Men brought up with female siblings less sexy

London: Males who grow up with female siblings are less sexy, says a study.

Having a large number of sisters makes men no less heterosexual but their mannerisms and body language may be seen as less aggressive than those brought up amid the rough and tumble of a male dominated household.

Researchers discovered that the ratio of males and females in a family growing up together can influence the sexual behaviour, reports the Telegraph.

Genes may determine personality and behaviour but the environment during early life shapes it, according to the journal Psychological Science.

A team of psychobiologists from the University of Texas in the US experimented with new born rats, separating them into litters either male dominated, female dominated or equally mixed.

They found sexual behaviour was influenced more by the male-female ratio of the litter in which they were brought up than the one to which they were born.

When it came to mating, the male rats brought up in a litter of mainly sisters spent less time mating than those brought up among male rats or in an equally divided litter.

This was because they were not being invited to do so by the females who signal their availability by wiggling their ears or 'dart hopping' - an established rodent come on!

According to David Crews, the study author, what applies to rats may have implications for humans too.