I WILL NEVER forget the moment when one of my Harvard classmates raised her hand and objected to the use of the term “black market”, which she found unacceptably demeaning to her race. It was a Philip Roth moment, a militant provocation — and the economics professor ducked. He was black too, and despised political correctness. But after a pause he said: “We will use the term ‘shadow market.’ ” And we used it, for the whole bloody semester. For in that bastion of censorship that was Harvard in the early 90s, no one dared to challenge anything labelled, however absurdly, as “discrimination”.

In contrast to my undergraduate education in Britain, where I once joined a demonstration out of pity for the four people making it, my time at Harvard was a swirl of activism. We women walked the streets with torches to “take back the night”, not knowing that the incidence of rape had been wildly exaggerated by feminists searching for a cause. The African-American professor Cornel West staged sit-ins and made protest hip-hop records, demanding that Harvard hire more black lecturers while seeming to treat his own obligations more lightly. The Gay and Lesbian Soc held earnest debates about what language was acceptable, debates whose conclusions changed every month, like Animal Farm. It was exhilarating. But it was also frightening to find freedom of expression challenged in the world’s greatest seat of learning.

Not much has changed, if the strange case of Larry Summers is anything to go by. On Tuesday night Mr Summers became the first Harvard President to suffer a no-confidence vote from his faculty — a vote which may not lead to his dismissal but which speaks volumes about the vintage battle between the Left and the Centre-Left. Mr Summers’s crime had been to tell a conference on diversity that “intrinsic aptitude”, as well as socialisation and discrimination, could help to explain why fewer women achieve high-level academic careers in science and mathematics than men. The hysterical response represents one of the most astonishing displays of collective closure of the academic mind. An MIT biologist, Nancy Hopkins, walked out of the Summers conference saying she was “going to be sick”, displaying a pathetic lack of feminist backbone and total disrespect for the spirit of academic inquiry.

Gauche Summers most certainly was. When professors are mutinous about your “dictatorial” management style (Cornel West has flounced off to Princeton after Summers accused him of a shortage of scholarship), and angry that fewer women are getting tenure, it is risky to suggest that innate differences make men outperform women. And arrogant. But wrong? What is most striking about the shrill debate that has followed his remarks is the apparent lack of evidence to contradict him. Summers said he felt that the clash between legitimate family desires and employers’ desire for “high power and high intensity” was a big factor in the paucity of women in science and engineering. That has got to be right. Many talented women simply choose not to fight on up a ladder that sucks up 60 to 80 hours of their week. But Summers felt there were also “issues of intrinsic aptitude”. “I’d like to be proven wrong on this one,” he said. But as yet, he hasn’t been.

The funny thing is that the same self-styled feminists who are most hysterical about Summers’s venture into gender differences are the first to extol the unique virtues that women supposedly bring to work. With more connections between the brain hemispheres women are empathising and multi-tasking while Men from Mars do their puzzle solving or feeling sad in more focused regions of the brain.

The Harvard matrons are most furious about Summers’s reference to the bell curve of ability: the idea that more men do spectacularly well or disastrously badly in their field, while more women are clustered around the mean. This does not mean that there are no women geniuses; it just means that there seem to be more men ones. Equality of outcome seems a completely pointless notion when you are talking about the very highest levels of academic ability.

We shouldn’t pick and choose when to acknowledge the fact of difference. Summers says that “Catholics are substantially under-represented in investment banking . . . white men are substantially under-represented in the National Basketball Association . . . and Jews are under-represented in farming”. Preference and opportunity play a part. But what about aptitude?

Women currently make up 35 per cent of faculty at American universities, but only 20 per cent of professors in science and engineering. Should that be 50 per cent? Of course not. But if equality is not proportionality, what is it? If we accept differences, how can we require that those differences are ironed out at some aggregate level?

There is clearly a complex relationship between biological factors and social environment. We know that men are better at rotating 3D objects in their minds. Psychiatric studies suggest that while girls mature more quickly in the parts of the brain that handle verbal fluency and handwriting, boys’ brains mature faster in the regions concerned with mechanical and spatial reasoning. So maybe some of our stereotypes aren’t so stupid. But of course they influence performance. The brain is very susceptible to suggestion. Canadian researchers have shown that women perform better in a maths test if they are told that women usually do as well as men, than if they are told that men do better.

Some of the most interesting questions are about men, not women. Why do so many more boys than girls suffer from autism, attention deficit disorder and schizophrenia? Such boys are in an uncomfortable place, even if a few are at the “top” of the bell curve.

As genetics converges on the social sciences, we will get nearer to answering questions of nature versus nurture. That is incredibly exciting. Those at Harvard may want to close their minds to it. But we shouldn’t let them.

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