The Left’s most rigid taboos involve the biology of race and gender, as the Harvard psychologist Steven Pinker chronicles in The Blank Slate. The book takes its title from Pinker’s term for the dogma that “any differences we see among races, ethnic groups, sexes, and individuals come not from differences in their innate constitution but from differences in their experiences.” The dogma constricts researchers’ perspective – “No biology, please, we’re social scientists” – and discourages debate, in and out of academia. Early researchers in sociobiology faced vitriolic attacks from prominent scientists like Stephen Jay Gould, who accused them of racism and sexism for studying genetic influences on behaviour.

Studying IQ has been a risky career move since the 1970s, when researchers like Arthur Jensen and Richard Herrnstein had to cancel lectures (and sometimes hire bodyguards) because of angry protesters accusing them of racism. Government funding dried up, forcing researchers in IQ and behavioural genetics to rely on private donors, who in the 1980s financed the renowned Minnesota study of twins reared apart. Leftists tried to cut off that funding in the 1990s, when the University of Delaware halted the IQ research of Linda Gottfredson and Jan Blits for two years by refusing to let them accept a foundation’s grant; the research proceeded only after an arbitrator ruled that their academic freedom had been violated.

The Blank Slate dogma has perpetuated a liberal version of creationism: the belief that there has been no evolution in modern humans since they left their ancestral homeland in Africa some 50,000 years ago. Except for a few genetic changes in skin colour and other superficial qualities, humans everywhere are supposedly alike because there hasn’t been enough time for significant differences to evolve in their brains and innate behaviour. This belief was plausible when biologists assumed that evolution was a slow process, but the decoding of the human genome has disproved it, as Nicholas Wade (a former colleague of mine at the New York Times) reported in his 2015 book, A Troublesome Inheritance.

“Human evolution has been recent, copious and regional,” writes Wade, noting that at least 8 per cent of the human genome has changed since the departure from Africa. The new analysis has revealed five distinguishable races that evolved in response to regional conditions: Africans, East Asians, Caucasians, the natives of the Americas and the peoples of Australia and Papua New Guinea. Yet social scientists go on denying the very existence of races. The American Anthropological Association declares race to be “a human invention” that is “about culture, not biology.” The American Sociological Association calls race a “social construct.” Even biologists and geneticists are afraid of the R-word. More than 100 of them sent a letter to the New York Times denouncing Wade’s book as inaccurate, yet they refused to provide any examples of his mistakes. They apparently hadn’t bothered to read the book because they accused Wade of linking racial variations to IQ scores – a link that his book specifically rejected.

Some genetic differences are politically acceptable on the left, such as the biological basis for homosexuality, which was deemed plausible by 70 percent of sociologists in a recent survey. But that same survey found that only 43 percent accepted a biological explanation for male-female differences in spatial skills and communication. How could the rest of the sociologists deny the role of biology? It was no coincidence that these doubters espoused the most extreme left-wing political views and the strongest commitment to a feminist perspective. To dedicated leftists and feminists, it doesn’t matter how much evidence of sexual differences is produced by developmental psychologists, primatologists, neuroscientists and other researchers. Any disparity between the sexes – or, at least, any disparity unfavourable to women – must be blamed on discrimination and other cultural factors.

Former Harvard president Lawrence Summers found this out the hard way at an academic conference where he dared to discuss the preponderance of men among professors of mathematics and physical sciences at elite universities. While acknowledging that women faced cultural barriers, like discrimination and the pressures of family responsibilities, Summers hypothesised that there might be other factors, too, such as the greater number of men at the extreme high end in tests measuring mathematical ability and other traits. Males’ greater variability in aptitude is well established – it’s why there are more male dunces as well as geniuses – but scientific accuracy was no defence against the feminist outcry. The controversy forced Summers to apologise and ultimately contributed to his resignation. Besides violating the Blank Slate taboo, Summers had threatened an academic cottage industry kept alive by the myth that gender disparities in science are due to discrimination.

