Why are Stone Age RPGs obsessed by getting women pregnant?

I love prehistoric fiction of the Clan of the Cave Bear, Mother Earth Father Sky sort. So if I spot a ‘serious’ Stone Age or Ice Age RPG I buy it.

Two of the recent (ish) ones I’ve bought - Wurm and Paleomythic - have rules for getting pregnant. On top of that they both have rules for increasing your probability of conceiving. Which is utterly pointless, because the authors can’t do statistics, so haven’t noticed that their ‘normal’ chance of conception is outrageously high.

Wurm: for most people - every time a man shags a woman (p41) the player of the man rolls 2d6. If he gets a double she’s pregnant. Then you roll on the table to see if it will be a girl, a boy or twins.
That’s about 17% chance of getting preggers on the first date, and if you have sex once a day then its 99.4% by the end of 4 weeks.

Wurm: for people with a special ability: if either of the couple have the Might of the Bison special ability, then the player of the man rolls 3d6. Again, if he gets a double she’s pregnant.
This is presumably for tax reasons, or some other reason you really need to get pregnant on the first
date (44%) or by the end of the week???

Paleomythic: for most people - every time a woman shags she has a 1 in 6 chance of getting pregnant. (It actually says on p62

“a person has a one in six chance of becoming pregnant every time they copulate”

so presumably men and lesbians can get pregnant too?)
So again about 17% chance for the first date, and Ms Once a Day will have a bun in the oven by the end of the month.

Paleomythic: for people nominated as the recipients of a fertility ritual - the next time they shag, they have a 2 in 6 chance of conceiving. That’s 33%, for those couples who just can’t wait until the end of the month.

Do the writers think that prehistoric people come into heat like cats, horses or elephants, so they need a huge probability for any one shag? Do they think stone age people only have sex by the light of the silvery moon, so you have to boost the fertility rate to keep your population going? Or do they think that stone age people had nothing to do all day but shag?

I’ve just checked Mythic Rome, and it has zero rules about getting pregnant. The nearest thing is a section about Roman attitudes to abandoning unwanted children. Do you guys have any examples of not-stone-age RPGs with rules on getting pregnant?

I envision scenes like these in these Prehistoric RPGs:

Old Wise Woman: hello Ms Bonks-Like-Bunnies. What can I do for you?
Ms Bonks-Like-Bunnies: According to our local shaman, Dances-With-Anthropologists, I’ll conceive my first child at 18 and not reach the menopause until 42.
Old Wise Woman: So?
Ms Bonks-Like-Bunnies: My partner, Statistics-Hunter, says that means we’ll have 1 child a year, so that’s 25 kids. So I really, really, really need to know… Have you invented reliable contraceptives yet?
Old Wise Woman: Sadly, no. With a 1 in six chance of conception with every shag, I can only offer the real-world, stone age people’s solutions of abstinence, abortion or infanticide. Or you could move to some marginal environment where there is so little fat in your diet it curtails our tribe’s unfeasibly high fertility.
Ms Bonks-Like-Bunnies: I don’t like any of those options.
Old Wise Woman: You could go on a quest to the Clan of the Cave Bear and beg then for some of their fictitious herbal tea from which acts as a morning after pill?
Ms Bonks-Like-Bunnies: Hmm…maybe.
Old Wise Woman: Or hope that most of your kids get trampled by stampeding mammoths?
Ms Bonks-Like-Bunnies: That’s a bit rough!
Old Wise Woman: Well then, your only two alternatives are… One - invent subsistence agriculture and climb that demographic curve up to a horrendous infant mortaility rate.
Ms Bonks-Like-Bunnies: And two?
Old Wise Woman: Hope your kids become PCs or NPCs and you are in a game system with a lot of TPKs and murder-hobos!


I never heard about that. This is so weird.

That does seem excessive. The authors are probably dimly aware that infant mortality was a lot higher in the past, and are seeking to make up for this, but without (naturally) doing much research.

