Ever since the mid-1800s, when Charles Darwin articulated the theory of evolution and the Moravian monk Gregor Mendel discerned the basic principles of heredity by crossbreeding peas in his garden, scientists, philosophers, social scientists and theologians have debated the implications of genetics on the origins, meaning and future of human life.

In the second half of the 20th century, one of the most prominent scientists to spar in that arena was geneticist Richard C. Lewontin.

Dr. Lewontin devoted nearly his entire academic career to the study of genes, the unit of heredity by which traits are passed from parent to offspring. But he was perhaps best known for arguing the limits of genetics in determining the nature of a person or a population — a case he made forcefully, even combatively, especially when his research allowed him to rebut what he regarded as racist ideas of genetic determinism.

“I happen to be a person who thinks that genes influence everything,” Dr. Lewontin told the Boston Globe in 1996. At the same time, he cautioned against what he derided as “genomania,” warning that “one should not fall victim to genetic nuttiness.”

Dr. Lewontin died July 4 at his home in Cambridge, Mass. He was 92. His death was announced by Harvard University’s Museum of Comparative Zoology, where he taught and conducted research for 30 years before his retirement in 2003. A son, Timothy Lewontin, said the cause has not yet been determined but that Dr. Lewontin had stopped eating some time ago.

Dr. Lewontin belonged to a cadre of academics, also including Harvard colleague Stephen Jay Gould, whose writings and influence spilled over from the peer-reviewed pages of scientific journals into more mainstream outlets such as the New York Review of Books. Their debates also spilled over into politics; a Marxist, Dr. Lewontin opposed the Vietnam War and dedicated his book “The Dialectical Biologist” (1985), written with Richard Levins, to the communist philosopher Friedrich Engels, “who got it wrong a lot of the time but who got it right where it counted.”

In particular, Dr. Lewontin carried on a years-long intellectual boxing match with Edward O. Wilson, another colleague at the Museum of Comparative Zoology. Wilson received the first of two Pulitzer Prizes for his book “On Human Nature” (1978) laying out the tenets of sociobiology, which seeks to explain animal and ultimately human behavior through evolution.

“Biological determinist arguments all have a similar form,” Dr. Lewontin once wrote in a takedown of sociobiology, dismissing such arguments as all envisioning the same flawed model of society.

“It is not surprising,” he wrote, “that the model of society that turns out to be natural, just and unchangeable bears a remarkable resemblance to the institutions of modern industrial Western society, since the ideologues who produce these models are themselves privileged members of just such societies.”

Dr. Lewontin’s first major work was the book “The Genetic Basis of Evolutionary Change” (1974), in which he challenged the notion that genetic variation could explain differences among racial and ethnic groups.

Studying protein types in the blood of people classified as West Eurasians, Africans, East Asians, South Asians, Native Americans, Oceanians and Australians, he determined that “around 85 percent of variation in the protein types could be accounted for by variation within populations and ‘races,’ and only 15 percent by variation across them,” David Reich, a Harvard University geneticist, wrote in the New York Times in 2018. “To the extent that there was variation among humans, he concluded, most of it was because of ‘differences between individuals.’ ”

Like-minded thinkers pointed to such findings to underscore the absurdity of racism, sexism and other forms of prejudice that assumed innate differences among different human populations. Race, Dr. Lewontin argued, was little more than an “indication of the power of socioeconomically based ideology over the supposed objectivity of knowledge.”

On the basis of such research, Dr. Lewontin objected to the relevance of IQ tests measuring human intelligence. When an international consortium of scientists undertook the Human Genome Project, a decades-long effort to sequence the genes of humankind, he rejected the notion that any such map, no matter how complete, could provide a comprehensive understanding of human life.

To those with whom he disagreed, or whose ideas he saw as having fallen prey to the scientific and philosophical ill of reductionism, he at times evinced little patience. “I don’t want to worry,” he once told the Times, referring to a scholar whose work he regarded as lacking merit, “about what some fairly dumb person says or doesn’t.”

Richard Charles Lewontin was born in New York City on March 29, 1929. His father was a fabric broker, and his mother was a homemaker.

Dr. Lewontin received a bachelor’s degree in biology from Harvard in 1951 before pursuing graduate studies at Columbia University, where he received a master’s degree in mathematical statistics in 1952 and a PhD in zoology in 1954. He taught at institutions including the University of Rochester in New York and the University of Chicago before joining the faculty at Harvard in 1973.

His wife of more than 70 years, the former Mary Jane Christianson, died three days before he did. Survivors include four sons, David Lewontin of Seattle and Stephen Lewontin, James Lewontin and Timothy Lewontin, all of Cambridge; seven grandchildren; and a great-granddaughter.

Dr. Lewontin’s books included “Not In Our Genes: Biology, Ideology, and Human Nature” (1984), co-authored with Steven Rose and Leon J. Kamin; “Biology as Ideology: The Doctrine of DNA” (1992); and “It Ain’t Necessarily So: The Dream of the Human Genome and Other Illusions” (2000).

In the latter book, Dr. Lewontin offered a summation of his philosophy of knowledge, which he had pursued throughout this life with uncommon rigor, but always with a gimlet eye.

“Even though the world is material and all its phenomena, including human consciousness, are products of material forces, we should not confuse the way the world is with our ability to know about it,” he wrote. “Like it or not, there are a lot of questions that cannot be answered, and even more that cannot be answered exactly. There is nothing shameful in that admission.”