Men, we know, are from Mars, and women are from Venus. Mars, in this metaphor, is a place of carnal obsession and emotional autism; a planet whose inhabitants think about sex every seven seconds and get in fights all the time. Venus, by comparison, is a warm and hospitable place of social interaction and empathy, but not a great deal of sex. So the popular wisdom has it. Jon Snow, the Channel 4 newsreader, is from Mars. “Sex comes into every evaluation of a woman, there’s no doubt about it,” he said in an interview last week. Every time he meets a woman, he weighs her up as a potential sexual partner, and, he thinks, other men do the same. “It’s a natural animal element of sustaining life.”
As a happily married man, with many female friends and colleagues, it would perhaps be imprudent of me to comment. But the Mars-and-Venus stereotype, the sexually voracious man and the demure woman, has a strong hold. How accurate is it?
There are obvious evolutionary reasons why men and women would have different approaches when it comes to sex; why a man who behaved in a certain way might expect to have lots of descendants, but a woman who behaved the same way would not. Men and women are similar in many ways, but they are usually different in one: their sexual organs. We should not be surprised if they also have different psychological systems to determine how they use those organs.
Dr Diana Fleischman, an evolutionary psychologist at the University of Portsmouth, puts it simply: “If a man has sex with 100 women in a year, he might have 100 babies. If a woman has sex with 100 men in a year, she might have one baby and a very sore bottom.” This is due to what is called the “obligate parental investment”: a man’s minimum investment towards a child might be a couple of minutes’ work and a teaspoonful of sperm; a woman’s minimum investment is nine months of pregnancy and a painful and potentially dangerous labour – and that’s before the question of who raises the child is addressed.
This imbalance means that we should expect men to be more motivated to have sex, says Dr Fleischman, and women to be choosy about their partner. It’s something we find elsewhere in the animal kingdom – and, intriguingly, when the parental roles are reversed, so are sexual habits. “Male sea horses get pregnant, for example. And they tend to be choosy, because they bear the higher cost.”
And it’s not a Just So story, which evolutionary psychology is sometimes accused of. In one review of the literature, “not one study found that women think about sex more than men,” says Dr Fleischman. One trial, published in the Journal of Sex Research, found that men think about sex – on average – 34 times a day, compared with women’s 19. Dr Fleischman mentions another that put the figures much lower – about once a day for men, once every several days for women – but consistently, the findings are that men think about sex more than women do. “Men have more intrusive thoughts, too – it’s harder for them to ignore thoughts about sex,” she says.
It’s not just thinking about it. Usually, men’s sexual activity is limited by how often women will consent to sex – but there is a natural experiment that shows what would happen if it was limited by how often men consent. That natural experiment is, of course, the lifestyles of gay men. “If you look at gay men and women,” says Fleischman, “you’ll see that gay men have a lot more partners than gay women do.” Having to gain consent from a man is a far lower bar to clear, she says, than gaining consent from a woman.
This could be because of some fundamental difference between gay men and straight men, other than their sexual preference – but it doesn’t seem to be. “If you have two men, and they have the same sex drive, but one is limited in how much sex he has by men, and the other is limited by women, one is going to have a lot more sex than the other,” says Fleischman, adding with a laugh: “My boyfriend always says, ‘I wish I was gay. It’d be so much easier’.”
It seems, then, that the “sex-mad man” and “cuddle-hungry woman” stereotypes are broadly accurate.
And so they are – but we should be careful with them. Stereotypes are useful because they often give us good information about groups, says Prof Nicholas Epley, a University of Chicago psychologist and author of Mindwise: How we understand what others think, believe, feel and want. “You’ve learnt that tigers are dangerous,” he says. “You see a tiger, you’d be rightly scared, even though this particular tiger might not attack you. If you see a beaver, you’re not. Your stereotypes of tigers and beavers are working admirably in that situation.”
Our stereotypes of groups of people generally point us in the right direction as well. “We learn things about groups of people. We learn things about conservatives and liberals, and football players and professors, and men and women,” says Prof Epley, and those things are usually, broadly, right. Those stereotypes are about what separates groups, not what unites them.
“The stereotypes are about the things that make men and women apparently different from each other. One is more interdependent, one is more independent. One is more sociable, the other more competitive.” And one is more sexually rapacious than the other.
But focusing on the differences exaggerates those differences. All of the above stereotypes have a degree of truth – but the effect is far less pronounced than we imagine it to be. For example, the study mentioned above found that men think about sex 34 times a day. That’s quite a lot – about twice every waking hour. But it’s not every seven seconds, as myth has it, and women apparently think about it pretty often themselves. And, as Prof Epley points out, the groups “men” and “women” will overlap. Dr Fleischman agrees: “The men who think about sex the least will think about sex less than the women who think about sex the most.”
And, again, it’s not just thinking about it. There are lots of scenarios in which females might seek casual sex, or sex outside their partnership, “maybe to get better genes than their mate has, or maybe to get status, or maybe to get resources”, says Dr Fleischman. (I should stress that this is not a conscious thing; we’re talking about evolutionarily successful strategies, not deliberate calculation.) It’s obviously difficult to get good statistics on how often people cheat on their spouses, but evidence of human infidelity can be found in another, unexpected place: gorilla testicles.
Male gorillas have small testes, because even though they have large harems of females, those females only mate with one male, so there is no “sperm competition”. Chimpanzee females, by contrast, mate with multiple males in their group when receptive, and males have very large testes, so that they can get more sperm into each female and maximise their chances of being a father. “Human males have testes smaller than those of chimps, which leads people to say we’re less promiscuous than chimps, which is true,” says Dr Fleischman – but our testes are much larger than those of a gorilla.
Equally, there are lots of scenarios in which it makes evolutionary sense for men to be less sex-obsessed: “If you’re a smaller male, the best strategy might be for you to be a good dad. In general, it’s more adaptive for men to be motivated for sex, and for women to be more coy, but the stereotype is definitely overstated,” Dr Fleischman says.
Jon Snow might be right, to an extent – many men probably do think about sex with every woman they meet, and most men think about sex more than most women. But the difference between the sexes is less than we imagine. If we assume that every man we meet is sex-mad and every woman uninterested, then we’ll get it wrong with embarrassing regularity.
We may think men are from Mars and women are from Venus, but as Prof Epley puts it: “The truth is more like men are from Iowa and women are from Illinois.”