Monday, July 12, 2010

The Nature of Evolution

A while back, you might remember I stirred things up when I declared that there was evidence for evolution, that it wasn't a theory in crisis, etc. In terms of the culture war, underestimating the enemy is the worst thing you can do. In terms of truth-telling, it's just false to say that evolution is a failure or on the verge of collapse. Over and over, I emphasized that creationists can continue to be creationists, that we don't have to believe evolution, that we can still remain skeptical and search for other explanations. I just wanted to acknowledge that there's a good case, a really good case, to be made for evolution. That's really not such a big deal, but people still don't seem to understand it.

Which brings me to the subject of this post. I recently received an email suggesting that I needed to define what I meant by "evolution" when I wrote,
There is evidence for evolution, gobs and gobs of it. It is not just speculation or a faith choice or an assumption or a religion. It is a productive framework for lots of biological research, and it has amazing explanatory power.
Back when I was writing the series that explained my initial "Truth about Evolution" post, I intended to write something about what evolution is, but it slipped my mind. So here we go.

In its most basic form, evolution is a kind of development, a change over time. In biology (broadly speaking), the word was originally used to describe the development of an individual organism from an egg. Later, through early ideas of recapitulation, it came to describe the development of whole species. As a development, evolution doesn't necessarily describe the origin of the thing developing.

Since evolution as development is a broad concept, it can describe lots of things. Evolution could be just a change in the composition of a population's gene pool. Evolution could be the origin of new varieties or new species. Evolution could be the grand development of all living things on this planet from a single ancestral population. It's this flexibility of the term that presents a problem. As a creationist, I don't really have a problem with evolution as changes in allele frequency. Nor do I care much about the origin of varieties or species. It's universal common ancestry thing that I can't accept (for biblical reasons, as I've detailed elsewhere). So how do I and other creationists describe our position? What words should we choose?

In creationism, the longstanding solution to this problem has been redefinition of existing terms. Use evolution only to refer to the objectionable forms ("fish to Gish"), or bring in terms like microevolution and macroevolution to describe evolution we're OK with (the former) and evolution we object to (the latter). This gives us the advantage of precision in writing or speaking, and the whole micro/macro evolution thing allows us to introduce the idea that not all kinds of evolution are objectionable.

The problem with the approach is that these novel definitions are not the standard ones and they tend to obfuscate more than explain. It happens on both sides. I can't tell you how many people out there think that speciation is some kind of falsification of creationism. Why? Because they think objections to evolution are objections to all "development or change over time." On the other side, denial of evolution can lead lay creationists to assume that species fixity is creationism because creationists objection to evolution as "development or change over time."

As I've argued before, I think pandering to people's ignorance by playing around with definitions is bad. It's only going to make the confusion worse. That's why I've been trying to avoid using these creationist-only definitions. I'm not consistent yet (bad habits are hard to break), but I'm working on it.

In the case of "evidence for evolution," I meant evolution in the standard, conventional sense. There are observations of allele frequency changes in populations (Darwin's finches, for example), evidence of speciation (as explained in Darwin's geography chapters in Origin and elsewhere), and there is evidence for universal common ancestry (genetic code, protein homology, core metabolism, etc.). For some of that evidence, I'm content to accept the evolutionary interpretation. For other evidence (particularly of universal common ancestry), I think there is another explanation.

If you're looking for an explanation of this evidence for universal common ancestry, check out this blog post. And if that explanation is not good enough, you can always denounce me as a debate dodger.

Feedback? Email me at toddcharleswood [at] gmail [dot] com.