The average American man will live until the age of 76, while the average American woman will live until 81, according to the latest CDC data on American life expectancy.
This gender gap isn’t just an American phenomenon — it’s true across countries, races and even species, as Time Magazine reports studies have found that female apes live longer than their males counterparts.
While previous research from Duke University has linked the shorter male lifespan to testosterone’s role in risky behaviors, a new study is finding that the mortality gap could be embedded even deeper into biology, all the way in the chromosomes.
The new study, conducted by the University of New South Wales, was published in the journal Biology Letters, and revealed that across many different animal species, whichever sex had the identical sex chromosomes lived an average of 17.6% longer than the sex with nonidentical chromosomes, according to Science Magazine.
The study followed 229 different animal species and found that having un-matching or shorter chromosomes resulted in a shorter lifespan, despite gender, according to the Sydney Morning Herald. The trend remained in species like bullfrogs or birds, where it is the males who have matching chromosomes, and thus lived longer.
But not as much longer, as the Guardian reports species where the males had matching chromosomes, they only lived 7.1% longer, whereas when females had matching chromosomes they lived 20.9% longer.
The study also found that estrogen appears to prevent aging by protecting the ends of an individuals chromosomes, the Guardian reports.
One of the study’s co-authors, Zoe Xirocostas, told the Guardian that while their findings clearly point to chromosomal homogeny being important to longevity, additional factors such as “predation, risky behaviours, establishing territories and access to quality nutrition” also have important impacts on lifespan.