Consider a group of humans at a bronze-age to early iron-age technological level colonizing a new earthlike planet. There is just one difference - there exists on the planet something which changes the nature of human sexuality - and the colonists don't know what it is, nor can they stop it from having its effect.

Normal Human sexuality could be summarized as being (usually) private, nocturnal and selective, and can occur at any time due to humans' concealed and extended estrus.

The change (which occurs within a few decades of colonization as the source is revealed) changes human sexuality to (usually) public, diurnal and unselective, only occurring for 5 days each 28 or so of the human female reproductive cycle. Men are only interested in women in heat when said women are present (due to the woman's pheromones), and are very strongly driven to act upon their desires (i.e. in rut), as are the women who are in heat. Women become selective for the day of maximum fertility. Men can only stay in rut for a day or two before they become exhausted. When in heat, a woman wants to become pregnant. The rest of the time, women are totally disinterested in sex/pregnancy and the men they come into contact are similarly disinterested, and they are able to think even more logically than non-estrus humans. When not in heat, the limit of sexual behavior between men and women may be to ask a member of the opposite sex if they would be interested in getting together the next time the woman goes into heat.

While this is a question on human sexuality, I'm not interested in the prurient aspects - I'm sure we could all imagine the immediate results of the changes I suggest on an interpersonal level. I'm looking for an answer that gives a broader view of the effects this change could have on the way human society structures itself and the things it makes, particularly the infrastructure of settlements. I want to find ways that humans could maintain or improve their technology under such conditions, if that is possible.

In addition, I am interested in what would happen if after a long period of isolation (say, several thousand years), a colony beginning with this change (that had managed to maintain a reasonable level of development) came into contact with an advanced society such as ours, and our whole modern society "caught" the same "disease" about month later, globally (airborne trigger).

In neither case will a cure be available within any foreseeable timeframe, certainly not within several human lifespans, by which time it will have become the norm.


It has been shown in chimpanzees (who show just this behavior) that when a female becomes mate-selective at her time of greatest fertility (i.e. at ovulation), she retires with the chosen male, who usually becomes the genetic father of the offspring of the resulting pregnancy. Hence, it would be possible to determine the biological father with some degree of accuracy without needing to resort to DNA tests.

Those of us who are either women or who live with one would know that women can predict their cycles to an accuracy of a day or so.

When not in heat, there is nothing stopping a woman from taking birth control pills that would prevent a pregnancy despite wanting to get pregnant when in heat, and nothing would prevent a woman taking abortive drugs after the fact once her heat had passed.

So, to reiterate the question:

How would each society adapt to this situation in terms of its social organization and infrastructure?

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    $\begingroup$ Does the 5 days occur at the same time for all women or is it random for each individual? $\endgroup$
    – Vulcronos
    Commented Sep 17, 2014 at 19:42
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    $\begingroup$ I am not sure exactly what you are asking but What effects would a change in the nature of human sexuality have on society and infrastructure? is way too broad. You could probably write dozens of books on each of the thousands of possiblities. $\endgroup$
    – Chad
    Commented Sep 18, 2014 at 1:09
  • $\begingroup$ @Vulcronos, the women's heat periods would be no more synchronized than women's menstrual cycles are in reality. On any given day, 5/28 of women of reproductive age would be in heat, given that the average length of the human cycle is 28 days. $\endgroup$
    – Monty Wild
    Commented Sep 18, 2014 at 1:28
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    $\begingroup$ That is just too broad I think for an SE Site. $\endgroup$
    – Chad
    Commented Sep 18, 2014 at 2:09
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    $\begingroup$ Maybe this would be a more solid question without the fluff about interplanetary societies, colonization and diseases. It sure blurred the focus on the main concept of the effect of a different sexual nature on society, at least for me. $\endgroup$
    – Alex
    Commented Oct 21, 2014 at 8:04

10 Answers 10


This would have major impacts across society. First, pornography and prostitution, gone. However, any concept of father hood? Also gone. Since sex is so common, without any DNA testing it would be impossible to tell who the father is. Over time, that would lead to a system of female inheritance. Since you don't know who your father is, all family ties would be through females and so property would follow that line.

Additionally, there would only be single mothers. Perhaps the government would set up a program where all men pay a child tax, to help care for and support the children in the clan, but women would basically be on there own as far as kids go.

Too keep society functioning, I would imagine getting rid of weekends for females and just have all females off while in heat so everyone else could continue working. There would also be major thoughts about the change in society. Some would embrace it and set up areas to go to while in heat. Others could try to keep up marriage and isolate themselves from anyone else of the opposite sex to stay faithful.

