Eugenics and the Modern Synthesis, Part II

For the Legacies of Eugenics series, Jessica Riskin continues to explore how the neo-Darwinian ‘modern synthesis’ was simply nonsense.

By Jessica RiskinMarch 24, 2026

• Science & Technology

• History

• Politics

This is the second part of the 14th installment in the Legacies of Eugenics series, which features essays by leading thinkers devoted to exploring the history of eugenics and the ways it shapes our present. You can read the first part here. The series is organized by Osagie K. Obasogie in collaboration with the Los Angeles Review of Books, and supported by the Center for Genetics and Society, the Othering & Belonging Institute, and Berkeley Public Health.

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JULIAN HUXLEY PERSONIFIES the conjunction of genetics, eugenics, and the modern synthesis. His connection with evolutionary theory was familial. His grandfather, Thomas Henry Huxley, was a naturalist and polemical Darwinist who referred to himself as “Darwin’s bulldog.” Upon first reading On the Origin of Species (1859), he exclaimed to himself, “How extremely stupid [of me] not to have thought of that!” and wrote to Charles Darwin professing himself “prepared to go to the Stake” to defend the theory. His enthusiasm apparently overflowed his metaphors as he also said, “I am sharpening up my claws & beak in readiness.”

Darwin and T. H. Huxley didn’t agree on everything, though. Darwin had exactly the opposite reaction from Huxley’s when he read an essay by Huxley entitled “On the Hypothesis That Animals Are Automata, and Its History,” in which Huxley argued that all organic beings, including people, were essentially automatic machines, their consciousness a mere “collateral product” of the mechanism. “If I were as well armed as Huxley,” Darwin remarked wryly to a mutual friend, “I would challenge him to a duel on this subject.” To Darwin, as to Jean-Baptiste Lamarck, living beings were not passive machines, but full of creative agency.

Julian Huxley seems to have inherited his grandfather’s automaton-like model of organisms. Describing the “machinery of heredity,” the younger Huxley wrote that many people disliked the idea of a “hereditary force pushing men blindly along predestined roads” and so they reacted by “belittling and discounting” the power of biological inheritance. But science, he said, didn’t give a fig about people’s “likes or dislikes.” Sure, Lamarckism might seem a nicer idea—you might like to hand on the results of your life’s work to the next generation—but scientists must face facts, and “facts take no account of what we human beings think or desire.”

Also from his grandfather, Huxley inherited the mantle of protector and interpreter of the Darwinian faith. From the start, he said, Darwinism had suffered from uncertainties about what caused organisms to change, producing new variations. Even Darwin himself had been “inclined to allow some weight to Lamarckian principles.” This confusion had led to a period of “eclipse,” and a “reaction against Darwinism,” according to Huxley. But happily, the theory had been rescued by August Weismann, Gregor Mendel, and William Bateson. The resulting “particulate” mechanism of heredity had allowed evolutionary biology to unify around a methodology of combinatorial calculations. The “rebirth of Darwinism” on this new, mathematical foundation enabled biology to rival physics in its reductive methodological unity. Huxley’s “reborn Darwinism, this mutated phoenix risen from the ashes,” was founded upon the eradication of the idea that organisms played any role in influencing the course of evolution.

Lamarck was the modern synthesis’s public enemy number one, and his role was all the more important since the founders of neo-Darwinism actually disagreed on some fundamental matters. Bateson never quite accepted the “chromosome theory,” the idea that the hereditary matter of the genes was contained within the chromosomes, which Weismann and Hugo de Vries both believed. Meanwhile, Weismann assumed, with Darwin, that variation was gradual, and that evolution was a slow accumulation of tiny changes, while De Vries and Bateson introduced the idea of big, sudden jumps, or “mutations,” an idea that Huxley adopted, as did the Columbia University embryologist and early geneticist Thomas Hunt Morgan, pioneer of the experimental use of Drosophila (fruit flies) in genetics research. But whatever their position on chromosomes or the pace of evolutionary change, the members of the modern synthesis could all agree on what became their founding principle: there can be no inheritance of acquired characteristics.

