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In this world, women generally live naturally longer lives than men. The typical female lifespan would be 125- 150 years, and a male would be 30-35 years. Our society attributes this to an ancient curse that God placed on the first man for disobeying him in the garden of eden and eating a fruit from the tree of life. While the first man and woman both ate from the fruit and were equally guilty of this sin, they were punished differently. Women would experience pain and possibly death in childbirth, while men would see their biological lifespans drastically reduced. This curse would be passed down through their children and infect all future generations.

I am a scientist who has spent his life researching this topic. Rather than accept the myth portrayed by our religious leaders that has been indoctrinated into us since childhood, I hypothesize that there are biological reasons for the differences in lifespans. Ignoring social and cultural reasons in human society, as well as access to medical care, what in our biology would cause this vast difference between the sexes?

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    $\begingroup$ Ever heard of the Darwin Awards? Around 90% of the winners are men. $\endgroup$ – Renan Nov 10 '19 at 21:27
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    $\begingroup$ In Russia, the life expectancy at birth is about 67.5 years for men and 77.4 years for women. That's 10 years difference, in a real-life modern country. $\endgroup$ – AlexP Nov 10 '19 at 22:43
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    $\begingroup$ It's not just doing stupid things. Men generally thinks they're tougher, so they delay going to hospital/doctor. In general, sure, men are actually "stronger", but your muscle mass ain't gonna do jack against cancer. Men are usually the ones that get diagnosed with late stage terminal diseases. $\endgroup$ – Nelson Nov 11 '19 at 8:55
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    $\begingroup$ Average lifespans can be dramatically altered by deaths during infancy and childhood (lower infant mortality rates account for a large part of why the average lifespan has gone up over the decades). Is that sort of answer acceptable, or should men die of old age sooner than women? $\endgroup$ – Kat Nov 11 '19 at 15:44
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    $\begingroup$ Also war and military-service - as well as attempt to root-out possible future soldiers/warriors will often disproportionately effect males. By all means, mercenaries and foregeing armies would rape, kill and starve women too... and air-bombing would kill women too... but knights, phalanx &c, and trench-war would usually be males against males. $\endgroup$ – Baard Kopperud Nov 11 '19 at 22:48

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Radiation and fat cell distribution in the body.

You've got a lot of options to accomplish your goal. Indeed, as other answers have pointed out the gap you're hoping to explain already exists, though it isn't as wide as in your setting. In that spirit, I'll suggest a potential agent which also has some real-world basis: radiation.

There is some evidence that some forms of radiation are more hazardous to men than to women. The explanation I've seen is that there are some sex-linked differences in how fat is stored in the body, and arrangements more common in women tend to physically shield vital organs. So radiation has the same effects in women as in men, but the tissues damaged by the radiation are less likely to be those comprising vital organs. Men, on the other hand, tend not to have such protection.

You can fiddle with the details to suit your setting better (especially if those are the average life expectancies you want), but the vital elements are: persistent, low-acuity environmental hazard which is invisible to casual detection; lethal effects of that hazard only occurring after a long period of exposure causing damage to accrue until a "noticeable" threshold is reached; and an unrelated physical structure largely restricted to women (for other reasons which exist without the hazard) which happens to also have a protective effect.

This kind of setup also suits the scenario well. Radiation sickness and various cancers can certainly seem supernatural or divine, even to trained physicians, until enough relevant research is undertaken and understood. And the nature of randomness and average effects among groups would make the different outcomes very difficult to understand before discovery of the specific mechanisms underlying those outcomes.

If you'd like to look at a novel in which this idea is explored, and with similar relevance, I can recommend

Seveneves by Neal Stephenson. I recommend it all on its own, but it also has some interesting descriptions on how radiation hazards exist and operate on human bodies, and also gives some decent scale and scope for how much of an "advantage" women as a group might have against this specific hazard

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This exists in reality

I mean, not as much as the gap you're talking about, but in general men live shorter lives than women. This organizes it in a nice easy table to compare various cultures, first world vs. third world, etc. The gap seems to be on average about 4-5 years.

