My story takes place in an isolated community where the people realise the importance of genetic diversity. They will have some problems relating to inbreeding if they don't get fresh genetic material, so it has become a custom for the young women to seek out travellers/outsiders for simple couplings hoping to conceive. The young men of the community consider a new mother who has had a baby this way to be a more desirable partner than a childless/virgin/barren woman. I believe their social conditioning overrules any atavistic disinclination to take care of offspring that are not biologically their own. It has become a rite of passage for a young woman to seek out a sperm donor.

Is the above reason given sufficient to justify this as a social custom?

Another world building quandary... I had thoughts that a mother with more than one child would be considered even more desirable, although it might be a challenge for young women to become mothers to two or more children in short order.

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    $\begingroup$ Reminder to close-voters : please explain the reason(s) that led you to close the question. As I'm tied to believe that sociology can give objective answers and that the question induces simple yes/no answers, it's hard for me to understand why it's opinion-based and to give advices accordingly. Worse, it's impossible for the querent to improve their post :). $\endgroup$ May 12, 2023 at 20:38
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    $\begingroup$ Just gonna note that real world communities with less monogamy (in close proximity) actually have more inbreeding (and therefore less genetic diversity) because children don't know if they are half siblings. This is a legitimate issue in certain poorer communities where woman have several children with multiple fathers. $\endgroup$ May 12, 2023 at 22:02
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    $\begingroup$ I have heard of real-world Far East people who live in small isolated communities and have the custom of offering outside visitors sex with their women, even married ones. Precisely to maintain genetic diversity. $\endgroup$ May 13, 2023 at 8:28
  • $\begingroup$ "Is the above reason given sufficient" sufficient for whom? 10% of your community? 50%? 90%? $\endgroup$
    – Mast
    May 13, 2023 at 16:40
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    $\begingroup$ I don't see how preferring women, who are already mothers, to childless women can be favorable for genetic diversity? In the extreme case, that just means that there will be only one mother per generation and a whole bunch of childless women. That doesn't seem to create a very great degree of genetic diversity to me. I believe that the optimal policy to create as high degree of genetic diversity as possible would probably be to prefer the women with the least amount of children. It feels like this would maximize the entropy of the gene distribution, which intuitively feels favorable. $\endgroup$ May 14, 2023 at 20:51

14 Answers 14


The Social Rule Alone is Insufficient

Social rules are memes (in the original since of the word). They are ideas that spread because they prove some kind of selective fitness for the society that keeps them. Even if the reason for a social rule sometimes falls away to be replaced by tradition/nostalgia, at the time an odd social rule is coined, there should be some equally odd pressure that causes the odd rule to be more selectively fit than the defacto rule. That means that at some point in your people's recent history, there has to be a thing that made copulating with mothers more practical than avoiding it.

But this is not easy. In general, mothers are less attractive across most civilizations for 2 very pragmatic reasons:

  1. Raising someone else's kid is a lot of work, and people tend to prefer the path of least resistance.
  2. Motherhood proves that there is a better chance that another man is around who may decide to protect "his woman" or "his child" making mothers generally less safe to open relations with.

This means that mothers will only be the more attractive partners in a society where they offer some safety, assurance, or level of easiness that outweighs the extra risk, uncertainty, and work involved. Don't get me wrong, there will always be outliers in a society who prefer mothers, but for it to become the common preference would require some major outside force that exceeds a random shift in popular views.

Suggestion: Make Female Sterility Common & Marriage Expensive

As a general rule, the more often you come across defective products, the more you care about proving that they are not defective before you buy them. For example, most of the plate armor you see from the Renaissance period has at least one major dent in it... even if the armor never actually saw combat. As firearms got better at penetrating plate armor, it became very important that blacksmiths prove thier armor by shooting it with an actual gun. The tell-tail bullet dent became a mark of evidence showing that the armor was proven to stop bullets which was far more important than any other feature the armor could have.

In pretty much any time period other than the Renaissance, you would never consider buying "damaged" armor like that. It was just assumed it could stop what it was designed to stop often enough, but the failure rate of armor had gotten so high that Proofed Armor became more desirable than undamaged armor.

Likewise, if you live in a civilization that has strict marriage laws like large dowries, no-divorce, or guarantied alimony from divorces, then marrying a barren woman would feel a lot like getting shot through the armor you paid good money for. Pair that with a high rate of infertility, and suddenly the risk of marrying an unproven women becomes so great that the cost of supporting a single bastard child becomes a minor inconvenience compared to how attractive it would be to know that your wife can have children in a world where that is a rare and desirable thing.


