"Evolution is only a theory," says the creationist, using "theory" in the common sense of an "idea" or "speculation." When a scientist, however, says that evolution is a "theory," they use the word in its scientific sense: "a set of reliable, general principles that explains a variety of phenomena." To demonstrate the way in which evolution is a theory (in the scientific sense), let's compare it to the "Bible science" of creationism. Creationism is not a theory at all. It should come as no surprise that creationism isn't a theory. The theory of evolution, after all, isn't a tenet. Creationism, in fact, is an anti-theory, something that requires explanations rather than providing them.
Why do pythons have hip bones?
Evolution explains that some vestigial elements remain when a species evolves. As long as the vestigial feature doesn't harm the reproductive ability of the creature, there's little evolutionary pressure to be rid of it, and the feature might hang around. Creationism has no general principle by which to make sense of a python's hip bones. One can invent some quality in the Creator to explain the hip bones—whimsy, craftiness, deceitfulness, or whatever. One can also say that the Creator originally created snakes with limbs but then cursed them with limblessness. Regardless, the anti-theory of creationism calls for a special explanation rather than providing an explanation based on general principles.
Why are there rattlesnakes, ticks, tapeworms, disease-causing bacteria, tsetse flies, and other destructive creatures?
Evolution explains that the ability to harm other organisms is a common element among survival traits. Creationism has no general explanation for why a well-meaning, intelligent Creator would create such things. Many creationists say that the world has fallen from grace, but this is an additional idea that patches a hole in creationism, not a general principle or even an element of creationism proper.
Why is childbirth painful for humans?
Evolution suggests that the big human head is a recent evolutionary change, as is walking upright (and thus having narrow hips). These two changes conspire to make human childbirth difficult. Creationism has a hard time explaining why a well-meaning, intelligent Creator would design women to suffer in childbirth, so there's another parallel but independent tenet: that women are under a curse from the Creator.
Why are people mortal?
Evolution explains that immortality of the phenotype is not necessary for survival of the genotype. Creationists have no general principle to answer this. Instead, they have yet another patch. Our perfectly designed foreparents sinned and brought down the curse of mortality on humankind.
Why do most amphibians, reptiles, birds, and mammals have four limbs and none of them have six?
Evolution explains that they all descended from a population of four-limbed pre-amphibians. Creationism has no general explanation but rather discerns a special preference for four-limbed vertebrates in the Creator, or perhaps a conservative approach to morphology.
Why are men bigger and more aggressive than women? Why do they generally hold more power than women?
Evolution explains that sexual dimorphism is common among species, as are sex differences in behavior. Sex differences reflect differences in successful reproductive strategy between the sexes, and they create more efficient communities or pair bonds by letting the genders divide labor and specialize. Creationism has no general explanation but rather infers some favoritism for men or a curse on women.
If perception and reason are divine faculties, why do they profoundly fail to discern basic properties of the world (e.g., that it's a spinning ball revolving around the sun)?
Evolution explains that perception and reason are capacities that evolved to help individuals survive and prosper. Perceiving the world as a giant spinning sphere wouldn't have done much good for an early homonid. Creationism does not explain why the Creator would give humans a set of perceptual and intellectual tools that, for the vast majority of human history, has not been up to the task of knowing the score.
Why is complexity found among organisms but not among natural, inanimate objects?
Evolution explains that organisms are complex from their behavior down to their bones all the way down to their DNA because they embody all the successful complexity that they’ve developed bit by bit over billions of years. But nonliving things are comparatively simple because they have no system for generating or preserving complexity. Creationists have no general principle to explain why the Creator made organisms complex but didn’t make inanimate objects complex at the same time. Why isn’t there a face on the moon or an even number of days in a year? Why don't the stars form clear constellations? Why aren’t there stairs or ramps built into mountain slopes?
August, October 2005
National Center for Science Education