So the question is, why? And the answer is: it's complicated. Well, it's not that complicated, you can just say 'because men are men', but that doesn't answer it, or you could say 'because men have a Y chromosome and higher testosterone levels', but that's only marginally better. You could also say:

"Because men typically engage in more destructive behaviors, like smoking or becoming overweight, engaging in riskier and more physically demanding activities on a whole, and that the typical male biology develops such that the average man has a body which takes more of a toll because estrogen seems to develop the female body to protect it more",

which is both a mouthful and a bit closer to the truth, but on the flip side is just a bunch of vague reasons which collectively all contribute but are not satisfying individually. Or, as I say, 'It's complicated'. Check here, here, and here if you want to do some research on your own.

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    $\begingroup$ I'm sort of missing a "Therefore widening the gap isn't that weird in-universe". $\endgroup$ – Gloweye Nov 11 '19 at 10:23
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    $\begingroup$ I thought it was because of the metabolism of men being faster causing metabolic processes like cellular mitosis to proceed at a faster rate decreasing telomere length among other things. $\endgroup$ – whn Nov 11 '19 at 15:23
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Ignoring social and cultural reasons in human society,

Well, don't do that. What kind of terrible scientist are you? At least do your study across difference cultural and economic groups. This is pretty basic stuff.

I hypothesize that their are biological reasons for the differences in lifespans

There are a whole bunch of androgen-related things that reduce longevity, especially with regards to immune responses being reduced.

It has been observed that men with their knackers chopped off live longer (and don't go bald, as a sort of bonus).

This applies to other species, too.

Note that the magnitude of these effects is probably dwarfed by the contribution of the social and cultural factors you are so thoughtlessly disregarding.

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    $\begingroup$ Dying early, and losing hair? Sound like (quite literally) toxic masculinity! $\endgroup$ – Chronocidal Nov 11 '19 at 8:46
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    $\begingroup$ Human male, huh? You're still better off than most spiders, which are often eaten shortly after sex, or anglerfish males, which are 100x smaller than females, don't get to eat, literally fuse with the female as their only goal in life, and are essentially just a swimming sperm bag with rudimentary eyes. $\endgroup$ – John Dvorak Nov 11 '19 at 14:31
  • $\begingroup$ @Chronocidal It is. Pretty much it's the whole point of mating. "Look at me, I'm so X yet I'm still doing OK! My genes must be top notch to keep me alive through all that crap.". The X can be anything that's detrimental to one's health and survival, like testosterone, risky behaviour, bright-colored feathers, large antlers, etc. Literally, anything that's impressive and makes you more likely to die/get killed. Males are expendable and they know that (at least at biological level, because denial is a strong and versatile tool) $\endgroup$ – Agent_L Nov 11 '19 at 16:16
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    $\begingroup$ @Agent_L there's a certain amount of species-centricity in your statement there; it isn't globally true, merely very common. $\endgroup$ – Starfish Prime Nov 11 '19 at 16:33
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The difference in average life spans for elephants is roughly as big as you describe. They are elephants, so it can't really be cultural, but it is behavioural and not biological. Female elephants live in herds, and if a female gets so old or sick that she can't stay alive without help, she will be supported by her herd essentially because her knowledge and wisdom are useful to the herd. Male elephants live on their own, so once they are too old to take care of themselves, they die.

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    $\begingroup$ Minor nitpick: Elephants are one of the few animals known to have "culture" - traditions and practices passed down by generations. However, this likely doesn't affect the answer - these practices don't include binge drinking, driving sports cars, deep frying cheese, dynamite fishing, or the many cultural practices that skew life expectancy in humans. $\endgroup$ – James_pic Nov 12 '19 at 11:20
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For any question that asks why a living system would be a certain way, the answer always lies in evolution.

Every biological trait you can observe has evolved. Even something as seemingly universally detrimental as aging happens the way it does because it represents an optimal evolutionary solution to the various forces at play. Exactly what those forces are and which of them plays the largest role is still a matter of some debate, but everyone agrees that aging is happening for some reason.

So to answer your question we should ask another. "Why would it be evolutionarily advantageous for men to live shorter lives than women?"