Depending on how predictable the schedule is, humans could either continue working together and have females in heat remove themselves, or be forced to split into two separate groups to keep men from being in constant conflict with each other over the latest women.

While most ancient societies valued children highly, it would likely be even harder to practice any sort of birth control or controlled population growth.

If our world suddenly had the same issue, the most amusing change would be advertising. Since sex isn't constantly appealing, an advertisers main hook would be gone for most of the month.

Everything else would be chaos. Any type of coed organization from schools to sports would collapse. Family ties would break down as men and women felt betrayed. Births would skyrocket as women want to be pregnant.

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    $\begingroup$ Actually, it has been shown in chimpanzees (who show just this behavior) that when the female becomes selective at her time of greatest fertility (i.e. at ovulation), she retires with a chosen male, who usually becomes the genetic father. $\endgroup$
    – Monty Wild
    Commented Sep 18, 2014 at 4:34
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    $\begingroup$ Regarding contraception: There would be a market for contraceptives which are administered before the heat-period and stay active until it is over. These could be pharmacological or physical and hard to remove (contraceptive implant). There might also be research into drugs which suppress the heat/rut, but it would be easy for the author to just handwave them away with "all research was unsuccessful so far". $\endgroup$
    – Philipp
    Commented Oct 6, 2014 at 16:49

Well, extrapolating from chimpanzees and dolphins, the results might be rather grim.

Males and females have contradictory goals in species where multiple mates are an option. The reproductive expenditure in males is minimal compared to the huge expenditure of females. Therefore they follow contradictory strategies. Males use a quantity over quality strategy while females use quality over quantity. Males will knock up any female but females will be selective.

Males can fertilize many females but they can't ever be sure which females carry their young unless they control access to the females during estrous and usually always. But the females don't necessarily view any particular mate as the optimum mate so they try to escape mating restriction. The males respond by forming alliance with other males to control the females, especially in their narrow reproductive windows.

Since the only reason for males to join an alliance is to improve their chances of passing on their genes, males have little to no incentive to form alliance with any other than close blood kin. That way, regardless of who succeeds in impregnating females, some of their genes get passed on.

The base social unit chimpanzees and dolphins is a group of males who are father, sons, brothers, nephews, cousins to each other. They spend most of their time capturing females, corralling them and fighting other male groups to steal their females. In general, they kill any non-related male they come across especially infants and juveniles.

Human societies eerily follow genetically optimal paths even though they have no concept of genetics or evolutionary theory. For example, in many small scale cultures, sexual fidelity of women in marriage is not strictly enforced and marriages are usually temporary. That means that no man can ever know child of his wife of the moment is his or not. In every known instance of such societies, men concentrate their paternal attention on their nephews and nieces born of their sisters. That way, at least some of their effort is guaranteed to go towards their own gene line.

Therefore, it's likely that human society with chimpanzee like mating conditions would adopt a chimpanzee like social structure. The base social unit would be a group of related men.

It's important to note that just because men could only mate episodically does not mean that their reproductive goals would not dominate their lives. Species devote time to reproduction based on the payoff off of reproductive success not how often they actually mate.

Men would attempt to control as large a group of women as possible at all times. With human technology, men could much more easily physically control women compared to chimpanzees or dolphins having to control females with just the males own bodies. Women would likely be treated as chattel.

Close personal relationships between men and women would be rare. Men would tend to view all women of reproductive age as interchangeable. Women would attempt to be more selective but the men would not allow them to do so. Since selectivity and romance might lead to jealousy and lethal conflict, the Men's moral culture might actively view selectivity, romance and even love as immoral and dangerous perversions.

"Marriages" would likely be one group of men sending their daughters out to close but not to closely related group of men for the purposes of forming military and economic alliances. New family groups of males would arise from multiple births to traded daughters from the same male group. Males would always stay with their families but women would get sent out although possibly in batches.

Close inbreeding would be a constant problem. Overall genetic diversity would be low. Entire male family groups could be wiped out by single disease.

When women came into estrous, they would be especially isolated or controlled not only to control access but to prevent violent quarrels among men. A detached woman with no controlling male group would be regarded as source of violent conflict and therefore very dangerous. A detached woman in estrous might be killed on sight just to prevent open war.

Since their sexuality only turned on episodically, men and women would emotionally bond with members of their own sex and would like socialize only within their own sex. Each sex would have it's own distinctive subculture.

