Teaching Evolution: Theodosius Dobzhansky: Genetics of natural populations

February 27, 2019 • 10:30 am

by Greg Mayer

Readers may recall that last spring I began what Jerry called a “mini-MOOC” on evolutionary biology. Because I began making posts fairly late in the semester, I got to only seven installments before the semester ended. I’m teaching the same course, BIOS 314 Evolutionary Biology, this spring, and so I’d like to start up again.

In the class I have the students read a series of what I regard to be classic papers or extracts–—one each week—and these are what I want to share with WEIT readers. Each reading is accompanied by a brief biography and illustration of the author, and a small number of study questions, designed to guide the student in understanding the reading. I sometimes assign these questions as homework essays, or include them on exams. When possible, I will provide links to the readings. The installments so far have been Charles Darwin, A.W.F. Edwards, George Gaylord Simpson, Charles Lyell, Alfred Sherwood Romer, Alfred Russel Wallace, and Richard C. Lewontin. We pick up with Theodosius Dobzhansky. Dobzhansky was a key figure in the “Modern Synthesis” of evolutionary biology in the 20th century (as described below). Jerry had intended to do his doctoral work with “Doby” (as he was known later in his career; students from earlier knew him as “Dodik”), but wound up studying with Dick Lewontin, who had been a student of Doby’s, and thus Jerry is Doby’s academic grandchild.

Theodosius Dobzhansky (1900-1975) was a Russian-American geneticist who was arguably the most important evolutionary biologist of the 20th century. Completing (although never formally receiving) an undergraduate degree at the University of Kiev, he began his career conducting field studies of coccinellid beetles and laboratory experiments on Drosophila. In 1927 he received a fellowship to come to America and work with T. H. Morgan at his famed “fly room” at Columbia University. As a geneticist working at the epicenter of American genetics, Dobzhansky was well aware of the important empirical and theoretical advances being made in genetics; as a field worker and experimentalist, he was able to tie these developments more closely into the phenomena of natural populations. He synthesized the theoretical, experimental, and field approaches in his classic book Genetics and the Origin of Species (1937). It was through this book, much more so than through the previous synthetic, but more theoretical, works of Fisher, Haldane and Wright, that the biological community as a whole became aware of the developments in evolutionary biology, and the book inspired an outpouring of work carried on in the same synthetic spirit. Dobzhansky is well known for his two aphorisms, “Nothing in biology makes sense except in the light of evolution”, and “Heaven is where, when the experiment is over, you don’t need statistics to figure out what happened.” His major works include Genetics and the Origin of Species (3rd ed., 1951), Mankind Evolving (1962) and Genetics of the Evolutionary Process (1970). His monumental 43-paper series on the “Genetics of Natural Populations” (1938-1975) has been reprinted, with extensive historical and biographical commentary, as Dobzhansky’s Genetics of Natural Populations I-XLIII (1981), edited by Lewontin, Wallace, Moore, and Provine.

Dobzhansky, Th.1951. Genetics and the Origin of Species. 3rd ed. Columbia University Press, New York. Excerpts from Chap. III. “Mutation in Populations” (pp. 50-55, 70-75) and Chap. V. “Adaptive Polymorphism” (pp. 108-123, 129-134).

Study Questions:

1. What is blending, as opposed to particulate, inheritance? What are the consequences of the two sorts of inheritance for the evolutionary process? What analogy does Dobzhansky use to illustrate the effect of blending inheritance?

2. How does Dobzhansky see the “stored” genetically variability of natural populations and the generally deleterious nature of mutations nonetheless leading to populations being adapted to their conditions of existence?

3. Can a phylogeny be estimated for infraspecific variants? [We usually think of phylogeny being estimated for species, so that we can say, for example, lions and tigers share a more recent common ancestor than either does with the house cat. But could we construct a phylogeny for, say breeds of house cat? Or subspecies of tiger? Or mitochondrial haplotypes of the lion? See Dobzhansky’s Fig. 4 (p. 113 in the reading) for his answer.]

4. What is balanced polymorphism? How does balanced polymorphism relate genetic variability and natural selection?


22 thoughts on “Teaching Evolution: Theodosius Dobzhansky: Genetics of natural populations

  1. Not sure if I’ve told this Dobzhansky story previously on this site, so here it is. He visited Dave Suzuki’s lab in Vancouver BC when I was there on sabbatical. They had a fly stock that interested him and they set up a vial culture for him to take. One of the graduate students advised him that, while it is not illegal to bring flies into the US, it probably would be easier just to keep the vial in his coat pocket as he went through customs. His response (imagine it in a thick Russian accent): “You think maybe I have never smuggled any flies?”

    1. I don’t think there is any such textbook that has this content. It is pretty common for more advanced classes to not use a text, since they don’t fit the better vision of the instructor.

