Popular belief has always held that males of our species live shorter lives because they take more risks, drink and smoke more and are less likely to take advice from their doctors (all true).
But research by scientists at UNSW Sydney suggests that the reason may have less to do with the Aussie male’s penchant for a beer and more to do with the type of sex chromosomes humans share with most animal species.
Most animals have XY or XX chromosomes in their genetic makeup – and the research team wanted to find out if the pattern of women outliving men was repeated across the animal kingdom.
Looking at lifespan data in primates, other mammals and birds, as well as reptiles, fish, amphibians, arachnids, cockroaches, grasshoppers, beetles, butterflies and moths (just to be sure of their facts), they found across the broad range of species, the sex with different chromosomes (such as XY) died on average 17.6% earlier than the sex with the same chromosomes (like XX).
Why is this the case?
The theory is that the smaller Y chromosome in sexes with XY (male chromosomes) is less able than the XX (female) chromosome to protect a person from unhealthy genes in the X chromosome, which may later develop into a health threat.
Women don’t have this problem – because a healthy X chromosome can stand in for another X that has ‘bad’ genes.
Interestingly, the researchers also found in species where males have two of the same sex chromosomes such as birds, butterflies and moths, males only lived an average 7.1% longer than females.
But in species where the sex chromosome pattern is the other way around – like humans – females live 20.9% longer on average than males – suggesting that being the male of the species could still be fundamentally life-shortening.
Could the reason be a failure to not do what the female of the species wants?