The male society would likely be structured and hierarchical with great emphasis on ritual, respect and likely dueling. Males would mostly fight or train to do so. They would shun productive labor and see warrior as the ideal male. For the higher status males, they would rather starve than get their hands dirty.

Women's culture would likely be less hierarchical, would be based on status linked to age and number of sons. Since men would view women as interchangeable, women would not have status based on their mates rank or favoritism from males. Instead, status would likely depend on skill of assisting in child birth and general raising of children.

Boys would have to be raised by women at least to weaning age. In a bronze age culture that would be around 4. In known cultures where boys and girls are separated, the usual age is 7. Women will try to favor their own offspring so women will nurse and raise their own sons as much as possible. Therefore, a man's mother might be the only women he views as special and with affection. He might visit her and care for her specially.

A women's ultimate status therefore will be linked to the status of her sons. A women who gives births to only sons will have a high status while a woman who gives birth only to daughters will have none.

If men fought constantly, then women would likely perform most productive labor. That is the pattern in all low-tech militaristic extant cultures. However, that might conflict with containment.

Architecture would be based on walled compounds with the women/children's quarters in the center and the men's quarters surrounding. Men would likely sleep in barrack like arrangements.

It's likely that art and literary themes would be vastly different. Sexual beauty would not be an important theme. Romance would likely be unknown. Most literature and art would concern masculine power struggles and conflicts over status and loyalty to elders.

As the society grew more large scale (assuming it could given it's fractious nature) the most dominate male groups would have the most females. In groups with a lot of females, there might be enough females for each male to start corralling his own set away from the other males. At first, this might seem like a good way to use abundance to avoid conflict but eventually each male would stop looking at his relations as allies and start seeing them as competitors. Aristocratic male groups might be treacherous and prone to blow apart while lower class groups would be more mutually supportive and bonding.

As technology advances, there might be a subtle power shift if women did most of the work. As society became less violent, productive work would increasingly provide economic power and most of the work would still be done by women. The condition might be like the early industrial era with aristocrats still strutting around while the emerging productive class quietly took over. Men might still value fighting but fight little. They would likely just laze about. Superficially they would order women about and still control them sexually, but in all other matters women would maneuver men to do what the women wanted. Since men would consider all non-military matters as beneath them, this would be easy.

An obvious story potential would lay in some humans being born in each generation immune to the altering-effect and having the natural human mating pattern of always interested. Such individuals might be regarded as dangerous and be hunted.

A woman that was always sexually receptive would likely get raped to death if she couldn't disguise her availability. On the other hand, the magic wand pheromones simply might not ever manifest and no man would ever show any interest in her.

A male with sex always on his mind would likely be regarded as insane and prone to unnecessary violence. Out of frustration he might try to have intercourse with non-receptive females resulting in injury. (This happens in some over-bred domestic species of birds when the males lose the ability to distinguish when females are in season.)

If the reversions were relatively common, say 2% of the population, they might create a special caste for them and isolate the "afflicted' men and women together. They might develope some special task or function which only the reversions could effectively carry out.

If women went into estrous in sync with women near by, then all the women in a male group might activate at once. This could cause the male group to be vulnerable to attack. Male groups might divide into mating and guarding groups, likely based on lot or strict rotation. The mating groups would sequester themselves in the women's quarters for the duration and the guards would stay away for the duration.

Contrariwise, women in estrous could be used as weapons. If men lost control in their presence, then sending a few receptive women into a group of enemy males would make them helpless, if another male group could attack from outside of the range of female hormones.

That's about all I think of for now.

