Some have theorized it's related to the greater power of men in society, or differing sexual expectations of men when compared to women.Laumann prefers an explanation more closely tied to the world of sociobiology.Birds do it, bees do it, and men do it any old time. The sources of women's libidos, by contrast, are much harder to pin down.But women will only do it if the candles are scented just right -- and their partner has done the dishes first. It's common wisdom that women place more value on emotional connection as a spark of sexual desire.Women's desire "is more contextual, more subjective, more layered on a lattice of emotion," Perel adds.
It is more about the anticipation, how you get there; it is the longing that is the fuel for desire," Perel says.
By contrast, women may be more open to same-sex relationships thanks to their less-directed sex drives, Bailey says.
"Women probably have the capacity to become sexually interested in and fall in love with their own sex more than men do," Bailey says.
"They won't necessarily do it, but they have the capacity." Bailey's idea is backed up by studies showing that homosexuality is a more fluid state among women than men.
In another broad review of studies, Baumeister found many more lesbians reported recent sex with men, when compared to gay men's reports of sex with women.