Rhianna Benson
Human beings are living longer now than ever before, but one thing has stayed the same: the age-old pattern of women having higher average life expectancies than men.
Interestingly, however, this reality isn't just limited to Homo sapiens.
In fact, it's the case for the vast majority of adult mammals: females enjoy much longer lives that their male counterparts - an average of 12 per cent longer, to be precise. It's only really birds, insects and reptiles that see boys outliving girls.
For years, scientists have attempted to conjure up explanations for this, with genetics at the forefront of many theories.
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It was previously found that women having two X chromosomes seemed to work in their favour in terms of longevity, with experts believing their genes could protect them from major, potentially dangerous genetic mutations that men's genes are said to be prone to.
In a new study, however, researchers also looked into the influence of mating rituals and proneness to risk, diving deep into the common evolutionary traits of more than 1,000 animals species, all of which tend to see females outliving males.
The team conducted their study (cited by Metro) within a zoo, so as to control exterior, life-threatening factors, like predators or a lack of food.
It was found that the gender most responsible for rearing offspring lived the longest - and in the vast majority of these cases, this gender was female.
Girl mammals, the scientists ruled, were living an average of 16 per cent longer than their zoo-based male counterparts.
Emphasising this point, the group referred to the example of chimps, who can famously live with their mothers for up to a decade.
As such, the longer a female chimp lives, the longer she can give care to her babies.
Intriguingly, it was also found that males in predominantly one-partnered species were inadvertently shortening their lifespan by using energy - including bodily weapons like sharp teeth and claws - to attract a female mate. Though they noted this fact isn't really applicable to humans in a post-caveman world.
"Species often live considerably longer in zoos than in the wild, and abundant resources and managed reproduction in zoos may lower individual survival costs associated with growth and reproduction," they discovered.
"For example, the influence of sexual size dimorphism on male survival tends to be lower, and the individual cost of producing offspring appears to have no effect on female survival in zoo settings."
Dr Johanna Staerk, the lead author of the study, went on to apply the team's finding to the human world.
"Our findings may help explain why differences in [average life expectancy] between men and women are so consistent across time and cultures," she explained.
"Specifically, female-biased [average lifespan] appears to be common to chimpanzees and gorillas, suggesting that longer life expectancies for females are a characteristic long embedded in our evolutionary history."