Genes May Affect The Age You Have Sex

Is the age at which you have sex for the first time a matter of genetics? A new study says, Yes — at least in part. Research published Monday in Nature Genetics reveals that genes affect when people lose their virginity, as well as the age at which they have their first children. Although the researchers point out that sexual and reproductive behaviors still rely heavily on environmental factors, their study suggests that the link between genetics and sexual behavior is stronger than you might think.

For this research, scientists worked with a huge pool of participants. They began by studying the genes of more than 125,000 people registered with the UK BioBank, and then corroborated their results by analyzing DNA from over 250,000 people from Iceland and the United States. The scientists were ultimately able to identify 38 sections of DNA that influence when people have sex for the first time. Some of these factors seem fairly unsurprising, particularly those that have to do with the biological processes of reproduction, such as the age at which the body begins to release sex-related hormones and when puberty starts. But other factors are less intuitive, not affecting sexual development directly, but instead influencing personality and behavior. For example, the researchers found that a certain gene associated with risk taking was linked to having sex at a younger age, while a gene tied to irritability was associated with having sex later.

Figuring out the genetic component of sex — particularly when people begin having sex for the first time — is important because the age at which a person has sex is linked to other key issues like educational and health outcomes. John Perry, a Cambridge geneticist and lead researcher on the project, explained to Scientific American, “If you look in [scientific] literature, relatively early ages at first sex and first birth have been associated with lower educational achievement, poorer physical health, poorer mental health—a complex web of negative stuff.” The age at which a person starts puberty and has sex for the first time has even been shown to affect their risk for certain diseases decades in the future. Study co-author Ken Ong told The Verge, “Puberty timing and age at first sexual intercourse appear to be adverse for diabetes, heart disease, and a number of cancers, particularly reproductive hormone cancers.”

As significant as these results are, it’s important to note that genetics are only one among many factors that influence when people have sex for the first time. There are a variety of environmental factors, including cultural and religious background, family dynamics, peer behavior, and economic issues, that also shape when people begin having sex. In fact, the scientists believe that these external factors play a significantly larger role than genetics do. “We were able to calculate for the first time that there is a heritable component to age at first sex, and the heritability is about 25 percent, so one quarter nature, three quarters nurture,” Perry told the Guardian. Thus, your genes, by themselves, don’t determine your sexual behavior — but they may affect how you make important sex-related decisions and predispose you to act in certain ways.

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