Smallest population able to maintain regular sacrifices?

[Batcathat]

This is kind of a weird question, but the good thing about forums like these is that they usually have people with weird knowledge.

Anyway, I have an idea involving a city that regularly executes/sacrifices people for important and magical reasons. What I'm wondering is how big of a city it has to be for the sacrifices (I'm thinking maybe a few every month or so) not to have too much of an impact on the population. Basically I'm wondering what the smallest sustainable population would be for this to work long term.

The tech level is approximately early medieval, with some magic (but mainly for the upper class so it probably won't affect the population numbers very much) and the city is very isolated so the effect of immigration/migration on the population numbers should be pretty negligible.

[Catullus64]

This is kind of a weird question, but the good thing about forums like these is that they usually have people with weird knowledge.

Anyway, I have an idea involving a city that regularly executes/sacrifices people for important and magical reasons. What I'm wondering is how big of a city it has to be for the sacrifices (I'm thinking maybe a few every month or so) not to have too much of an impact on the population. Basically I'm wondering what the smallest sustainable population would be for this to work long term.

The tech level is approximately early medieval, with some magic (but mainly for the upper class so it probably won't affect the population numbers very much) and the city is very isolated so the effect of immigration/migration on the population numbers should be pretty negligible.

When you say that the population is isolated, does that mean that wars with neighboring cities are infrequent? Because having a steady supply of captives to sacrifice drastically reduces the strain on your own population.

A few sacrifices every month is pretty small potatoes. I've heard estimates that the Aztec empire, with a population well into the millions, was able to sustain tens of thousands of human sacrifices each year, but again, that includes a lot of enslaved persons from wars. My guess is that sacrifice rates like you're describing would be demographically invisible in any population exceeding a couple thousand. (Note that demographically invisible is not the same thing as insignificant; people tend to care about being ritually murdered, and if they feel like the religious legitimacy of the sacrifices is questionable, they will raise a fuss.)

[Batcathat]

When you say that the population is isolated, does that mean that wars with neighboring cities are infrequent? Because having a steady supply of captives to sacrifice drastically reduces the strain on your own population.

Yes, wars would probably be very rare so using captives is probably out. The idea is that they primarily use convicted criminals from their own population (but if they don't have enough criminals, they might have to find some... "volounteers").

My guess is that sacrifice rates like you're describing would be demographically invisible in any population exceeding a couple thousand.

That's what I'm thinking too, but as it's mostly based on a general feeling in my case, I figured I should ask around.

(Note that demographically invisible is not the same thing as insignificant; people tend to care about being ritually murdered, and if they feel like the religious legitimacy of the sacrifices is questionable, they will raise a fuss.)

Of course, this is only about the mechanics of it all, politically and socially it would obviously be a big issue even if it didn't affect the population numbers that much.

[Catullus64]

Yes, wars would probably be very rare so using captives is probably out. The idea is that they primarily use convicted criminals from their own population (but if they don't have enough criminals, they might have to find some... "volounteers").

Or just... volunteers, no quote marks needed. It may seem implausible to a modern, but if it is genuinely believed (and, given that you've mentioned magic, possibly true) that these sacrifices bring divine favor and prosperity to the city, then I don't think it would be too difficult to find volunteers, especially in a time of crisis. If these sacrifices are important to the wellbeing of the community, than that community's value system will encourage volunteering. Lavish living leading up to the event, a special stipend (or even social mobility) for your family, a fancy parade, a deluxe tomb at the public expense; I can see all of these motivating a person to step forward.

I see the use of condemned criminals as sacrificial victims pop up a lot in fiction, and it seldom reads right to me. It seems kind of like tossing the gods your leftovers, and I would think that any god important enough to receive state cult would be offended. You wouldn't dare offer the god a sickly and starving bull, why offer a morally degenerate person? If the god's not picky, why would you honor criminals by making them into divine offerings? I suppose the idea could be that it's not an offering, but a punishment for the criminal's offense against the divine, in order to exculpate the community; but in that case I don't think would be proper to call that a sacrifice.

[Batcathat]

I see the use of condemned criminals as sacrificial victims pop up a lot in fiction, and it seldom reads right to me. It seems kind of like tossing the gods your leftovers, and I would think that any god important enough to receive state cult would be offended. You wouldn't dare offer the god a sickly and starving bull, why offer a morally degenerate person? If the god's not picky, why would you honor criminals by making them into divine offerings? I suppose the idea could be that it's not an offering, but a punishment for the criminal's offense against the divine, in order to exculpate the community; but in that case I don't think would be proper to call that a sacrifice.

