There is a species that is quite sentient. Its members know about the world, they have hopes and dreams and great aspirations of what they might do with their lives. They are intelligent, creative, caring, empathetic and deeply feeling individuals. However, this particular species bears a heavy curse. The male partner dies less than one day after mating. This is not the result of ritual, cannibalization or necessity, but a reaction of their biology itself.

They (assuming they are told or they figure it out) realize what fate holds for those that partake. The female partner shall live, while the male shall perish. Sadly, there is no guarantee that their sacrifice will result in a child, nor do they have any way to stop the impending death when it is set in motion. But the question is, would they make the sacrifice, knowing full well the consequences and risk?

There are a few more stipulations:

  1. Males can only potentially impregnate one female.
  2. Males will live a normal, full length life, if they do not partake (Barring disease or accident).
  3. There is no way to artificially inseminate or otherwise avoid natural reproduction in the case of furthering the species.
  4. Females that are able to bear children are likely to bear more than just one; between two and four. More than four is rare and zero is uncommon, but both cases have been documented.
  5. There are no documented cases of successful childbirth after one or both parents have lived beyond 1/3 of their lifespan.
  6. Diseases the parents have are likely to transfer to offspring. Only healthy individuals are recommended. Though uncommon, healthy children sometimes come from unhealthy parents.

So, can this species persist? How would a culture form regarding the two genders? Would society pressure individuals to reproduce, despite the cost of life? What other unforeseen implications would this have?

Note: I've seen a few people concerned about child birth mortality rates in pre-medicine times. You can safely assume that majority of pregnancies have consistently had minimal mortality rates, even during the darkest of times. At the highest child deaths throughout history have only occurred at about 1:10000 children (a tradeoff for killing off one of the parents perhaps), and that number goes down significantly with technology and medicine.

  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$
    – Tim B
    Commented May 9, 2016 at 17:56
  • $\begingroup$ In Greg Egan's Orthogonal universe, both sexes are sentient. Females split into four children, thereby ceasing to be. Males care for the children thereafter. If females abstain from sex, they eventually split anyway. $\endgroup$ Commented Jun 16, 2016 at 19:28
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    $\begingroup$ Of course, humans survive after all. Every male I know who has reproduced has immediately gone from being snowboarding, motocrossing, mountain biking, kickboxing, energy filled beast with abs and steely eyes to a shambling pasty drone who only leaves the house to work and go to ikea. Which is basically death, but with the added downside that you have to stay conscious. $\endgroup$ Commented Sep 21, 2017 at 9:37

13 Answers 13


This would naturally lead to a decisively asymmetric society. My expectation would be that it would look more like a slavery society, where women have male slaves.

Why? Economics. Why take the time to educate someone who may mate and die, when you can spend that time and energy to educate someone who will pass on that knowledge to the next generation. It would be natural to have women be highly educated. Meanwhile, the species depends on the sacrifice of males to continue. This would certainly be a highly ritualized process, which is most easily done with a strict caste system. Given the differences in education and the relationships that are called for, it may be hard to tell it apart from slavery.

Given this, unlike Bryan, I would not expect anything remotely resembling monogamous marriage. There's scores of disadvantages to it, and no advantages. There's no way for the male to be a father in their children's life. If a man and woman loved each other, there would be almost nil incentive to mate, meaning their genes would not propagate... ever.

The only way I could see this working is if the mother beget children via another man (a slave), while being in love with her husband. However, that's about as complicated of a relationship as you can get, and a terribly complex cultural model to permit that dynamic range of male rights. If your story did have that, you would want to build the entire culture around explaining why it occurs... it's just that unusual looking.

And I agree with Bryan that 4 children is no where near enough.

