New research has found a possible genetic explanation for why women live longer than men on average. It seems that the gene that makes male mice stronger than female mice also weakens their immune system. Researchers discovered this by creating mice with two mothers and no father, through genetic manipulation. Apparently the gene responsible is carried by both males and females, but its action is suppressed in females – dramatically so for the “fatherless” females.

This is potentially important if the same effect is true in humans. Lifestyle differentials have borne much of the blame for higher levels of male mortality – men have tended to adopt riskier behaviour when young (leading to more accidents), and to have drunk and smoked more when older (leading to higher rates of disease); however, if the underlying reason for differences in mortality is genetic, then attempts to eradicate the longevity gap are doomed to failure.

But is the same genetic factor likely to be present in humans? Indeed, there is evidence that women are less robust in response to certain external factors – smoking and drinking generally have greater health consequences for women than for men. It is also dangerous to extrapolate the results from tests on small mammals to their consequences for humans. It is, though, an interesting addition to the debate on gender and mortality.