Evolution *is* a Theory, and That’s Fine

Conservative candidates are now routinely asked to take a stand on whether they “Think evolution is just a theory” or whether they are among the fallen who “Believe in evolution”. These exchanges nearly bring up my breakfast on their own merits and have the added disadvantage of mis-educating the public about the nature of scientific inquiry and theory.

The dismissive remark “Evolution is just a theory” implicitly equates “theory” with the spontaneous speculations of the guy four bar stools down from you whom the bartender has at last cut off. In science, a great theory — evolutionary theory, for example — is a serious intellectual effort to explain the data we can observe and to generate hypotheses about the data we can’t. Calling a biology professor “a noted evolutionary theorist” is a compliment in the scientific community, not an implication that he is stupid, misguided or refuses to accept reality.

The alternative to conservative politicians deeming evolution “just a theory” is for them to intone “I believe in evolution” or “I accept evolution.” These sound to my ear inappropriately similar to statements of faith, e.g., “I believe in the transmigration of souls”, “I accept Jesus Christ as my personal savior”. If “evolution” in this faith statement refers to the theory of evolution, then this is the wrong terminology. Scientists don’t believe in theories per se, they believe that particular theories do a good job explaining what has been established not through faith but via empiricism. If new data disconfirm the theory, a scientist wouldn’t say “It doesn’t matter, I have accepted such and so theory and with God as my witness that’s an end of it”. Rather any scientist worth his or her salt says the theory must be wrong and therefore has to be discarded or changed.

If on the other hand the word “evolution” in the statement “I believe in/accept evolution” refers to the observable data on whether evolution ever happens, this is also a conflation of the workings of faith with those of science. You can take a colony of drosophilia and let them fly through a maze, putting sugar at the end of a right fork in the maze and nothing at the left. In a few days, the flies who tend to turn right and get the sugar will be outbreeding those who tend to turn left and pretty soon you will have a colony of right-turning flies. At that point, you don’t “believe” that natural selection can happen, you have directly observed it as a fact. You don’t have faith in this context any more than you have faith that water turns to steam if you heat it to 100 degrees Celsius.

Journalists (e.g., debate moderators) could do a service to the political process and the scientific education of the public by asking the basic question differently:

“People have long tried to explain where the creatures on this planet, including human beings, come from and why they have the characteristics they do. We have data from our observations of living beings today, from the fossil record, from laboratory studies, and from a range of other sources such as the breeding and domestication of animals, and we want some explanation to account for it all. Do you think that these data are better explained by evolutionary theory or by creationism?”.

[Cross-posted at The Reality-Based Community]

Keith Humphreys

Keith Humphreys is a professor of psychiatry at Stanford University. He served as a senior policy advisor at the White House Office of National Drug Control Policy from 2009 to 2010.