A recent study of twins suggests that there is a genetic link to the age at which a person first engages in sexual intercourse. As the New Scientist reported:
"It's not like there's a gene for having a sex at a certain date," says Nancy Segal, a psychologist at California State University in Fullerton who led the new study. Instead, heritable behavioural traits such as impulsivity could help determine when people first have sex, she says.
As genetic determinism goes, the new findings are modest. Segal's team found that genes explain a third of the differences in participants' age at first intercourse – which was, on average, a little over 19 years old. By comparison, roughly 80% of variations in height across a population can be explained by genes alone….
As for the specific genes involved, another team previously found that a version of a gene encoding a receptor for the neurotransmitter dopamine is associated with age at first intercourse. Others have linked the same version of the gene – called DRD4 – to impulsive, risk-taking behaviour.
Whole New Scientist article here.