This principle didn’t just bring the members of the modern synthesis together but allowed them to add new elements to their doctrine as well. For instance, with the addition of genetic mutations as a crucial element of the theory came a heightened importance for randomness: not only were genes assigned to offspring randomly in sexual reproduction, but mutations, according to those who believed in them, also occurred at random. This reinforced the passivity of organisms as the objects of biological fortune.

The passivity of the organism provided the rallying point for the modern synthesis. Organisms could never vary as a result of their own actions but were entirely subject to outside forces. Apparently failing to see a contradiction, the modern synthesis founders rejoiced in the idea that they themselves could become these outside forces. “It is as if man had been suddenly appointed managing director of the biggest business of all,” Huxley wrote, “the business of evolution.” He even coined a new term, “transhumanism,” to describe the human control of human evolution: “The human species can, if it wishes, transcend itself […] We need a name for this new belief. Perhaps transhumanism will serve.” Humanity, he said, was “on the threshold of a new kind of existence.”

Another word for becoming the managing director of evolution was “eugenics.” Like Bateson, Huxley celebrated the intimate relations of neo-Darwinism and genetics with eugenics. “Mendelism has swept all before it,” he marveled, noting that Darwin’s natural selection, Mendel’s laws, and Sir Francis Galton’s eugenics had all been born in the same moment. The  “great single fact underlying Mendelism” was of obvious relevance to eugenics: the “fact” (really more of a fiction) that there are separate, independent units of inheritance that “segregate from each other clean and entire.” It seemed wonderfully convenient, a kind of LEGO of the human constitution.

How, though, to distinguish the eugenically fit from the unfit? As a “rough-and-ready” method, Huxley liked the idea of using salaries: the higher the salary, the fitter the person. That was simple enough, but it led to a eugenic conundrum. Wealthy people had fewer children on average than poor people. Professionals and landowners had fewer children than unskilled laborers. You might think it would have occurred to Huxley that in strictly Darwinian terms, the laborers’ higher reproductive rate meant they were the more fit, since for Darwin “fitness” simply meant reproductive success. But apparently not. Instead, he lamented that those with a relatively “poor physique and low mental type” were reproducing like crazy while those whose spots at Oxford had come to them with their birth certificates were having maybe just two children. This would lead to “a progressive deterioration of the average of the national stock.”

Huxley offered an illustration that was Mendelian in its mathematical elegance: suppose that for every 100 laborers, three were outstanding and seven defective, while for every 100 professionals, seven were outstanding and three defective. Then suppose that the professional class remains about the same size while the laboring class doubles every two generations. In the original generation, outstanding and defective people each make up five percent of the overall population; but after two generations, the percentages would be 3.8 and 6.2, and after five, they would be three and 6.8, and so on. You can see where this is going. Moreover, this was assuming “no migrations between class and class occurred, which would make things worse.”

The same problem preoccupied Ronald Fisher, an English mathematician and geneticist whose work was foundational to the modern synthesis. Fisher asserted (on no evidence) that inheritance was strictly “particulate”; that mutations were effectively random, having no shaping forces or causes; and that biologists should just face the fact that natural selection was the only mechanism directing evolution. Yet natural selection didn’t seem to be doing a great job of it. Fisher, too, worried about poor people having more children than rich people, which he called the “inverted birth-rate.” He was a devout Anglican, but he doesn’t seem to have trusted his God to cope with the situation either. Convinced that social classes were “genetically differentiated,” he fretted that the current trend was leading to a degradation of the human race.

This was no idle speculation; Fisher meant to do something about it. During his career, he served as the inaugural chairman of the University of Cambridge Eugenics Society, held the position of Galton Professor of Eugenics and head of the Department of Eugenics at University College London, and edited the journal Annals of Eugenics. He was a man of action. As a solution to the inverted birth-rate problem, for instance, Fisher proposed that the state make family allowances proportional to salaries: the higher the salary, the higher the allowance. This would encourage the rich to breed more and the poor to breed less. Leonard Darwin, a son of Charles Darwin, had made a similar proposal, suggesting income tax rebates to families who had more children, since only wealthier professionals paid income taxes. But he had cautioned that it would be essential for state administrators to verify that no artisans or laborers had made it into the class paying income taxes and therefore receiving the rebates.

