Thursday, September 07, 2006

Has Anyone Seen Evolution?

Has anyone ever seen the evolution of a new species from ancestral species? This question points to the fundamental difficulty in Darwinian evolutionary theory, a difficulty stressed by creationists and intelligent design proponents. If the evolution of new species occurs usually over long periods of evolutionary history, then no human being has ever directly observed this history, and so the evolutionary scientist must spin out scenarios that are more or less plausible, but still open to doubt.

Darwin admitted that he could not lay out the step-by-step pathway of the evolution of species based on clearly observable evidence. In the concluding chapter of The Origin of Species, he wrote: "Any one whose disposition leads him to attach great weight to unexplained difficulties than to the explanation of a certain number of facts will certainly reject my theory." Here he foresaw the rhetorical strategy of the intelligent design proponents who rely on negative argumentation--pointing to gaps in Darwinian science and then inferring that ID must be true by default.

Darwin recognized that the ID theorists were unable to offer a positive theory of their own that would explain exactly when, where, and how the intelligent designer does his work. He asked: "Do they really believe that at innumberable periods in the earth's history certain elemental atoms have been commanded suddenly to flash into living tissues? Do they believe that at each supposed act of creation one individual or many were produced? Were all the infinitely numerous kinds of animals and plants created as eggs or seed, or as full grown? And in the case of mammals, were they created bearing the false marks of nourishment from the mother's womb? Although naturalists very properly demand a full explanation of every difficulty from those who believe in the mutability of species, on their own side they ignore the whole subject of the first appearance of species in what they consider reverent silence."

A few years ago, I lectured at Hillsdale College as part of a week-long lecture series on the intelligent design debate. After Michael Behe's lecture, some of us pressed him to explain exactly how the intelligent designer created the various "irreducibly complex" mechanisms that cannot--according to Behe--be explained as products of evolution by natural selection. He repeatedly refused to answer. But after a long night of drinking, he finally answered: "A puff of smoke!" A physicist in the group asked, Do you mean a suspension of the laws of physics? Yes, Behe answered. Well, that's not going to be very persuasive as a scientific answer. And clearly Behe and other ID proponents prefer not to answer the question.

Some Darwinian biologists would say that we have seen the evolution of new species--for example, in the work of Peter and Rosemary Grant studying Darwin's finches in the Galapagos Islands. There are 14 species of finches in the Galapagos. In 1977, there was a severe drought. As a result, finches with small beaks found it hard to eat the hard seeds that were left over from the drought. Finches with large beaks more adapted for eating these seeds were more likely to survive. So here, the Grants proclaimed, was natural selection in action!

The creationists and ID proponents say that this shows microevolution but not macroevolution. Natural selection was favoring some varieties of finches over other varieties. But this did not create a new species. In fact, the Grants saw that in 1983 the rainfall returned to normal, and the effect of natural selection was reversed. And yet they speculated that if there were at least one drought per decade over a 200 year period, this would push natural selection towards transforming the medium-sized ground finches into a new species. But the problem with this scenario is that it is only a speculative extrapolation that has not yet been observed.

Darwinian scientists insist that the difference between microevolution and macroevolution is only a difference in degree. As Darwin argued, every variety is an incipient species. At some point, the evolutionary change in a variety becomes so great that it becomes a new species. It's like the evolution of language. Every human language has various dialects. And eventually the cultural evolution of a dialect can turn it into a separate language, although it may be impossible to say when a dialect becomes a new language.

But then the Darwinians need to shift the burden of proof back on their critics. The species of finches found in the Galapagos are not found anywhere else in the world. But they resemble the finches on the mainland of South America. We might infer, therefore, that the ancestors of the Galapagos finches migrated from the mainland and then radiated out across the islands, so that eventually the evolution of varieties created new species. What's the alternative? If the intelligent designer did it, why did he specially create finch species unique to the Galapagos that resembled the finches on the mainland? Of course, we can't deny the possibility that this reflects some arbitrary choice of the designer that we can't explain. But Darwin thinks that his explanation is more inherently plausible.