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    $\begingroup$ 4 children is more than enough -- assuming that the male-to-female ratio is skewed in favor of the males. If 3 of 4 children are males, and you have an average of 2 children per pregnancy, then you can continue your race with only 2 pregnancies per female (and have 1 additional male left over) $\endgroup$
    – subrunner
    Commented May 6, 2016 at 8:21
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    $\begingroup$ "that's about as complicated of a relationship as you can get" -- I've seen worse on Reddit relationships. $\endgroup$ Commented May 6, 2016 at 9:30
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    $\begingroup$ @subrunner That's true, so long as you don't have deaths from anything else in life =) That ratio is pretty difficult to maintain in an evolution setting. Once a sentient species takes hold, however, that ratio could be enough. $\endgroup$
    – Cort Ammon
    Commented May 6, 2016 at 15:55
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    $\begingroup$ @SteveJessop "Still a better love story than Twilight" $\endgroup$
    – Michael
    Commented May 6, 2016 at 17:02
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    $\begingroup$ It seems quite likely that rather than marry one man and mate with another, the women may marry each other and use a man simply as donor material. This already happens in our society, though obviously in a smaller percentage and with a lot less male corpses. $\endgroup$ Commented May 6, 2016 at 19:33

I think it highly unlikely that a species such as this would develop with equal mental capacity between males and females. Evolution's pretty ruthless, and intelligence has a fairly high energy budget - not to mention a lot of difficulties with human childbirth are just down to the size of our brains. Big brains on Earth are risky things, and the only reason humans have them is because they let us adapt our environment to give us a strong boost in survival.

So if the males won't survive long past sexual maturity (I'm assuming a strong urge in males to impregnate females, strong enough to override the urge for self-preservation), why waste the energy and body mass and difficulties (assuming they have heads like ours) in birth when males would be just as useful if they were dumber, yet affectionate and cute and fun to play with and look after. The females with all their intelligence would end up in charge of everything, raising their daughters to inherit the world and their sons to breed.

So you end up in a symbiotic relationship where the males depend on the females for a hospitable environment, and in exchange give up their relatively short lives so the females can reproduce. I suspect the females would have to have more male children than female, and be less (or at least differently) emotionally attached to them.


You'd get significant sexual dimorphism.

Firstly, there's no reason for the males to be intelligent, there's no apparent advantage to it. It's a lot of energy to burn for such a short lifespan. I'd also expect them to be considerably smaller.

Since one sex is intelligent and the other not, you'd need a system by which the females picked partners. Are they strong? They can't risk fighting as males are not disposable. Are they colourful or showy? Devious? A mix of all the above?

Sex balance among the spawn: You'd need significantly more males than females. At least one male for every litter that a female would bear in her lifetime, per female offspring, per litter. They'd have to breed like rodents. You'd probably need to have a flat minimum of one female and four males per litter to increase population at all. This still only allows a maximum of 4 litters per female, which is ridiculously low in the real world.

The males mating to death? Not such a problem. Though in these cases they mate with as many females as they can before they crash and burn, and for some reason nobody has mentioned the elephant in the room that is the praying mantis.

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    $\begingroup$ I have a praying manttis outside my window right now, and it's no elephant. $\endgroup$
    – frank
    Commented May 6, 2016 at 14:44
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    $\begingroup$ @frank, it's not in the room either by the sound of it $\endgroup$
    – Separatrix
    Commented May 6, 2016 at 14:46
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    $\begingroup$ I think this is the biggest hurdle - unless males are born by at least a 2:1 ratio, and the average male death results in at least 2 births, then the species will certainly die out. Inbreeding will be a significant problem as well, particularly in small communities, but the male/female ratio and births per dead male are the biggest factors. $\endgroup$
    – Adam Davis
    Commented May 6, 2016 at 19:42
  • $\begingroup$ See also: anglerfish $\endgroup$ Commented May 7, 2016 at 0:34
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    $\begingroup$ @Timbo the male anglerfish isn't exactly dead. Just no longer an independent entity. $\endgroup$
    – Separatrix
    Commented May 7, 2016 at 6:59

A species could easily exist like this, provided they had some more unique biology. For example, the female of the species could have the ability to store the sperm from the union for an extended period of time. In most mammals, sperm only lives for a few days inside the female, however in numerous worms, reptiles and insects, the sperm can remain viable for weeks or even years in some cases. This would eliminate the need for repeated mating with the male, and allow a single female of the species to continue to give births even in a prolonged absence of males within the community.

