Diversity matters, be it in the make-up of Parliament, among our television presenters or in our boardrooms. It matters in science and technology, too. However, particularly in the physical sciences and engineering, the numbers of women remain persistently low. Articles about the lack of senior women in science abound, with a recurrent visual motif of a leaky pipeline out of which young women spill in depressingly large numbers.

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However, in subjects such as my own - physics - or engineering or mathematics, the problem is compounded by the fact that, too often, women never even enter it in the first place. The contrast is stark with subjects such as biology and chemistry, for which the undergraduate cohort is approximately 50:50, even worse in comparison with veterinary medicine or nursing, where the undergraduate population is overwhelmingly female (which in itself is hardly healthy).

Nevertheless, for subjects with a substantial undergraduate intake, the leaky pipeline remains an apt metaphor: as you look further up the career ladder, for each of these subjects there is a steady decline in the number of women.

We need to ask not only why the pipeline spews out the women as they progress, but also why some subjects are never seen as attractive in the first place to our brightest young girls. Maybe there is an element of nature in this debate, but I¡¯ll leave that hotly disputed topic aside. It is remarkably difficult to construct clean experiments to resolve the issue, ones in which no hint of cultural bias can enter into experiments to work out whether male and female babies really do differ in their reactions to people and objects (the split that researchers such as Simon Baron-Cohen like to make).

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But whether such a difference exists or not, undoubtedly our society - as in most developed countries - conveys not-so-subtly different messages to boys and girls about cultural norms.

Wander into a toyshop and it is obvious that toy manufacturers want to segregate toys by gender, which sets a tone of differentiation between what boys and girls are expected to do and be from the earliest age. Never mind the ridiculous body proportions of a Barbie doll, most of her ¡°career options¡± are stereotypically female, and even the computer engineer version¡¯s laptop and clothes are unremittingly pink.

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Boys¡¯ toys also promote a very narrow range of apparent career options, with no ¡°action¡± vet or nurse on display. Advertisements for boys¡¯ toys stress words such as ¡°power¡± and ¡°battle¡±, for girls it¡¯s ¡°love¡± and ¡°magic¡±, implying an unhealthy degree of passivity.

Maybe it¡¯s progress that Barbie is at last allowed to aspire to be a computer engineer, but she hasn¡¯t spread her wings far enough in my view. Stroll next door to the Disney shop and you¡¯ll find numerous ¡°princess¡± dresses to fuel a young girl¡¯s imagination to grow up to be, well, a princess. Hardly a realistic career aspiration for the majority, Kate Middleton apart.

Go online to buy a T-shirt for your daughter and you can find one with the catchy slogan ¡°I¡¯m too pretty to do math¡± blazoned across the front in fetching pink letters. The message is clear to young girls and they appear to be heeding it. Society expects them to be wafting around with long hair, long Snow White dresses adorning impossible figures, and ignorant of how to work out their credit card interest or the mpg of their nippy little car, let alone get to grips with relativity or design a bridge. What they are allowed, even encouraged, to do is to cuddle a cute kitty (hence, I would assert, the large number of female vet students and biologists) or exhibit their nurturing side in preparation for a lifetime as a nurse or childminder.

Why are we as a society so inert in accepting these gendered (and other) stereotypes that permeate the way we bring up our children? Some scientists may be geeks, but female geeks should be just as acceptable as male ones.

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Some scientists may be scruffy, but if you¡¯re pretty (or handsome, nicely gendered words there) and like clothes, it doesn¡¯t disqualify you from being a scientist. Female scientists can have families, you¡¯re not excluded from that either. In short, we need to celebrate the fact that scientists and engineers, collectively, are smart, interesting people with rich lives whose other attributes are just the same as the rest of the population.

Recent statistics show that boys in England are twice as likely as girls to do the combination of physics, chemistry and biology at A level, and (if only a single science is taken) five times as likely to do physics on its own. Girls taking a single science overwhelmingly opt for biology.

Choices at A level clearly determine what university courses can be taken. By 18 it is too late to rectify this imbalance. If we are convinced that diversity matters, we need to work a lot harder at overturning cultural stereotypes, and try in every way we can to ensure that girls believe the full spectrum of opportunities is open to them.

We must identify and promote new role models to alter the resolutely passive and decorative young women who represent ¡°success¡± as girls encounter it each day through their TV screens, and ensure that work-experience placements offer them the full breadth of opportunities. Only then can we be sure that their aspirations are not limited and thereby their choices implicitly curtailed.

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