Evolutionary scientists have never had difficulty explaining the male orgasm, closely tied as it is to reproduction.But the Darwinian logic behind the female orgasm has remained elusive. Women can have sexual intercourse and even become pregnant - doing their part for the perpetuation of the species - without experiencing orgasm. So what is its evolutionary purpose?Over the last four decades, scientists have come up with a variety of theories, arguing, for example, that orgasm encourages women to have sex and, therefore, reproduce or that it leads women to favor stronger and healthier men, maximizing their offspring's chances of survival.But in...