One source regarding the phenomenon: http://www.sciencedirect.com/science/article/pii/S0960982211012528


Yes as long as they produced hundred of children from only one pregnancy. Four is just not enough. Even an intelligent species would be extinct if males had a life long reproduction limit of four. Imagine living in the Middle Ages when having a couple stillbirths was very common. Now imagine that each family can have no more than four children. This would be disastrous, is the reason black widows produce a large number of offspring at a time.

So a large litter of several dozen to a hundred children would be need. This could be accomplished by laying eges perhaps.

The females would be the domainate gender in society. Males would probably be viewed as little more then cattle. Male rape would be a common thing.

As society progressed the males would eventually get some rights. Laws would be passed preventing them from being taken against their will. This would lead to a society were only the elder males would reproduce.

They would probably look at sex much differently than we do. There would be no casual sex. The person you had sex with would have to be literally someone to die for. The sex act would probably become highly ritualized.

Marriage could still envolve but it would have a very different meaning then what we have to day.

  • $\begingroup$ According to the question, elderly males cannot reproduce: "There are no documented cases of successful childbirth after one or both parents have lived beyond 1/3 of their lifespan." $\endgroup$
    – zeta
    Commented May 6, 2016 at 4:57
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    $\begingroup$ In medieval Europe, families might typically have around a dozen children (with less than half living to adulthood), not a hundred. Clearly each man doesn't need to produce dozens or hundreds of children for the species to survive, since human women did not each produce several dozen or a hundred children. There isn't time and childbirth was a killer. Agreed, though, that 4 is too low per male when there's high infant mortality. $\endgroup$ Commented May 6, 2016 at 9:35
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    $\begingroup$ A "marriage" in that society could be simply a promise to mate at a later date when both partners have reached sexual maturity and having children is convenient for the female (so actually more like a betrothal). The male might live with the female so she can stop any other female from mating with him before she does. $\endgroup$
    – Philipp
    Commented May 6, 2016 at 9:39
  • $\begingroup$ @sumelic I said they would wait till they were Elder, I didn't say that we all the way to the elderly. I just meant that they would wait till the last possible age that they could still reproduce $\endgroup$ Commented May 6, 2016 at 14:07
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    $\begingroup$ Could there be Spartacus revolts where males use technology to overcome the females? Eg, would it be evolutionary stable if groups of brothers keep enslaved females and reproduce in turn with their joint wife? That would be like a ruler-for-year-then-banishment system. $\endgroup$ Commented May 9, 2016 at 15:22

While it is perfectly viable that the result of this trait is a society separated by gender and probably ruled by females (this does not necessitate that males are slaves; could be treated as heroes that are ready to make the ultimate sacrifice), it is also possible - and, in my view, more interesting - to have human-like societies.

The key to that, is to treat the male mate as nothing but a sperm donor. Then you can have a standard family of a female and male that decided/was allowed/was lucky enough to give up mating. The availability of males that are ready to sacrifice their life so that the couple can have a baby can be explained by having two classes, a ruling class that enjoys life exactly like humans with the exception of (reproductive) mating, and a class (possibly slaves) from where the "life-donors" are picked. Not much different from societies that send low-class soldiers to defend the borders really. Alternatively you can have something similar to the Aztec flower wars and capture enemies for reproduction; something somewhat more justifiable than sacrifices to gods.

In other words, for every "normal" family, you need 2 males and one female. Come to think about it, it could even be two females and one male. The existence of upper class males is trivially explained: their parents wouldn't want to see their life "wasted" (perhaps there's even a castration ritual to ensure it).

Overall, I love your idea and it's brimming with potential!

  • $\begingroup$ Under all cases of intelligent males not enslaved, the biological limitation would be shattered. $\endgroup$
    – Joshua
    Commented May 6, 2016 at 15:34

It is hard to think of a reason why such a system would be beneficial in an evolutionary sense, but it is not entirely implausible. Consider a species such as chimpanzees, where the aggressive males use a lot of their energy fighting with each other, and a dominant male will typically kill the children of other, rival males if he gets the chance. Perhaps this species shared an environment with a particularly dangerous predator, making the males even more aggressive. The dominant male is the protector of the group, with the females doing most of the work raising the children. Next, the species' main predator dies out, rendering the aggression of the males superfluous and their aggression causes more harm to the species than good. Then, a particular male has a genetic defect that causes him to die after mating, which is passed on to his offspring. Groups carrying this defect may wind up being more successful than those without since they waste less energy on fighting, causing the trait to be retained as the species moves toward sapience.