Evolutionary biology is a wonderfully complex subject and so there are plenty of possible reasons this sort of sexual dimorphism might evolve. Perhaps the most plausible though is an exacerbation of an existing trend we observe in primates. There is a pattern that between the two sexes of a primate species the one that lives the longest is the one that spends the most time caring for offspring. In species where males take on the majority of child-rearing duties, males tend to outlive females, and in species where males don't participate in childcare females outlive them. From an evolutionary perspective, this makes sense because post-reproductive individuals can increase their fitness by caring for their offspring and potentially their offspring's offspring.

So, if the evolutionary origins of your species involved social groupings in which males did not participate in childcare, regardless of the modern societal norms, that would explain their differing lifespans.

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    $\begingroup$ evolution also has a flip side some of the things happen because they didn't have a bad side effect so didn't cause die out. Human leg hair, it has no positive or negative side effects at this length so just hung around. $\endgroup$ – WendyG Nov 12 '19 at 15:18
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The females eat the males after mating.

https://www.youtube.com/watch?v=Os3OBJSlpUc&start=77

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    $\begingroup$ I do like that one, it was my first thought $\endgroup$ – WendyG Nov 12 '19 at 15:19
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All answers talk about testosterone levels and doing reckless actions. But in modern world this accounts for maybe 2-3%. The real culprit is selection shadow and grandmother effect.

Selection shadow: after an individual has mated and produced sufficient offspring, rest of their lives does not matter much. We are talking about wild hominins. Thus a human dying at the age of 40 or 80 does not matter much. Most of them will not see those ages anyway because of other factors. Thus humans are not adept at surviving longer because they don't need to.

Grandmother effect excludes human females from the above rule, which also is the reason humans are one of the very few animals that has menopause in the first place. In a social species like humans, grandmothers takes care of their young (even in wild) while the mothers continues their struggle for survival and more offspring. Because of menopause grandmothers cannot continue their own reproduction efforts dedicating themselves for this role. This ensures the children are taken care of, and the fit mother does not pause their survival and reproduction activities for so long for a human child to become a fit individual. Thus a tribe with healthy grandmothers are more likely to survive.

This ensures women with stronger genes that allows them lead healthy life at their later ages, causing the disparity between males and females. From this point to your desired number is simply extending the the time passed since menopause is evolved.

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  • $\begingroup$ You're answering the "why" not the "how". $\endgroup$ – arp Nov 16 '19 at 5:56
  • $\begingroup$ Why it happened here on Earth is how it could happen in somewhere else. $\endgroup$ – Cem Kalyoncu Nov 17 '19 at 7:26
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Nagging.

So think about it. Women far outnumber men in this society. Perhaps initially it's the result of a war. But from that point on, every young man born into this world knows his father probably only for a few of his early years, and is otherwise hounded and hen-pecked by his mother, grandmother, aunts, great-aunts, great-grandmothers, etc, etc, for his entire life.

Wouldn't it make him want to check out early?

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  • $\begingroup$ This is great. The main character can find the male counterpart to the amazons, fabled for their longevity :) $\endgroup$ – Mad Physicist Nov 12 '19 at 19:37
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Semelparous

A species is considered semelparous if it is characterized by a single reproductive episode before death.

The best known examples are probably the anglerfish and preying mantis, though it includes many spiders and at least one mammal. One thing to note is that all these creatures are at the small to very small (at least the males are) end of the size scale, so a human is a very large creature follow this particular model. If you want to try this approach then you don't want to bother investing so much energy into the males, make them much smaller add always having multiple births and you're all set.

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    $\begingroup$ Semelparity is not directly linked to size, but it is indirectly linked - these are species that are very likely to be killed before they get a chance to mate once, let alone a second time, so if they do luck out and find a partner it makes sense to put all of their energy into that one mating. You don't need humans to be small, just make their environment very, very dangerous and have them lead mostly solitary lives, where the chances of running into a partner before getting killed is low. $\endgroup$ – IndigoFenix Nov 14 '19 at 11:42
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Half of your question sounds like you're taking that religious nonsense seriously, are you sure you're a scientist?

