Large Brain

Figure 20: A picture of the human brain.

The link between warm-bloodedness and large brain size is fairly indirect. Brain tissue is vulnerable to changes in temperature. Human brains addle when heated to 108 degrees Fahrenheit even for a few minutes, and higher cerebral functions become erratic when the brain is chilled below 90 degrees Fahrenheit. So warm-bloodedness and a constant body temperature are prerequisites for a large brain. It may be that warm-bloodedness evolved first, and the evolution of large brains followed. (Bakker, 1986)