The root of pan-adaptationism?

There’s been a fair bit of recent discussion about why most biologists are (uncritically) adaptationists. I don’t dispute this but think it’s worth reconsidering why. Some have argued that this is because of intuition (adaptation just makes sense). However I think a better explanation lies in how we teach - or fail to teach - evolution and acknowledge that teaching non-adaptive evolutionary processes is difficult. Most biologists haven’t had a full course in evolution. Instead, most have had a week or two in their college introductory biology class and if lucky, one week in their high school biology class. If they went to graduate school, they likely had no coursework that explicitly considers evolutionary biology. This is also true for most teachers, so most do not understand evolutionary biology with enough comfort to go beyond well-trodden examples of adaptations to explore with students how and why evolution may not be adaptive.

We also must recognize that understanding sources and effects of non-adaptive variation is difficult. It takes a certain depth of education in evolutionary biology to be able to teach non-adaptive processes well. Understanding drift, mutation, and recombination depends more heavily on understanding of statistics and probability, topics that are also generally lacking for most scientists and educators.

Another problem is more philosophical, but I think equally important. I wrote the following in my Teaching Statement for my tenure packet several years ago.

“One of Darwin’s most important contributions, many have argued[1], is that he replaced “typological thinking” with “population thinking.” For typologists, the “wild type” is central to all scientific inquiry; for population thinkers, the “wild type” is an average of many individuals whose variation is the subject of study. Yet this dichotomy still pervades biological education and research. Nearly all of what we are taught in biology begins with a description of discrete characters with certain function: this enzyme performs that reaction, this species lives in that environment. This may be a necessary starting point, but we rarely progress to illustrate that these “facts” are actually average population phenotypes that may not actually exist in any one individual. In my discipline of microbiology it is almost impossible to study single individuals, so the entire field relies on populations usually without recognizing this point. This shortcoming in our curricula likely contributes to how readily we overemphasize differences among individuals and to the widespread doubt of the effectiveness of evolution.”

Here, the relevant point is that if most students believe in an idealized wild-type, then diversity is underestimated and under- appreciated. Appreciating genetic drift is therefore even more remote. If we wish to tackle these problems with biology education, one solution might include developing examples that includes both adaptive and non-adaptive processes. Building in concepts of probability and effects of population size (think conservation genetics) would also be very helpful. Above all, getting teachers to invest more than the standard “one week at the end of the semester” to teach evolution would be a huge victory, one that would benefit all of our education in biology.

[1] Mayr, E. Evolution and the Diversity of Life, 1975; Sober, E. “Evolution, Population Thinking, and Essentialism” in Conceptual Issues in Evolutionary Biology, 1994.