Stay or stray? Study delves into sexual behaviour

Scientists said Wednesday they had amassed the first evidence to back theories that people fall into two broad categories — promiscuity or faithfulness — when it comes to sex. Why humans seem to be an exception among mammals on the matter of sexual relationships has long been a puzzle. Other mammalian species are emphatically polygamous or monogamous as a group. But as everyone knows anecdotally, Homo sapiens do not fall into one neat category or the other. Everyone knows of couples that are sexually faithful, but also of men cut out to be cads rather than dads. What has been lacking are the statistics to show these differences, which is a key step to explaining them. Now a team at the University of Oxford say they have found just that.

We observed what appears to be a cluster of males and a cluster of females who are more inclined to ‘stay,’ with a separate cluster of males and females being more inclined to ‘stray’ when it comes to sexual relationships.

Rafael Wlodarski, an experimental psychologist and study co-author

One source was an online questionnaire on sexual habits, completed by 585 North American and British respondents between the ages of 18 and 63, who on average were nearly 25. The other was data obtained from 1,314 British men and women — an investigation based on something known as the “2D:4D” ratio. What lies behind the 2D:4D idea is that the length of one’s ring finger indicates the level of the hormone testosterone to which one was exposed in the womb. The longer your ring finger is, compared to your index finger, the higher the likely concentrations of foetal testosterone. This in turn has been linked to a higher statistical likelihood of promiscuity. Put together, the datasets showed that 57 percent of men were more likely to be promiscuous, and 43 percent faithful.

What happens in the womb might have only have a very minor effect on something as complex as sexual relationships.

Robin Dunbar, a professor at the Oxford unit that did the research

Science