Teaching Natural Selection - Don't Give Up

We just had a research paper on our Darwinian Snails lab published, and while perusing the journal where it appears, I came upon another paper that reviewed some of the many studies which have been done over the years on students understanding of natural selection. Written by Ryan Gregory from University of Guelph, the first half of his paper is just a description of natural selection, which was not what interested me. But below this he lists 42 (!) different studies examining students understanding of natural selection, an impressive collection dating back to the 1970s. Perhaps not surprisingly, the problems have not really changed over time. In our study we found four common misconceptions: willful change; directed variation; intra-generational change; and population change. These and a couple more (use and disuse, for instance) are the same in virtually all the studies. Particularly common seem to be anthropomorphic explanations for evolution—species "want" or "try" to evolve to meet some new environmental condition. At every level tested from middle school to upper level biology majors in college, and in many different countries, invariably less than 50%, and usually closer to 5-10% had an accurate understanding of evolution by natural selection.

Gregory goes on to ask why natural selection is so hard to understand. As he puts it, "natural selection is elegant, logical, and notoriously difficult to grasp" and he makes the good point that it must be harder to get than we biologists think because no one laid out the theory clearly until 150 years ago, relatively recent for a theory that doesn't require any sophisticated technology to discover. It's not hard because of religious beliefs—many studies have shown that belief in evolution has little correlation with understanding of evolution. It's also not hard solely because of poor instruction. Again, many studies have shown that students understanding often doesn't improve that much after being taught about natural selection. We found the same thing. Our Darwinian Snails lab is quite successful—we saw large learning gains on 3 of the 4 common misconceptions around natural selection among students completing the lab. Nevertheless, when we asked students to write an overall description of natural selection they didn't improve.

Since the obvious explanations are not correct, Gregory suggest that these misconceptions come from the way we humans are wired. We tend to think teleogically (things happen for a purpose) and anthropomorphically (things act with intent). This manifests itself not only in misconceptions, but in the way that even knowledgeable biologists talk about natural selection. It's hard to avoid using words like "want", "learn", "choose", "they adapt to", and other phrases that imply intent and purpose when describing evolution. In fact its hard to resist those terms in many scientific subjects. In an earlier paper, we found the exact same problems in understanding diffusion and osmosis. Even I myself, with years of writing labs on evolution, am not sure I would get all the questions right on one of these misconception tests without putting my thinking cap on and concentrating, because its so easy to slip into that anthropomorphic style of thinking.

In light of all this, the most tantalizing result in our paper was a comparison between introductory biology and upper level biology students (principally in evolution classes). By the time students reach college, they have generally been taught natural selection at least once and often two or three times in middle and high school. Moreover, natural selection is in the news all the time, both implicitly in scientific news stories involving evolution, and explicitly in the U.S. debate over teaching evolution in schools. So students have a lot of exposure to the ideas when they arrive at college, and generally get another good dose on the theory in the introductory biology class.

That's why it surprised us that the students in upper level classes actually improved more than those in introductory biology courses on some of the questions we asked. The effect was not big, but it was significant, and we had enough students in the study (more than 500 across many different institutions) to pick up smaller effects reliably. This hints that multiple exposures to a subject can eventually bring about an "aha" moment of recognizing and overcoming a misconception, and indeed it may take multiple exposures to counteract such deeply held misconceptions as those around natural selection. "Don't give up!" is the message.