Skip to main content

Dads Have Been Older than Moms since the Dawn of Humanity, Study Suggests

Using modern human DNA to estimate when new generations were born over 250,000 years, scientists suggest that fathers have been having children later in life than mothers throughout human history

Shot of a young happy couple relaxing on the sofa while talking to their two young adorable kids at home

Men have consistently had children later in life than women throughout human history, suggests a study. The research used genetic mutations in modern human DNA to create a timeline of when people have tended to conceive children over the past 250,000 years, since our species first emerged. The timeline suggests that men have, on average, conceived children around seven years later then women.

Without historical records, knowing at what point in their lives people had children is tricky. In recent years, sequencing technologies and large genetic data banks have allowed researchers to mine DNA for clues. But previous estimates have been limited to approximately the past 40,000 years. To look further back in time, Richard Wang, an evolutionary geneticist at Indiana University in Bloomington, and his colleagues tracked spontaneously arising mutations in modern human DNA.

All children have new mutations that their parents don’t. These mutations emerge when DNA becomes damaged before conception, or owing to random errors during cell division. Research suggests that older parents pass on more mutations than younger parents, with differences between men and women.


On supporting science journalism

If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.


Mutation tracker

Wang and his colleagues used software to comb through data from a study of around 1,500 Icelanders and their parents that tracked age of conception and genetic changes between three generations. The program learnt to associate certain mutations and their frequencies with the age and sex of parents. The team then applied the newly trained model to the genomes of 2,500 modern people living around the world, to identify mutations that emerged at various points in human history.

By dating when these mutations emerged, the team was able to map out the average age of mums and dads over the millennia. The researchers found that 26.9 years was the overall average age of conception during the past 250,000 years. But breaking this down by sex showed that men averaged around 30.7 years when they conceived a child, compared with 23.2 years for women. The numbers fluctuated over time, but the model suggested that men consistently had children later in life than women.

The longer generation times for men can be generally explained by the fact that men are biologically able to have children later in life than women, bringing up the average age of fatherhood, says Wang.

Social pressure

The finding could also point towards social factors, says Mikkel Schierup, a population geneticist at Aarhus University in Denmark, such as pressure on men in patriarchal societies to build status before becoming fathers.

Population geneticist Priya Moorjani at the University of California, Berkeley, says the model doesn’t account enough for other factors — including environmental exposure — that could shape when mutations pop up. This means that mutations with various causes might be unfairly attributed to the age of parents, potentially skewing the results of studies such as this, Moorjani and others argued in a preprint posted in June.

Although this is a valid concern, Wang says that his team’s study does account for some other mutation-causing factors. Definitively reconstructing when people became parents will require sampling more populations, says Schierup. In the meantime, this study provides “sensible estimates” that can help researchers to gain insight into the lives of early humans, he says.

This article is reproduced with permission and was first published on January 13 2023.

Freda Kreier is a freelance journalist who likes writing about the natural world, DNA and the distant past. You can find more of her work at www.fredakreier.com.

More by Freda Kreier

First published in 1869, Nature is the world's leading multidisciplinary science journal. Nature publishes the finest peer-reviewed research that drives ground-breaking discovery, and is read by thought-leaders and decision-makers around the world.

More by Nature magazine