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    $\begingroup$ Care to add a TL;DR at the top? Wordy, but comprehensive; +1. $\endgroup$
    – HDE 226868
    Commented Oct 25, 2014 at 17:12
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    $\begingroup$ +1 this is a well thought out answer, but compared to chimpanzees for example the difference between human male and female physical strength is less pronounced and even simple tools can seriously close the gap. A large female population would have a good chance of resisting repeated attempts at rape and kidnap by a smaller male population, especially with agricultural tools at their disposal. Even unarmed, only a little over half of violent rape attempts are completed, and a UN study in Italy found a figure as low as 1 in 7. Human women aren't exactly helpless. $\endgroup$ Commented Oct 25, 2014 at 17:55
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    $\begingroup$ This scenario reflects the optimum reproductive outcomes for both men and women. Women won't resist the system but will instead seek to foster it. Women seek to capture the best genes and a mating system which was random would frustrate that effort. They will seek a means of restricting which males have access and this provides one as well as providing physical and material security for themselves and their offspring. It prevents the serious danger of males killing infants not their own to force the woman back into estrous. $\endgroup$
    – TechZen
    Commented Oct 27, 2014 at 14:06
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    $\begingroup$ Fathers do not ally with unrelated men against their own daughters and Mothers do not ally with unrelated women against their own sons. Lineage trumps all other loyalties. Men and women compete far more strongly against members of their own sex than the opposite sex. Women will never form a cohesive alliance against men and men will never for a cohesive alliance against women. The idea that women and men for cohesive population in conflict is a very recent political invention. Most restraints on modern women arise from other women, usually older controlling younger. $\endgroup$
    – TechZen
    Commented Oct 27, 2014 at 14:15
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    $\begingroup$ As a point of interest, the last few paragraphs relating to alternate breeding patterns might even be how humans arose from chimpanzees in the first place. In fact, one of those special tasks or functions for which the 'afflicted' is uniquely suited might indeed be, you know, coherent civilization. $\endgroup$ Commented Oct 27, 2014 at 14:17

I think your initial presumption should be clarified a bit. Human sexuality is not naturally private, nocturnal, or selective. Those attributes of sexuality are socially constructed and did not exist for the majority of human evolution. Privacy in any respect was really only created during the Industrial Revolution. Prior to that, families slept, and screwed, in common rooms. Only the tiny upper class had private bedrooms.

Agriculture brought about selectivity and provided motivation for monogamy that didn't exist in nomadic tribes. All pre-historic tribes which have survived to modern times share one idea - shared fatherhood. They believed that multiple men contributed to the formation of children. Most believed that women required a constant supply of semen in order for their child to develop properly. Children were thus raised by the tribe in common, and it was not resource-expensive for someone to care for children which were not their own. Once we settled down into agricultural societies, resource scarcity became much more common, famines killed off many with regularity (about every 5 years there would be a massive famine due to soil nutrient depletion), and it became extremely expensive for someone to raise a child which was not their own. This motivated men to control the sexuality of women and created the situation we've preserved to modern times of women bargaining sexual liberty for material security.

Sex was radically important to human survival. Prior to the development of language and reasoning, human survival (as a species) was pretty dicey. Compared to other animals, we are weak, slow, have no venom or fangs or natural armor, etc. We have great endurance and this allowed us to chase game to exhaustion, but that's not terribly useful for individuals. Humanity survived because of strong group cohesion. And people stuck together because of sex. Sex bonded them together and provided motivation for everyone in the tribe to stick with the tribe, to protect the tribe, and to share that game they hunted down with the tribe. This extreme necessity to be accepted by the tribe both for survival and to maintain access to sex partners led to brain development. Dealing with social situations can be very complex (especially without language) and those with the brainpower to manage it had a distinct survival advantage.

You lump all chimpanzees together in your question, and this is wrong. Bonobo chimpanzees, for instance, use sex primarily as a means of social bonding and for conflict resolution. They have mostly hidden estrus, and estrus has no influence on how actively they seek sexual interaction with others. Bonobos are our closest genetic relatives, and the primates most similar to humans in terms of sexual morphology (things like genital size, ejaculate density, sperm competition, limited sexual dimorphism, etc).

If the humans were without language, I think they would certainly go extinct were their sexuality to change as you describe. With language and technology, however, the effects would be muted and probably not lethal. Most animals have a sexuality like you describe. Those animals are also much better prepared for survival. They're strong, fast, have fangs or venom, etc. They don't rely as much upon group cohesion to survive and many don't join together in groups at all. Humanity with language, reason, and technology would, I think, be equivalent to those species with that sort of sexuality and other survival traits. Humans would have little to no reason to join together in societies, and unless economic concerns forced them to stay together, they would probably dissolve given enough time. Lack of strong selective pressure for positive sociability traits might lead to the sort of things seen in most animals where sex is for reproduction instead of pleasure, like men taking women by force and abandoning them.

I have a bit of a problem with you indicating that a lack of motivation to seek sexual pleasure would result in people being more logical. Rational thinking is inextricably bound up with emotion. In the book 'Neurological Origins of Individuality', the author describes a man who, due to an accident, loses the capacity to experience emotion. An unexpected side effect is that he becomes incapable of making decisions. At all. He could list the 'pros' and 'cons' of two choices, and no matter how lopsided the lists were, he was not capable of performing the act of actually making the choice. Emotion is necessary to carry out even the most logical thinking. To presume that sex (and the complex emotional relationships that come along with it) detracts from peoples ability to reason is inaccurate.

