I just finished reading an article discussing human brain size and its relationship to behavior and intelligence. It seems that over the past 20,000 years man’s brain has decreased in size from 1500 to 1350ccs (10%). Women’s brains are lighter in the same proportion.
What does this mean? We’re obviously smarter, so how can our brains be smaller? Throughout recent history our brain to body size ratio (EQ) has remained relatively constant, so the decrease in our brain size has been accompanied by a decrease in body size. There are theories that attempt to explain this phenomena, but no consensus has been reached in the scientific community.
One theory, which I label the Climate Theory, suggests that the warming of the earth has decreased the need for large bodies to protect against the cold. Twenty thousand years ago the earth was in the last stages of an ice age, and the earth has warmed steadily since that time. Natural selection, operating during this period, favored smaller bodies which use less energy, so humans began to shrink – body and brain.
There is a second much more interesting theory about the decrease in size of human beings; the notion that we small-brained moderns are “dumber” than our predecessors. The story goes like this. Among the thirty or so domesticated animals, the wild ancestors had bigger brains than their more docile descendants AND were more clever at surviving. For example, a wild dog is more resourceful than a domesticated dog. Of course, the domesticated dog has his master to help him get thorough life so he can give up whatever brain function the wild dog needed for survival.
What does this data mean when applied to human beings? Scientists have looked at brain size in people as a function of population density and have found that people living in larger groups have smaller brains. That is those living in densely populated areas had smaller brains than nomadic types. Of course, agriculture and the domestication of animals helped drive this because they set the stage for people to live closer together and created a differentiation of roles in those cultures. Over time, strength and the ability to fight became specialized so the majority of men could live their lives without having to be physically aggressive.
If we buy the analog with domesticated animals, then we too, like them, have become less clever – at least as it relates to the ability to survive. We have essentially domesticated ourselves, and, in doing so, taken advantage of our newly acquired free time to intellectualize.
But one question still remains. What would have happened if our big brained, clever ancestors would have had time to think? Would they have acquired knowledge faster than we have because they were more clever or is it a zero sum game?