Something had to be done about the mixed-up birth rates in Huxley’s view as well. “To a biologist,” he wrote,

three things seem most sinister. The first is the differential multiplication of the classes. The second is the license for self-perpetuation allowed by our present system to a large number of subnormal tendencies which in any other species of organism would be eliminated by natural selection; and the third is the progressive sterilisation of good heritable qualities [because rich people had too few children].

Huxley applauded Leonard Darwin’s proposals, which also included the idea that the state should condition relief to poor families on their having a maximum of two children. With a third child, “the relief would automatically cease.” As a member of the British Eugenics Society, and later its president from 1959 to 1962, Huxley developed various other proposals for eugenic programs. He sat, for instance, on the society’s Committee for Legalising Eugenic Sterilisation.

Even those few who were skeptical of eugenics accepted the basic premise of human inequality. One example is J. B. S. Haldane, a British geneticist, physiologist, science popularizer, and founding contributor to the modern synthesis. Haldane was heterodox relative to his co-founders. For instance, he expressed doubts about the practicability of eugenic policies. He pointed out that these often assumed a distinctly non-Darwinian (even anti-Darwinian) understanding of “fitness” and that it was contradictory to believe in both the fixity of innate racial characteristics and the threat of race degeneration, or, for that matter, the possibility of race purification. Haldane questioned whether it made sense to equate economic success with biological value. He said that while he wholeheartedly approved of some aspects of the “eugenic programme,” he thought others were vehicles for racial and class prejudices.

Nevertheless, in a book of essays entitled The Inequality of Man (1932), Haldane endorsed Bateson’s “Scientific Calvinism”: a person’s destiny is written in their genes. And he derived from this idea a lesson regarding inequality, or as he called it, “diversity”: “If innate human diversity is an ineradicable fact, the ideal society is one in which as many types as possible can develop in accordance with their possibilities.” It sounds perhaps innocuous, when phrased that way, but consider what it meant in practice.

As an example of the scientific treatment of social questions such as those caused by “human diversity,” Haldane considered “the problem of the American Negro.” Many Americans, he wrote,

hold that the negro is definitely inferior to the white man, and should, as far as possible, be segregated from him. Others believe that he should enjoy the same rights. The biologist cannot decide between them. He can point out that the negro’s skull is more ape-like than the white’s, but his hairless skin less so, and so forth.

What the scientist could do, however, was to reveal that “the birth-rate of the negro population exceeds the death-rate” in the countryside, while it was the opposite in towns.

So if you keep the negro out of cars, factories, and so forth, or frighten him away from contact with whites by an occasional lynching, you drive him back to the cotton fields where he lives healthily and breeds rapidly, thus creating a negro problem for future generations. But if you extend the hand of fellowship to him you also infect him with your maladies, besides establishing in your midst a reservoir of disease germs.

In the American Civil War, according to Haldane, the “number of negroes thus killed was far greater than the casualty list.” And if “to-morrow the coloured population of the Southern States, but not the white, were given free access to cheap whisky and methods of birth control, the number of negroes would probably begin to fall off!”

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In 1942, Huxley published a kind of constitution for evolutionary biology, in which he gave the “modern synthesis” its catchy name. Soon afterward, he got a chance to apply its principles on a global stage. During the final stages of World War II, in April 1945, representatives from 50 countries created an international organization, the United Nations, hoping it would help avoid another world war. Huxley was the inaugural director general of UNESCO: the United Nations Educational, Scientific and Cultural Organization. His project was to harness the modern synthesis to UNESCO’s mission of human unity. Before the war, he had written a vehement debunking of the idea of “race” as a biological category. Human races were not biologically distinct, he wrote, and “race” was therefore “a pseudo-scientific rather than a scientific term,” a myth that dangerously fueled prejudice. When he assumed his position at UNESCO, the experiences of the Second World War had cataclysmically confirmed his warning.

