Tuesday, November 13, 2007

Defining Evolution: Getting Terms Right

Recently I defined intelligent design (ID), said ID isn't science, and looked at the problem with naturalism. This post is loosely related to those.

As Jon has twice emphasized the importance of understanding our terms when discussing evolution, we really should ask: What does the word “evolution” mean? It can be kind of slippery.

1. Change over time
The most general and least controversial use of the word is simply to say that things change over time. Many things evolve: individual people evolve, languages evolve, recipes evolve. And yet this use will occasionally raise hackles.

2. Microevolution
When speaking about biological creatures, microevolution is those changes that occur within a species to emphasize certain traits. Breeding dogs until you have a particularly long-haired variety is microevolution. Drug resistance is another example – if an infection is not wiped out by a drug, the surviving pathogens will probably not be as strongly affected by the drug in the future.

3. Macroevolution
This is what most people mean when they say “evolution.” This is the gradual change of one species into another, sometimes referred to as descent with modification or speciation. This is that piece that is theorized but has never been observed in nature nor in the fossil record.

Why this is important: A special brand of equivocation
Getting our terms correct is important because evidence for one is often applied to another kind – specifically, evidence for microevolution is often passed off as evidence for macroevolution.

A couple of years ago I saw a Doonesbury cartoon that did this very thing with drug resistance. It uses the idea of being treated with ancient, and useless, drugs as a scare tactic to get people to accept evolution. The only problem with this is that “creationists” don’t have any issues with microevolution. It is speciation that we question.

Why do people mix things up like this? In my more charitable moments I attribute it to intellectual laziness. In my less charitable moments, I attribute it to dishonesty. I’m open to other interpretations if they’re offered, though.

Summing it up
This is post is not meant to be an argument against Darwinian evolution. My primary goal here is to make readers aware of the bait-and-switch that goes on with the word “evolution” and to help you guard against it. My secondary goal is to encourage any evolutionists who visit to be careful and clear in their terminology. The equivocation isn’t going to work much longer – more and more people are becoming aware of it. You’re going to have to argue your case with actual evidence of speciation if you want to get anywhere. If you decline, you’ll only make the creationist’s job easier. Which, of course, isn’t really a bad thing at all :-)


Martin LaBar said...

I think that quite a few people would call speciation microevolution, and reserve macroevolution for the supposed origin of families, orders, and phyla.

Jon said...

Nice descriptive post. I don't know enough about science to interact with Martin's comment above, but I think you do a very nice job explaining this issue. Keep up the good work! I am glad that I was able to inspire you to great heights.

ChrisB said...

Martin, I've seen microevolution used that way, but I'm confident the more correct usage is what I've posted above. That confusion is why I try to avoid using either micro or macro in conversation/debate; I prefer to use speciation as it makes what I'm arguing clearer.

Jon, thanks for the encouragement!

Jon said...

For anyone interested, Dr. Douglas Groothuis (Denver Seminary) has a great lecture about ID here.