The age people have sex for the first time, and become parents for the first time, are partly controlled by their genes, a team at the University of Oxford has shown.
Hundreds of genetic markers have been discovered that can be used to predict sexual behavior as well as personality traits and future health, a paper published in Nature Human Behaviour has demonstrated.
Lead author Professor Melinda Mills, director of the Leverhulme Centre for Demographic Science at the University of Oxford, said: 'We already knew that childhood socioeconomic circumstances or level of education were important predictors of the timing of reproduction. But we were intrigued to find not only hundreds of new genetic variants, but also uncover a relationship with substance abuse, personality traits such as openness and self-control, ADHD and even some diseases and longevity.'
By conducting a genome-wide association study, the team searched the entire human genome to determine potential relationships between reproductive behaviour and particular genetic variants. The study of genetic datasets of over 930,000 individuals led to the identification of 371 specific genetic variants, which are believed to be indicative of the timing of first sexual experience and giving birth. The team calculated a genetic score, with all genetic loci combined explaining around five-six percent of the variability in the average age at sexual debut or having a first child.
Researchers showed that key genes related to follicle-stimulating hormone (FSHB), implantation (ESR1), infertility and spermatid differentiation impacted age of first parenthood. They also demonstrated that polycystic ovary syndrome could lead to later first birth for affected women.
The study also found individuals who were genetically prone to postpone sex or first birth had better later life health outcomes, though it was noted higher socioeconomic status during childhood plays a large factor as well.
There are still further questions given the limited resources of a single study. For example the participants studied were of European ancestry only, meaning the results were 'only applicable to European-ancestry groups, with a need for further cross-ancestry discovery research', the study authors noted.