Genes may determine how early or late we lose our virginity, said Michael Winter in USA Today, at least according to a new study of twins separated at birth. “But don’t start watching your watch, kids.” The study, led by psychologist Nancy Segal, didn’t find evidence of a “sex clock,” just inherited behavioral traits, such as impulsiveness, that could be behind the age-virginity correlation.

The study’s evidence of a genetic predisposition for “sexual precociousness” is pretty “modest,” said Ewen Callaway in New Scientist. Segal found that genes accounted for a third of the differences in the participants’ age of first sexual intercourse—on average, a little older than 19—compared with roughly 80 percent for height. And the study “sidesteps” social factors, like cultural and family expectations.

But it did find that the genetic link was weaker for twins born before 1948, said Randall Parker in the blog FuturePundit, when social mores led more people to delay sex. As “old cultural constraints” fall away, we are freer to “follow genetically driven desires and impulses.” Genes probably do push some people to have sex earlier, or later, but many of us fall in the genetically “more malleable” camp.