Also, one thing which you didn't address but I was sort of just assuming... I assume that along with these other changes, people would also be "freed" from the negative consequences of abstinence? Sex is on the same level of Maslow's Hierarchy of Needs as breathing, sweating, sleeping, eating, etc for a reason. Abstinence is not healthy. It increases risk of heart disease, several types of cancer, death (a study of a town in Ireland over decades showed men with lower sexual activity had an increased risk of death from any cause), depression, anxiety, it reduces the effectiveness of the immune system and even sense of smell. If the physiological changes which alter their sexuality don't change that aspect, you might want to consider a significant increase in mortality due to heart disease, cancer, suicide, etc.

Some sources if the topic interests you: 'Sex At Dawn', 'Sex At Dusk', 'Good Sex Illustrated', 'Sex And God: How Religion Distorts Sexuality', the 'Sociology of Sex' course from The Teaching Company (if you can find it), 'History of Sexuality' by Michel Foucalt

  • $\begingroup$ When I mentioned chimpanzees, I specifically did not include bonobos in that group, though that may not have been clear. As for the logicality aspect, I meant that, save for when in heat/rut, people would waste less time thinking about what they'd do during that time. $\endgroup$
    – Monty Wild
    Commented Feb 8, 2015 at 21:45
  • $\begingroup$ This answer relates a lot more to my leanings, but then I am a pessimistic feminist. men would double down on threatening their women to keep them in line. As much of history women were considered to be the lustful ones, look how they were treated. $\endgroup$
    – WendyG
    Commented Aug 7, 2018 at 16:55
  • $\begingroup$ Celibacy in the long term might have detrimental effects (despite being relatively common historically in various cultures) but inability to eat or breathe kills quickly. If Maslow really put sex and food on the same level, then it can't have been for its importance to biological health. $\endgroup$
    – Batperson
    Commented Jul 3 at 22:18

Given that humanity has evolved from what we believe were such species, I would expect that any such society would not be as successful as ours. We evolved our current forms of sexuality precisely because they were more successful.

In your description of human sexuality you miss the most important factor behind the vast majority of human sexual activity - it is an important part of human pair bonding. Recent studies suggest that when it comes to conception women are actually programmed to seek very different partners to those they would form a relationship with. Even at a base, instinctual level almost the entirety of the sexual activity within this relationship is motivated by the desire to bond and form a closely knit unit, and not to conceive. Without this "recreational" sexual activity, it is unclear to what level male/female relationships would develop. Without the support of such a relationship, new and expectant mothers may face significant difficulty.

In humans, as compared with other species, the male and female are remarkably equivalent in the overwhelming majority of qualities and abilities. However, relative to other species, human pregnancy is especially restrictive - a heavily pregnant cow is not nearly as restricted in its movement as a heavily pregnant woman. Worse, excessive exercise during pregnancy is heavily associated with miscarriage - and strenuous agricultural work would be more so. This means that for a period of time a pregnant woman will contribute less and demand more. Also, human newborn are unusually helpless for an unusually long period of time - it is perhaps 4-5 years before they have any real hope of fending for themselves, and much, much longer before they have a good chance.

Now, it is possible that a woman will be sufficiently supported by her family or wider society, but there are difficulties here. Firstly, in an early agrarian society life expectancy is short and mortality at all stages of life, especially infancy, is high. Even in our own world, the typical response to high infant mortality is a higher birth rate. Families will most likely be very broad but lack depth. Relative to modern families there will be fewer elderly relatives per young child, less attention to go around, and less spare capacity in the system to support them. The "dreadful algebra of necessity" creates a kind of terrible paradox for children - they are both loved and unwanted, both essential and disposable. In our own world, impoverished children have had a terribly bad lot in life and most societies throughout most of history have done very little to help. It seems unlikely then that a pregnant woman or new mother, unable to depend on the father, could reliably depend on significant support from society. Furthermore, by limiting the development of pair bonding, any "family" will be restricted to female ancestors and their descendants (of both sexes). Realistically, extended families will comprise somewhere between a quarter and a half of the individuals that would have been included in a pair bonded society.

In a bronze- to iron-age society, I would expect all of this to dramatically increase the depth and duration of periods of poverty and hardship, exacerbating food shortages and severely limiting the supply of surplus labour that could be turned to technological development.

