Research by scientists at UNSW Sydney suggests the real reason may be less related to human behaviour and more to do with the type of sex chromosomes we share with most animal species.
In a study published in Biology Letters, researchers from UNSW Science’s School of Biological, Earth and Environmental Sciences analysed all available academic literature on sex chromosomes and lifespan and they tried to establish whether there was a pattern of one sex outliving the other that was repeated across the animal kingdom.
Specifically, they wanted to test the unguarded X hypothesis which suggests that the Y chromosome in heterogametic sexes those with XY (male) sex chromosomes rather than XX (female) sex chromosomes is less able to protect an individual from harmful genes expressed on the X chromosome. The hypothesis suggests that, as the Y chromosome is smaller than the X chromosome, and in some cases absent, it is unable to ‘hide’ an X chromosome that carries harmful mutations, which may later expose the individual to health threats.
Across that broad range of species, the heterogametic sex does tend to die earlier than the homogametic sex, and it’s 17.6 percent earlier on average.
This study confirms that the unguarded X hypothesis is a reasonable explanation for why one sex outlives the other on average.