Anyway, you're talking about male/female life expectancy which is, first of all, a statistical value. Each generation has lots of factors that can influence it - from economic crises and wars to the state of roads in the country, availability of medical care and so on. Also, when talking genders, consider this - some countries still have official lists of professions prohibited to women, which would include stuff like heavy metallurgy or mining. Not because men are naturally stronger as someone would think, but because historically men are viewed as disposable material while women are the givers of life and have to be preserved by all means. This is reality in many cultures, but the way.

But honestly, all of it doesn't really matter when talking about lifespan of species. You're "messing hot with round" - biology and statistics, the latter being influenced by aforementioned factors and a lot more, while biologically men could live the same amount of time as women - just look at those mediterranean villages in Italy or other such places with unusually high life expectancy unrelated to gender.

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Exaggarate stuff that exists in real life.

  • Super-testosterone. Male balding is really annoying, and comes from our hormones destroying the hair (apparantly). What if males have some extra-awesome-but-destructive hormon? It could attack the aging part of the cells directly, aging men faster than women. Perhaps it bestows men the ability to heal faster (useful for fighting). "Burning the candle in both ends". Imagine a black market for "male healing shots", for women..

  • XY vs XX. Men have conditions that women don't. Research them, and crank them up to 11. Colorblindness - make some interesting visual problems. Make cancer a male-specific problem, and discover it. Diabetes-like conditions. Alzheimers. Make everyone a bit suicidal, and men more successful at it. Pick and choose ;)

The societal consequences are interesting. Will you care as much about health and safety, when your time is so much more precious? Will society care (even less) about men in war (they'll die soon anyway). Perhaps that snowball takes off with things like "men don't need safety equipment, tsktsk, just put them to work."

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"I hypothesize that there are biological reasons for the differences in lifespans."

There are, and testosterone seems to be the main culprit. Men live fast and die young because their primary sex hormone makes them strong in the short run, but then weakens them in the long run, contributing to cardiovascular problems (particularly hypertension and atherosclerosis), a weakened immune system, not to mention hair loss. Men have other sex hormones, of course, which probably compound the problem.

According to one story, eunuchs often live 20 years longer than men with testicles. (That last link gives a great explanation)

Estrogen, on the other hand, is an antioxidant that actually protects women's health in the long-run.

I'm wondering...If this is a sci-fi or fantasy story that you're writing, why not exaggerate the difference in lifespans? The numbers you give are pretty close to reality, though I think men average closer to 70-75 years instead of 55-60. I think it would be really interesting to read about a society in which women live to, say, 125, while the men all die at, I don't know, 30? Just a suggestion.

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As others answered, there must be long term evolutionary pressure to extend the lifespan of females. There may be no such pressure for males, or much less, or even opposite pressure. Others have proposed what such pressures might be and I won’t elaborate here. Rather I’ll propose how the resulting longevity genes benefit only females and never their sons.

So, in this world, genes for 150 year female lifespan must result in the increase of those same genes in the subsequent generations. However, these genes for longevity must either not be passed to male descendants or are substantially counteracted by some genetic or environmental factor.

Perhaps the easiest way to explain a genetic cause for this significant sex based difference is to use a sex determination system other than the familiar human XY system. Humans have two sex chromosome (XX in females, XY in males), but this is not the only possible system. Some creatures determine sex through the presence or absence of one or more chromosomes. For example, if the X chromosome is present, the embryo will be female, but if the X is missing the embryo will develop male.

Now, imagine that all the genes needed for the development of long life are also present on the X sex chromosome. In this case, every female of this species would have the genes for long life and would pass them to her daughters but would never pass these genes to her sons.

Using this alternate sex determination system provides the scientific basis for significant sex based physiological differences in a species far beyond what we might consider reasonable in our own species.

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Make laws like in Russia which has the greatest life expectancy difference along with the cultural specifics. Make the police protect preferentially women, the healthcare treat preferentially women, make higher punishments for crimes committed against women and higher to male perpetrators than female. Make men lose everything including real estate on divorce. And obliged to supply the former wife. Make only males serve in the military under harsh conditions. Make females retire earlier and with higher pension. Make females receive higher grades in the universities "because she is going to marry anyway". Make "true man" culture where the men are required to go fight over any request by the woman and are shamed for seeking medics help. Make the emergency services to save females first. Make males to be expected to fully supply and pay for women they date. In short, everything Russia-like

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