by Greg Mayer
Our seventh installment of Teaching Evolution is an extract from The Genetic Basis of Evolutionary Change by Richard C. Lewontin. As regular WEIT readers will know, Dick was Jerry’s Ph.D. dissertation advisor (and mine too in the de jure sense, since my de facto advisor, Ernest E. Williams was retired). In this book, Dick summarized and critiqued the initial results of the “find ’em and grind ’em” school of population genetics, which studied electrophoretically detectable allelic variation in soluble proteins. In the extract chosen, he lays out the basic questions of population genetics, and how, historically, they have been addressed. It turns out that protein electrophoretic data were inadequate to our needs, leading to a further “struggle to measure variation”, leading eventually to nucleotide sequencing. The last of Dick’s books mentioned below is a collection of reviews from the New York Review of Books; it contains “Sex, Lies, and Social Science” (and the subsequent exchange), which along with Peter Medawar’s takedown of Teilhard de Chardin, and E.E. Williams’ takedown of Soren Lovtrup, is among the best book reviews ever.
Richard C. Lewontin (b. 1929) is Alexander Agassiz Professor of Zoology Emeritus in the Museum of Comparative Zoology at Harvard University. One of the most influential population geneticists of the 20th century, he studied under Th. Dobzhansky at Columbia. His work has centered around what he has called “the struggle to measure variation”, and the interpretation of that variation in terms of the evolutionary forces acting on populations. In 1966, he and Jack Hubby at the University of Chicago, and, independently Harry Harris in England, introduced the technique of protein gel electrophoresis to the study of genetic variation in natural populations and showed that there is abundant variation in nature. His student Marty Kreitman was the first to use DNA sequencing to study variation, which, like electrophoresis before it, has revolutionized empirical population genetics. Lewontin’s books include The Genetic Basis of Evolutionary Change (1974), Human Diversity (1982), The Triple Helix (2000), and It Ain’t Necessarily So: the Dream of the Human Genome and Other Illusions (2000).
Reading:
Lewontin, R. C. 1974. The Genetic Basis of Evolutionary Change. Columbia University Press, New York. Extracts from Chap. 1, “The Structure of Evolutionary Genetics” (pp. 3-6), and Chap. 2, “The Struggle to Measure Variation” (pp. 19-38 and pp. 86-94). (access to entire book)
Study Questions:
1. What does Lewontin see as the most essential part of Darwin’s contribution? Why does this contribution make the study of genetic variation crucial for the study of evolution?
2. What are the “classical” and “balance” schools of population genetics? What are the views of these schools on the nature and amount of variation in natural populations, the modes of natural selection acting in natural populations, and the genetics of speciation?
3. What degree of variability in populations is inferred from the study of visible mutations, and from the study of the results of artificial selection? How do these estimates compare to one another?
4. How would DNA sequences, as opposed to mere identification of protein alleles (as is done in electrophoresis), provide richer information for addressing the questions posed by Lewontin? In particular, how would they provide better data on the nature of selection? (The answer to this is not in the reading.)
Sub
This was the textbook in my graduate class in population genetics, taught by Rollin Richmond at Indiana University in 1975 or thereabouts. It is still on my shelf as both a keepsake and a reference.
Greg, this would be a good time to give some thought to meaning of “variation” and how it should be quantified and analyzed. Lewontin was fundamentally wrong about that subject. It is important to get this right, or else we will make mistakes when describing, analyzing, or explaining genetic variation.
I would certainly wish to read more about this problem.
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Does the DNA sequencing vs electrophoresis have anything to do with seeing the alleles within a groups of related genes that can function together and therefor reveal more information rather than seeing the alleles as individual bits of information without the related genes? I assume this might be because several genes might work together to influence the phenotype and thus be selected together. Am I even close?*
*Be kind…I’m was history/anthropology major! 😬
I’m campaigning to get Dick some credit for the neutral theory. Two years before Motoo Kimura nailed his flag to that mast, Dick wrote the discussion section of the Lewontin and Hubby paper in which he pointed out, very clearly, that among the several possible explanations for the high level of electrophoretic variability was that it was the result of neutral mutation. He did not commit himself to this possibility, but it was the first clear statement of the neutral theory for within-population polymorphism.
Reblogged this on The Logical Place.
I’ve been struggling with understanding what counts as a new environment in the norm of reaction sense, hence what traits are and what is “under genetic control” exactly.
Maybe I should grab some more advanced texts!
I did not do the recommended reading but am interested in this article: Sex, Lies, and Social Science
Richard C. Lewontin
There are only a few paragraphs available. This is part of a book he wrote?
I got it. Thanks so much!!
It Ain’t Necessarily So: The Dream of the Human Genome and Other Illusions 2nd ed. Edition
by Richard Lewontin (Author)
It looks like these books would be available through Barnes and Noble or a library.
Science in the Bedroom: A History of Sex Research
by Vern L. Bullough
Basic Books, 376 pp., $25.00
The Social Organization of Sexuality: Sexual Practices in the United States
by Edward O. Laumann and John H. Gagnon and Robert T. Michael and Stuart Michaels
University of Chicago Press, 718 pp., $49.95
Sex in America: A Definitive Survey
by Robert T. Michael and John H. Gagnon and Edward O. Laumann and Gina Kolata
Little, Brown, 300 pp., $22.95