As for modern society suddenly catching the disease, I have far fewer fears. With the high levels of social security enjoyed by modern civilisation, established charitable organisations and well developed systems of state support, society would largely continue unchanged. There would probably be increased pressure on housing as people lived separately rather than together, but otherwise we know that single parents and their children are able to live very good lives.


The ability to think more logically when it is "not time for sex" could help the Society to be stable. Female politicians may be precluded from taking decisions on those 5 days (and also to going to work, to avoid influencing Male politicians). Same for policemen and policewomen, judges and the military, and you have a good system. Better if there are no weapons on private hands.

But the system will have a hinder in that women in heat are still there, and not hiding, so competition between them for males and between males for women in heat could cause injuries and killings. Also, a male trying to have sex with a woman in heat that (for some reason, like a sexual disease in the man) is not interested in him can cause rapes.

A society that acknowledges these changes and "rides the wave", forgetting religious prejudices in the process, may survive and prosper. But if these people come to Earth later, while we still have here rapes, murders and there are tons of wild weapons around, it might be a disaster. Moreover if you note that there is a lot of religious people in this world.

  • $\begingroup$ My idea was that when a woman is in heat, she is always interested, she can't help it, and if she was in the presence of men during that time, none of them would get any work done at all. $\endgroup$
    – Monty Wild
    Commented Sep 18, 2014 at 2:22
  • $\begingroup$ Always? Even if the nearest man is deformed or has gonorrhea? $\endgroup$
    – Envite
    Commented Sep 18, 2014 at 8:45
  • $\begingroup$ Always interested, though not absolutely forced to participate. If a prospective mate is that bad, I'd say refusal is pretty likely, especially if there is a better choice nearby. Think chimpanzees, not robots. $\endgroup$
    – Monty Wild
    Commented Sep 18, 2014 at 9:12
  • $\begingroup$ This is why the answer points to rape. A man might be forced by the pheromones of a woman in heat to have sex with her against her will. $\endgroup$
    – Envite
    Commented Sep 18, 2014 at 9:15
  • $\begingroup$ Yes, now I think about it, I would agree. Rape would be rarer though IMO. $\endgroup$
    – Monty Wild
    Commented Sep 18, 2014 at 9:17

The most obvious result would be that there would be no concept of a family. Now the concept of a family influences a lot of things; for one, the concept of inheriting goods might not develop; without that, also the concept of property would be less strong. A lack of sexual/compassionate bindings would probably give a very individualistic society. It would also affect religion, since the concept of a father-like god in the sense we understand it would probably not develop. It also might decrease the likelihood of a single leader person also in other contexts like politics.


My initial response is to think of something along the lines of a conservative Arabic family structure, though with women even more tightly controlled as a burka won't be enough. This only lasts for a week per month, so perhaps it would only be strict isolation for that week, but otherwise a fully integrated member of society.

Romance is not just sex, so traditional family structures could still persist. Pair bonding would still develop, all the benefits of 'traditional' families would remain intact, just with women being isolated at home for a week when not pregnant. Then considering the implication of being in rut, boys would need to be turned out of the home by the time they hit puberty else they may mate with their mothers or sisters, and daughters would need to be married off before puberty as well.

Either women are isolated for a week each month (which is a considerable amount of time), or they will cause massive disruption as all males in the vicinity go into rut (cue lots of violence between fighting males and rape of nearby females). In the interest of safety, culture will likely dictate isolated imprisonment of women nearing their estrus to reduce the constant risk of all the nearby men being put into rut, not to mention issues of uncertain parentage and inbreeding.

The lack of interest in sex outside of being in rut may be taken advantage of - women could be sent to a kind of convent during their estrus. Men would simply stay away from it, and thus remain uninterested in sex. Women not in estrus could guard the facility and keep the other women imprisoned within it, and likely run by post-menopausal women.

Perhaps men would live in a barracks until they can establish a household of their own, and women would live in a convent until a man claims her. This would probably result in wealthier older men forming a household and developing a harem. Sons be sent to the barracks as soon as they might hit puberty, while daughters are either married off before puberty or sent to the convent.

Women who have recently given birth would be a serious risk as there is no means of determining when exactly they will become fertile again. Breastfeeding delays the return to fertility, but by a wildly uncertain duration, so they could unintentionally cause a serious disruption as they send all the men into rut. This may require mothers to remain isolated until their cycle returns to predictability. This may result in women being isolated for most of their lives - only be outside when prepubescent, when pregnant, or postmenopausal. Unmarried or non-breeding women would only be confined one week per cycle, but will there be any significant numbers of these?

