Why do women live longer than men?
March 18, 2010 at 1:46 am #12964ManBearPig89Participant
Hello, i’m a first year biology student (so no flaming please!)
I was just thinking of this: why average age of women is higher than men’s…
In Norway the average life- expectancy for women is 81,4 years, and for men, "only" 76 years.
Why is it that women live longer than men, when most women stop reproducing at the age of 40 (?), when many (?) men can reproduce almost all their life?
For a long time, i have known that women live longer, but it does not make sense to me. After all, they are the one’s who have to cary children and give birth, often several times, "wasting" tons of energy.
Many fish die after giving birth (or at least they die after "making sure" their eggs is not eaten by some other fishes).
The obvious reason we live so long today, at least in the west is becouse we have so much food, and also good helth- care. I did a search for the life expectancy at birth in Sierra leone ( won the price for the most shitty country to live in 2009) and it was for men 39,2 years and for women 43,6 years… And they don’t have anything to eat, nor a very good health- care system 😛 Also a women in SL produces 5,88 children on average…
how can this be?
help please! 😮
here are som demography for Sierra leone
March 18, 2010 at 6:50 am #98351JackBeanParticipant
1) the men are little (much) more endangered by life style, that is wars, hunting, nowadays many adrenalin sports, motorbikes and cars…
2) if human women died after giving birth, we wouldn’t be here anymore, because human kids are unable to do anything, so women must take care of them. But not only in the first generation, but also in the second generation (as grandmothers), so that they help mothers to take care about family and they can thus have more kids
March 18, 2010 at 7:57 am #98354
This is due to several factors. Like JackBean said, the life style of men is something that cuts off several years from their average life expectancy. This is especially prominent in some countries, such as in Russia where the difference in favour of women is almost 14 years.
However, there certainly are genetic factors involved, because even in countries where there is realitvely little "unhealthy" activites among men (such as Japan), the difference in life expectancy is several years.
It appears that men are simply more prone to "acute" medical emergencies such as heart attacks, whilst women are more likely to succumb to long-lasting ailments such as cancer or dementia.
Why this is so? I think it is not known for sure, but e.g. sex hormones may play an important role. Also, this is just speculation, but it might have something to do with metabolical rates: men, on average, have higher energy consumption due to bigger muscle mass (even if measured per unit of weight). In nature, animals with high metabolism tend to die quicker when compared to similar-sized animals with slow metabolism. Maybe this can also contribute to the fact that men kick the bucket so soon 🙂
March 18, 2010 at 4:27 pm #98372SmigParticipant
I think that, before answering this question you need to ask another question. What causes people to die naturally?
I honestly don’t know what are the latest findings there but I’d bet we don’t know for sure and answering this question is essential to answer yours.
For example, is there a timer in our DNA that stipulates when we’re supposed to die? What causes the hormonal changes through the course of our lives? What can influence those causes? Can an intrinsic hormonal difference accelerate the process? Is it something hardwired in the Y chromosome?
March 19, 2010 at 3:05 am #98384mithParticipant
you can check the CDC mortality rates or the WHO also has some stats. Basically, men get in more accidents and have problems such as prostate cancer
March 19, 2010 at 7:44 am #98390quote Smig:
There is quite a lot of knowledge on this, but it is true that why we need to die is still unclear.
The shortening of telomeres is a long-known phenomenom which ensures that at some point our cells cannot replicate any more. However, the body has enzymes to rebuild telomeres but in most cells the genes for this enzyme are downregulated, meaning that it is never expressed and the cells eventually die. So at least to some extent it seems that the body "intends" to die. But then again, it has been suggested that the lack of telomerase is there to prevent cells from dividing uncontrollably – cancer cells typically are able to express telomerase enzyme and replenish their telomers, and thus become "immortal". So maybe we die of old age because our cancer-preventing mechanisms prevent also sufficient tissue regenration eventually. Though of course the gradual build-up of mutations in our genomes means that if nothing else kills us, cancer eventually does.
Most hormones and their effects are also fairly well known. And some of the phenomena related to hormonal functions are indeed hardwired in the Y chromosome, or more precisely, are dictated by the genes in the Y chromosome even if the final gene product was coded for in another chromosome. For example, the manifold levels of testosterone production in men may be one of the reasons why the male body "burns out" faster.
Cancers, in general, are bit more common in women but this has probably much to do with the fact that women just live longer. More importantly, men are about twice as likely to have a cancer associated to poor life style, such tobacco smoking or excessive alcohol use. Thus, if there were no lifestyle differences between the sexes, women would have more cancer and many men would probably die of cardiovascular disease or such before they even have time to develop cancer.
