RIO DE JANEIRO, BRAZIL – A group of Australian researchers claim to have finally solved the mystery: it’s not about the gender, but rather about the chromosomes.
According to a study published on Wednesday, March 11th, by the scientific journal Biology Letters, and disclosed by BBC News, having two copies of the same chromosome is associated with a longer life, suggesting that the second copy provides a kind of protective effect.
All cells contain chromosomes that carry long fragments of DNA. In most species, males have a smaller sex chromosome than females: males have one X chromosome and one Y chromosome, while females have two X chromosomes.
“The sex with the smaller chromosome actually tends to die earlier in a wide range of species,” explains Zoe Xirocostas, co-author of the study and researcher at the University of New South Wales, Australia.
In birds, males live longer on average, but this is because they have two Z chromosomes, while females have one Z and one W chromosome.
Massive ‘superiority’
According to information reported by the BBC, women live longer than men in all countries of the world. According to data published by the World Health Organization (WHO) in April last year, women live at least 1.4 years longer than men, although there are regions where this difference exceeds three years.
In a number of South American countries, this gap is even more striking. In Mexico, for instance, the life expectancy of a man at birth is 74 years, while women can live 79.2 years. In Brazil, the difference is similar: men 71.4, women 78.7.
‘A backup’
Humans have 23 pairs of chromosomes. The #23 pair is known as the sex chromosome because it determines gender.
But if a woman inherits an abnormal gene on the X chromosome of one of her parents, she has a ‘backup’. “If she has a working copy of a gene, her body automatically uses it, canceling the one that doesn’t work,” says Xirocostas.
On the other hand, men do not have that same ‘backup’. So if men inherit an abnormal gene on their sex chromosome, they are more exposed to genetic diseases that can affect their life expectancy.