One interesting prospect would be to abandon the idea of family groups and go with something akin to medieval monasteries - women would have a large collective residence around which much farming and industry will go on. Women not in estrus can tend the grounds and interact with men who tend them as well, while women nearing estrus or recent mothers at risk of returning to fertility would be confined to interior labors (where no men are allowed). Male children would be sent out to join some kind of fraternity, and these fraternities would fund the convents (much like generous patrons funded the medieval monasteries). In order to keep birth rates up, the champions of the sponsoring fraternities could be invited inside for a time to father some children.

Men would probably do most of the primary labor (collecting raw materials and farming/fishing/hunting), as well as trading expeditions or conducting warfare, while women would take over much of the more sedentary labors in workshops (not being allowed to roam about the countryside for much of the time).

There is a potential problem there - with men having no interest in sex without being in rut, and not having a good handle on who exactly their children are or providing an inheritance specifically for them, it may be difficult to convince men to not be selfish. Why reduce their own standard of living to support potentially unrelated women and children? This is why the older rich men with their own strictly controlled harems seems more plausible to me, but it may be possible for a large fraternal organization to keep their own stable of women (could be more or less egalitarian - though the potential for women in estrus to be used as a weapon/decoy to allow the other women to escape captivity would probably keep relations amicable).

  • $\begingroup$ pair bond becomes a lot less likely when you don't have ot be around the woman all the time to ensure mating access. female assesment and choice enforces manogomy, those are gone. $\endgroup$
    – John
    Commented Jul 4 at 2:21

Your people are bronze age/iron age, so they already had a culture before this happened to them. They won't revert back to being 'pure animals' because they retain all sorts of cultural stuff outside their sexuality and reproduction. Making a few up: blacksmiths are revered; taboos against eating meat on religious festivals; only women can be tax accountants. :-)

Two possible cultural outcomes from your scenario are illustrated in Esther Friesner's novels The Psalms of Herod and the Sword of Mary. In the first it is an isolated religious community where the Alpha Male monopolises all the women. In the second it is a city which seems more similar to our own cities. The difference with your scenario is that men in Friesner's world are interested in sex all year round, so prostitution does exist - hand jobs and blow jobs only.

If you do want to go all the way back to 'everything will become animal' then things to consider are:

  1. There is a theory that monogamy evolved in primates to limit infanticide by males. Paper Abstract. After all, if you kill her kid, the woman/primate will stop breast feeding it and come back into heat and thus YOU can father her next offspring. So infanticide could become much more common in your society. Whether that is viewed as murder or not will be a cultural issue. Whether the mother of the baby happily mates with the murderer during her heat, then bashes his head in with a rock next week when she's back to normal psychology is dependent on whether you want your sexuality change to simultaneously rewire all sorts of other human psychology.

  2. Most primates only have one kid at a time. That kid has grown up and 'left home' by the time the next one comes along. That makes their societies very different from human ones, where a woman could have, say, a newborn baby, a four year old, an 8, 12 and 16 year old all dependent on her. If, as some folk have suggested in other answers, the men are ducking out of the childcare, then the burden on mum becomes huge. Childcare includes education, public healthcare, etc. Humans farm this out to relatives and complete strangers (teachers, family doctor, etc). If your men do none of this, then boys are being taught survival skills, life skills and how to be men entirely by women.

  3. In polygynous animals about 5% of the males are responsible for 95% of the matings. About 80% of the males die as virgins. They never win any fights, or never win enough fights to get a female. If you go down the route of men fighting for women, then you'll need to think about what happens to these 80% of (sexually frustrated) guys. Old men, middle aged men and teenagers never get laid - only guys in the prime of life with fighting experience get the gals. And to be frank, the gals - if working on the animal model - are fully in support of that system. John hits middle age? Janet will trade him in for a younger model.

Additional Thoughts: Decades back when I was a student I recall being quoted a study on American newlyweds who were actively trying to have a child. It took them on average 6 months to conceive. Mr & Mrs Average have to shag their way through 6 of the wife's fertile times before conception happens.

So thus there is something else to consider for your impact on society. A culture where the women have roughly 6 heats before they conceive is very different from one where On Heat = 100% Guaranteed Pregnancy.

Meanwhile contraception... the most likely contraceptive pills for out culture to race to develop will be ones that stop the woman coming into heat. After all, no heat = no interest in sex = no pregnancy = zero failure rate on the contraceptive!


