It’s widely known that on average, women live longer than men. However, researchers now claim there is a genetic reason.
The primary reason for women’s longevity has puzzled experts for generations. Recently, a team of international researchers produced a report stating that it is mainly due to something called the ‘’heterogametic sex theory.’
Scientifically, men are known as the heterogametic sex, because their sex chromosomes do not match – they have one X and one Y. According to the experts, this puts them at a disadvantage compared to females, who have two X chromosomes.
Due to their combination of XY chromosomes, males are more prone to harmful genetic mutations and disease. In turn, this leads to an earlier death for men on average.
Dr Fernando Colchero, study author at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, told the Daily Mail, “We believe that the heterogametic sex is partially the answer.”
“We found that there are factors which are tightly linked to our evolutionary history that contribute as well.”
Research around women living longer than men dates back to the 1740s, and has been consistently proven across nearly all countries. Currently, the average global life expectancy is 73.8 years for women and 68.4 years for men, according to Our World in Data.
Figures have varied over the years, but women have consistently maintained the higher average age. The same has proven true in the animal world, with female mammals typically outliving their male counterparts. In some instances, the reverse is true, the Daily Mail reported. In many birds, insects, and reptiles, males are the longer-lived sex.
To finally get to the bottom of the lifespan gap, researchers studied records from 528 mammal species and 648 bird species in zoos worldwide.
Like humans, 72 per cent of mammals showed a female life expectancy advantage, while 68 per cent of birds showed a male advantage. This led them to the heterogametic sex hypothesis.
Study author Dr Johanna Stärk at the Max Planck Institute for Evolutionary Anthropology told the Daily Mail, “Basically, if you have two copies of the same genes, it’s better than one.”
Dr Stark also added that the Y chromosome often contains long pieces of repetitive DNA which may be harmful.
The team admitted that there are other lesser factors that contribute to female’s longer-life span, some of which include sexual selection, environmental pressures, and parental care.
The researchers found evidence that the sex that invests more in raising offspring tends to live longer. Because female mammals are usually the primary caregiver, they have evolved to survive until their offspring are independent.
The research team said there are likely social and behavioral factors not considered in this study that could also play a role.