As I have argued previously, none of this denies the work of the Creator in his original creation of the laws of nature--including evolutionary mechanisms--that could eventually bring about the evolutionary history studied by the Darwinian biologist. But it throws into doubt the assumption of special creationism and intelligent design theory that the Creator had to repeatedly intervene in the history of life to perform special miracles to create irreduciblly complex structures of life. Why do we have to assume that God was either unable or unwilling to employ the general laws of nature to carry out his creative plan?

I have written a post on the evolution of Darwin's finches in the Galapagos.

9 comments:

John Farrell said...

Superb post. That story about Michael Behe is hilarious! Nothing like a few beers to loosen the tongue....

wmr said...

Larry,

This is OT, but I just discovered it. The author differs strongly from you on 'teaching the controversy'.

Intelligent Design not science by Richard Olmstead, who "is a professor in the department of biology at the University of Washington and curator of the Burke Museum of Natural History and Culture."

Larry Arnhart said...

I agree with Olmstead that ID hardly seems testable and therefore is weak as a putative scientific theory.

But what's wrong with allowing students to discover this for themselves? Doesn't it seem unreasonable for biology teachers to tell their students, We declare that ID is not science, and therefore we will not allow you to even discuss it in this class. Furthermore, we won't even allow you to consider the criticisms of evolutionary theory offered by biologists like Michael Behe. Doesn't this actually play into the hands of the ID proponents by making it look as if the Darwinians are dogmatic in their refusal to consider criticism?

wmr said...

So, I guess you're saying that in your opinion the "advances in genetics and developmental biology that have provided explanations for the origin of many complex structures in recent years" are appropriate subjects for a high school biology class.

Why is it unreasonable for biology teachers to tell their students, "Intelligent design offers no testable hypotheses and, instead, offers only an explanation for observations of complex structures and phenomena in biology that must be taken on faith."?

If you want to teach "criticisms of evolutionary theory", why is ID a topic superior to teaching that "Darwin didn't understand the role genes and chromosomes play in inheritance, so his theories about inheritance have been replaced by new ones that offer more explanatory power. In fact, many of Darwin's ideas about evolution have been greatly modified in this way."?

Larry Arnhart said...

This semester, one of the readings for my course on evolution is Dembski & Ruse, DEBATING DESIGN. Here the students can read chapters by Kenneth Miller and Michael Behe debating whether evolutionary theory can explain "irreducibly complex" mechanisms like the bacterial flagellum. The latest research in genetics and developmental biology comes into play. So the students learn a lot about the latest biological research even as they work through this debate.

So isn't that good? Why shouldn't that be done in a high school biology class?

John Pieret said...

Why should it be done in a biology class, where there is little enough time to cover actual biology and with biology teachers, the majority of whom have no qualifications to teach the subject? If this must be done, shouldn't it be in a course properly labeled as philosophy/theology?

Besides, creating a high school course on philosophy will be a way to get all those philosophy graduate students off the streets.

wmr said...

You say, "So isn't that good? Why shouldn't that be done in a high school biology class?"

First answer, from the linked article (did you actually read it?): "It takes a foundation in the basics of any discipline to be able to grasp the subtleties at the cutting edge of a field, so it is understandable that in high school science classes, the focus is on learning the basic facts and theories along with learning how scientists go about their inquiry to understand nature."

Second answer depends on your answer to this question: how much older and smarter are your students than the average high school student taking an introductory biology class?

wmr said...

Oh, and one other question: how many of your students took a biology class in high school?

Anonymous said...

""It takes a foundation in the basics of any discipline to be able to grasp the subtleties at the cutting edge of a field, so it is understandable that in high school science classes, the focus is on learning the basic facts and theories along with learning how scientists go about their inquiry to understand nature."

That is so much fucking bullshit. It takes years of PROPAGANDA to learn how to delude yourself even further.

I know people who have no formal education who soundly whip arguments of other scientists and professionals, just because you've gone through some academic obstacle course, doesn't mean you know how to think.