Men do, nevertheless, have the deck stacked against them by biology.

From Catching Up from The Economist.

Interesting throughout. I must admit that without any real thought, I had just sort of assumed that the differential in age was simply a matter of nature. As it is, to a point, but their explanation provides a more robust explanation.

All of which is good news if you are male. Men do, nevertheless, have the deck stacked against them by biology. One way the cards are marked is that female mammals (women included) have two X chromosomes, whereas males have an X and a Y—the latter being a runty little thing with only a small complement of genes. Females’ “spare” X chromosome protects them from genetic mutations on the other one. Males have no such protection. Women are thus carriers of, but rarely suffer from, diseases like haemophilia which are caused by the mutation of X-chromosome genes. In birds, by contrast, it is the males who have matched chromosomes while females sport the runt. As a result, male birds tend to outlive their mates.

A further biological difference between the sexes is in the lengths of their telomeres. These are sections of DNA that protect the ends of chromosomes from decay. Men’s telomeres are shorter than those of women, and also degrade more quickly. Both of these attributes have been linked to reduced lifespans.

But some are more equal than others

The biggest biological difference between health of the sexes, however, can be summed up in a single word: testosterone. Testosterone is the hormone that more or less defines maleness (though women have it too, in lesser quantities). It promotes both aggression and risky behaviour. It also suppresses the immune system, which is why castrated tomcats and rams live longer than those that have not been neutered. The same applies to people. A study on eunuchs found they live 13.5 years longer than men who are intact.

Testosterone-driven behaviour means that men are more likely than women to die in accidents, and more likely to die from the violence of others. They are also more likely to kill themselves. These things are particularly true of young adults. Men are two-and-a-half times more likely to die in their 20s than women are. Testosterone may also explain the differences between the sexes in risky behaviours like smoking and drinking.

But blaming testosterone for male risk-taking explains only the “how”, not the “why”. For that, you must turn to evolutionary biology. It is no coincidence that the gap between the sexes’ mortality is widest in people’s 20s. This is the peak period for reproduction. Men are fighting each other, and showing off to the girls, in a competition whose prize is, in an evolutionary sense, immortality itself—the passage of their genes to the next generation.

To stake a claim in the afterlife, as any religion will tell you, you must make sacrifices in the present one. In actuarial terms, therefore, the Longevity Science Advisory Panel reckons that even if men adopt healthy lifestyles, women will continue to outlive them. A gap of between one and two years of life expectancy (at age 65) will persist indefinitely. That, if you are a man, might seem unfair. But if it does, then think of it as the price of eternity.