Life expectancy in Australia has improved significantly for both male and females in the last century.
According to the Australian Institute of Health and Welfare, a boy born in recent years can expect to live to the age of 80.5 years and a girl would be expected to live to 84.6 years compared to 47.2 and 50.8 years, respectively, in 1881–1890.
Highlights
- Life expectancy is less related to our behaviour and more to the chromosomes we carry to our cells, the study found
- The data on sex chromosomes was collected on 229 species
- Animals with two of the same sex chromosomes tended to live on average 17.6% longer
Why do women live longer than men?
The general belief is that men live shorter lives than women because they take bigger risks, have more dangerous jobs, drink and smoke more, and do not seek medical advice as often.
But researchers at the University of New South Wales say they have cracked the mystery and claim it’s less about the behaviour and more to do with something deep inside the nucleus of our cells.
Lead researcher and PhD student Zoe Xirocostas says males of most animal species die earlier than females because their smaller Y chromosome is unable to protect an unhealthy X chromosome.
UNSW researcher and lead author of the study, Zoe Xirocostas. Source: Supplied
"We studied a wide range of species, 299 in total, and of those species we studied humans, mammals, fish, insects, reptiles, amphibians and arachnids," she said.
In humans and other mammals, females have two of the same chromosomes (XX) while males have two different chromosomes, X and Y.
'Unguarded X'
During the study, Ms Xirocostas tested the ‘Unguarded X’ hypothesis which suggests that the Y chromosome is smaller than the X chromosome which expresses harmful genes that cause adverse health effects.
“The sex that has two long chromosomes is less likely to be at risk of bad genes on one of the X chromosomes because the other chromosome can take its place," Ms Xirocostas told SBS Greek. "However, if there’s a bad gene on a male’s X chromosome the Y chromosome is not able to take the X chromosome’s place. So, it will have to deal with those bad genes unlike the females who have two of the X chromosomes.”
Writing in the journal Biology Letters, the team reported that animals with two of the same sex chromosomes tended to live on average 17.6% longer than those that had different ones.
“We looked at lifespan data in not just primates, other mammals and birds, but also reptiles, fish, amphibians, arachnids, cockroaches, grasshoppers, beetles, butterflies and moths among others,” she says.
Interestingly, in birds, butterflies and moths it is the male that has the same sex chromosomes (ZZ) while the female has different chromosomes (ZW). In these species, the males tend to outlive females by seven per cent, the study found.