In June 1951, after lengthy negotiations, UNESCO issued a “statement on the nature of race and racial differences,” asserting that “scientists are generally agreed that all men living today belong to a single species, Homo sapiens, and are derived from a common stock.” The statement said that races were always mixing and changing, that the differences within races were at least as big as the differences between them, and that there was no scientific evidence to support the idea that races differed “in their innate capacity for intellectual and emotional development.” Twelve geneticists and anthropologists consulted in the preparation of the statement, sending contributions and criticisms, and then Huxley composed its final wording together with a fellow founder of the modern synthesis, the Russian-born American geneticist Theodosius Dobzhansky. (Fisher, however, opposed it, saying he thought human groups had important, genetically caused differences in their innate intellectual and emotional capacities.)

But although Huxley believed in human unity, he staunchly opposed the idea of human equality: “Our new idea-system must jettison the democratic myth of equality,” he declared. “Human beings are not born equal in gifts or potentialities, and human progress stems largely from the very fact of their inequality. ‘Free but unequal’ should be our motto.”

In a kind of mission statement for UNESCO, Huxley presented eugenics as an important part of the program. People might disagree about the nature and value of excellence in various areas, he thought, but surely there could be no dispute about “a healthy constitution, a high innate general intelligence, or a special aptitude such as that for mathematics or music.” In order to bring about an international betterment of human beings, UNESCO must ensure “that the eugenic problem is examined with the greatest care […] so that much that now is unthinkable may at least become thinkable.” Above all, eugenics must be developed as a fully scientific endeavor, since “in the not very remote future the problem of improving the average quality of human beings is likely to become urgent; and this can only be accomplished by applying the findings of a truly scientific eugenics.” Huxley here returned to his favorite theme. “Biological inequality,” he wrote, “is, of course, the bedrock fact on which all of eugenics is predicated.”

Another major figure of 20th-century evolutionary biology who emphasized the biological inequality of humans was the Harvard entomologist E. O. Wilson. He recited the same catechism—no inheritance of acquired characteristics—and subscribed to Bateson’s “Scientific Calvinism,” to which he gave a catchy new name: “sociobiology.” In his manifesto, Sociobiology: The New Synthesis, published in 1975, he endorsed the old idea of genetic differences distinguishing people in different social classes. “Sociobiology” would be a science designed to “monitor the genetic basis of social behavior.” Wilson proposed that “ethics […] be removed temporarily from the hands of the philosophers and biologized.” Human populations, he thought, might “diverge genetically […] in ethical behavior,” in which case ethics would require an “evolutionary approach” and “no single set of moral standards [could] be applied to all human populations, let alone all sex-age classes.” The book set off a storm of controversy. Looking back on it in 2004, Wilson attributed the response to the radical politics of the mid-1970s. He wrote with evident bitterness that his ideas had been perceived as a “threat to Marxist ideology”:

In academia’s now necktie-free zone, race was a radioactive issue, deadly to any who touched it without extreme caution. Talk of the inheritance of IQ and human behavior were punishable offenses. Anyone who dared mention these subjects in any manner other than formulaic condemnation was at risk of being called a racist.

Necktie or no necktie, it’s hard to imagine what else you would call someone who promotes the idea of genetically based “human racial variation in behavior” and intelligence as Wilson did; it could almost be a dictionary definition.

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Virtually all of the powerful voices in 20th-century evolutionary biology promoted the modern synthesis, with its core principles of genetic determinism, the passivity of living organisms, and human inequality, from which they drew eugenic implications. They saw eugenics, genetics, and evolution as essentially the same: several aspects of one science.

To get an idea of how deeply eugenic ideas were built into the foundations of the modern synthesis, let’s listen in to a panel discussion on “eugenics and genetics” at a London conference in 1963. Many of the major figures in evolutionary biology and genetics are here. Huxley and Haldane are among them. One of the presentations is by Joshua Lederberg, a Stanford University geneticist who has recently won the Nobel Prize in Physiology or Medicine in 1958. “Most geneticists,” Lederberg says, are “deeply concerned over the status and prospects of the human genotype. Human talents are widely disparate,” he continues, and much of the disparity “has a genetic basis.” He, too, shares the perennial worry that rich people have few children compared to poor people. We “sinfully waste a treasure of knowledge,” he suggests to his audience, “by ignoring the creative possibilities of genetic improvement.” Lederberg thinks eugenic breeding would be too slow and clumsy, requiring generations to get results, and lots of trial and error. Instead, he urges biologists to devote themselves to developing techniques of genetic engineering as a faster and more sophisticated mode of eugenic improvement.