This industry, supported by more than $200 million from the National Science Foundation, persists despite overwhelming evidence – from experiments as well as extensive studies of who gets academic jobs and research grants – that a female scientist is treated as well as or better than an equally qualified male. In a rigorous set of five experiments published last year, the female candidate was preferred two-to-one over an equivalent male. The main reason for sexual disparities in some fields is a difference in interests: from an early age, more males are more interested in fields like physics and engineering, while more females are interested in fields like biology and psychology (where most doctorates go to women).

On the whole, American women are doing much better than men academically – they receive the majority of undergraduate and graduate degrees – yet education researchers and federal funders have focused for decades on the few fields in science where men predominate. It was bad enough that the National Science Foundation’s grants paid for workshops featuring a game called Gender Bias Bingo and skits in which arrogant male scientists mistreat smarter female colleagues. But then, these workshops nearly became mandatory when Democrats controlled Congress in 2010. In response to feminist lobbying, the House passed a bill (which fortunately died in the Senate) requiring federal science agencies to hold “gender equity” workshops for the recipients of research grants.

It might seem odd that the “party of science” would be dragging researchers out of the lab to be re-educated in games of Gender Bias Bingo. But politicians will always care more about pleasing constituencies than advancing science.

And that brings us to the second great threat from the Left: its long tradition of mixing science and politics. To conservatives, the fundamental problem with the Left is what Friedrich Hayek called the fatal conceit: the delusion that experts are wise enough to redesign society. Conservatives distrust central planners, preferring to rely on traditional institutions that protect individuals’ “natural rights” against the power of the state. Leftists have much more confidence in experts and the state. Engels argued for “scientific socialism,” a redesign of society supposedly based on the scientific method. Communist intellectuals planned to mould the New Soviet Man. Progressives yearned for a society guided by impartial agencies unconstrained by old-fashioned politics and religion. Herbert Croly, founder of the New Republic and a leading light of progressivism, predicted that a “better future would derive from the beneficent activities of expert social engineers who would bring to the service of social ideals all the technical resources which research could discover.”

This was all very flattering to scientists, one reason that so many of them leaned left. The Right cited scientific work when useful, but it didn’t enlist science to remake society – it still preferred guidance from traditional moralists and clerics. The Left saw scientists as the new high priests, offering them prestige, money and power. The power too often corrupted. Over and over, scientists yielded to the temptation to exaggerate their expertise and moral authority, sometimes for horrendous purposes.

Drawing on research into genetics and animal breeding from scientists at Harvard, Yale, Johns Hopkins and other leading universities, the eugenics movement of the 1920s made plans for improving the human population. Professors taught eugenics to their students and worked with Croly and other progressives eager to breed a smarter society, including Theodore Roosevelt, Woodrow Wilson and Margaret Sanger. Eventually, other scientists – notably, in England – exposed the shoddy research and assumptions of the eugenicists, but not before the involuntary sterilisation or castration of more than 35,000 Americans. Even after Hitler used eugenics to justify killing millions, the Left didn’t lose its interest in controlling human breeding.

Eugenicist thinking was revived by scientists convinced that the human species had exceeded the “carrying capacity” of its ecosystem. The most prominent was Paul Ehrlich, whose scientific specialty was the study of butterflies. Undeterred by his ignorance of agriculture and economics, he published confident predictions of imminent global famine in The Population Bomb (1968). Agricultural economists dismissed his ideas, but the press reverently quoted Ehrlich and other academics who claimed to have scientifically determined that the Earth was “overpopulated.” In the journal Science, ecologist Garrett Hardin argued that “freedom to breed will bring ruin to all.” Ehrlich, who, at one point, advocated supplying American helicopters and doctors to a proposed program of compulsory sterilisation in India, joined with physicist John Holdren in arguing that the US Constitution would permit population control, including limits on family size and forced abortions. Ehrlich and Holdren calmly analysed the merits of various technologies, such as adding sterilants to public drinking water, and called for a “planetary regime” to control population and natural resources around the world.