the joys of being a dad....
Why a good dad loses interest in sex: New study reveals dad duties get in the way of time between the sheets
Men that put the hours in being a good dad have less sex
Study tracked lives of young men in the Philippine Islands
Found after having a baby a man's testosterone levels drop
By Fiona Macrae Science Correspondent
PUBLISHED: 21:08 EST, 14 February 2014 | UPDATED: 06:29 EST, 15 February 2014
It is not just women who tend to lose interest in sex after having a baby. Men do too.
New fathers make love less often, and it seems that the better they are at being a dad, the less sex they end up having.
Lee Gettler, of the University of Notre Dame in Indiana, tracked the lives and hormones of 433 young men from the Philippine islands.
He found that the most testosterone-fuelled men were also the most likely to become fathers.
However after having a baby their levels of the male sex hormone dropped along with the amount of sex they had.
Dr Gettler also found an increase in the hormone prolactin, which is normally associated with breastfeeding, particularly among men with the most hands-on approach to parenting.
It is thought the hormonal changes make a man more responsive to the needs of his child.
Dr Gettler told the American Association for the Advancement of Sciences annual conference: Mothers undergo substantial biological change with pregnancy and birth, yet there has been a tendency to think of the father as kind of inertly along for the ride.
The study of a group of men in the Philippine Islands revealed a man's testosterone levels drop once he has had a child
But it is not just mothers who respond to the demands of parenthood.
I think evolution has shaped male physiology to help men invest in their children and provide good care for them.
Dr Gettler added that the drop in libido could well be natures way of stopping the new father from straying.
But it is not for ever as hormone levels return to normal within a year or two.
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