The other presentation before the panel discussion begins is by Hermann J. Muller, a professor of zoology at Indiana University, who proposes improving the gene pool by creating a list of men chosen for their eugenic fitness and having them make donations to sperm banks. Then, couples “idealistic enough to prefer to give their child as favourable a genetic prospect as can be obtained” could choose to use these men’s sperm instead of the husband’s inferior stuff.

After the presentations comes the panel discussion, initiated by Francis Crick, who has just won the 1962 Nobel Prize in Physiology or Medicine with James Watson and Maurice Wilkins. Rosalind Franklin didn’t share the prize; she died of cancer in 1958, the same year that Crick restated the Weismann barrier as the “central dogma of molecular biology”: information can flow only from DNA to protein, and never the other way. Therefore, no bodily change can inscribe itself in the DNA and be inherited by the next generation.

It’s curious that Crick called this a “dogma,” since he certainly meant to endorse it, and “dogmatic” is usually no endorsement. But he was accurate, if inadvertently so. A dogma, according to the Oxford English Dictionary, is a “tenet or doctrine authoritatively laid down, esp. by a church or sect.” The insistence that living beings couldn’t possibly transform themselves heritably originated as an explicitly religious doctrine, as we’ve seen, for instance, with Weismann. But the dogma remained powerful long after its advocates stopped insisting that each living form had a divine origin and even forgot that anyone had ever attached it to such a religious worldview. “No inheritance of acquired characteristics” served the interests of successive established authorities in science, religion, and government, and made a seamless transition from religious dogma to scientific dogma.

“Let us take up this whole question of eugenics,” invites Crick in his opening remarks at the 1963 conference panel, adding that “on a long-term basis we have to do something.” Introducing a new twist to the discussion, he then observes, “I do not see why people should have the right to have children,” and he muses that it would be a fairly simple matter for a government to sterilize the whole population by putting some chemical in the food supply, and then reverse the effect only for those people “licensed to bear children.” This might have the effect of getting “across to people the idea that their children are not entirely their own business and that it is not a private matter.” Crick elaborated:

If one did have a licensing scheme, the first child might be admitted on rather easy terms. If the parents were genetically unfavourable, they might be allowed to have only one child, or possibly two under certain special circumstances. That seems to me the sort of practical problem that is raised by our new knowledge of biology.

Another discussant, a British biochemist named Norman Pirie, mentions that some people believe humans have an innate desire to have children, but he thinks, on the contrary, “most of the impulse to have children is a cultural one, built up by the kind of stories you read, the kind of pictures you see; I do not think it is a basic impulse at all. The impulse is sexual […] the children are inadvertent.” An American anthropologist named Carleton S. Coon, who churns out books arguing that the human races are biologically distinct and arranged on a spectrum of excellence, responds: “I think that [people] want both sexual pleasure and children. This business of women wanting to have children can become overpowering; I think there is a hormonal basis for that.” But he has a remedy in mind—“Adoption of children sometimes seems to fill the bill so far as the maternal urge is concerned: plenty of women have a tremendous maternal urge which is satisfied perfectly well with someone else’s children.” Crick pronounces this “a very good example of how one could get round one of these problems.”

Still, realizing that the “proposal of licensing that [he] somewhat playfully suggested might, or might not, be acceptable in our present social system,” Crick also proposes a more “socially acceptable” policy—“simply to encourage by financial means those people who are more socially desirable to have more children.” He thinks the “most obvious” way of doing it is to impose a child tax on the less socially desirable. How to distinguish the more desirable from the less? Crick, like Huxley and Fisher, thinks wealth would do the trick: “It is unreasonable to take money as an exact measure of social desirability, but at least they are fairly positively correlated.”