    2. We use Futuyma and Kirkpatrick, Evolution (4th ed.), as a textbook. These classic readings are in addition to about a chapter a week from that text. There are three reasons for these classic readings. First, ever since I learned genetics as an undergraduate from a brilliant professor, Eugene Katz, who used a historical approach, so that his students learned not just the “facts” of genetics, but the evidentiary and experimental basis of those facts, I have been a fan of a historical approach. After his class, I could tell you not just that DNA is the genetic material, but also go through the evidence that showed that to be the case. My evolution course does not take as thoroughgoing a historical approach, but uses elements of it. Second, it introduces students to the primary literature– the monographs and papers in which scientific results appear– rather than just the distillation of those results found in textbooks. (Textbooks can be great, but they’re not the same as the primary literature.) I would add that some of the readings I use– e.g., from the Origin, this piece by Dobzhansky– have also historically been very persuasive in the arguments they make, so they are models of scientific reasoning. And third, don’t know your past, don’t know your future.


      1. I can see how it would be quite useful for the undergrad to read the original books or papers as well as do some of the classic experiments. Otherwise it’s a bit like jumping to the end of a mystery novel; knowing who dunnit misses the point of how and why. Of course, for myself, man of lesser intellect, I often get the old and often mistaken ideas and the newer corrected ones muddled.

        1. This is how philosophy typically works (the joke is “secondary sources are for graduate students” – who have to know what others have said to try to be original, rebut interpretations, etc.)

  2. “What are the consequences of the two sorts of inheritance [blending versus particulate inheritance] for the evolutionary process? ”

    Evolution by creeps or evolution by jerks is one answer.

  3. In 1930, the distinguished Russian biologist Nikolai Vavilov visited the US and tried to persuade Dobzhansky and Grigori Karpachenko, who were on research fellowships here, to return to the Soviet Union. Doby decided to stay in the US, becoming a citizen in 1937, and pursued the great career in evolutionary genetics covered in this episode of the MOOC.

    Karpachenko, on the other hand, took up Vavilov’s offer. They were both arrested by the NKVD as enemies of the people in 1940 and 1941. Karpachenko (who had earlier famously demonstrated speciation in action through allopolyploidy) was executed on July 28, 1941. Vavilov died in prison camp. {See: “The Murder of Nikolai Vavilov” by Peter Pringle.]

  4. Excellent post, and very good study questions. Ukrainians might disagree with the assertion that Dobzhansky was “Russian”. Although he was Russian-speaking he was born in Nemyriv, Ukraine and educated at the University of Kiev.

    Like Greg and Jerry I have Dobzhansky as my academic grandfather. I met him in 1963 when Dick Lewontin sent me to New York City to hand-carry some data to Dick’s lab in Rochester. He was very gracious in an old-fashioned European way, and gave me a tour of his lab and introduced to his assistants. When I questioned the logic of one explanation he gave, he explained his position by simply repeating what he had originally said (I had the good sense to thank him as if this clarified everything).

    He was loved by his students. He took academic arguments personally. Jim Crow, who was often in disagreement with him on the forces responsible for genetic variation, said he could tell whether Dobzhansky was upset at him, because then the letter from Dobzhansky would start “Dear Crow” instead of “Dear Jim”.

    1. Joe– Thanks for the comment, and I’d like to follow up on one point–Dobzhansky’s ethnic self-identification. When I did a Dobzhansky exhibit in our library here, a local Ukrainian objected to calling him Russian. But Nemirov was part of the Russian Empire (ruled by the “Czar of All the Russias”) at the time of his birth, and I believe he was Russian Orthodox. I can find in his writings various references to Russian literature, and other of his colleagues have referred to him as “Russian”. I asked a Russian colleague whether he could identify the ethnicity of the name “Dobzhansky”– he said it was Polish. In a time of empire, languages and ethnicities may have blended more fluidly, but, at the same time, adopted the name of the rulers. Did Dobzhansky, either in his writing, or to you personally, identify as Russian or Ukrainian?


      1. I don’t know anything beyond banalities about Dobzhansky, but it does seem to me that this may well be a classic case of (deliberate attempts?) to blur the line between political affiliation of place of origin (historical and current) and language spoken (or other ethnic characteristics).

      2. In my contact with Dobzhansky in 1963, and in a couple of subsequent times when I attended lectures he gave at scientific meetings, he did not say anything about his ethnicity. Just being in the Russian Empire would not settle the matter, at least not for most Ukrainians, who were also in it. I believe that he was Russian-speaking rather than Ukrainian-speaking. So he might well have self-identified as “Russian”, but the matter is at least complex. Ask Texans who were born there, but whose family language was Spanish.

  5. Can you make the source reading available on the web? The US copyright on a 1951 publication would have long since expired, so you wouldn’t be violated that.

    I doubt the mildly curious here would try to go purchase or other wise find a copy of the book to play along. (particularly if each installment relies on a different book.)

      1. Actually, you might need an ophtalmologist after reading a few pages. But it is better than nothing.

  6. That second quote really strikes home for someone who is attempting to infer homologies by using, among other things, maximum-likelihood evolutionary models.

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