I see your point, but in this case it's less about sacrificing people to the gods and more about needing their blood to fuel magic (including the magic that keeps the city safe) so I don't think it would apply in this case (though I could see someone spinning it in-universe as sacrificing to the gods, I might use that). There's also people giving away or selling some of their blood while still alive (sort of like real world blood donors) but the idea is that killing someone gives the blood more power (and, of course, provides more blood).

[LibraryOgre]

Gonna depend on birth rate, of course, but also the natural death rate (which we will assume this is in addition to; they MIGHT be sacrificing the infirm, which would mitigate this a lot).

So, we're talking Natural Population Growth rate.

I'm not going to crunch the numbers from that site, but it looks to mostly be about 1-3% per year, so we'll say 2% per year. We will also assume that a combination of magic and technology makes these numbers more or less accurate to the population of our fictional setting.

So, you can manage 2 people, per hundred, per year, and keep a stable population. Population of 1000? 20 people. Population of 10,000? 200 people.

Now, you're probably going to want to be under that... I'd cut it down to 1 per 100, or even 1 per 500 or 1000, if you want the society to be stable or increasing in number. They might also use prisoners of war (no cost to their growth rate), but you might also see issues as their society starts expanding... is it enough to do the sacrifice in just the main city, or do you need to do these sacrifices at every major population center?

Lots to consider, but my verdict is: Probably about 1% of the population is a good maximum from a population growth standpoint. Likely going to want it smaller, though.

[Batcathat]

Lots to consider, but my verdict is: Probably about 1% of the population is a good maximum from a population growth standpoint. Likely going to want it smaller, though.

That fits well with what I have in mind both for number of sacrifices and size of the city. I certainly don't need very exact numbers, just something that doesn't seem completely ridiculous. Thanks a lot.

[Mechalich]

There are ways to choose your sacrifices so as to limit their impact on your population and its growth.

If you sacrifice the old and infirm who have already reproduced successfully and are likely to die shortly anyway this may actually allow for increased population growth through distribution of resources to the young. You can also do this via infant sacrifice of those who have minimal long-term viability due to obvious medical conditions (this is an alternative to the commonplace pre-industrial practice of infant abandonment).

If you sacrifice men rather than women, the impact on your population's growth potential is minimized, since the ability of women to bear children is the limiting factor. However, this will almost certainly lead to polygyny (though any culture that embraces human sacrifice probably already has this anyway).

If you can identify infertile people (via magic or some other means), you should sacrifice them preferentially over all others.

Or just... volunteers, no quote marks needed. It may seem implausible to a modern, but if it is genuinely believed (and, given that you've mentioned magic, possibly true) that these sacrifices bring divine favor and prosperity to the city, then I don't think it would be too difficult to find volunteers, especially in a time of crisis. If these sacrifices are important to the wellbeing of the community, than that community's value system will encourage volunteering. Lavish living leading up to the event, a special stipend (or even social mobility) for your family, a fancy parade, a deluxe tomb at the public expense; I can see all of these motivating a person to step forward.

Grim as it may be to discuss, it's also highly plausible for people in a society were sacrifice is an accepted practice to commit 'suicide by god.' Suicide is actually a distressingly common cause of death (there are a number of countries in the modern world with 2% or more of all deaths attributable to suicide) and while historical data is somewhat hard to come by, it may have been even more common in pre-industrial societies. If even 50% of the suicidal choose sacrifice as their method, that could easily be 1% of the total population.

[sandmote]

One idea I've heard (but doesn't seem widely accepted, so take it with a grain of salt) is that a lot of cities had high immigration from the countryside but negative population growth from all other factors. Cramped conditions, limited food imports, limited potable water, and a lack of organized methods for waste removal tend to have some severe effects on population growth.

Killing a few people who were living the countryside and left because the family farm can no longer support them might not have any noticeable effect on the population. Might not even impact the death rate, depending on who is being killed and how.

[Quizatzhaderac]

So I think the biggest thing is deciding the demographics that get sacrificed. Also, I'm assuming you want there to be some kind of conflict around this? If so, what exactly do you want that conflict to look like?

Is there any tangible benefit to the families of the sacrificed? For example maybe a parent's sacrifice guarantees their children will be fed. Or maybe noble families must regularly produce a sacrifice to maintain their standing.

So in most cases I'd expect the elderly first.

Children might also make sense if people find themselves unable to support all their children.

Healthy young adults will require special explanation. Most of the cost of raising them has been spent and most of their potential remains.