Extraordinary though it may seem, those at the panel who objected to these proposals were in a distinct minority and were not biologists. They included Jacob Bronowski, a mathematician and philosopher; Colin Clark, an agricultural economist; the Reverend Hubert Carey Trowell, an Anglican minister; Derek de Solla Price, a historian of science at Yale University; and Alex Comfort, a doctor and hospital administrator who would soon become famous as the author of The Joy of Sex: A Gourmet Guide to Lovemaking (1972). Comfort said he wasn’t sure if people had a right to have children, but he was quite sure “that no other persons have the right to prevent them.” Bronowski offered the most vehement response. “I find myself out of sympathy with much that has been said,” he told the others.

Indeed, we might achieve the same effect in a simpler way—by eating the children of the unfit, as Jonathan Swift suggested that the Irish poor should eat their own children. But what problem are we trying to solve? What genes are we trying to boost? Muller asserts in his paper that there are reasons to believe that the human population is deteriorating, and Huxley […] also implied this. I know of no evidence for that.

Trowell had another counterargument. By a eugenic logic, he suggested, polygamy should be preferable to monogamy since it allows great men—kings or chiefs—to sire lots of children. But he thought human societies had mostly shifted away from polygamy toward monogamy, and he doubted whether the human race had degenerated as a result. To this, Haldane wittily responded that he agreed this was a problem for eugenic reasoning, which also implied “a Turk should always get the better of an Armenian or a Jew in a business deal” (presumably referring to the history of polygamy in the area that is now Turkey). At which Huxley chimed in humorously with “Ceteris paribus!”

James Watson, a co-discoverer of the structure of DNA with Crick and a principal figure in 20th-century genetics, achieved notoriety in the early 2000s for insisting that human races differ in intelligence and other qualities. He said it crassly, insistently, and publicly, and there was a backlash. But the striking thing is that, in substance, what Watson said was absolutely standard: the idea of innate inequalities among groups of humans—races, social classes, sexes—has been commonplace among the major figures in genetics and evolutionary biology from the late 19th century into the early 21st.

Even more commonplace has been the idea that there is “significant genetic variation in human mental abilities,” as Richard Dawkins, biologist, writer and best-selling promoter of the modern synthesis, has expressed it. Dawkins writes that there may or may not be such variation, but it “cannot be denied” that humans must necessarily have been genetically unequal in mental abilities in the past, since he assumes we’ve gotten smarter over time simply by natural selection favoring the individuals in the population whose genes rendered them smartest. This reasoning, he says, shows “the inadvisability of dogmatic and hysterical opposition to the very possibility of genetic variation in human mental abilities.”

Agreed, being dogmatic and hysterical is always a bad idea. But here’s a calm and thoughtful objection. The modern synthesis has foundered in each of its basic tenets. There have not turned out to be “particulate” genes or, for the most part, straightforward correspondences between individual segments of DNA and bodily traits, let alone cognitive or behavioral ones. Research over the past several decades has demonstrated ever more ways in which living beings have evolutionary agency, playing various roles in shaping the course of evolution. Regarding the claim that there might be “significant genetic variation in human mental abilities,” the assumptions on which it’s predicated are all false. It can’t even be right or wrong: it’s just nonsense.

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Works Consulted

Bashford, Alison. 2022. The Huxleys: An Intimate History of Evolution. Chicago: University of Chicago Press.

Kampourakis, Kostas. 2017. Making Sense of Genes. Cambridge, UK: Cambridge University Press.

Keller, Evelyn Fox. 2002. The Century of the Gene. Cambridge, MA: Harvard University Press, 2002.

Provine, William B. (1971) 2001. The Origins of Theoretical Population Genetics: With a New Afterword. Chicago: University of Chicago Press.

Radick, Gregory. 2023. Disputed Inheritance: The Battle over Mendel and the Future of Biology. Chicago: University of Chicago Press.

Smocovitis, Vassiliki Betty. 1996. Unifying Biology: The Evolutionary Synthesis and Evolutionary Biology. Princeton, NJ: Princeton University Press.

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This essay is an adapted excerpt from Jessica Riskin’s book The Power of Life: The Invention of Biology and the Revolutionary Science of Jean-Baptiste Lamarck, on sale this week. Part I of the excerpt was published yesterday.

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Featured image: From the cover of The Power of Life: The Invention of Biology and the Revolutionary Science of Jean-Baptiste Lamarck, 2026, by Jessica Riskin.