Monday, February 21, 2005

An evolving position

When you read books and Web sites dealing with evolution, you can't help being drawn into the controversy between two firmly entrenched camps - the die-hard Darwinists, who believe that every aspect of life on earth can be explained by Darwin's theory of natural selection, and the equally zealous anti-Darwinists, who denigrate Darwin's ideas and consign them to the same scrapheap of 19th Century falsehoods where Freud and Marx have already been laid to rest.

(I use the neutral term "anti-Darwinists" rather than the pejorative and often inaccurate term "creationists," which is favored by the pro-Darwin side. Not all anti-Darwinists are Biblical fundamentalists, and the current debate should not be lazily caricatured as a rehash of Inherit the Wind.)

Personally, I'm inclined to look for the truth somewhere in the middle ground between the two sides, both of which can be dogmatic, stubborn, and unreasonable, even cruel in their personal attacks and invective.

Despite what the anti-Darwin forces maintain, I think there is a great deal of evidence to support the contention that the various species on earth today have evolved from earlier species, a process that has taken millions of years. While the fossil record is not as complete as we might like, paleontologists have found good transitional forms between reptiles and birds, and between land-dwelling quadrupeds and whales. There is an excellent series of horse fossils showing how the earliest horse, Eohippus, evolved into progressively larger horses, along the way losing two of its four toes. Analysis of the genomes of living species also tends to support the thesis of common descent, with closely related animals having more genetic sequences in common than more distant relatives. And micro-evolution, at least, has been observed in the laboratory - in the breeding of exotic mutant fruitflies - and in the wild, where insects have developed resistance to pesticides, bacteria have developed resistance to antibiotics, and populations of insects and birds have undergone measurable changes in response to environmental pressures.

It is possible for anti-Darwinists to poke holes in some of this evidence, of course. Nothing in science, or any other field of empirical investigation, is ever 100% certain. There will always be weak spots to exploit. But the thrust of the evidence is strong enough to convince me that the general world picture painted by Darwinism is true. The estimable naturalist will not be joining Marx and Freud in the trash heap anytime soon.

Still, the Darwinists, or at least the most vocal among them, are probably overstating the case when they suggest - or even say openly - that evolution by natural selection explains everything. This seems to be more of a philosophical conviction, or even a quasi-religious commitment, than a conclusion actually warranted by the evidence. In fact, the anti-Darwin side, for all its excesses and tendentious nitpicking, does make some good points.

For one thing, Darwinism has nothing useful to say about abiogenesis - the origin of life. How the first living cell emerged from nonliving antecedents remains a mystery - actually a greater mystery than in Darwin's day, when the cell was believed to be a simple glob of protoplasm. Thanks to electron microscopy, we now know that the cell is a fantastically complex assembly of organic machines, more elaborate and sophisticated than any factory. The origin of such dazzling complexity, and above all of the encoded information in the genes that makes it possible, is a question that Darwinism - or scientific materialism as such - seems to have very little hope of answering.

Then there is the problem of the first large-scale emergence of living creatures, the Cambrian Explosion, circa 530 million years ago. Pre-Cambrian rocks show traces of soft-bodied creatures like worms, as well as microscopic organisms, but these relatively minor developments pale in comparison with the vast array of creatures that appear at the very start of the Cambrian Era. Fifty phyla of animals (more than the number of phyla on earth today) pop into existence with disconcerting abruptness and with few obvious predecessors. Something other than gradualism seems to be involved here.

Finally, there are the large jumps that incremental, progressive evolution is hard-pressed to explain. How, for instance, did egg-laying creatures evolve into creatures that bore live young? What sort of transitional reproductive apparatus can be imagined that lies halfway between laying eggs and giving birth? Yes, I know the duck-billed platypus and other monotremes are egg-laying mammals, but that's just the point - they lay eggs. They do not reproduce in some "transitional" manner that involves aspects of egg-laying and aspects of live birth. And it is hard to know what would constitute such a halfway position. In this area, it seems more logical to imagine a sudden jump from egg-laying to live birth - and yet a sudden jump is precisely what Darwinism forbids.

In the end, there ought to be room for intelligent compromise. Darwinism explains a lot, but perhaps not everything. It is only hubris that keeps the extremists on both sides from acknowledging any validity to their opponents' position.

My guess is that Darwinism will eventually share the fate of Newtonian physics. Once thought to explain everything in the physical world, Newton's laws have since been relegated to secondary status, encapsulated within the larger framework of quantum theory. Darwin's views may someday be seen in a similar way - as a useful, groundbreaking, brilliant, but only partial explanation.

And if this happens, should anyone really be surprised? After all, what were the odds that a naturalist writing by candlelight in the age of horse-and-buggies would have the last word, for all time, on the deepest mysteries of life?

Update (Feb. 22): After posting this comment, I realized that one paragraph may have been misleading. Just to be clear, when I say that there were more phyla in the Cambrian Era than there are today, I don't mean to suggest that there was greater diversity of life at that time than there is now. Although the number of phyla has declined from 50 to 37, the diversity within each phylum has greatly increased. As just one example, a single phylum, Chordata, contains all vertebrates - fish, reptiles, birds, and mammals. Still, the relatively sudden appearance of so many distinct body plans (mostly in a time frame of 5 to 10 million years) is problematic for Darwinism and may require some new thinking.


Blogger Brins said...

That's a good point about the Newtonian physics - it may seem sufficient to explain everything, but in reality it's only scratching the surface of a greater whole.

I don't know much about biology, but from what I've seen from some experts (and a book review here), you're supposed to accept Darwinism completely or you're an idiot. I've even heard that said!
It makes me wonder: were they as patriotic with Newton as well?

Nice essay.

February 26, 2005 2:15 AM  
Blogger Michael Prescott said...

The fervent Darwinist Richard Dawkins, author of The Selfish Gene, once famously wrote, "It is absolutely safe to say that if you meet somebody who claims not to believe in evolution, that person is ignorant, stupid or insane (or wicked, but I'd rather not consider that)."

By "evolution," it is clear that he meant Darwinism, as opposed to any alternative theory or approach. He makes this obvious in his recent defense of his much-quoted statement, a defense which can be read at .

As for Newton, a number of leading physicists circa 1900 said confidently that all the major questions in physics had been answered (by Newtonian principles) and that there would be nothing for the next generation to do except fine-tune a few details. This was before Einstein, and before the whole revolution of quantum physics which has transformed the field.

March 02, 2005 11:55 AM  

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