Adaptation or happy coincidence?
By Katy Love

It was the year that “A Streetcar Named Desire” won the Pulitzer Prize. But in 1948, Dr. Alfred C. Kinsey was interested in a less dramatic look at desire as he released his study “Sexual Behavior in the Human Male.” It sold more than 200,000 copies when it was released. The follow-up, “Sexual Behavior in the Human Female” became a best-seller when it was released in 1953 – the same year Playboy published its first issue. This post-war era marked the beginnings of the current open discourse about sex. From Cosmo to Kiegels, sex is a hot topic in our society; a constant source of conversation, fascination and research. But there are still some mysteries about human sexuality, and one of the most enduring is why women evolved to have orgasms.

“The adaptive value in men is real straight forward – a great experience when you deliver gametes,” says Randy Thornhill, distinguished professor of evolution at the University of New Mexico. “The question is, why do women orgasm?”

Theories about the adaptive value of the female orgasm are prolific and include the possibility that female orgasm might not be an adaptation at all. Some think orgasm creates a pair bond, giving the female motivation to become emotionally involved with her partner. At the point of orgasm, the hormone oxytocin is released into the brain creating sensations of pleasure and possibly bonding the beneficiary on the person that created that pleasure. Another idea, the “pole axe” holds that women need to assume a prone position in order to help insemination occur. As such, the orgasm is there to create feelings of fatigue so that the female feels the need to rest afterwards, allowing time for insemination to occur. Yet another theory, the “upsuck” hypothesis, suggests that the orgasm actually helps pull the sperm up into the reproductive tract with muscle contractions.

The “upsuck” hypothesis is currently the most well accepted by scientists like Robin Baker, an evolutionary biologist at the University of Manchester, whose research shows that the timing of the female orgasm to the male orgasm can either help or hinder sperm retention, which will either help or hinder fertilization. Taking Baker’s work a step further, Thornhill showed that females have the ability to make the sperm-retaining effects work towards selecting a better mate. He found that women will orgasm more often with partners that have bilateral symmetry. This physical trait has been found to be an indicator of such things as higher growth rate and better immune systems,...