Do you like beards? I like beards. But I know plenty of women who don't. Most adult men I know don't have beards. Which is weird, when you think about it. Because beards are a biological signal. A signal that says, "I am a sexually mature male, ready for mating. I have excellent genes and will impregnate you with fine children. Mate with me ladies." They are the human equivalent of peacocks' tails.

From an evolutionary standpoint, shaving off beards makes no sense, so why do many men do it? I'll tell you why. It's because human beings are highly complex social animals embedded in highly complex social systems. Culture, fashion and what-other-people-do have an enormous influence on us. So much so they can completely confound our biological programming. So when evolutionary psychology looks at mate choice in humans, it needs to bear in mind this inconvenient fact. Which means I take this recent Telegraph headline, "Stressed men prefer larger women", with something of a pinch of salt.

This reports on a study in PloS ONE in which they gave some white, male, Westminster undergraduates a mock job interview, then showed them pictures of women of a range of body types, and asked them which they found attractive. They found that the "stressed" students picked slightly larger women than the control group. And concluded that when we experience acute stress (indicating, perhaps, a threatening environment), we become more attracted to bodies that suggest maturity as it makes us feel safer.

I know we shouldn't get exercised about subheadings, which are generally not written by the author (and certainly not by the scientists). But, I give you: "Tightening one's belt in a recession is usually considered prudent, but women may be advised to do the opposite after a study found that in tough times stressed men turn to larger ladies for comfort." Oh no, we thought we were supposed to be thin, but now we might have made ourselves too thin for boys to like us! Let us cry hopelessly into our pillows ladies.

Thing is, there's a massive difference between the adrenaline and cortisol burst from a 10-minute mock job interview, and the complex physiological effects of long-term stress such as unemployment, poverty or economic uncertainty. A recession, for those at the sharp end, is really nothing like a few minutes of embarrassment.

To be fair, neither the scientists nor the bulk of the article make the recession comparison, they simply talk about stress. But there are other problems. White university undergraduates in London are not representative or typical of all human beings. Not only are they young, educated, well-fed, but they are embedded within one particular complex social system. Jane Austen's heroines develop accomplishments such as embroidery and piano playing to impress potential husbands. I think my boyfriend is a lot more impressed by me always carrying a penknife than my grade one piano certificate. The sensible strategies for life in one complex social system are not necessarily the sensible strategies for life in another complex social system. We can't draw conclusions about all humanity, or about our evolutionary programming, from the behaviour of 80 London undergraduates.

There are also other possible explanations for these results. We live in a culture that sends us messages about what we are supposed to look like, and what we are supposed to find attractive. You see thousands of images of young, scantily clad women with unnatural body shapes every day. Of course this influences what people actually do and think. But even more, it influences what they think they think. And what they say they think. It may be that many men naturally prefer slightly larger women than we're presented with as the cultural ideal, and this is overlaid by an idea of what we are "supposed" to like. Perhaps stress makes this natural preference leak out more. Part of their brain is too busy worrying to remember what they are supposed to like. This isn't a possibility the scientists seem to have considered. Innate preferences is all, let's ignore the effects of cultural programming.

There are thousands of psychology papers published every day. Why is it that a small and limited study, finding a very small effect, gets covered in the science media when so much else doesn't? Is this article, ironically, just another example of the cultural obsession with women's weight, which pop evolutionary psychology so studiously ignores?

http://www.guardian.co.uk/commentisfree/2012/aug/10/stressed-men-prefer-big-women