GURPS 4e has a pregnancy rule, but you have to dig for it. Low-Tech Companion 1 has a page on Reproductive Medicine within the section on low-tech medicine in general. The relevant passage is:

A sexually active woman must roll 3d for pregnancy each
month unless she’s already pregnant. If she takes no special
countermeasures, she becomes pregnant on a 6 or less.

6- on 3d6 is 9.3%.

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As @JGD what are the mortality rates like?

Those GURPS pregnancy rules were based on my looking for anthropological studies of mean intervals between births in low-tech societies, and then doing the math. Adding 10.8 months to conceive to 9 months pregnancy gives 19.8 months, or a bit under two years. If the roll were 5 or less, it would be 21.6 months plus 9 months, or 30.6 months, just about two and a half years. Something in that range is the right order of magnitude, at least.

One thing those rules didn’t take into account was lactational amenorrhea and associated lower fertility. On the other hand, they did mention nonprocreative sex, which at least some low-tech societies certainly knew about (classical Latin has at least seven distinct verbs for various sexual acts); the assumption that all sexual acts were procreative is partly a product of Christianity, which for many centuries treated nonprocreative acts as criminal offenses.


Loss of 1d fatigue points during early labor, and 2d during late labor; doubled on a failed HT+1 roll, with TL bonuses if attended by a skilled midwife; if cumulative fatigue exceeds FP, then further fatigue also costs hit points; critical failure results in serious bleeding, which costs hit points directly. It would be possible to work out the risk of mortality from this, but it was fairly low. A realistic treatment might well have assumed a higher risk.

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Of course the classic non-Stone-Age game for this is Pendragon, which to summarise:

Each wife, paramour, etc. of the default male knightly character rolls a d20 each year:
1-10 nothing
11 mother and child die
12 child born, mother dies
13 twins born, mother lives
14+ single child born, mother lives.

so an average live births per woman per year of 0.5.

Children under 15, including any newborn, roll a d20 each year and die on a 1-2. So a child born alive has a ~23% chance of making it to adulthood.

I believe there may be modifiers for wealth, but I can’t find them offhand.

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Also age modifiers and standard of living penalties.

Before his passing, Greg Stafford had redone the tables so there were different tables for different age ranges (I think his website is a 404 error now or I would link) making the odds tougher and tougher.

I tell you what… the difference between 25 and 26 can be really rough :cry: Speaking from experience…

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All of his website is preserved, if anyone needs it I can dig up a link.

I love a lot of what Greg did, but clarity of rules was not his forte, and he seems to have had a bad habit of issuing a new book that replaced some of an old book with a different title, but not all of it… I’ve run the Uther period of Pendragon myself and my word the moment you step outside the details from the core book or GPC you’re falling off a cliff as far as rules support is concerned.

But I’ve found some modifiers in the core book v5.2. Impoverished gives you -15 to everything (so every active woman gives birth exactly once a year, and lives, but 85% chance per year the child dies anyway). Poor has no modifier to childbirth but -3 to child survival (25% death rate per year). Rich drops child death rate to 5% per year; Superlative does the same, and +5 to childbirth, meaning 11/20 a single child with the mother surviving and only 5/20 nothing (rates of maternal death, and twins, are unaffected).

There’s nothing I can see in the core book about the woman’s age though it’s an obvious addition to make.

I can’t help thinking… where’s the fun in the child mortality game mechanics?

I mean there’s historical accuracy on child mortality… and then there’s the fact that I’ve gamed with someone who has had a lot of miscarriages, and another person whose wife had a stillbirth, so as a GM I would never, never, never include that in a game.

Meanwhile, as a player… so my choice is either (1) fridging the wife/kid to allow me to roleplay a grief-stricken parent who has just lost a kid, or a grief-stricken husband who has just lost a wife, or (2) treating the dead wife/kid as a life event roughly equivalent to “Your barn washes away in a flood. You’ll have to build another”.