You said "a few a month", so let's assume 3* 12 *70 = 2,520 people would be sacrificed over a full life.

For the elderly, let's assume half of people make it to 70 and it's just what you do at that age, so you'd need a population of about 5,000.

For infants, you could manage maybe 10% and still have population capable of growth. Examples aren't appropriate to discuss per forum rules. So 25,200 people, which is also about what you need for an ancient city state.

For young adults it depends on the economic system. I'd say maybe 2% in an agrarian society. So 126,000.

[Batcathat]

Thanks to everyone for your input. Lots of interesting ideas that I might end up using in some way, always good to get a different point of view on things.

Is there any tangible benefit to the families of the sacrificed? For example maybe a parent's sacrifice guarantees their children will be fed. Or maybe noble families must regularly produce a sacrifice to maintain their standing.

The idea is to primarily use convicted criminals (so there will probably be some fairly Draconian laws or at least harsh punishments) but I like the idea of rewarding the family of voluntary sacrifices, it seems like a logical conclusion to people selling their blood like I talked about earlier.

[Quizatzhaderac]

Hmmm.. maybe the power of a death sacrifice is proportional to the ability of a person to produce blood? That way a 70 cancer patient is just a less useful sacrifice.

And/or maybe the magic from multiple sources can't be added, so one pint from a hundred people is sometimes no replacement for all of one person's blood.

The criminals
So there's a couple of ways the law could "work" to be regularly sentencing a lot of people to death. They all basically come down to not having a good legal system as good legal systems typically results in crimes being discouraged.

The law could be vague (undue vexation), confusing (gnostic turpitude), or beyond one's control (vagrancy).

Another random idea
A person can ask the priesthood for a new identity, this will typically be a person in debt or a criminal or something.

The priests do some divination ritual thing, possibly leading to you being sacrificed.

If you live, you take a new name and are given a parcel of land. Your new identity is morally and legally free of any consequences of the old life.

When people talk about a person sacrificing themselves, they don't distinguish between the outcomes.

[Tvtyrant]

The effects of the sacrifice are going to change the amount of people who can safely be sacrificed. If they get mass healing, or can insure crop success, or whatever other magical mass mojo you can think of they aren't going to die as early or as often. You could even get a feedback loop where the population surges but requires ever greater sacrifices to keep it surging, which causes a kind of volatility as crime slows down and they either need to put mandatory maximum ages on people or invade their neighbors more frequently.

[Martin Greywolf]

Here I go, up to my usual pedantry.

The tech level is approximately early medieval, with some magic (but mainly for the upper class so it probably won't affect the population numbers very much)

Your first problem. It's not that cities didn't exist in early medieval period, it's that they were extremely rare, with very few exceptions that were mostly in Romen empire remnants of some sort (parts of Outremer, Byzantium, Greek cities, Rome itself). Early medieval Florence has 1 000 people in it, while Constantinople has 150 000, Rome 80 000, Thessaloniki 40 000, Poitiers has 8 000 (this being one of the largest cities in one of the most arable areas of Europe). Sure, Luozang has half a million at this time, but that isn't early medieval, the term applies to Europe and Europe only.

Also note that Poitiers and Florence are busy trade hubs as well, and Constantinople, Rome and Thessaloniki will decline to as little as 30 000-50 000 so...

Another issue, very much related to this, is how densely populated the countryside is. A town needs to import almost all of its food, and pre-modern, that means you have less that 5% of population living in the city. Or rather, 5% is the high medieval estimate, eraly medieval is likely much lower. Which means that our busy trade hub of Florence has 1 000 people in the town and another 19 000 people in the villages around it - assuming a reasonable 500-1000 people per village, you get a total of 19-38 villages necessary for this city.

Poitiers with 9 000 people has rural population of 180 000, with 180-360 villages. Constantinople with 150 000 pop has a monstrous rural population of 3 million, needing 300 000 - 600 000 villages, or to put it in different terms, damn near entire Greece, to sustain it.

Also note that the absolute highest number of people that can farm land from a single town/village/point of origin is about 5000, provided they are surrounded by arable land. More people than that and you need to farm lands that is so far away from town you are better off founding a village there by virtue of travel time alone. That means that a city that has its farmers within its walls can have, at the absolute best, 250 city-dwellers and 5 000 farmers. That's... not really a city, maybe a market town? Or just a really big village.

The only way to fix these bottlenecks is to magic your agriculture into being way, way more productive - maybe that's what the sacrifices are for?

