THE CONTRACTING CEREBRUM CONUNDRUM

Contrary to expectations, the human brain has been shrinking in size over the last 20,000 years.  The average male brain once had a volume of about 1500 cc; however, it is now about 1350 cc--a difference about the size of a tennis ball. Female brains, which were slightly smaller to start with, have also shrunk proportionately.

One theory is that 20,000 years ago, individuals had to be a lot more self-reliant and had to have extra intelligence because no one else would be providing them with food, shelter, medical care, clothes, and protection from predators (trying to avoid being eaten can especially require a lot of thought and concentration). This theory would be consistent with observations about wild animals who have become domesticated, as they almost always evolve to smaller brains after several generations of living off of the largesse of humans. The only flaw with this hypothesis is that although it may explain why not as much intelligence may be needed in modern times and why a smaller brain would be adequate, it does not account for why evolution would affirmatively favor the smaller brain instead of just leaving it at its older larger size.

The second theory is that evolution resulted in the brain of each person developing more slowly than it used to and that a modern brain is simply an old-fashioned juvenile brain which never grew to its full adult potential. It is believed that individuals with full adult brains would have been a lot more aggressive than those with juvenile brains. As societies formed and there was less and less self-reliance and more dependence on the group, aggressive individuals with adult brains who went around committing self-indulgent orgies of rape, murder, and pillaging would be executed by the group and their genetic contributions eliminated.

Under either theory, evolution is favoring the preservation of less intelligent individuals who need to be supported by others and is eschewing smarter individuals who are self-reliant. In other words, no matter how counter-intuitive it may seem, the highest and most-evolved life forms vote for Democrats.

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