How fatherhood will change your body’s chemistry

Lithograph of a father instructing his children in geography
Lithograph of a father instructing his children in geography - Bettmann

If there’s one feature of family life that has changed most visibly over the last few decades, it’s the sight of fathers with their children. Whether in London or New York, it seems I’m just as likely to see a man carrying his baby in a sling or pushing a buggy down the street as I am a woman. Fathers are involved in their children’s lives more than ever – changing nappies, gently feeding, organising playdates.

It’s a subtle social revolution. But for American anthropologist Sarah Blaffer Hrdy, it also prompted a fascinating scientific question: why have biologists so neglected fatherhood?

It’s strange how long researchers have assumed that there has always been a rigid division of labour between the sexes. Even now, despite abundant evidence of women hunters and warriors from prehistory onwards, there’s a lingering assumption in evolutionary biology that women’s bodies are geared for motherhood and that men have evolved to shoot and leave. In short, men are the hunters and women are the carers. In her remarkable new book Father Time, Hrdy’s compelling argument is that we have been misdirected.

Born in 1946 into a well-off, patriarchal family in Texas, Hrdy’s own father was stereotypically hands-off. It was in her children’s generation that she witnessed a palpable shift. When her first grandchild was born in 2014, she recalls “watching a man totally immersed in nurturing a baby, and doing so entirely by choice”. And it wasn’t just her son-in-law. Fathers everywhere, she noticed, were being encouraged to bond with their babies and were enthusiastically seizing the opportunity. In 2021, one in five stay-at-home parents in the United States were fathers. Thirty years ago, it was closer to one in ten.

Should we be surprised? “Behavioural flexibility, after all, is a human speciality,” writes Hrdy. Aka fathers in Central Africa have long been known to spend almost half their time with their infants. In the 1990s, one surprised Western anthropologist couldn’t help but notice how emotionally attuned these men were to their babies. Societies in which “men spend more time in contact with mothers and children are less bellicose and exhibit lower rates of violence.”

Sarah Blaffer Hrdy, author of Father Time
Sarah Blaffer Hrdy, author of Father Time - Dan Hrdy

Recent studies confirm that men’s bodies respond viscerally to parenthood, just as women’s do. Hrdy notes that “men undergo remarkably similar endocrinological and neurological transformations” as women when they spend extended periods of time near children. Testosterone levels fall in men who are involved in looking after their babies, just like the testosterone levels of women fall when they become mothers. The cultural act of choosing to be a hands-on father unlocks the latent natural potential to be a better father.

This is a profound observation with far-reaching consequences. Too often, modern societies have been designed around the idea that our behaviour is fixed by biology, that old-fashioned gender roles are natural. But the scientific evidence suggests otherwise. When given social permission – or in Hrdy’s words, when our binary gender straitjackets are loosened – we have the capacity to behave differently. Policymakers might do well to remember this when considering parental leave and other family policies.

Hrdy has taken one of the final big myths of human evolution – that childcare by men is peripheral or unimportant – and knocked it firmly on its head. Her 1981 book The Woman That Never Evolved, along with her influential later work, Mother Nature and Mothers and Others, placed females firmly in the evolutionary story as independent, strategic agents rather than the passive creatures that her male contemporaries often framed them as. In the vein of her earlier work, this book reminds us that human child-rearing, unlike in some other species, is and always has been a communal activity involving people beyond the mother. Father Time will change minds, but more importantly, it points the way to a different type of science, one that takes into account how culture shapes biology and doesn’t stand apart from it.

It is also a reminder that Hrdy is, without exaggeration, one of the most important thinkers in evolutionary biology since Darwin. She was her Harvard professor’s first female graduate student in 1970, and her life since then has been spent blazing a trail. Her beautiful writing retains as much power to astound and educate as ever.


Angela Saini’s latest book is The Patriarchs: How Men Came to Rule. Father Time is published by Princeton University Press at £25. To order your copy for £19.99, call 0808 196 6794 or visit Telegraph Books

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