Study finds that having children suppresses your sex drive. THEY say having a family changes a man forever.
But it may not just be a sense of duty that drives new dads to swap evenings in the pub for quiet nights at home.
Scientists have discovered fatherhood can halve testosterone levels and stop men from straying.
A study has found that when men become fathers, their bodies suppress production of the sex hormone, making them more interested in parenting than mating.
American researchers studied more than 600 men over a five-year period in their twenties.
During this time, around a third had a child with their partner.
The scientists found that this group started off with the highest testosterone levels, but having their first child made their production of the hormone plummet.
Lead author Christopher Kuzawa, associate professor of anthropology at Northwestern University, said: “Testosterone boosts behaviours and other traits that help a male compete for a mate.
“Raising human offspring is such an effort that it is co-operative by necessity, and our study shows that human fathers are biologically wired to help with the job.
“Previous studies have found that married men and fathers have lower testosterone levels than single men, but this is the first to suggest that having children actually causes the fall.”
The researchers measured testosterone levels in a group of 21-year-old childless men from the Philippines. Over the next five years, the childless men saw an average age-related testosterone decline of 14 per cent, but for those who became fathers, the typical drop was 34 per cent.
For those with a child under one month old, the decline was around 50 per cent, but it remained consistently lower than their childless counterparts until their offspring was at least a year or two old.
The men who reported caring for their child for between one and three hours per day saw the greatest decline, which the authors said was not accounted for by stress or sleep deprivation