In some ways, this is a (much) more extreme version of a process that occurred in human evolution. Most primates have a baculum (penis bone) that allows them to easily mate with many females consecutively. Humans lost this ability, presumably because it promotes a more monogamous lifestyle, which in turn encourages males to expend more energy on raising their offspring. In this species, the males were so aggressive that dying was better for their offspring than not dying.

One interesting effect of this situation is that many typical male-female behaviors will be reversed. In most animals, females are the 'selective' sex while males will typically mate whenever they get the chance, since females sacrifice more in reproduction. If the males die after mating, they will naturally become a lot more selective in who they mate with, to ensure the maximum potential for their children's survival. Females will have to expend the main effort in order to prove their value to a potential partner.

It is almost certain that sex will become intertwined with religion in some sense or another. Males will probably see it as the culmination of their being and view it as the sacred death or something of the sort. One possibility is that some males will become celibate priests who assist in raising the children of the community instead. Or, to give it a darker twist, perhaps the leader of these celibate males, a 'high priest' (who may retain the baby-killing drives of the 'dominant male' that led to this situation in the first place) will act as a 'divine judge', killing the children of the 'unworthy' males who mated without offering him proper tribute.

Or maybe the females will run the society, and males will simply become property who are sold off by their mothers.


Another example of an existing setting with a similar system of reproduction is Greg Egan's Orthogonal trilogy, set in a Riemannian universe and beginning with "The Clockwork Rocket". The alien species that the trilogy follows are six-limbed shapeshifters which reproduce by the fission of the mother into two pairs of twins. This typically occurs after mating with a male, but can also take place spontaneously past a certain age. The first book follows Yalda, a rare "solo" who consumed her twin in the womb. As she is not expected to reproduce due to the lack of a twin, she is allowed to study and attends university, encountering a group of other females who avoid spontaneous reproduction through a drug, and the social implications thereof.

Later in the trilogy, a relativistic generation ship is launched to save the homeworld, though this is plagued by the difficulties caused by their system of reproduction. Various solutions are explored, including the use of deliberate starvation in order to simulate a famine and so limit reproduction.


The "selfish gene" meme suggests that males will attempt to mate regardless of their fate, in an effort to pass their genetic material along to the next generation, so social, cultural and even economic and political structures will be developed around that and the inevitable consequences.

Since males pass on after mating while females live long productive lives, the first order effect is society and everything built around it is matriarchal. Males will compete furiously to attract females and impregnate them, but it is a buyer's market, and the females can be very selective in choosing who they mate with. The competition will change males into something like peacocks, with elaborate displays of beauty, health, athleticism, intelligence and wealth in order to attract a mate. This is not entirely one sided for the males; they will preferentially mate with females who display robust health and resources in order to ensure that their offspring have the greatest chance of success.

Biologically, there might also be a high degree of dimorphism between the males and females of the species; there is a deep sea anglerfish where the male becomes a tiny parasite attached to the female after mating, feeding off the female's bloodstream. Males might go the other way in becoming massive in order to physically exclude competitors for the females. I also expect that males will outnumber females by large margin as part of the evolutionary process.

Males will be living mayfly lives, so will not be contributing much to the society at large, and indeed social and economic structures might be developed to shelter and support males after they reach sexual maturity, and also act as a benevolent society to dispose of the dead males and pass on their estate (such as it is) to the female who is bearing his child. There might be some fraud among the females, especially if they know the males will not be around to complain if a female makes a false claim of pregnancy after a deployment or business trip. The families of males will be monitoring the situation carefully, and doing what they can to ensure breeding success.


As other answers have said, there is no evolutionary incentive for males to be intelligent, so evolution will reduce them to nothing more than horny little puppies.