Also, the reason women would go away to try to get pregnant is also practical because it minimizes the 2nd risk of marrying a mother. When your wife got pregnant from some random passer-by, there is less risk of the man returning and being a threat to you than if it was Chuck from down the street.

  • $\begingroup$ Comments have been moved to chat; please do not continue the discussion here. Before posting a comment below this one, please review the purposes of comments. Comments that do not request clarification or suggest improvements usually belong as an answer, on Worldbuilding Meta, or in Worldbuilding Chat. Comments continuing discussion may be removed. $\endgroup$
    – L.Dutch
    May 15, 2023 at 17:18

This is a...

Dun Dun Dun!!!!

Frame Challenge

The young men of the community consider a new mother who has had a baby this way to be a more desirable partner than a childless/virgin/barren woman. I believe their social conditioning overrules any atavistic disinclination to take care of offspring that are not biologically their own.

So, before I answer this question, I am both a Male and a Father - which gives me some authority to speak on this topic.

I am also a firm believer that many of our societal norms have a very real biological basis. You may disagree, but that is the position from which this frame challenge comes. Even with very strict Religious and Moral codes to offset the worst of these Biological impulses, Biology still ends up winning.

First issue:

The average man's primary drive is to have sex with as many child-bearing age women as they possibly can. You might say that this proves your theory. It is my contention it does not. Children, especially small children take up a lot of time, effort and Energy. That means they are not going to have that excess time, effort and energy for the act of procreation. In short, exhausted mothers who have been up at all hours of the night breast feeding and looking after their children don't have the energy to have Sex (and we are presuming everything is consensual here).

Second issue:

Flowing from the statement about time effort and energy, this is true for the father also (not so much in the infancy years, but definitely later on) - Without wanting to sound like I'm crapping on step-dads (cause I'm not) - the 'reward' of parenting is seeing your kids grow and mature, in seeing the little bits of you be refined and made into a capable young adult. When raising a child that is not biologically yours, that reward is gone.

Does that mean people don't Step-Parent, of course not! but even the best Step Parents struggle for the very simple fact that the child is not 'theirs'.

Third Issue:

Men tend to get possessive over Women of Breeding age. If you look at many of the religious cults that practice polygamy, you'll see multiple instances where all the high-status men (the Elders/Leaders) hoard all the young fertile women to themselves. And Men have the physical ability to enforce their will by being bigger, stronger, more disagreeable and more willing to use violence.

So - those are the top 3 issues that I see, and I'm not sure how you can overcome them specifically.

However - here are some things to help with your society:

1: If you want men (particularly young men) to do something stupid and against their nature, say it's Manly and make it so doing that thing makes them high-status to women. For example - fighting in a war and dying horribly is (in strict evolutionary terms) very stupid and dying is against most peoples nature. But put a Man in Uniform, with a full rack of medals on his chest and have people call him a Hero - now he's an elligable mate for Women, so his risk is rewarded.

2: Religion has had a long history of enforcing moral codes that would seem to be in opposition to our fundamental nature. I said above that Biology always wins, and I believe that - however just because countries that enforced Monogamy have long, juicy and sordid histories of infidelity, doesn't mean that on the whole the rules didn't have some effect. An enforce Religious aspect could help mitigate the biological impulse - or at least, get you into that wonderful area of story writing where you have tension between two competing ideas.

3: Women set the rules of the Game, Men play to win. Women are the gatekeepers to Sex, Men are the gatekeepers to Relationships. The latter part of that you might have trouble with - because Men will have sex with just about anyone, but getting them to stick around is the hard part - but if you take those presuppositions into account, you might find a series of systems where the Men are incentivized by the Women to do this.