Finally, one could argue that there is no such thing as a "natural" death (or the other way round: death is always natural – it is only natural that you die if you receive a shot in the head or have a terminal cancer). If you think about it, people basically always die of some disease or trauma: for very old people it is typically cancer, pneumonia or respiratory/circulatory failure. None of these events are "natural" causes of death, they are either contageous diseases or medical emergencies. If a child or a middle-aged adult had such a condition, it would never be termed "natural" death. And how can you determine the point when someone is so old that it is just fine to die of one of those reasons? Nobody just dies because the "time is up", they die because their body suffers some kind of trauma that is big enough to end their life. The likelihood of such an event just is much bigger for old people but that aside there is no real difference.
March 19, 2010 at 9:59 pm #98415butterfly1Participant
Humans are simply the host bodies for genes. I think our dna is probably programmed to end renewal of cells at a certain age as it would not be of benefit to the next generation of genes to be in host bodies that were struggling to survive against overcrowding and over competion of resources before they had had chance to reproduce the next host body.
March 20, 2010 at 3:00 am #98421ManBearPig89Participant
Some pretty good answers here, thanks!
Is it so that DNA is instructed to make leathal mutations (cancer) at "a late stage" in a Gene- host’s life?
I think it’s a pretty big sacrifice for our genes to destroy it’s host- body (in humans today at least), becouse only 50% of a parents gene’s are past on, than 25% etc. in the end, the "origanal" genes are "wiped out" through the generations. On the other hand, if lats say somone that can live forever, like an elf, is killed thats it for the genes…
For the genes it would be best to live forever in one organism, than instruct the organism to stay in one place away from any danger for the rest of time 😀 💡
// rant! 😆
March 20, 2010 at 10:17 am #98431quote butterfly1:
As far as I know, this often suggested idea that organisms die in order for their offspring to have more resources and less competition is wrong. The latest view (though not probably accepted by everybody) is that the genes only function to reproduce themselves. They do not function for the good of the species or for the good of the offspring of their "host". They do not want to actively kill their "host" organism, because that would kill them as well.
Why we die of old age and why the telomeres keep shortening apparently has more to do with protecting the host from succumbing to cancer before the genes have had time to multiply (i.e. to have children). The multicellular body has created means to prevent uncontrolled cell division. Also, our bodies accumulate harmful mutations that eventually break down the integrity of the body. If it was possible, the host body would live forever and keep producing more and more offspring (i.e. copies of the original genes). The genes in us do not know when all the space is filled and resources used – that is where competition via mutations takes place. For the same reason, the genes do not work for the good of the species, the individual or their offspring. Their only "goal" is to replicate their own copies.
This can actually be seen in many "lower" organisms, such as bacteria: they do not die of old age. They simply multiply and multiply and multiply as long as they can. If the genes wanted to "make way" for their offspring, the bacteria should also die of old age so as to allow the offspring have more room and resources. Of course, with organisms multiplying by binary fission it is bit hard to tell who is the parent and who is the child, but if you think of the process as kind of "budding" (bit like in the yeast, for example), the idea may become more clear.
So, apparently, complex multicellular organisms die of old age because their bodies have developed these "suicidal" means of preventing cancer or maybe some other similar problems, not because they wanted to make room for others. If the genes in you or I got to choose, they’d replicate themselves forever and fill the Earth with their own copies. Only because of mutations and chance events there is such a big competition that it cannot happen 🙂
March 20, 2010 at 10:34 am #98432quote ManBearPig89:
No, as far as I have understood, this is not the case. Most of the mutations happen because the DNA fails to repair itself – with few exceptions (like B lymphocytes), the cells always try to repair the mutations. Even in the B cells all other mutations except somatic hypermutation are corrected if possible. So in this light, mutations are an unwanted and potentionally disastrous event for the cell. But they do happen, and that is what gives tools for evolution.
It is a popular view, though, that the host bodies are just "discarded" after they have fulfilled their purpose (that is, they have had children). But I have read quite a few prominent evolution biologists and geneticists saying that this might not actually be the same (see my previous answer in this thread).
For example, a human male can basically have children during his whole life, so why would the genes destroy this "replication machine" on purpose if it is working? Unless, of course, some other reasons force them to do so (mechanisms that limit cell division and regeneration).
Of course, there are dozens of species that apparently live just to breed: the salmon in North America that die almost right after they have laid their spawn, or male spiders and praying mantises that often become food for their spouse. Even these cases have an explanation, but unfortunately I don’t remember exactly how they are explained.
