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Tuesday, February 28, 2012

Exam Question #4

Now that you've tried Exam Question #1, Exam Question #2, and Exam Question #3, let's see how you do with this one.
Many evolutionary biologists think that population genetics is the key concept in understanding evolution but biology students often complete several years of courses without ever learning about effective population sizes, mutations rates and the importance of random genetic drift. Why? Is it because population genetics is not a necessary key concept in evolution?


  1. Just from what I've seen, I'd say it's because this area of biology is heavily math-based, and many students would avoid it for that reason.

  2. Evolution IS population genetics. Evolution is the change in allele frequencies over time. Therefore, delay in teaching about mutation rates, etc., cannot be because population genetics is not a key concept in evolution.

    However, effective population size and mutation rate are math. Calculus, even. Many freshmen, even many sophomores, haven't completed calculus. Most are shaky about it. Many instructors (including me, sadly) aren't comfortable with the math. We can tell about many important parts of evolution with words, so we do. And then there are so many other aspects of biology that students need to learn! We can't do population genetics much at first, and it's easy not to get to it at all.

    Failure to emphasize the importance of genetic drift is a little different. This concept gets passed over because although we all know (and teach) that it happens, many don't realize how "creative" it can be. Even if we do, it doesn't as easily lend itself to good story telling.

  3. Evolution IS population genetics. Evolution is the change in allele frequencies over time.

    uh huh.
    So paleontologists aren't studying evolution?
    No, I'm afraid the study of biological evolution requires a more...dare I use the term...pluralistic approach than your standard reductionist boilerplate suggests.

    I'll tell you why population genetics gets left out of many introductory biology courses: a) time constraints and priorities; b) the vast majority of students--and introductory-course-teaching professors--find it boring as hell. All the textbooks have Hardy-Weinberg and the whole 9 yards, but it's abstract and conceptual and mostly modelling instead of empiricism. Biology students either want to become health professionals or they think animals or plants are totally cool. Calculating allele frquencies seems far from those interests.

    1. Paleontologists are studying the visible effects of change in allele frequencies over time.

      Animals and plants ARE cool. The coolest thing about them is how they got to be so cool. That is where pop gen is needed. You cannot understand speciation and other population-level processes without it.

    2. @Chas,

      By that logic, should we stop teaching students to do linkage maps out of three-point crosses in intro genetics as well? I was not under the impression that cool was supposed to over-rule knowledge in a university.

      -The Other Jim

  4. Because the way biology is taught is so very very very very wrong. (And yes, the requirements for getting into med school, in the USA at least, do have a lot to do with it.)

    Until biologists realize that they have to base the teaching of their discipline on a solid understanding of mathematics and computing, the discipline will continue to be looked down upon as a soft science.

    1. Yes, and the widespread prevalence of mathematical and statistical errors in the peer-reviewed literature attest to the poor quantitative preparation of most biologists (including geneticists).

  5. Chas Peterson said:

    So paleontologists aren't studying evolution?

    So morphological changes in the fossil record did not have a genetic basis?

    I'd agree with your argument on population genetics in introductory courses, but second- and third-year students should be able to warm up to it. I think that a paucity of popgen in biology classes reflects the interests and disinterests of the instructors.

  6. Because, and I quote from a quote in Lynch 2007 PNAS, "population genetics isn't inspiring". Hell, I *hated* that stuff all through undergrad, and thought it had no relevance whatsoever to the biology I found interesting. Perhaps in the few instances we had popgen shoved down our throats, the instructors thought in a similar manner, or didn't entirely understand populations (and drift!) themselves. The way drift is taught makes you think it only applies to endangered species on the verge of extinction, as in "selection breaks down" kind of thing. It's not taught as a process in parallel with selection, perfectly plentiful in massive populations as well. Selection is taught as an all-or-nothing process: if you're good you're selected for, if you suck you're removed. No middle ground, no probabilistic models, nothing.

    Perhaps it doesn't help that popgen is also typically taught by some variant of an ecologist or evolutionary ecologist -- those folk tend to be vehemently adaptationist, as it would deeply offend them to learn that perhaps not every beak parameter they spent 20 years of their lives measuring is that way because of a deeper (ie, adaptive) purpose. In fact, I find ecologist the most difficult to talk to about non-adaptive evolution... that probably has some effect on what people learn in class as well.

    At the end of all this, the importance of popgen is obscured and people move on to more inspiring things, like fossils and butterflies. Forgetting, of course, that evolutionary biology is a science with rigorous theoretical and mathematically foundations.

  7. The consensus seems to be that evolution is taught very poorly in university. I agree.

    We are allowing students to graduate from university with degrees in biological sciences but with no real understanding of evolution and how it works. That's our (professors') fault and it has to change.

    Is it any wonder that the general public fails to appreciate the solid science behind evolution?

    Introductory evolutionary biology needs to be taught from a population genetic perspective and that means that students have to understand genetics. If that's too hard for them then they will flunk the course. Good riddance, I say, they probably shouldn't have been in university to begin with.

    Professors who are incapable of teaching introductory evolution correctly should be replaced or fired. Those with tenure can be assigned to other courses. Perhaps they could teach a course on Rudyard Kipling in the English Department or a course on evolutionary psychology in some humanities department.