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    $\begingroup$ The religion idea is definitely something to consider. Maybe if mothers are given special reverence in their religion and their religious leaders tell them it's manly to take care of single mothers. Religious conditioning and peer group pressure would certainly overcome biology. $\endgroup$ May 13, 2023 at 0:07
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    $\begingroup$ @Emeraldminer - I wouldn't say 'overcome' biology - I think it's probably best expressed as 'providing a check and balance to Biology'. I mean there are many cultures that place religious reverence on motherhood (looking at you Abrahamic religions with your 10+ child families) - so it's not too much of a stretch to have some religious aspect in there. $\endgroup$ May 13, 2023 at 5:02
  • $\begingroup$ To make you point about exhausted mothers stronger: breast feeding is a contraceptive. This is why wet-nurses were a thing, so women could have as many children as possible in a short a time as possible $\endgroup$
    – No Name
    May 13, 2023 at 7:05
  • $\begingroup$ I believe that while technically everything you said is true, your interpretation of men is too simplistic and thus is not a valid answer. Yea, the desire for sex is the biggest single desire, but is only what 10% of the total men's emotions? There are desires for respect, success, emotional intimacy, safety, food etc... and there is a lot of room for maneuvering even inside the biologic constraints. ( For example, the men who don't consider the inbreeding will inbreed and destroy their offspring ) $\endgroup$
    – Richard
    May 15, 2023 at 10:59

There are some problems

  1. It would be much more likely that any children born from an outsider coupling would be more desirable, not necessarily the mother who made that coupling. As any subsequent child (with her non-genetically diverse partner) wouldn't have any diversity benefit.
  2. If this were the motivation of the society, men would have trouble finding a partner within the community at all. It would be better for them if they went outside their community to find a diverse bride and bring her back.
  3. It is more likely that the larger community would support mothers contributing to diversity, rather than relying on any kind of sexual partner to provide support.

Give the young men a great dread of childless women for fear they will prove barren. Make having children of great importance. Perhaps even have young men told that if they marry a woman who already has a child, they need not fear being childless themselves even if they are sterile.

If being a father is important to your status in society, that will also help.

The fathers being outsiders will help with suspicion, though expect some misery from women who are barren, and those inept at attracting men, and also wagging tongues claiming that this woman's child was not properly fathered by an outsider but by the boy next door.

It might also be considered a duty for the out-child to marry into the adoptive father's family, thus ensuring some benefit for them.

  • $\begingroup$ Yes, the flip side of a reverence for mothers would likely be superstitions forming against barren women. $\endgroup$ May 13, 2023 at 0:11

Polyarmory and promiscuity makes inbreeding worse

Being with multiple people tends to mean more uncertainty over parenthood. This often leads to worse inbreeding

Women who sought out outsiders to sleep with might sleep with the same outsider, so their children would have a tendency to be related. This would notably worsen the inbreeding issue. As such, the social conditioning wouldn't make a lot of sense.

Outside breeding could increase child survival.

As such, why not establish an active reason breeding with a native first was bad- suppose their extensive inbreeding depression had a tendency to make babies who didn't quite fit. They tend to be too big, because of large men and small women, and women who breed internally often die of childbirth.

Having a baby with an outsider loosens up stuff downstairs, and means that birth can be done safely and reliably. Having two babies with an outsider tends to make things even better. Such outsider babies are seen as good luck charms to counteract infertility, and so are treasured by the families.


A few things spring to mind:

  • pregnancy is proof of fertility, which avoids a certain amount of gambling away your best years.
  • outside genes bring the possibility of stronger, healthier offspring, which is good if you need children to do agricultural work.
  • first children are not necessarily as healthy or well adjusted as later children, but will be able to help run the household and raise their siblings in due course

Its a tricky balancing act to ensure that the child of the outsider is not rejected by their stepfather. The tradition that the first child inherits might be more difficult to apply here if wealth or status is inherited from the (step)father who might prefer his own flesh and blood to inherit, but ultimogeniture is a thing as is matrilinearity.


It has been so in the past that young widows in Europe had little problems to find a new husband, who could also already have children. This not only because they often had a better financial position than young women but also because they had already proven to be able to reproduce.

It has also already been taken up by science fiction writers, I remember a scene from a Robert A Heinlein book, one in the Lazarus Long series, where he had a young couple, girl pregnant, with him while landing on a planet in the early stages of development. The men there would prefer pregnant women or new mothers as wives, for the suspected proof of being able to get more children.

If you are writing a strong religion in your book you can attach a religious reasoning.
If you write a book mostly based on economics have the single mothers receive a bounty for each child they have before they marry, and have the men of the planet see the economic advantages of the child or children, like having someone to work for them well before their own children are old enough. (New planets/newly claimed lands have children working alongside their parents as a rule, or so you can claim.) And so on, each of your stronger lines in your book can be the reason man want to marry women who already have a child or children.

No links for the historic marrying of widows, I have read it somewhere and do not know how widespread it was, I just remember it being mentioned in some book.


Historically, children are economically valuable. In the modern world, children contribute little or nothing to the households they are part of and a primarily a burden on their parents - they require food and clothing and entertainment and shelter, and their contribution in return is, at most, doing a small amount of chores.

