Sexual precociousness is in our genes, new research suggests. A unique study of twins separated at birth finds a genetic link to the age at which a person first engages in sexual intercourse. The study was conducted with 48 pairs of twins separated at birth and 23 individuals. By having a large group to test, the researchers were able to rule out some factors that may have affected the results. Factors such as upbringing and social wellbeing cannot be cast aside though.
As far as results though, the team of researchers found that genes could only explain about a third of the differences in participants' age at first intercourse - which was, on average, 19 years old. In comparison, almost 80% of height variations in a population can be explained by genes alone. The team could also not rule out the effect of conservative mores which might delay the teen's first sexual experience. There was also another factor that could have had an effect on results. For example, the team found that female participants who felt unfulfiled in their home life and unhappy were more likely to have sex at a younger age. The team has also admitted that the study, and studies like it, could cause scientists to overestimate the effect of genes.
Other studies have found a gene encoding a receptor for the neurotransmitter dopamine is associated with age at first intercourse. This version DRD4 is also linked to impulsive, risk taking behaviour. Yet unlike other risky behaviours, such as drug use or reckless driving, sex serves an essential biological function. Most of our evolutionary past sexual behaviour hasn't been risk taking. It has been about reproduction and success of the species as a whole.
Sources:
http://www.newscientist.com/article/dn16876-genes-may-time-loss-of-virginity.html
Journal reference: Personality and Individual Differences (DOI: 10.1016/j.paid.2009.02.010)
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