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)