This wasn't true in the past. Children would have begun working on the family farm shortly after they learnt to walk, and their contribution continues to grow through life. By the time they're seven or eight, they have positive economic value. The hardest time for a new family then is the time between they start working on their own farmland and the time that they have children able to provide strong economic contributions to that farmland.

The reason, then, to prefer women with existing children is that these women come with free workers ready to help support the future children you will make with them.


Yes, it is perfectly plausible, especially if the community lives in a harsh or otherwise inaccessible environment like a desert or a tundra. In fact I vaguely recall that the Inuit did have a similar custom.

But you wouldn't want to make your community too capable militarily, because then it would be easier for them to steal children from surrounding communities instead, which for example the Eurasian steppe nomads did do.


In Greek mythology, single mothers seem to have had less difficulty marrying if the father was a deity. For example, Tyndareus doesn't appear to have had a problem with Zeus having fathered some of his children.

So maybe in your story the sperm donors are not just random guys, but are perceived as superior.

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    $\begingroup$ Considering the cost of travel in ancient days, travelers were wealthy people. That would give them superior status. High status males seem to be able to get access to sexual partners. "Power, the greatest aphrodisiac." - Henry Kissinger $\endgroup$
    – David R
    May 14, 2023 at 14:18

So, first we have to remember that genetics is something they may not have a good handle on.

Imagine an isolated township, heavily inbred. If there is any fertility issue in their gene pool, they will all have that issue in their genes. That's just how it works in small, inbred communities. Inbreeding and isolation go hand in hand, so it's likely such a group will look askance at young women who consort with the outgroups.

On the other hand, fertility issues were nearly always blamed on the woman: it was never his fault, she was barren unless proven otherwise.

So that proven fertility...Even with some outsider...That would be a strong draw in a group where infertility was common. We know there is nothing wrong with her, so if we marry her, we'll have kids too.

Of course that's fallacious, given that we know that the outcross is fertile, not the inbred choice, but, again, their knowledge of genetics is likely incomplete.

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    $\begingroup$ Sure, they might not know of genetics. For that matter, depending on the level of scientific knowledge of the time, nobody might know of it. Still, people noticed a correlation between the breeding of close relatives and the prevalence of inborn illnesses and defects very early in humanity's development. That's why incest is considered a sin or explicitly prohibited in nearly all human societies. $\endgroup$ May 13, 2023 at 8:51

What if you make the culture such where children are valued? It may be for the same reason -- increase of the work force -- like others mentioned, or something else. But, the cultural consequences I want to point out are

  • Raising children is a community affair instead of just be the job of the parents
  • The rank of a woman is directly tied to how many offsprings she has

The children of single mothers are vulnerable to abuse.

It's not very nice to think about, but the fact of the matter is that the children of single mothers are vulnerable to being abused by the men in their mother's lives. If you're the sort of man that wants to sexually abuse children, finding a single mother to hook up with is a good place to start, and that would provide an incentive for those sorts of men to choose to target single mothers to form relationships with.

  • $\begingroup$ "It's not very nice to think about" - I mean, this site exists primarily for entertainment value... $\endgroup$
    – NotThatGuy
    May 13, 2023 at 19:53
  • $\begingroup$ This is a real life problem but I feel writing it in a book as reason to marry mothers is promoting it and that is not acceptable in my view. $\endgroup$
    – Willeke
    May 15, 2023 at 4:23
  • $\begingroup$ For this to have a large enough effect as to be measurable, it would have to be accepted as normal. $\endgroup$
    – pipe
    May 15, 2023 at 7:47
  • $\begingroup$ @pipe It's a large enough effect to be measurable in real life, unfortunately. $\endgroup$
    – nick012000
    May 15, 2023 at 11:48

Simpler explanation: they're more mature

They've outgrown the primitive desire to "spread one's seed", and don't care much whether their children are biologically related to them.

So, if they still want children to love and care for and raise, which many people do, they'll prioritise women with "ready-made" children, to avoid having to go through pregnancy and all that.

In the real world, plenty of people date those who already have children, and plenty of people adopt. You don't need some extreme explanation. You just need to lean on the scales a bit if you want it to be more common.

  • $\begingroup$ Yes, but my idea was that mothers should get special reverence in that society and be almost universally viewed as much better marriage prospects than childless women. I still believe that this requires a new factor in social conditioning. $\endgroup$ May 13, 2023 at 21:44

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