11/02/2016 12:36 GMT | Updated 11/02/2017 05:12 GMT

Bodies, Brains and the Political Incorrectness of Falling in Love

This February The Huffington Post UK is running Making Modern Love, a fortnight-long focus on what love means to Britons in the 21st Century. Built on the three themes of finding love, building love and losing love, HuffPost will feature human stories that explore exactly what it is to be in love in modern times

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Falling in love is the one time we are allowed to break the rules. As a species, humans are slowly learning that if we want to spend our lives befriending, employing or teaching the best possible people, then we cannot let considerations of sex, gender or beauty cloud our judgement during the 'recruitment phase'.

However, the big exception to this is falling in love. When that happens, it appears we're allowed to do what we like. If memory serves - and I admit it was some decades ago - I, for example, initially selected my life partner on the basis that she seemed gorgeous and sparky. That was all very well at the time, but I am not sure I could defend it in retrospect as a considered, objective decision. Indeed, many people seem to make this one, all-important decision on the basis of equally flimsy, and possible even suspect, evidence. And yet, strangely, everyone seems just fine with that.

It is almost as if they hadn't even noticed that this is what's going on.

I am a university lecturer by day, but as a sideline I write books about the weird things which are unique to our own weird species: teenagers, middle age, womanly curves - things like that. Because of this, I like to spend my time thinking about how people make the most important decisions in their lives, and why they do not like analysing those decision-making processes very much.

At a book festival a few months ago, I claimed that the evidence suggests that we underestimate how important a woman's intelligence is to men who are seeking a life-partner, whereas we overestimate how important a woman's breast size is. Over the coming days the UK press translated this into 'Cambridge Professor Says Brains More Important Than Boobs", which was amusing as I didn't say that, I don't know if it is true, and I am not a professor.

What this suggested to me was that many people harbour a desperate hope that the world of romance is somehow meritocratic, and that we're not just driven by hormones, or lust, or fashion. But what is the evidence one way or the other?

First I must apologise for my gender-bias. I have mainly researched women's bodies and appearance, the main reason being that from a biologist's point of view, human female bodies are much more interesting that human male bodies. That's the main reason. Honest.

Anyway, it is actually quite easy to study heterosexual men's preferences for visual aspects of the female body, because computer technology now allows researchers to morph images of the female form into an infinite variety of permutations, about which male subjects can then be quizzed. The general trend is that straight men like hips which are noticeably wider than waists, bodily and facial symmetry, and various other indicators of health, youth and femaleness including straight legs, small hands and feet, smooth skin, luxuriant hair, and a rosy oestrogenic blush. Clearly less important are absolute body size, breast size and leg length.

This may seem a rather reductionist approach to attractiveness, but it certainly has some evolutionary biology to back it up. Throughout our species' history, men who hooked up with healthy, curvy, hormone-infused women with years of reproductive potential ahead of them ended up having large numbers of successful children. They, in short, were the men who became our ancestors.

In contrast, measuring the attractiveness of female intelligence is much harder. The thing itself is difficult to measure, men have trouble articulating what they like about it, and some insecure men mess up your data because they are intimidated by smart women.

However, once again, the evolutionary drive is strong. First of all, any man, whether of the hunter-gatherer or suburban variety, knows that if he can attract an intelligent partner then he can spend most of the rest of his life co-parenting his incredibly demanding and ridiculously slow-growing human offspring with someone who makes sensible decisions. And those decisions will be crucial in deciding whether those valuable children survive and thrive.

Even more importantly, intelligence is known to be highly heritable. On average, bright women have bright children, and because intelligence is the key to our species' success, any would-be father should want to buy into that. After all, you don't get to choose your own genes, but you can often choose whose genes they get to mingle with when you make your children.

And this is what we are left with: an inbuilt and completely politically incorrect preference for beautiful intelligent people, because we want some of that in our children. Although we normally conceal these urges to bubble away below our veneer of civilisation, we happily liberate them when romance, lust and love are in the air.

And before you ask, it seems that the amorous choices of straight women and gay people are equally non-PC. But that's another story.