This is a very complex topic and I’m not sure if I can explain it properly, but I hope you got my point! And of course it is possible that there is much that we still do not know and the real situation is something between these two views. Nonetheless, this is an extremely curious topic.
March 23, 2010 at 12:42 am #98552skepticParticipant
In evolutionary terms, the main theory as to why women live longer is the ‘grandmother’ theory.
This theory says that humans evolved long life so that women can survive long enough to help their grandkids. In this way they enhance the survival and eventual reproduction of their grandkids, which (of course) means their own genes survive. Thus, women living long enough to be grandmums, and care for their grandkids, is selected for in evolution. There is a lot of empirical evidence that, in primitive societies, children who have living grandmothers, are more likely to survive.
In lots of ways, the real problem is why men live as along as they do. There is little empirical evidence that having grandad around enhances the grandkids chances of surviving. It may be that males live as long as we do by sheer accident. Because we share enough genes with the women to share the benefit of long life. However, this question is still moot.
February 3, 2011 at 9:25 am #103387AnonymousParticipant
I think…While both men and women have testosterone and estrogen, men have higher testosterone levels and women higher estrogen levels. Estrogen tends to increase immune system activity, whereas testosterone can dampen it. Also, estrogen causes women to have more HDL (good) cholesterol and less LDL (bad) cholesterol than men on average, which decreases their risk for heart disease and stroke. However, engaging in regular exercise can shift the balance, increasing HDL and decreasing LDL and HGH also play an important role in it…
February 4, 2011 at 4:26 am #103390RapParticipant
To Butterfly1, I agree with Biohazard, it makes no evolutionary sense for an organism to be programmed to die in order to give more room to its offspring. If dying is a given, though, it may make evolutionary sense for an organism to sacrifice itself for its offspring. I think that if there were genes that made it possible to live and reproduce forever, and there was an evolutionary path to those genes, life would have found it.
I think that women live longer than men because of the grandmother effect mentioned above, but also in primitive societies, men are expendable. 10 women and one man means ten babies next year, 10 men and one woman means one baby next year. A tribe cannot afford to lose many of its women, but it can afford to lose many of its men. Thats why in primitive societies, men are more likely to wage war, not women. There’s no reason why that value system should not be encoded in the DNA to some extent.
February 4, 2011 at 3:24 pm #103398
Excellent words there.
But in a way life has already found a way for an organism to life forever, or at least for a very long time. This can be seen for example with bacteria or plants. A bacterium in a suitable environment essentially lives forever. Admittedly, it is hard to keep track who or what is the first bacterial cell after several cell divisions, but the point is that those organisms do not die of old age. Instead, they simply keep dividing on and on. Of course one could argue that dividing indefinitely is not living indefinitely when it comes to any single organism.
But if you consider plants, some of them (most notably trees) do not exhibit this animal-worldish way of reproducing a finite time and then stopping it and dying. Instead, trees keep producing offspring for long time, some of them hudreds if not thousands of years if nothing happens to them. Of course, in the end they die too, but it is bit difficult to tell if it is "old age" or something else 🙂
Anyway, what I’m trying to say is that ageing must be a sum of many things, and none of those things alone is something that cannot be avoided by the tools evolution has given to organisms. Together, however, they make creatures die of "old age" – some later, many sooner!
From the evolutionary point of view it is quite interesting that often males and females are born in approximately similar numbers despite the fact stated by Rap, that you only need a few males to fertilize dozens of females, or even more. In many species this obviously has a lot to do with competition: the nature makes males to fight for their right to have offspring, thus ensuring that the best genes survive. But if so, why not make 2/3 males and 1/3 of females to make the competition even more fierce? Or make 1/3 males and 2/3 females simply to allow for more babies to be born. Also, human males are born at a slightly higher rate than females, is this because more males get themselves killed before they reach adult age?
February 4, 2011 at 4:20 pm #103401DarbyParticipant
It seems what you’re looking for is the evolutionary rationale for aging, which is what really clears the field for offspring. But not every organism ages. Even discounting asexual reproducers (as mentioned above, how "old" is a bacterium?), why is there variation in sexual reproducers?
February 4, 2011 at 8:15 pm #103405skepticParticipant
The reason for equal numbers of males and females is differential evolutionary pressure.
If there are normally more females, which seems the optimal reproductive ratio, then there is an evolutionary advantage to producing more males. So evolution supports those who make more males. In the long run, it all balances out with equal numbers of male and female offspring.
February 5, 2011 at 2:31 pm #103417RapParticipantquote Darby:
Yes, if organisms could live forever, why should there be aging? "clearing the field for offspring" does not work, because why eliminate one reproducing organism in favor of another? If an old organism has demonstrated fitness in dealing with the environment by living to an old age, why should it be programmed to die in favor of other younger organisms who might not be so fit?
