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Genetics performs necessary position in age at first intercourse and start

  • Hundreds of genetic drivers influence sexual and reproductive behavior
  • Combined with social factors, these can affect longevity and health

An Oxford-led team, in collaboration with Cambridge and international scientists, have discovered hundreds of genetic markers that determine two of life’s most momentous milestones – the age at which people first have sex and become parents.

In an article published today in Nature Human Behavior, the team linked 371 specific areas of our DNA, called genetic variants (known locations on chromosomes), 11 of which were gender-specific, to the time of first sexual intercourse and birth. These variants interact with environmental factors such as socio-economic status and date of birth and are predictors of longevity and later illnesses.

The researchers conducted a Genome-Wide Association Study (GWAS), a search across the human genome to see if there was a link between reproductive behavior and a particular genetic variant. In the largest genomic study to date, they combined multiple sources of data to examine first-sex age (N = 387,338) and birth (N = 542,901) in both men and women. They then calculated a genetic score, with all of the genetic loci together explaining about 5-6% of the variability in mean age at sexual debut or the birth of a first child.

Professor Melinda Mills, Director of the Leverhulme Center for Demographic Science at the University of Oxford and Nuffield College and lead author of the study: “Our study discovered hundreds of other genetic markers that shape this most fundamental part of our lives and have the potential for deeper understanding of infertility, diseases in later life, and longevity. ‘

The genetic signals were driven by social factors and the environment, but also by reproductive biology, with findings on follicle-stimulating hormone, implantation, infertility and spermatoid differentiation.

Professor Mills adds, “We already knew that socio-economic circumstances, or childhood education, are important predictors of when to reproduce. But we were intrigued not only to literally find hundreds of new genetic variants, but also to uncover a link to substance abuse, personality traits like openness and self-control, ADHD, and even predictions of some disease and longevity. ‘

Professor Mills says, “We have shown that it is a combination of genetics, social predictors, and the environment that promotes early or late onset of reproduction. It was amazing to see that the genetics underlying early intercourse and fertility are related to behavior reversal like ADHD, but also addiction and early smoking. Or those with a genetic tendency to postpone sex or first birth had better health outcomes and longevity in later life, which is related to higher socioeconomic status in childhood. ‘

Genetic factors that determine reproductive behavior are closely related to diseases later in life, such as type 2 diabetes and cardiovascular diseases.

“It is exciting that the genetics that underlie this reproductive behavior can help us understand disease later in life.”

Professor Mills concludes, “The early onset of the sexual journey has its roots in childhood inequality, but it also has links to health problems such as cervical cancer and depression. We found particularly strong links between early sexual debut, ADHD, and substance abuse such as: B. early smoking. We hope our results will lead to a better understanding of teenage mental and sexual health, infertility, disease later in life, and helpful treatment. ‘


The study Identification of 371 Genetic Variants for Age in First Sex and Birth Associated with Externalizing Behavior (DOI: 10.1038 / s41562-021-01135-3) can be found here after the lifting of the embargo: https: //www.nature. com / articles / s41562-021-01135-3.

Funding was given to MCM by the European Research Council, SOCIOGENOME (615603), CHRONO (835079), ESRC / UKRI SOCGEN (ES / N011856 / 1), Wellcome Trust ISSF, Leverhulme Trust and Leverhulme Center for Demographic Science, NB by the ERC. made available GENPOP (865356), to FCT from LabEx Ecode, French National Research Agency (ANR) Investissements d’Avenir (ANR-11-LABX-0047), to MdH from Swedish Heart-Lung Foundation (20170872, 20200781, 20140543, 20170678, 2018070607 and 20200602), Kjell and Märta Beijer Foundation and Swedish Research Council (2015-03657, 2019-01417). The donors played no role in the study design, data collection and analysis, the decision to publish, or the preparation of the manuscript.

Leverhulme Center for Demographic Science:

The Leverhulme Center for Demographic Science (LCDS) was founded in 2019 to establish an internationally recognized and interdisciplinary center for demographic science that will disrupt, realign and increase the value of demography in science and society. For more information about the Trust, please visit and follow the Trust on Twitter @LeverhulmeTrust

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