Sunday, August 01, 2004

Sisson, Part Four

In my previous postings about Edward Sison's essay in William Dembski's anthology Uncommon Dissent I focussed on the numerous scientific blunders Sisson saw fit to include.

But Sisson addresses other topics as well, among them whether it is really plausible that several generations of scientists are all mixed up on the subject of evolution. To argue that it is, indeed, plausible, Sisson points out that “there are of course many precedents for the general proposition that the reigning theories of an era may be false”(P. 77). The example he chooses to focus on is continental drift.

Nowadays it is well accepted that the continents are not fixed land masses, but rather, well, drift. For a long time, however, continental drift was considered absurd, becuase no one could provide a force adequate to the task of moving such large masses.

But there was a lot of circumstantial evidence to suggest that at one time the continents were closer together than they are today. For example, fossils found along the coast of Africa seemed to match very well with fossils found on the coast of South America. If animals could not travel freely between these land masses in earlier times, how do we explain this matching?

A number of scientists suggested that the continents used to be connected by a series of now submerged land bridges. There was no direct evidence for the existence of such bridges, but hypothesizing them did allow scientists to make sense of all the data that is now cited as evidence for drift. Since there was no credible alternative, the land bridges were accepted as plausible.

Later, the theory of plate tectonics was developed. This provided the missing force capable of moving continents, and drift was quickly embraced.

Sisson wishes to persuade us that evolution is about to go the way of the mythical land bridges. He writes:

The parallel between the evolution debate and the continental drift debate is quite striking. In unintelligent evolution, it is assumed that there cannot be an intelligent designer since humans have never perceived one, just as it was assumed that continents can't move since humans had never seen them move. Thus, to establish the factual existence of the mechanism for change in species (the equivalent of the land bridge), it is necessary simply that a scientist imagine a non-intelligent solution. That imagined solution - sequential muttions to germ cell DNA resulting from unintelligent processes, followed by a take-over of the population by individuals possessing the mutations - necessarily becomes a fact, regardless of the astounding odds against the occurrence of those events. Only its details - the specific mutation processes by which this operates - await actual observation. This two stage presentation - the “fact” of common descent and the “theory” of the details of how common descent actually works - is exactly how biology textbooks describe the matter. (P. 79-80) (Empahsis in Original).

Every time I think I've read the silliest thing imaginable, someone like Sisson comes along to prove me wrong. Sisson has the analogy completely backward. It is the assumption of intelligent design that is playing the role of the land bridges in biological history. Let me explain.

The argument against continental drift had nothing to do with the failure of humans to see the continents move. The problem was that to move such large masses against the resistance of the surrounding air and water a massive force was required, and there was no force known at the time that was up to the task. At one point gravity was suggested as the only force capable of causing the continents to drift, but it was shown rather conclusively that this was not an adequate explanation.

The problem with drift was that it suggested something that, as far as anyone knew at the time, was in stark violation of basic principles of physics. That's a pretty sound reason for rejecting a theory. By contrast, the hypothetical land bridges contained no such violation. Once the theory of plate tectonics provided a force that was capable of causing continents to move, the land bridges were cheerfully abandoned almost overnight.

Prior to Darwin's work, there was no known natural force capable of explaining the complexity of living creatures. As a result, it was simply assumed that there must be a supernatural intelligent designer capable of producing the complexity of nature. That there was no direct evidence of such a designer was neither here nor there. All other explanations required far greater leaps of faith.

Of course, there was quite a bit of circumstanital evidence for the proposition that species were not fixed. This evidence was noted by people like Erasmus Darwin (Charles' grandfather) and Jean Baptiste de Lamarck. But neither was able to suggest a plausible mechanism to explain how species changed over time, and they were quite rightly ignored. In the analogy, they played the role of drift boosters prior to the discovery of plate tectonics.

Darwin changed that first by showing that the sheer quantity of circumstantial evidence for common descent was far greater than previously thought. More importantly, he suggested the outline of a mechanism that could explain such descent. Minus an accurate theory of heredity, there was no way for him to flesh out his ideas in a compelling way. But it was clear to scientists what sort of research needed to be done to assess the validity of his ideas. In other words, Darwin's ideas were clearly fruitful, even if the verdict would turn out to be against him.

More than a century later we have a massive body of work in both theoretical and applied genetics that shows that natural selection is workable both in theory and practice. Genetics textbooks are loaded with well-understood mechanisms that cause genes to change over time. The hypothesis that various complex structures evolved via natural selection has led time and time again to important discoveries about biological structures. By contrast, the hypothesis of ID has never led to anything, and was never supported by anything more than the inability of scientists to come up with an alternative explanation.

Sisson, like all ID proponents, pretends that natural selection is just some abstract principle invoked by scientists to avoid dealing with the problem of biological complexity. In reality, the hypothesis that natural selection is the primary shaper of evolution continues to form the basis of countless research projects. This is a role that the hypothetical land bridges, or the equally hypothetical intelligent designer, never played.

Finally, we come to the distinction between the fact and the theory of evolution. If Sisson were correct that there was no remotely plausible natural mechanism for explaining common descent, then he would be right to protest this distinction. But the problem scientists actually face is quite different: There are many known forces capable of causing evolution, and in any given circumstance it may be hard to determine which force was actually working. Sometimes the disputes in this regard get rather heated. Consequently, scientists who write for the public are at pains to point out that such disputes as there are do not concern common descent, but rather with alternative explanations for that descent.

Sisson is surely aware that virtually every biology department in the country has a division devoted to evolutionary studies. Do you think Sisson has ever wondered for one second what goes on in all those labs? Has he ever wondered what is being reported in all those journal papers that get published every year? Or do you think he is someone who has read a few pages of people like Gould and Dawkins and has decided, in his supreme arrogance, that he actually knows something about the subject he is addresing?

Whatever the answer to that last question, one thing is clear: Sisson is a charlatan. He knows nothing about biology, but feels no shame in accusing scientists of the crassest sort of studipity and skullduggery. Small wonder he is so welcome among the ID's.