An idea that intrigues me is the "red queen" effect. An organism is born with a set of genes to combat disease, parasites, predators, etc. (DPP). The DPP evolve to counteract these defenses. So its a genetic arms race, and the older an organism is, the more subject it is to newly evolved DPP.The organism species must keep evolving just to stay even with the DPP, like the red queen tells Alice that she must keep running just to stand still. At some point, it makes no sense to encode longevity, it won’t work anyway. But, unless encoding longevity brings some kind of penalty, why encode for lack of longevity?
August 2, 2011 at 9:16 am #105802matrix23Participant
Actually it’s statistically proven that women live longer than men! Look around and you will notice men do a lot of heavy jobs which wear the body out more quickly. This also due to a deeper factor involving the blood. You see, women tend to have an iron deficiency because of menstrulation. The iron in our blood equals age for our cells, and because men have more iron, their cells age faster. Also, women tend to vent their frustration better then men because men are often taught to internalize their emotions, which leads to stress. So yeah. Now you know
August 4, 2011 at 12:58 pm #105827scottieParticipant
Speculation does produce some interesting thoughts. 🙂
Serious research does however point us in a direction that has some answers to this question
Thomas Perls & Ruth Fretts have done some such serious research.
They are summarised here
http://www.cmu.edu/CSR/case_studies/wom … onger.html
An extract (with my emphasis)
"Men and women alike have seen profound gains in life expectancy in this century. Since 1900, the average national increase in life expectancy in developed countries has been 71 percent for women and 66 percent for men. This increase cannot be explained by physiological or evolutionary theories. Rather, swift changes in knowledge of health and disease, changes in lifestyle and behavior, and advances in medical technology have greatly improved the chances of both sexes’ living to old age.
In the past two decades, however, there has been a notable deceleration in the extension of life expectancy in women. The reasons for this decline are still being debated. Some researchers feel that women in developed countries are close to reaching the natural limits of human life span, and so their gains in life expectancy must inevitably diminish.
But some sociologists have discounted this reasoning, pointing instead to women’s changing roles in society. As more women have taken on behaviors and stresses that were formerly confined to men–smoking, drinking and working outside the home–they have become more likely to suffer from diseases that were traditionally considered "masculine." Mortality from lung cancer, for example, has almost tripled in women in the past two decades. Smoking seems to be the "great equalizer" for men and women: current actuarial data from Bragg Associates in Atlanta show that on average middle-aged female smokers live no longer than male smokers do."
August 7, 2011 at 8:27 am #105857JackBeanParticipant
Noone except you is suggesting, that the lifespan could increase by 70% in about 4 generations by evolution :-O
August 9, 2011 at 6:16 pm #105883WinterImpParticipantquote Rap:
This assumes that natural selection happens only on an individual and never on a group level. But there is plenty of evidence that that is not the case and the mechanism is easy to visualize. Given a population of a species that had no reproductive controls/generational turnover versus one that did, the sub-population with the immortal individuals would overbreed, exhaust the resources of its local ecosystem, and perish, leaving the other population successfully outcompeting it and passing on its genes for mortality. The selection has to happen at the individual level but what impacts the group often does impact the individual, so that’s not a barrier.
August 10, 2011 at 7:20 am #105889quote WinterImp:
Hmmh. So what is keeping the immortals in their local ecosystem? If the ecosystems are completely separated, there cannot really be any competition between the two groups, can there?
Also, there are many species that are "immortal". For example virtually all prokaryotes do not die of old age, but just keep dividing as long as they can. And they indeed do exhaust all their resources in their local environment if they can and they die after that, because of that. The trick is to constantly look for new environments and only get back to old ones when they can again sustain growth.
So, why haven’t bacteria evolved to die of old age in order to conserve their environment? (:
October 3, 2011 at 4:43 am #106600mervParticipant
Sometimes they dont. Anyway, quality not quantity. How [italics]was[/italics] the game played?
October 3, 2011 at 6:57 am #106605quote merv:
Most certainly, the game is played both ways when it comes to living beings. Some go to the very extreme in terms of quantity and others of quantity. But in the end all organisms must have both numbers and quality to survive, it is just the ratio of those that keeps differing.
October 19, 2011 at 7:58 am #107022visionsenParticipant
I think it’s because women get heart conditions later in life and have stronger hearts; there are many theories on that. Also, women have stronger immune systems.
Men do have physically more demanding jobs usually – but even the men who don’t have such jobs still die sooner than their wives generally.
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