The issue then becomes how will a female who is ready to procreate identify a male with good genes? And the only answer that comes to mind is by looking at their mother.

I see a situation where an existing women has a bunch of these horny mutts at home, and her friend comes round and decides to have a baby with one of them. She will give birth to a litter of males, and after several attempts, the female child she always wanted.

Nature demands that there will be vastly more males than needed. This will lead to them being euthanised, as letting them go wild would create a problem similar to that of feral dogs (except that these would take leg humping to a new level.)

It would be possible, but not necessarily the social norm, for two (or three or four) females to form a committed lesbian relationship and have children via each others male offspring. However if they were both virgins they would still need to lose their virginity with the male of a more experienced female in order to get started. And their offspring would always carry some of that experienced female's genes, so she might want to be part of their lives.

Many species females have a naturally lower attraction for their relatives, to avoid incest. This is not so prevalent in males. Observation of the natural world shows horny, indiscriminate male monkeys trying to mate with close relatives and being rejected. On the other hand, the males of this species will need to clearly identify their mother as a provider and not a potential sex partner to avoid being thrown out of the brood for harrasing her.

Ants and bees offer a relevant model.

The sexual dimorphism of anglerfish (where the tiny male becomes a permanently attached sperm-producing parasite) is also of interest.


In response to Cort Ammon, I think there might still be some "monogamous marriage". I'm reminded of a short story I read where it is proved that homosexuality is almost entirely genetic (as there's still plenty of debate on this, let's just accept it for the sake of argument), and the characters discuss why that trait wouldn't be bred out. One answer is that the existence of same-sex couples who wouldn't have children meant communities had people who would use their resources to support their extended family's children, thus giving families with some recessive homosexual genes an advantage. In the same way, if genetic, love or chastity might not necessarily be bred out, as it may improve the couple's extended family.

That said, I do not think this would be the case, as the trait of the male dying would presumably have developed long before society did.

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    $\begingroup$ Hi Deimophobia. This isn't a discussion forum, and answers are expected to actually answer the question, not engage in discussion. You can take the quick tour for an overview of how our format works. I don't see any actual answer to the question as asked here, so this may very well be at risk of being deleted. I do hope you will stay around and learn the ropes; the Q&A format takes a little getting used to, but for clearly articulated questions, it does tend to work very well. You can review our help center for a more in-depth discussion on how the site works. $\endgroup$
    – user
    Commented May 26, 2017 at 21:08

I think the most adequate system would be that of bees: the male dies after copulating, but his gonads remain alive inside the female, producing sperm.

This would avoid the need for a skewed sex imbalance, too. Or even turn it around into a majority of females. The problem here would be that it would probably require reproduction to be a specialty of only a few females. Which would pose the question: who would be actually sentient, all females, only the "queens", only the "workers"?

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    $\begingroup$ I never heard or read about the gonads of males living within queen bees. For all I know queens store sperm for years. Other than that, +1 for the questioning about sentience. $\endgroup$ Commented Feb 5, 2023 at 14:57

Such society might survive and develop provided that women are able to keep man's sperm in their bodies for a prolonged time. They can then use it for subsequent fertilisations. They could possibly even get impregnated by multiple men and their sperms would compete for fertilisation inside the body. Similar scenarios are known in other animal species.

It would be a female dominated world, of course, but men's role would be very important and relatively enjoyable, I would say. Their role in the society would be purely ornamental and submissive. I expect that a teenage man would become a property of a woman, which would then own him and live with him as long as mutual emotions will lead them to a sexual intercourse. I would also expect that men would be told from childhood that this single experience is the ultimate the pinnacle of all earthly endeavour and pleasure - and they would believe that a wouldn't be afraid of death in the arms of their beloved woman. Women might probably keep sort of mausolea in their homes with photographs, clothes, possibly even embalmed body parts of their males. This would be viewed as entirely acceptable as male death would not be would not be feared, but quite natural and seen as a desirable culmination of their simple (and short) lives. I can even see situations when a man would beg his lady to do this thing with him already as older men would be viewed as loosers and parasites in society.


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