"Women have a larger interest in reproductive events because they have fewer opportunities for passing on their genes than men," said George Preti, a Monell Chemical Senses Center organic chemist...An Evolutionary Explanation for Sexual Smell Differences
"Men produce thousands of gametes every day, women just one every month," Preti said. "Their investment in a reproductive event is higher than men's, so they're more biologically attuned to who they're mating with."
Preti and other pheromone researchers suspect that mammalian olfactory systems actually evolved to detect chemical traces of genetic incompatibility in the odors of potential mates.
(Image: Someone Sniffs, a Creative Commons Attribution licensed photo from Orin Optiglot's photostream)
I write books. My latest is a YA science fiction novel called Homeland (it's the sequel to Little Brother). More books: Rapture of the Nerds (a novel, with Charlie Stross); With a Little Help (short stories); and The Great Big Beautiful Tomorrow (novella and nonfic). I speak all over the place and I tweet and tumble, too.