Friday, June 08, 2007 06/08/07-Evolution and Intelligence

In today's excerpt, the fallacy of thinking that evolution would always lead to complex intelligence:

"We are chauvinistic about our brains, thinking them to be the goal of evolution. And that makes no sense, for reasons articulated over the years by Stephen Jay Gould. First, natural selection does nothing even close to striving for intelligence. ... Over time the organisms acquire designs that adapt them for survival and reproduction in that environment, period. ... Every organism alive today has had the same amount of time to evolve since the origin of life--the amoeba, the platypus, the rhesus macaque, and [humans].

"But ... isn't it true that animals become more complex over time? And wouldn't intelligence be the culmination? In many lineages, of course, animals have become more complex. ... But in many lineages they have not. The organisms reach an optimum and stay put, often for hundreds of millions of years. And those that do become more complex don't always become smarter. They become bigger, or faster, or more poisonous, or more fecund, or more sensitive to smells and sounds, or able to fly higher and farther, or better at building nests or dams--whatever works for them. Evolution is about ends, not means; becoming smart is just one option. ... Organisms don't evolve toward every imaginable advantage. If they did, every creature would be faster than a speeding bullet, more powerful than a locomotive. ...

"[The brain has] disadvantages. ... First, the brain is bulky. The female pelvis barely accommodates a baby's outsized head. That design compromise kills many women during childbirth and requires a pivoting gait that makes women biomechanically less efficient walkers than men. Also, a heavy head bobbing around on a neck makes us more vulnerable to fatal injuries in accidents such as falls. Second, the brain needs energy. Neural tissue is metabolically greedy; our brains take up only two percent of our body weight but consume twenty percent of our energy and nutrients. Third, brains take time to learn to use. We spend much of our lives either being children or caring for children. Fourth, simple tasks can be slow. My first graduate advisor was a mathematical psychologist who wanted to model the transmission of information in the brain by measuring the reaction time of a subject pushing a button when they heard a loud tone. Theoretically, the neuron-to-neuron transmission times should have added up to a few milliseconds. But there were 75 milliseconds unaccounted for between stimulus and response--'There's all this cogitation going on, and we just want him to push his finger down,' my advisor grumbled. Lower-tech animals can be much quicker; some insects bite in less than a millisecond. Perhaps this answers the rhetorical question in the sporting equipment ad: The average man's IQ is 107. The average brown trout's IQ is 4. So why can't a man catch a brown trout?"

Steven Pinker, How the Mind Works, Norton, 1997, 152-4.


Post a Comment

<< Home