept cool if it is to function well. It follows that if the brain of an animal is not functioning well, the body that brain controls will not perform well either. Overheated brains, then, are sure roads to extinction in the highly competitive natural world. A couple million years ago, two groups of human precursors were competing for dominance in Africa. The group that won and subsequently evolved into Homo sapiens had, according to Falk, a better brain-cooling system. The evolutionary development that probably led to this advantage was a more extensive network of emissary veins, which permitted better dissipation of heat. This, in turn, allowed the evolution of larger brains and dominance by Homo sapiens. Other anthropologists, how ever doubt that such a minor change in the circulatory system could account for the emergence of modern man. (Shipman, Pat; "Hotheads," Discover, 12:18, April 1991.)
Comment. What an intriguing concept! Perhaps human male baldness also confers more cooling efficiency and is setting the stage for a new expansion of the human brain -- at least the male brain, sorry girls! More seriously, did the better blood cooling system develop in response to an enlarging brain, or vice versa? Even more seriously, it is simplistic to say that an organism just went ahead and evolved this way or that way. A bigger brain requires not only more cooling but a bigger skull, more neurons, more connections between them, and additional infrastructure. Saying simply that "a larger brain evolved" obscures the fact that many different, inheritable changes had to take place in synchronism.