Teaching How To Answer ‘Why’ Questions About Biology

Abstract

W HAT does it mean ask 'why' questions about common biological traits? What sort of an answer should we expect if we ask why some people have dark skin, or why males in polygynous species are larger than females, or why animals sleep, or why we have fevers when we have infections? When we ask 'why' a prevalent genetically influenced trait is the way it is, aren't we asking a different sort of question, requiring a different sort of answer than when we ask 'what', or 'how' or when? To evolutionary scientists, answer 'why' questions like these requires that we get past immediate causation explain in a more ultimate sense why these traits were favored by natural selection. In my Introductory Biology class at Henry Ford Community College, and in all of my Evolution and Behavior sections too, I spend about an hour, usually the first week of class, discussing how answer 'why' questions about common biological phenomena. My purpose is introduce students the rich explanatory power of selection theory, show the distinction between proximate and evolutionary answers, and discourage thinking. It's important do this near the start of the semester since it greatly influences how students think about most everything else they learn in the rest of the class. I have found too that by showing the students early on the explanatory and predictive power of selection-based thinking, they have little inclination contentiously object when evolution is discussed later in the class. After all, they've seen how it makes good scientific sense, how it helps them understand the 'meaning' of biological phenomena. Understanding the difference between proximate and ultimate (evolutionary) explanation is, I believe, so basically, critically, necessary scientific explanation of biological phenomena, that all introductory biology texts should thoroughly discuss this in the first chapters, but they rarely do. Many biology texts don't even mention this anywhere. Some include this in animal behavior chapters, but these are rarely read since behavior is, curiously, not a topic often covered in high school or college biology classes. To make the difference between proximate and ultimate explanations clear my students, I start with a list of five or six questions in a grid of three empty columns (see Figure 1) which we fill in step by step as the students are invited suggest I don't tell the students right away that the first column is answers, that the second is proximate answers, and that the third is evolutionary answers based on natural selection. Of course all sorts of different questions other than those I've listed here work just as well as long as they ask about common biological phenomena. They should be interesting though, and ideally should include some that relate behavior as well as anatomy or physiology, and one, such as menopause, that requires an inclusive fitness (kin selection) explanation. And, at least a couple should be designed elicit answers like the first two or three on this list are almost guaranteed do. It's best mostly use phenomena students are familiar with like skin color and sleep. I usually include the Coolidge Effect, however (see description below), even though most students are unfamiliar with it so it needs be explained. If I'm short on time I substitute Why do we have fevers? or some other question that doesn't require explanation. Almost inevitably most students answer the first question by saying for protection or to be camouflaged, and they answer the second by saying to be rested or rejuvenated. I write these in the first colunm and label it teleological answers. Wait a minute, I say, These are not good scientific Camouflage and being rejuvenated are, at best, the effects of turning white and sleep, aren't they? So how can they be the causes? I then devote five minutes or so describing why answers are not scientifically satisfactory. I explain that thinking mixes up cause and effect, making it seem that the effect or supposed purpose is the cause, and that if we wish understand why something biological is the way it is, we need identify causes, not effects or 'purposes.' The students typically are surprised that they didn't give proper scientific In my experience it's rare that a student has ever been cautioned about thinking. It makes me think that many textbooks should pay more attention discussion of scientific thinking. Tom Shellberg teaches at Henry Ford Community College in Dearborn, Ml 48128.