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According to Wikipedia and many other sources, women live substancially longer than men (over 5 years in the U.S.).

Men can reproduce for much longer than women. So longer living men would have the most offspring, while the longevity of the women would be more or less irrelevant in reproducing. These offspring would be the product, on average, of men and women where the men are older than the women.

So why do women live longer than men? Am I misinformed, or what don't I get?

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  • $\begingroup$ In my place it is the vice versa :) $\endgroup$ – azam Apr 2 '15 at 15:44
  • $\begingroup$ I believe reproduction itself has something to do....i seem to recall that links have been seen between sexual reproductivity and shortened lifespan. See this, for example: Bowen RL, Atwood CS. Living and dying for sex. A theory of aging based on the modulation of cell cycle signaling by reproductive hormones. Gerontology. 2004; 50: 265-290. $\endgroup$ – Cantona's Collar Apr 3 '15 at 10:17
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The best explanation I have come across so far is that male sex hormones have an adverse affect on longevity.

The effect may simply be that a high testosterone level suppresses the immune response against a variety of infections.

There was a recent study about korean eunuchs from a few hundred years back, that found that "The average lifespan of eunuchs was 70.0 ± 1.76 years, which was 14.4–19.1 years longer than the lifespan of non-castrated men of similar socio-economic status."

That's a pretty hefty difference and a strong argument for testosterone as risk factor for an earlier death. This would also vibe well with reports about increased risk of cardio-vascular death in steroid users.

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Behaviour

I would think that the most important causal factor between this difference is behaviour. Men probably smoke more than women, probably eat more junk food and are eventually more stressed. Men also probably take more risks and have more accidents. This last point might have been very important at an earlier time when men were hunting outside while the females would work inside the cave. Depression is more prevalent in men as well and it is possible that might affect health. These differences in behaviour might be caused by genetic (and epi-genetics) differences (sexual chromosomes) or by culture.

Oestrogen

There was a time where some doctors thought that the different was due to oestrogen but I think that this hypothesis has been ruled out.

The Y chromosome is short

Men have a Y chromosome while women have two X chromosomes. At each mitosis, the chromosomes get shortened (telomere are shortened). It is possible that the presence of the Y chromosome may explain some of the observed difference due to its small size. However, according to @cantona'sCollar the Y chromosome is often lost in somatic cells and therefore the difference of length between the X and the Y chromosome doesn't seem to be a good explanation.

Grandmother hypothesis

While women stop reproducing earlier than males, women often provide more care to their grandchildren than men do. As a result of this behaviour, genes coding for longer lifespan are beneficial by the fact that they help other copies of themselves (found in the grandchildren) to thrive (kin selection).

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    $\begingroup$ Depression is more common in women not in men: nimh.nih.gov/health/publications/depression/… Also, I would say that the roots of different behaviors are most likely to be in the genes since lifespan of men are shorter than women in most cultures. My guess would be the effect of testosterone. Men are more prone to take risks - even the life threatening ones - because of this hormone while women are more likely to choose the safer path. $\endgroup$ – ecagl Apr 2 '15 at 22:38
  • $\begingroup$ I edited my answer to basically redraw some claims that were wrong or at least had little support. Thanks for your comment. $\endgroup$ – Remi.b Apr 2 '15 at 22:54
  • $\begingroup$ In reasonably fit people, men die from cardiovascular events at least 5 times more than women even after adjustment for smoking, cholesterol, high blood pressure, blood glucose, etc. This endocrinology paper of August 2013 attributes some of that to estrogen. I do agree that telomere length and mitochondrial DNA play a role, but isn't telomere length maintained on non-X chromosomes in women longer than men, or am I mistaken? $\endgroup$ – anongoodnurse Apr 3 '15 at 2:06
  • $\begingroup$ I have no idea if telomere shorten faster in all chromosomes in men. In this kind of discussion it is important to not forget the cause-consequence framework. It is possible that men died earlier because of more risky behaviour (such as hunting) and in consequence they would have relaxed selection at later age allowing late acting deleterious alleles to accumulate on the Y chromosome and things like that. $\endgroup$ – Remi.b Apr 3 '15 at 2:08
  • $\begingroup$ I should say that the bit about Y chromosomes does not seem right. A "-Y" abnormal karyotype in somatic cells is frequently seen in older men (>70 years of age) and it doesn't seem to necessarily correlate with any clinical abnormalities. $\endgroup$ – Cantona's Collar Apr 3 '15 at 10:14

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