Among our ancestors, bigger brains meant more creativity and, according to Dr Geoffrey Miller, an ambitious young researcher based at the Max Planck Institute in Munich, women fancy creative men, which is why men have always produced far more art than women. Art, according to his theory, is really a sophisticated version of a large bank account or a Porsche - yet another way for boys to attract girls.
The fact that we have brains three times as big as our primate relatives is conventionally explained in practical terms - hunting, manual dexterity, tool-making. The idea that something as frivolous as love - sorry, mating strategies - could have anything to do with it has rarely been considered. What Miller has done is to pick up a rather neglected idea lying in the evolutionary toolbox ever since Darwin and used it to put desire in the driving seat.
We all know that our genes are selected for their survival value: those that make the animal faster or cleverer, upping its chances of survival, are passed on, those that don't are weeded out. But all animals also have features that have no obvious immediate survival value. The peacock's tail is the classic example. The point about the peacock's tail, or the elk's antlers, or elaborate birdsong, is that the females fancy the owner. The better the tail, the more sex the male gets. This is the evolutionary principle of mate selection.
What is radical about Miller's theory is the suggestion that, besides being turned on by desirable physical features, females also choose males for their imagination and creativity. Many species respond to newness: female birds respond more favourably to males with a greater variety of song and humans are no exception. The early hominids didn't only choose their mates because they were high- status hunters, they also fancied them because they told good jokes or stories, made music or turned out beautiful drawings and carvings.
"People attribute such high-culture religious, mystical function to cave art," says Miller. "They don't seem to have ever considered the possibility that its function is analogous to graffiti - that it could have been produced mostly by young Homo sapiens males who were luring young females down into this cave and saying: 'Here, look at those bison I've drawn, aren't they cool?' So just as pea-hens encouraged more and more gorgeous tails, women's desire drove the human cortex to develop ever more elaborate folds.
But isn't this a typical academic male fantasy - not-so-bright women gazing with big-eyed adoration at clever, creative males? Why not men picking out talented female cave-painters? Unfortunately, it doesn't work that way. There are the inescapable facts that women can have far fewer children than men and that they invest far more time and energy in them. The result is that they have to be more choosy about whom they have sex with. "Because males are so indiscriminate," says Miller, "women have less need for artistic courtship displays."
So while women can get all the attention they need with a few physical signs, men have to work harder to show they have something more long-term to offer. In fact, far from promoting the idea of the doe-eyed female, Miller believes our courtship behaviour developed when society was matriarchal and centred on bands of females. The women protected each other and brought up the children, while the males hovered round the edge trying to attract a mate.
"Male scientists have been reluctant to recognise that, for the most part, adult male hominids must have been rather peripheral characters in human evolution," he says, "except as bearers of traits sexually selected by females for their amusement value or utility."
Another immediate objection to the theory is that if it is men who are being chosen for their brains and creativity, then they should end up brainier and women should be their dumb companions, which clearly isn't the case.
In fact, this doesn't happen because there is a kind of genetic bootstrap effect to female choice - technically known as the "law of the equal transmission of characters". The genes that are involved in male intelligence are just as likely to appear in a couple's children of either sex. Then the slightly more intelligent daughter fancies a slightly more creative man and so the brains of both sexes grow.
In an attempt to move from the level of provocative speculation to empirical results, Miller did some research. He reasoned that if art and culture were really forms of male sexual display, then you should not only find much more of it done by men but also it should be done when men are at their most sexually rampant.
He conducted a large study involving thousands of works of art in recent centuries. Searching through museum catalogues, dictionaries and encyclopaedias, he logged the output of several thousand philosophers, writers, composers and musicians - jazz, rock and classical. The result was that men produced more than 80 per cent of all publicly available art: a total of 15,364 works of culture by men and 1,643 by women. Not only that, but male output peaked between the ages of 20 and 30, exactly the time when men are also at their strongest, most sexually active and most likely to commit murder - an extreme example of male aggression.
"Old hat," retort his feminist critics, "that's simply a sign of patriarchal suppression." To which Miller replies that the "patriarchy" theory doesn't explain why it started in the first place, which his theory does. "I have nothing to say about individual differences," he says. "What I am interested in is how humans as a whole got to where they are now. In modern society there are certainly biases that prevent women from producing culture to the extent that they would like. But a sexual selection theory of culture doesn't in any way imply that today women can't or shouldn't or won't produce culture."
So hopeful male Valentines should forget those tedious flowers and chocolates and be creative instead. Take a leaf out of the Palaeolithic seduction book and paint your own cave.
Bear in mind also that the item that got the best response in a recent edition of the slated Babes with Attitude TV show was not something about firemen's hoses or embarrassing confessions, but the starlet who told how hubby had proposed after leading her to a room filled with lighted candles and 80 wedding dresses. It works.