Even in the no child mortality, silly pregnancy rates of Paleomythic there’s also another (probably unintended by the game designers) in-game conversation bubbling under. Namely…

GM: What’s your character called?
Me: Morg the Manly-Man.
GM: You’re not playing a woman, then?
Me: Nope. Because I want to avoid The Awkward Conversation and The Real-Life Argument.
GM: The what?
Me: The Awkward Conversation. You know, the one which goes… I’m using the 1 in 6 pregnancy rules, so your character is now preggers. Ok well I can’t wrestle ogres and climb Mount Everest when heavily pregnant, and I can’t be a stealthy ninja while carrying a crying baby. You are trying to nerf my character/take away my fun/force me to retire the character. But I liiiiiiiike playing this character. So I guess my character is having an abortion.
GM: Um, er…
Me: Swiftly followed by The Real-Life Argument where players with opposing views on pro-life and pro-choice shout at each other and make the game toxic. So nope, not playing a woman. Any questions?


I also don’t use these sorts of rules as they are Not Fun and/or remove player agency:

  • You’ve just had a fight with Vikings - roll to see if any of your wounds get septicaemia and kill you slowly as your flesh rots away.
  • Ah, you’ve put on a hat. Your encumbrance now means you can no longer walk and chew gum at the same time.

I think that they’re intended to drive you towards (a) getting enough money for your knight to afford a very high standard of living to increase his children’s chances of survival, (b) encouraging your knight to take every possibility of getting an heir, (c) a vaguely mediaeval attitude towards the lives of children (“if it lives, bring it back when it can lead an army and/or get married”).

In practice I’ve generally seen it played as your option 2 - yes it’s sad but we have to keep fighting the Saxons now.

(Various iterations of the books allow for female PCs, but AFAICT none of them has ever dealt with how any of this might affect them.)

We’ve since come up with our own home brew version including a flow chart, but I’ve seen some campaigns where knights get rich when their first 3 wives all die and they inherit their land. It’s incredibly dark and can really diminish wives to assets.

Doing the math:

  • There is a 10% chance of the mother dying per year, so her expected survival after getting married is 10 years.
  • During that time, she will bear five children.
  • There is a 10% chance of the child dying at birth, so 4.5 children will survive being born.
  • There is a 20.6% chance of the child reaching age 15 (0.9 to the power of 15), so the average number of children in the next generation is 0.93, of whom 0.46 will be daughters.

Conclusion: The population will decrease by a factor of two in each generation.

That might make sense if the campaign is set in the Waste Land, rendered sterile by the wound of the Fisher King. But it doesn’t seem to be a viable society.

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The GM in the long Pendragon campaign I played came to similar conclusions, and revised that system, although I don’t know exactly how. My PC had a wife and three young children die in a great plague, but found another wife in the course of an adventure, who survived to the campaign’s end.

Yep. Our flow chart has a ‘Do you want your children to die? Then use the standard rules’ box.

We decided on rolls until age 5, when children would go away to be pages and became technically invulnerable until they became potential future player characters ten years later.

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I’m pretty sure Rolemaster had rules for pregnancy and childbirth, as one of my mates took the piss out of it in the mid-90s for this very reason.

We mostly played Cyberpunk (where everyone has super-reliable contraception and takes precautions against 2020s STDs, which were assumed to be nastier than 20th century ones) or Vampire (where we can’t get anyone pregnant and passing diseases on takes an awful lot of blood exchange).

It is strange, but obviously people who write stone age games must get obsessed about it.

Still, it could be worse - someone could write a game about a group of hunter-gatherers and base it on the more sensational anthropology papers about the Yanomamo tribe - “This game features colossal levels of murder and kidnap! It’s offensive!” - “But it’s in-game statistics reflect this paper I read!” repeated until everyone is sickened or bored.


Rolemaster had rules for practically everything once you got into the Companions.

…yup, here we are, the first Companion even, though it’s intended for PC background generation. You get a number of conceptions (presumably over a lifetime, or at least lifetime-to-date); number of children per conception; infant mortality rates (though nothing later than that); and chances of having to roll on the Birth Injury Chart. Which gives specific injuries in RM game terms, rather than “mother dies”, so that part seems more aimed at pregnant PCs or NPCs during the campaign.