There is plenty of material in the earlier answers to make them nearly comprehensive; so while I agree with those earlier answers, I will only expand on a devil's advocate view for the fun of it:

For women, due to both sexual dimorphism and having to bear all the burdens of pregnancy, these urges (if unchecked) will cause them to be become woefully 2nd class citizens. They would likely be pregnant somewhat continuously from the age of 14 on, but unlike their 2nd class position IRL (just a hundred years back in America, and still extant in much of the world) in this fantasy they don't even have husbands protecting them or their children. For the last three months of pregnancy and two months after (to recover and nurse infants) they are much less capable of working for a living, with no adult partner to care and provide for them. That is an economic and social disaster for women; in this non-technological society no work means no food.

But there is an out! Presuming women are not owned by men and are free to act independently: They aren't beholden to husbands, or sons for that matter. So women can bond with each other in coalitions; societies of their own.

The purpose of their bonding is not sexual but to provide for and sequester each other when one of their members is in heat, so they never get pregnant, because they enter a voluntary state of confinement while they wait out their periodic temporary insanity.

This is a socialist solution. non-estrus females can do the hunting, gathering, herding and provide defensive military. Production from the group ensures women in heat are fed, sheltered and protected from any males.

Not to engage in the prurient details; but I will note that if denying their sexual urges by confinement is too much for them psychologically, then no matter how primitive the society it is relatively easy for women, alone or with others, to simulate the mechanics of the male role in sex.

What are the ramifications of the women's guild?

  • No children unless they say so.
  • When they do allow children, controlled and supervised mating means certainty about paternity for the father, which can then include agreement for child support and raising.
  • Broader social roles for women: They aren't the mother of six at the age of 20, and do not have to be a mother at all if (in their rational times) they do not wish to be.
  • They have exactly as many children as they want, when they want them.
  • Social cohesion and separate politics: They are bound to their sisterhood of some dozens; they have their own leaders, and such sisterhoods can form a wider regional guild; like one per village; so women can travel and have places to stay and be sequestered and protected during estrus; so they have groups to join if they choose to move elsewhere on a permanent basis.
  • They can raise their children, on their own, and instill in them the moral values the women choose, which will include for both genders an acceptance that women are in charge and males are subordinate workers.
  • As a result, most males will be raised without ever experiencing a women in heat; the women themselves will ensure that doesn't happen.

They can isolate males a year or two before the males enter puberty, and the males won't mind: Since they first learned to talk, the mothers have long explained the necessity of this isolation, and in fact it is a celebration of their impending maturity and taking on the role of support for their mothers and sisters, the role the men will believe they were born to do.

Perhaps if they do it well then someday, the mothers will deem them worthy, and grant them the right to father a few children of their own; and much like modern society, share the joys of their childhood and take pride in their accomplishments, even if they are raised and educated by the guild to be subordinate males.

In short, this scenario could easily become a pure matriarchy; only women decide who will be fathers, and then they raise males and females to believe this is the way society must be. The males only earn the right to be fathers through hunting, military service (and protection of women from rogue males), farming and other work on behalf of the women.

I will note that most societies of the past (and most today, for that matter) raise women in a culture that constantly reinforces the belief that they are the weaker sex, not just physically but mentally and morally, and thus are rightfully subordinate to males. The Bible says so explicitly!

In this fantasy world, a mechanism exists to reverse that dynamic, and I see no reason to think males would be any more resistant than females to being subjugated by culture in this way, if males are raised from birth to think so.

Remember that heightened rationality component: The women's guild gave them life, raised and fed them, protected them and educated them. Why shouldn't they be beholden to the guild, to their mothers and sisters, above all else?


The solution my early-iron-age settlers came up with is gender segregation enabled by the design of their settlements. Men live in one district, women in another, and between them is two districts, one for trade where both men and women can meet (and accept the risk that they may encounter or be a woman going into heat, who will not be able to avoid the consequences of that), and the other an area of parkland where people in heat/rut do what they have to do.

Since male-only and female only areas do not permit members of the opposite gender (unless infertile, e.g. menopausal women or male castrati), those wanting to avoid reproductive matters won't be in a position where it will be forced on them.

Women going into heat in the trade area (and any men following them) are sent to the parkland.

  • 1
    $\begingroup$ When women in heat want to get pregnant at all cost, they would try to get into the male area instead of the procreation park, because there they will have far fewer competition by other women and thus a much higher chance to get pregnant. $\endgroup$
    – Philipp
    Commented Oct 6, 2014 at 17:02

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