14 or 40? How genes may influence the age you lose your virginity

Your DNA doesn’t dictate exactly when you lose your virginity, but it may play a larger role in the matter than scientists had thought.

A new study identifies 38 specific places in the human genome that appear to be associated with the age at which people first had sex. These spots affect a range of genes, including some that seem to affect the timing of puberty and others that have been linked with risk-taking behaviour.

Altogether, the influence of these DNA variants accounts for about one-quarter of the variation in how old people are when they have sex for the first time, according to the study published Monday in the journal Nature Genetics. Environmental and cultural factors, along with individual choice, explain the rest, the study authors said.

“While social and cultural factors are clearly relevant, we show that age at first sexual intercourse is also influenced by genes,” John Perry, a researcher at the University of Cambridge in England, said in a statement.

Perry and his colleagues singled out these 38 pieces of DNA with the help of more than 125,000 contributors to the UK Biobank. Each of these volunteers — all between the ages of 40 and 69 — provided a blood sample for genetic analysis. They also reported how old they were when they lost their virginity. The median age was 18 for both men and women in the study.

The researchers sorted through all that data to find associations between specific DNA variants and the age at first sex, or AFS. Thirty-three of the variants were found in both men and women (though sometimes to differing degrees); four were seen in men only, and one was unique to women.

To see if their findings were just a fluke, they tested those same genetic variants in two other large groups — Americans in the Women’s Genome Health Study and Icelanders working with scientists at DeCode Genetics.