Richard C. Lewontin (1929-2021).

Richard Charles “Dick” Lewontin died at age 92 on 4 July, 3 days after Mary Jane, his wife of 73 years. Arguably the most influential population geneticist of the second half of the 20th century, Lewontin laid the theoretical and experimental foundations of modern evolutionary genetics. He was also a prominent social critic and philosopher of science. Born 29 March 1929 in New York City, Lewontin earned his bachelor's degree in biology from Harvard University in 1951. He then joined Theodosius Dobzhansky's genetics and evolutionary biology lab at Columbia University, completing his MS in mathematical statistics in 1952 and his PhD in zoology in 1954. In the years that followed, he held positions at North Carolina State University in Raleigh, the University of Rochester in New York, the University of Chicago, and, from 1973 until his retirement in 1999, Harvard. Throughout his academic career, Lewontin pursued what he called the central “problematic” of population genetics: describing patterns of genetic variation in natural populations and understanding the evolutionary forces that shape them. Because of the dearth of genetic markers, population genetics in the 1950s was strong on theory but weak on data. Then in 1966 came Lewontin and biochemist John Lee “Jack” Hubby with protein gel electrophoresis. This simple technique—detecting allelic differences in proteins that change their electrophoretic mobility—permitted the collection of protein polymorphism data in any species. On finding unexpectedly large amounts of genetic variation in populations, Lewontin and Hubby suggested that much of it might be selectively neutral. In biologist Motoo Kimura's hands, this idea evolved into the neutral theory of molecular evolution, which became the dominant paradigm in population genetics for decades to come. The unexpectedly similar levels of diversity across species revealed by these studies—the “Lewontin paradox”—remains a puzzle still. In 1983, a graduate student in his lab, Martin Kreitman, completed Lewontin's 30-year quest to quantify genetic variation, with the first study of DNA sequence variation in natural populations. Lewontin does not appear as an author on that paper; he refused to list himself as such unless he had contributed substantially to the research. Lewontin's theoretical work complemented his empirical work. He introduced game theory to population biology in 1961 and pioneered computer simulation in the field. With Ken-ichi Kojima, Lewontin coined the term “linkage disequilibrium” to describe the correlation among alleles at multiple loci, an idea central to both modern genetic mapping studies and population genomics. With Jesse Krakauer, Lewontin devised an early statistical test to distinguish between selective and neutral evolution, noting that demographic factors such as bottlenecks affect variation throughout the genome, whereas selection affects only targeted loci. The test had problems, but it underpins modern approaches to genome evolution. Perennially interested in the interaction between the organism and its environment, Lewontin also pioneered niche construction theory. Lewontin worked primarily on Drosophila flies but also coauthored important papers on mice and crickets. In 1972, he took on humans, using relatively crude data derived from serology and allozymes to map genetic variation. His finding was important and counterintuitive: 85% of all human genetic variation can be found within a single population, with only 7% segregating among continental groupings (or “races”). In other words, genetic variation shows remarkable uniformity across the human species. Subsequent studies confirmed these results. Fifteen years later, geneticist Rebecca Cann provided context: Our species is young and only recently ventured out of Africa, meaning that all human populations are closely related. A brilliant and unsparing critic, Lewontin found much to object to in applications of biological determinism to humans. Famously, he and Stephen Jay Gould savaged their Harvard colleague, biologist E. O. Wilson, after Wilson incorporated humans into Sociobiology , his 1975 survey of the adaptive basis of animal behavior. For Lewontin, the assertions of Wilson and others were naive and dangerous oversimplifications. With Gould, Lewontin went on to write an eloquent reminder of the pitfalls of one-dimensional adaptationist interpretation. Their wildly influential essay on the spandrels of San Marco is an appeal for pluralistic thinking. Lewontin wrote extensively (with crystal clarity) for the public both in his books and as a regular contributor to the New York Review of Books . Lewontin, a Marxist who resigned from the National Academy of Sciences to protest its involvement in military research, has been accused of tainting his science with his politics. If anything, though, the “dialectical” approaches that he championed allowed him to remain open-minded yet rigorous when thinking about complex biological patterns. He was dogmatically nondogmatic. His Marxism was arguably a key component of his scientific success. At Harvard, he designed his own research space, assigning the desirable corner office to the Drosophila “kitchen,” where fly food was prepared. The worst job, Lewontin insisted, should be done in the nicest part of the lab. The lab's centerpiece was an enormous table for meetings, rather than the wet lab. Science, Lewontin believed, was forged through discussion. At that table, Lewontin—animated, hands waving, spectacles awry—steered conversations that rampaged across disciplines spanning science, philosophy, politics, history, and sociology. Lewontin's legacy extends far beyond that table. He directly trained generations of scientists, including both of us, and inspired countless more. Despite his disdain for scientific celebrity, he received many awards, including the 2015 Crafoord Prize (shared with theoretical geneticist Tomoko Ohta). He also contributed to unexpected fields, collaborating in the 1950s, for example, with architect Buckminster Fuller to design geodesic domes. However, Lewontin was much more than just the sum of his intellectual contributions; he was a loyal mentor and a beloved friend.