How nature helps fathers stay faithful

WOMEN must have resorted to every ruse imaginable to ensure their husbands don’t stray.

But nature, it seems, has its own way of keeping married men – and fathers – faithful.

Scientists have found that testosterone levels are lower in husbands and fathers than in bachelors.

Carefree single men have the most testosterone – the male sex hormone which governs aggression and sexual appetite – while married men have less and those with the responsibility of children have the least. A study of more than 120 married and single men found that single men have almost twice as much testosterone as fathers of a similar age.

Experts believe the fluctuations could be nature’s way of encouraging men in relationships to settle down. Evolutionary psychologist Dr Nick Neave said: ‘It’s sensible from an evolutionary point of view.

‘ Testosterone prompts males to seek out female mates and to mate with them. So you might predict that testosterone levels in males looking for mates should be higher than in males who are in relationships and have found mates.’

The lower testosterone levels in men with children indicates the father’s value to the family, said Dr Neave, of Northumbria University. ‘When you have got a baby, you don’t want the new father casting his eye somewhere else,’ said Dr Neave. ‘In the animal kingdom, having two parents around has great benefits.

‘ We are quite cosseted now but that hasn’t always been the case. For most of our existence, having two parents around would have been a great boost to survival of the young.’

He said ultra-masculine men may not make the best fathers. ‘You don’t want males with high testosterone surrounded by young children. These men can be aggressive and have low levels of tolerance.

‘ This could be natural selection’s way of calming men down and making them more civilised when children are about.’

In all the men studied by U. S. researchers, hormone levels followed the normal cycle of peaking in the morning and falling during the day, the journal Proceedings of the Royal Academy B reports.

In the mornings, married fathers produced 33 per cent less testosterone than married non-fathers and 44 per cent less than single men.