On the Difference Between "Evolutionary Theory" and Scientific Fact

There's been a lot of discussion about Elliott Sober's talk at the University of Chicago. You can watch the entire talk and the questions & answers at [The Problem with Philosophy: Elliott Sober].

Most of the debate is taking place on Jerry Coyne's site [Can God create mutations? Elliott Sober says we can’t rule that out.] and on Jason Rosenhouse's blog [The Reason For the Ambivalence Towards the Philosophy of Science]. Things aren't going well for Elliott Sober and, by implication, for the philosophy of science.

I want to discuss another troubling aspect of Sober's talk. Throughout the talk he refers frequently to "evolutionary theory" or "the theory of evolution." This is consistent with the introduction by Robert Richards where he says they are considering "... the application of evolutionary theory to the humanities and social sciences" (27 sec). The title of Sober's talk is "Naturalism and Evolutionary Theory."

What do they mean by "evolutionary theory"? To me, evolutionary theory means the kinds of things that are discussed in Stephen Jay Gould book "The Structure of Evolutionary Theory." It includes things like population genetics and the potential influence of genome size on the fixation of alleles. It includes things like species sorting and punctuated equilibria. It even includes speculation about selfish genes and the level of selection.

Evolutionary theory does NOT include whether birds and dinosaurs share a recent common ancestor, the age of the Earth, the amount of junk DNA in our genome, or the causes of mutation. Those are interesting questions that bear on evolution but the answers to those questions are not a fundamental part of evolutionary theory. The are questions of scientific fact, in my opinion.

Do philosophers like Elliott Sober agree with this distinction? I don't think so. The main point of Sober's talk is whether evolutionary theory can show that mutations are random. He concludes that evolutionary theory cannot conclusively prove that all mutations arose by chance; therefore, there's room for God-directed mutations as long as their frequency is indistinguishable from randomness.

Sober has a paper that discusses this issue [Evolution without Naturalism]. Here's the part that describes "evolutionary theory" (page 5).

What is this thing called “evolutionary theory,” which theistic evolutionism is able to encompass consistently? It includes the origin of life from nonliving materials by physical processes, the branching genealogical process whose upshot is that current organisms are connected to each other by relations of common ancestry, the random origin of new mutations, and the processes that govern trait evolution within lineages, such as selection and drift. Among these several propositions, the idea that mutations are “random” may seem to be a sticking point.

This is not what I think of when I use the term "evolutionary theory." I don't think the origin of life is a part of evolutionary theory. I don't think that the random origin of new mutations is part of evolutionary theory. As far as I'm concerned, the discovery that mutations occurred preferentially in hotspots or that there was a base composition bias—which there is—would not refute evolutionary theory. I think my understanding of evolutionary theory is closer to that of the majority of evolutionary biologists and it's troubling to me that philosophers seem to use a different definition.

Here's another example from that same paper (page 4) ...

Although evolutionary theory is silent on the question of whether there is a God, it is not neutral with respect to logically stronger hypotheses about God. Consider, for example, the statement

Life appeared on earth about 10,000 years ago due to divine intervention.

This statement is inconsistent with evolutionary theory.

The Young Earth Creationist statement is inconsistent with all available scientific evidence on the age of the Earth. This evidence is so overwhelming that it is a scientific fact (sensu Gould) that the Earth is billions of years old. Why does Sober think that "evolutionary theory" plays a role here?

This is not just a semantic quibble. By confusing "evolutionary theory" with scientific facts Sober makes it much more difficult to follow his line of reasoning.

Is it true that the majority of philosophers of science use "evolutionary theory" when they should frequently be referring to scientific facts? Is it true that most philosophers think that the age of the Earth is a "theory"? Do they also think that evolution is only a theory?

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