Selections from the special section on
he world is divided into things that look as though somebody designed them (wings and wagon-wheels, hearts and televisions), and things that just happened through the unintended workings of physics (mountains and rivers, sand dunes, and solar systems).
No wonder Thomas Henry Huxley, Darwins bulldog, was moved to chide himself on reading the Origin of Species: How extremely stupid not to have thought of that. And Huxley was the least stupid of men.
Paradoxically, the extreme simplicity of what the philosopher Daniel C. Dennett called Darwins dangerous idea may be its greatest barrier to acceptance. People have a hard time believing that so simple a mechanism could deliver such powerful results.
The arguments of creationists, including those creationists who cloak their pretensions under the politically devious phrase intelligent-design theory, repeatedly return to the same big fallacy. Such-and-such looks designed. Therefore it was designed.
Yet the highly improbable does exist in the real world, and it must be explained. Adaptive improbabilitycomplexityis precisely the problem that any theory of life must solve and that natural selection, uniquely as far as science knows, does solve. In truth, it is intelligent design that is the biggest victim of the argument from improbability. Any entity capable of deliberately designing a living creature, to say nothing of a universe, would have to be hugely complex in its own right.
If, as the maverick astronomer Fred Hoyle mistakenly thought, the spontaneous origin of life is as improbable as a hurricane blowing through a junkyard and having the luck to assemble a Boeing 747, then a divine designer is the ultimate Boeing 747. The designers spontaneous origin ex nihilo would have to be even more improbable than the most complex of his alleged creations. Unless, of course, he relied on natural selection to do his work for him! And in that case, one might pardonably wonder (though this is not the place to pursue the question), does he need to exist at all?
The achievement of nonrandom natural selection is to tame chance. By smearing out the luck, breaking down the improbability into a large number of small stepseach one somewhat improbable but not ridiculously sonatural selection ratchets up the improbability.
Many people dont understand such nonrandom cumulative ratcheting. They think natural selection is a theory of chance, so no wonder they dont believe it! The battle that we biologists face, in our struggle to convince the public and their elected representatives that evolution is a fact, amounts to the battle to convey to them the power of Darwins ratchetthe blind watchmakerto propel lineages up the gentle slopes of Mount Improbable.
The misapplied argument from improbability is not the only one deployed by creationists. They are quite fond of gaps, both literal gaps in the fossil record and gaps in their understanding of what Darwinism is all about. In both cases the (lack of) logic in the argument is the same. They allege a gap or deficiency in the Darwinian account. Then, without even inquiring whether intelligent design suffers from the same deficiency, they award victory to the rival theory by default. Such reasoning is no way to do science. But science is precisely not what creation scientists, despite the ambitions of their intelligent-design bullyboys, are doing.
In the case of fossils, as Donald R. Prothero documents in The Fossils Say Yes [see the print issue], today’s biologists are more fortunate than Darwin was in having access to beautiful series of transitional stages: almost cinematic records of evolutionary changes in action. Not all transitions are so attested, of coursehence the vaunted gaps. Some small animals just dont fossilize; their phyla are known only from modern specimens: their history is one big gap. The equivalent gaps for any creationist or intelligent-design theory would be the absence of a cinematic record of Gods every move on the morning that he created, for example, the bacterial flagellar motor. Not only is there no such divine videotape: there is a complete absence of evidence of any kind for intelligent design.
Absence of evidence for is not positive evidence against, of course. Positive evidence against evolution could easily be foundif it exists. Fishers contemporary and rival J.B.S. Haldane was asked by a Popperian zealot what would falsify evolution. Haldane quipped, Fossil rabbits in the Precambrian. No such fossil has ever been found, of course, despite numerous searches for anachronistic species.
There are other barriers to accepting the truth of Darwinism. Many people cannot bear to think that they are cousins not just of chimpanzees and monkeys, but of tapeworms, spiders, and bacteria. The unpalatability of a proposition, however, has no bearing on its truth. I personally find the idea of cousinship to all living species positively agreeable, but neither my warmth toward it, nor the cringing of a creationist, has the slightest bearing on its truth.
The same could be said of political or moral objections to Darwinism. Tell children they are nothing more than animals and they will behave like animals. I do not for a moment accept that the conclusion follows from the premise. But even if it did, once again, a disagreeable consequence cannot undermine the truth of a premise. Some have said that Hitler founded his political philosophy on Darwinism. This is nonsense: doctrines of racial superiority in no way follow from natural selection, properly understood. Nevertheless, a good case can be made that a society run on Darwinian lines would be a very disagreeable society in which to live. But, yet again, the unpleasantness of a proposition has no bearing on its truth.
Huxley, George C. Williams, and other evolutionists have opposed Darwinism as a political and moral doctrine just as passionately as they have advocated its scientific truth. I count myself in that company. Science needs to understand natural selection as a force in nature, the better to oppose it as a normative force in politics. Darwin himself expressed dismay at the callousness of natural selection: What a book a Devils Chaplain might write on the clumsy, wasteful, blundering low & horridly cruel works of nature!
In spite of the success and admiration that he earned, and despite his large and loving family, Darwins life was not an especially happy one. Troubled about genetic deterioration in general and the possible effects of inbreeding closer to home, as James Moore documents in Good Breeding, [see print issue], and tormented by illness and bereavement, as Richard Milners interview with the psychiatrist Ralph Colp Jr. shows in Darwins Shrink, Darwins achievements seem all the more. He even found the time to excel as an experimenter, particularly with plants. David Kohns and Sheila Ann Deans essays (The Miraculous Season and Bee Lines and Worm Burrows [see print issue]) lead me to think that, even without his major theoretical achievements, Darwin would have won lasting recognition as an experimenter, albeit an experimenter with the style of a gentlemanly amateur, which might not find favor with modern journal referees.
As for his major theoretical achievements, of course, the details of our understanding have moved on since Darwins time. That was particularly the case during the synthesis of Darwinism with Mendelian digital genetics. And beyond the synthesis, as Douglas J. Futuyma explains in On Darwins Shoulders, [see print issue] and Sean B. Carroll details further for the exciting new field of evo-devo in The Origins of Form, Darwinism proves to be a flourishing population of theories, itself undergoing rapid evolutionary change.
In any developing science there are disagreements. But scientistsand here is what separates real scientists from the pseudoscientists of the school of intelligent designalways know what evidence it would take to change their minds. One thing all real scientists agree upon is the fact of evolution itself. It is a fact that we are cousins of gorillas, kangaroos, starfish, and bacteria. Evolution is as much a fact as the heat of the sun. It is not a theory, and for pitys sake, lets stop confusing the philosophically naive by calling it so. Evolution is a fact.