Thursday, July 26, 2007

Gradualism and Macroevolutionary Theory

For some time now I have wanted to juxtapose these quotations:

Richard Dawkins on the importance of gradualism for the plausibility of macroevolutionary theory:
Evolution is very possibly not, in actual fact, always gradual. But it must be gradual when it is being used to explain the coming into existence of complicated, apparently designed objects, like eyes. For if it is not gradual in these cases, it ceases to have any explanatory power at all. Without gradualness in these cases, we are back to miracle, which is simply a synonym for the total absence of explanation. Dawkins, R. (1995) River Out of Eden, Basic Books, New York, p. 83.

Stephen J. Gould on stasis and sudden appearance in the fossil record:
The history of most fossil species includes two features particularly inconsistent with gradualism: 1. Stasis. Most species exhibit no directional change during their tenure on earth. They appear in the fossil record looking much the same as when they disappear; morphological change is usually limited and directionless. 2. Sudden appearance. In any local area, a species does not arise gradually by the steady transformation of its ancestors; it appears all at once and "fully formed." (Gould, Stephen J., "Evolution's Erratic Pace," Natural History, Vol. 86, No. 5, May 1977, p.14).

Now I am sure that some readers will cry "quote-mining" as soon as they read this. So let me say for the record that Gould and Dawkins each have their ways of explaining why the fossil record is, in fact, consistent with macroevolutonary theory. However, their explanations differ significantly, and I do not find either one fully convincing.

More importantly, I wish to point out that I am submitting these quotations for the simple purpose of showing that the fossil record, taken as a whole, has features that pose problems for macroevolutionary theory. There is no scientific consensus on how to resolve those problems.

This information should not be suppressed, and should be presented to students.


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