The death of American geneticist Richard Lewontin

The most influential geneticist in half a century of evolutionary study, Richard C. Lewontin died on July 4, in Cambridge, Mass., At the age of 92, just three days after Mary Jane, the companion of his life. After studying at New York high school and then at Harvard University, he joined the laboratory of geneticist Theodosius Dobzhansky at Columbia University, one of the four prestigious founders of the “Evolutionary synthesis” neo-Darwinian, and defended his thesis there in 1954.

After the Second World War and the first atomic explosions, controversy rages among population geneticists as to whether the mutations caused by nuclear tests risk increasing the “genetic burden” of the species. More generally, we then realize that we do not know how to estimate the natural genetic variability of populations. Lewontin will resolve the matter. Essentially trained in mathematical approaches, he understands that the solution lies in finding a method of measuring variation in any species, without any choice of genes studied.

He joined forces with the biochemist John Hubby (1932-1996) of the University of Chicago, and both developed in 1966 the technique of “allozymes” (discovered simultaneously by the British Harry Harris), which consists of using the protein variation as an indicator of DNA variation, which we do not yet know how to sequence. Their two 1966 articles revolutionized the study of the evolution of species. On the one hand, it becomes possible for the first time to measure the kinship of two individuals or of two populations. On the other hand, we discover that practically all living species, including the human species, are much more “polymorphic”. (genetically variable) that we had imagined. We therefore realize that every living being is genetically distinct from any individual existing or having existed in his species.

New scientific revolution

The end of the controversy over the genetic burden will give birth to twenty years of a new controversy, in particular with the Japanese geneticist Motoo Kimura, to find out whether the genetic polymorphism is “neutral” or “selected”. Lewontin expresses the strength of this debate in his book The Genetic Basis of Evolutionary Change (1974, Columbia University Press, untranslated).

His laboratory at Harvard was at the origin of a new scientific revolution in the 1980s when he carried out the first studies of the variability of DNA sequences and showed that DNA polymorphism itself was much greater than that of proteins. This will ultimately reconcile the protagonists of the debate. “Selectionism / neutralism”, showing that the parts “Neutral” DNA can be used, by comparison, to highlight parts of chromosomes that are subject to natural selection.

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