Men ‘biologically wired’ to care for children

“On the contrary, the men who started with high testosterone were more likely to become fathers, but once they did, their testosterone went down substantially.”

It was the act of child care that seemed to reduce testosterone, he explained.

“Our findings suggest that this is especially true for fathers who become the most involved with child care.”

The biggest effect appears to be temporary, in the period immediately after bringing home the baby, with levels rising slowly after that, although not returning to pre–fatherhood levels.

The team studied 624 men in their twenties in the Philippines and followed them for four–and–a–half years. Dr Allan Pacey, a male sexual health expert at Sheffield University, commented: “To see dramatic changes in response to family life is intriguing. The observations could make some evolutionary sense if we accept the idea that men with lower testosterone levels are more likely to be monogamous with their partner and care for children.

“However, it would be important to check that link between testosterone levels and behaviour to be certain.”

The study found that testosterone levels fell on average by 34 per cent when men became fathers, with the biggest falls in those most involved in childcare.

Dr Pacey added that, as high levels of testosterone were also associated with a strong sex drive, lower levels could reduce the chances of a man ‘straying’. However, he cautioned that the paper did not prove that. He added: ‘Testosterone is the key hormone that defines male physiology. We know that levels correlate with a man’s sex drive, his risk–taking behaviour and social dominance. It has also been suggested that it may increase his attractiveness to women and help him find a mate.”