The tired trope of aggressive male sexuality is pervasive. The story goes like this: because men are full of testosterone and sperm as well as unhindered by the consequence of pregnancy, their sexuality is naturally brutish and promiscuous. Testosterone fuels aggression, billions of sperm want hundreds of outlets, and nature failed to offset these desires with physical dangers associated with reproduction.
The complement to this heterocentric sex story is that women, with their limited eggs, lack of testosterone and pregnancy burden are naturally chaste and self-protective. Any sexual adventurousness or licentiousness is only done to please men and keep them around so they will help with the child-rearing.
A simple and neatly packaged explanation of human sexuality. But it’s wrong. Let’s do some debunking.
Origins: The idea that testosterone is an aggression correlate comes from an experiment that found castrating male mice reduced combativeness. Naturally, culture extrapolated these findings to humans and claimed testosterone had the same effect on male humans.
Reality: In a 2009 study, European researchers administered either .5 mg of testosterone or a placebo to male participants before engaging them in a game of cooperation that involved negotiating money distribution with other players. They could make an offer as fair or unfair as they wished and those on the receiving end could choose to accept or decline. The findings? Testosterone recipients made fairer offers, a direct contradiction with common beliefs about testosterone and aggression. Researchers suggested thattestosterone influences a sensitivity toward status which is expressed as cooperativeness in pro-social situations.
The relationship between testosterone and sexual desire is a slightly different, albeit unclear story. There is evidence to suggest that testosterone influences sexual desire in males and somewhat less in females. However, our desires are also regulated and influenced by a myriad of psychological and external factors. Stress, diet and sexual beliefs likely have more of an effect on our sex drives than this hormone.
Origins: The biological definition of male and female has to do with size of gametes, where male gametes are always smaller than female gametes. Male gametes are often mobile and easily replenished, especially in the case of humans. The theory -- known asBateman’s principle, from Angus Bateman’s 1948 fruit fly research that studied phenotype distribution via genetic mutations among offspring -- states that females are choosier when selecting mates because of their limited lifetime gamete supply. To simplify Bateman's assertion: male reproductive success is positively correlated with number of female mates.
Reality: Modern researchers invalidated Bateman’s findings when they reanalyzed the original data. None of the findings were statistically significant and the study had many methodological flaws. In 2010, researchers in the UK put forth a contradictory reading on fruit fly sexual behavior that posited female promiscuity as essential to some species’ survival. The press release onEurekAlert says it best:
This study suggests that polyandry reduces the risk of populations becoming extinct because of all-female broods being born. This can sometimes occur as a result of a sex-ratio distortion (SR) chromosome, which results in all of the Y chromosome ‘male’ sperm being killed before fertilisation. The all-female offspring will carry the SR chromosome, which will be passed on to their sons in turn resulting in more all-female broods. Eventually there will be no males and the population will die out.
New York City Maps of the Star Homes