By Tom Kelly
For every woman expecting the earth to move, it would seem there are two with more practical motives.
From relieving boredom, to keeping the peace in a relationship or even curing a headache, the reasons for succumbing to the advances of the opposite sex are many and varied.
Romance and passion, it has to be said, come rather low down the list, according to a new book.
One woman even admitted to having sex just so her husband would put the rubbish out.
Cindy Meston and David Buss, authors of Why Women Have Sex, highlight 200 specific reasons.
"Research has shown that most men find most women at least somewhat sexually attractive, whereas most women do not find most men sexually attractive at all," conclude the authors, both psychology professors at the University of Texas.
Having apparently discounted physical attraction, the 1 000 women interviewed by Prof Meston gave a huge range of reasons for sleeping with a man.
One said she did it for a spiritual experience, proclaiming: "It's the closest thing to God."
why women have sex
But in most cases the explanations were far more mundane, with 84 percent admitting to having sex just to ensure a quiet life or to bargain-for household chores.
One woman explained: '"have sex to relieve the boredom - because it's easier than fighting. Plus it gives me something to do." For others, it provides an unlikely cure for a migraine or stress headache.
While it may not come as welcome news, some women have sex out of sympathy, with one admitting: "I slept with a couple of guys because I felt sorry for them."
But most have selfish motives, with financial or material rewards a major factor behind many sexual encounters.
In one survey of students carried out by the researchers, nearly one in ten women admitted to "having sex for presents".
Other reasons included: "He bought me a nice dinner", "He spent a lot of money on me early on" and "He showed me he had an extravagant lifestyle".
And rather than love or romance, for many women sex is just about fun.
Six in ten university students in one survey said they regularly slept with a male friend who was not their boyfriend.
One, who was at a different college from her boyfriend, explained it was because "life is too damn short to be waiting four years to have sex again".
Others confessed they did it to improve their sexual performance, with one explaining: "I have had sex with my boyfriend to make my sexual skills better."
The research concluded, perhaps predictably, that women are attracted to tall men with a deep voice, who smell good.
A symmetrical body also helps, since it is a genetic indicator of health and suggests he will give his lover strong children.
However, those who don't live up to this ideal can take some comfort. Their lower level of testosterone may win over the ladies too, because it suggests they are less likely to run off with another woman. - Daily Mail