I’m a little worried about teaching genetics

I start teaching my genetics class today, and usually I plunge right in to simple Mendelian genetics to get through the easy stuff quickly. I’m making a big change, though, for social and political reasons. In a country rife with neo-Nazis and racism, it’s a bad idea to encourage simplistic thinking about genetics — too many people know a little bit about Mendel’s pea plants (trust me, those traits were chosen for their discontinuous properties and apparent simplicity), a teeny-tiny bit about Darwin and selection, and turn that into sweeping pronouncements about the True Nature of Humanity, as understood by idiots. It’s embarrassing. So I’ve decided to start the genetics course with a little demonstration of humility. Think before you leap to conclusions about how genetics works!

This page on the myths of human genetics is extremely useful for that purpose, so we’re going to go through a few examples right there in the classroom, and show some of the data. There has been a historical tendency to shoehorn traits into a simple Mendelian model, and it’s easy to show that there are cases where that doesn’t work, at all.

We’re also going to take on that popular nonsense about finger lengths, which is just a classic example of overinterpreting tiny amounts of variation (which is still statistically significant!), and making grandiose claims about human nature as derived from a morphological feature. It’s little more than modern palmistry…I’ve even found a page on palmistry that just runs on at length about these ridiculous claims about personality derived from the length of your index finger. And then there’s Joseph Mercola, who claims that you can use finger length to predict your IQ, SAT scores, and of course, autism, in addition to your sexual preferences.

In the end, I’m going to give them a short list of basic intellectual and ethical ideas they ought to have when beginning a study of genetics.

  • Avoid value judgments. What is a flaw to one person might be a virtue to another.

  • Do not concatenate assumptions. An individual might have a particular trait, but it does not imply that they have another, and another, and another, creating a false picture from a single data point.

  • Genetics is a mighty fine hammer; it does not mean everything is a nail. In particular, individuals are the product of gene products interacting with each other and the environment. Don’t disregard one component at the expense of another!

  • Reductionism is essential for a beginning of understanding, but is not sufficient for a thorough understanding. We start simple because that’s what we’re sure of; but our purpose is to build a more accurate model on that foundation, that will inevitably be more complex.

  • We do not understand everything about heredity. An ethical culture refuses to stereotype people on the basis of limited knowledge…or worse, false knowledge.

  • Nullius in verba. Critically assess all claims.

On Monday we’ll review basic Mendelian genetics, which seems to be all students come out of high school knowing anything about (and even at that, they’ll make lots of mistakes). It just seems to me, though, that in the current political climate it is irresponsible to put off a discussion of the limitations of science and ethical concerns until the very end of the course.


  1. birgerjohansson says

    Here is another idea: “Complex things are bloody well complicated!”

    .. .. .. ..
    BTW I see that the convergent evolution of two different species have been sorted out at the gene level:
    “Genetic comparison of giant and red pandas offers clues about convergence” https://phys.org/news/2017-01-genetic-comparison-giant-red-pandas.html

    Predicted response from creationists:
    “If they evolved from bears and ferrets, why are there still bears and ferrets?”

  2. marcoli says

    Now, you be careful there, PZ! If you allow that tongue rolling and numbers of hairs on the middle phalanges does not apply to simple dominant versus recessive alleles, then next thing you know they will question your absolute authority regarding other things like white versus red eye color in Drosophila. This way lies madness! Mad-ness, I tell you !!! They will sit there with their arms crossed (in some partially unpredictable ratio) while you try to explain the lac operon, not believing a word of it unless they find out for themselves.

    No, but seriously, this sounds really interesting. I look forward to your report.

  3. kestrel says

    Read the link on myths of human genetics…how interesting to use cats instead of people for the examples! I spent a great deal of time learning coat color inheritance in rabbits. Reading about cat coat color and so on brought back many good memories.

    The class you describe sounds like a very fun class. And maybe they’ll learn other things too.

  4. cnocspeireag says

    What a splendid way to start a course! It’s many decades since I was a Chemistry undergraduate and we were so used to being crammed with data from day one. Much of the course was old and settled (we thought). One had to be an enthusiast already as little was added by most of my lecturers to grab the attention.

  5. a_ray_in_dilbert_space says

    PZ and others,
    I am wondering if anyone has read “The Violinist’s Thumb,” by Sam Kean. I am not a biologist or geneticist, but rather a physicist. However, there is a wonderful account of what happens when physicists get involved in biology regarding the fact that DNA codes for only 20 amino acids when it could conceivably code for 64. The physicists started coming up with models that were coded with error detection and correction. All wrong, of course.

    I am enjoying the book. It’s entertaining, but I’m wondering if it contains egregious errors. Thoughts?