Thursday, March 25, 2010


The previous entry, about death, brings up an important point about evolution: imperfection. Imperfection is one of the most important ways in which an evolutionary view of the world differs from a creationist one.

An all-powerful God ought to have created a perfect world. This God is supposed to have given humans free will and the ability to choose evil; therefore one might not expect any human utopias. But the natural world is also pervaded by imperfection. The only explanation creationists have for this is that God cursed the whole natural world during Adam’s fall—something that is simply not found in the Bible; it is something creationists just made up. I guess they think God gives them permission to just make stuff up and then proclaim it in God’s name. Stephen Jay Gould was particularly active in pointing out that imperfections are much better evidence for evolution than perfections.

The idea that organisms are perfectly adapted to their environments predates evolutionary theory. This idea was central to natural theology, in which the perfect fit of organism and environment was considered evidence of divine creation. English theologian William Paley, in his famous 1802 book Natural Theology, used perfect adaptation of organisms as evidence that a Supreme Being had created them. At the time Paley wrote his book there was no credible evolutionary theory that could challenge this view.

Natural theology is wrong in one particularly important way. Scientific investigation has found numerous examples of adaptation that are far from being a perfect fit between organism and environment. One example (Gould’s favorite) is the digestive system of the panda. The immediate ancestors of pandas were carnivores, but pandas are herbivores, living exclusively on leaves. Pandas have intestines that are better suited to a carnivore. In well-adapted herbivores, such as sheep, the intestines are up to 35 times as long as the body, while in well-adapted carnivores, the intestines are much shorter, only four to seven times as long as the body. With the help of bacteria, longer intestines allow herbivores more time to digest coarse plant materials, such as cellulose. Meat, in contrast, requires less digestive breakdown. Pandas have intestines that are in the carnivore, not the herbivore, range. The panda’s digestive system is, therefore, not well adapted to its function. Modern evolutionary scientists would attribute this to the recent evolutionary shift from meat to leaves in the diet of the panda’s ancestors: there has not been time for better adaptation in this case. A natural theologian, in contrast, would have a difficult time explaining this example of imperfection. Stephen Jay Gould used the sixth digit, or thumb, of the panda as another example of the imperfection of adaptation produced by the ongoing process of evolution rather than by the Supreme Being invoked by natural theology.

Another example of an imperfect adaptation is pain. The function of pain is to alert an animal to danger or possible damage. Victims of some kinds of strokes, and of leprosy, lose much of their ability to feel pain, and cannot feel the damage that they may do to their extremities. Healthy individuals feel pain and avoid movements that would damage their extremities. Excessive and prolonged pain, however, serves no useful purpose, and much of modern medicine is devoted to the control of excessive pain. Pain is therefore an adaptation, but an imperfect one—a fact to which all of us can attest. Those of us who experience little pain empathize with those who experience much, and if we were in charge the way God supposedly is, we would alleviate some of this pain.

The world is only as good as it has to be for organisms to win in the game of natural selection. It is not perfect, nor is there any evolutionary way for it to be. But at least evolutionists do not have to come up with an excuse for how a God of Infinite Love could allow pervasive and painful imperfections to mar the Creation.

Adapted from the entry “Adaptation” in Encyclopedia of Evolution (Facts on File, 2006, 2007).

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