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mario notaro

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If evolutionary success is analogous with reproductive success, why do men not live longer than women?

Men can generally reproduce up until the day they die. Women on the other hand, are able to reproduce only up until menopause, which happens roughly two thirds of the way through life. Thus, wouldn't it follow that longer lived men would have had more offspring than their shorter lived brethren? Conversely, women that had genes permitting them to live well past menopause would have no real evolutionary advantage over those that did not.

I have a few ideas about factors that could help explain this, but I want to see what others will say.

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    Aug 1 2011: A fine question, Mario!

    I am in now way an expert in medicine or biology, so my answer may be utterly false, but I'll give it a try.
    I think the fact that men are capable of reproducing almost all the way to their deaths is a strange happening, but in no way desired by evolution. Thinking back to our ancestors, they only lived to be about 40 years old, so there was no need for women to stay fertile any longer than this. Same goes for men theoretically, but perhaps because our reproductive system isn't as complex (I guess at least) we don't encounter these problems.

    All in all, the matter of men being capable of reproducing at an older age is in no way linked to how long we live. Correlation in this case does not imply causation.
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      Aug 2 2011: I totally agree with Sabin, at least in the matter of staying fertile till death. Male reproductive system is considerably simple, thus it can stay efficient for a long time, although with some age it gets only worse. It's like with contemporary technology - the more composed it is, the less durable it becomes.

      Referring to the men life expectancy, there are various factors that influence it, which are not connected to natural predispositions. First of all, it is cultural position of men in the society. Having position of protector of the family and main provider of money/food/etc (of course in last century it has drastically changed) they were working in worse conditions (e.g. heavy industry). Secondly, the psychological factors cannot be denied. Men are less talkative and as such, have more problems with dealing with emontions. This amplifies the stress factor that seriously impacts the life expectancy.
    • Aug 2 2011: Thanks for your responses guys. The fact that people only lived up until about 40 was indeed one explanation that I had in mind, but I find that it raises further questions: If it was extremely unlikely for a woman to live until her fifties, where did menopause come from? What ''advantage'' did it give those that had the trait? Did it develop as a way to stop reproduction once the probability of birth defects became too high? If so, doesn't that fly in the face of the life expectancy explanation for my original question?
      • Aug 2 2011: The longevity advantage for menopausal women may be that they no longer bore children. Birth defects aside, childbirth was the number one cause of death for women throughout history. It still is in some places. Older men may have been driven from the community to die, while older women cared for the young. Certainly males in some animal societies are driven out by the younger, now stronger males. Our nearest ancestors, gorillas and chimpanzees practice this. We may, in our primitive states, also held to the "dominant male" culture. If a woman made it to menopause, she could potentially live a very long life, relatively speaking.
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          Aug 2 2011: I just checked Wikipedia (what else) for some information on why women experience the menopause - there are two branches of a possible evolutionary cause:

          1 Non-adaptive, stating that "the high cost of female investment in offspring may lead to physiological deteriorations that amplify susceptibility to becoming infertile. This hypothesis suggests the reproductive lifespan in humans has been optimized, but it has proven more difficult in females and thus their reproductive span is shorter. If this hypothesis were true however, age at menopause should be negatively correlated with reproductive effortand the available data does not support this."

          2 Adaptive, namely:
          "The mother hypothesis
          The mother hypothesis suggests that menopause was selected for in humans because of the extended development period of human offspring and high costs of reproduction so that mothers gain an advantage in reproductive fitness by redirecting their effort from new offspring with a low survival chance to existing children with a higher survival chance.

          The grandmother hypothesis
          The Grandmother hypothesis suggests that menopause was selected for in humans because it promotes the survival of grandchildren. According to this hypothesis, post reproductive women feed and care for children, adult nursing daughters, and grandchildren whose mothers have weaned them. Human babies require large and steady supplies of glucose to feed the growing brain. In infants in the first year of life, the brain consumes 60% of all calories, so both babies and their mothers require a dependable food supply. Some evidence suggests that hunters contribute less than half the total food budget of most hunter-gatherer societies, and often much less than half, so that foraging grandmothers can contribute substantially to the survival of grandchildren at times when mothers and fathers are unable to gather enough food for all of their children. In general, selection operates most powerfully during times of famine."

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