Provided you go that route, 1 farmer produces enough for 1+1/20 of a person. To figure out how many times you need to boost the yield to get to your city pop, take 5 000 as max farmers, 5 250 as max supported pop and multiply that 5 250. That means that should your magic just double the yields, your city can suddenly support 10 500 people on 5 000 farmers. Which is pretty neat, because you don't need crazy agrimagic, just making that corn twice the size will do.

and the city is very isolated so the effect of immigration/migration on the population numbers should be pretty negligible.

Your immediate problem is, why is it a city then? The most plausible reason is probably a ramnent of a bygone empire, but it could be the one and only city-state left from the late stone age that actually figured out how to run a city state - that is no small task, a few would-be city-states probably floundered there.

Anyway, I have an idea involving a city that regularly executes/sacrifices people for important and magical reasons. What I'm wondering is how big of a city it has to be for the sacrifices (I'm thinking maybe a few every month or so) not to have too much of an impact on the population. Basically I'm wondering what the smallest sustainable population would be for this to work long term.

It really depends, but here's the thing: even historical Florence has a total population of 20 000 people in total. With the mortality rate of this period being at 10% or worse, we have 2 000 natural deaths per year. Even our "5 000 farmers with magical double yield"-topia has a total population of 10 500, meaning 1 050 deaths per year. Even that borderline market town village of 5 000 will see 500 dead a year.

Granted, most of those deaths are infants - compare average life expectancy at birth versus at 20, being 25 and 40 respectively - but still.

tl;dr If it is large enough to qualify as a city and has the corrseponding historical population, the 12 sacrifices per year are a drop in the bucket.

[Batcathat]

Your first problem. It's not that cities didn't exist in early medieval period, it's that they were extremely rare, with very few exceptions that were mostly in Romen empire remnants of some sort (parts of Outremer, Byzantium, Greek cities, Rome itself). Early medieval Florence has 1 000 people in it, while Constantinople has 150 000, Rome 80 000, Thessaloniki 40 000, Poitiers has 8 000 (this being one of the largest cities in one of the most arable areas of Europe). Sure, Luozang has half a million at this time, but that isn't early medieval, the term applies to Europe and Europe only.

This is part of the reason I asked the question, actually. I basically want the city as small as possible while still able to keep up the sacrifices.

The only way to fix these bottlenecks is to magic your agriculture into being way, way more productive - maybe that's what the sacrifices are for?

That is indeed part of what they're used for. I haven't decided on the details but it'll probably be something like super-efficent farms close to the city or possibly some sort of magical hydroponic farm.

Your immediate problem is, why is it a city then? The most plausible reason is probably a ramnent of a bygone empire, but it could be the one and only city-state left from the late stone age that actually figured out how to run a city state - that is no small task, a few would-be city-states probably floundered there.

That one I have covered, at least. While the sacrifices provide all sorts of useful magic, the main reason for them is to keep out the nasty things living outside the city. I won't go into details (and I haven't decided all of them) but basically it's rather dangerous to travel outside the city, not to mention live there. Enough that living in a city with regular human sacrifices is worth it to most people.

tl;dr If it is large enough to qualify as a city and has the corrseponding historical population, the 12 sacrifices per year are a drop in the bucket.

Good to hear. That was my own guess on the matter and most answers seem to point the same way. Thanks.

[Quizatzhaderac]

You can get a lot higher population density if you don't assume European climate and agriculture. There's a good reason most people don't live at such high latitudes.

Wet rice farming is almost twice as efficient (in terms of land) as wheat farming and can be used on poorer soil.

It's only slightly more labor efficient, so almost everyone would still need to be a farmer, but maybe they call come into the city for festivals or what-not if that's important. This will require lots of water and either flat or terraced land.

Maize and potatoes are much better than wheat, and grow in similar climates.

[Mechalich]

You can also increase local population density through access to a highly productive local fishery (which includes more than just fish, including shellfish, seabirds, and marine mammals), whether on a lake or bay.

Honestly, for a 'very isolated' city the best choice is probably an island anyway since it's the easiest geographical barrier to explain (mountains, jungles, and deserts are all viable as well, but introduce complications). In that case the city need not represent the entire population of the island, but it can serve naturally as the sole administrative center.

[Martin Greywolf]

You can also increase local population density through access to a highly productive local fishery (which includes more than just fish, including shellfish, seabirds, and marine mammals), whether on a lake or bay.

This is a trap. While fish and sea critters do give you some food, it has to make up for the fact that, well, a portion of your available coastline is not arable land. You can't really solve this by being more inland for the same reason you can't farm too far from the city - travelling takes time, and your fishing boat can't really use too many oars to remain profitable.

You could maybe make it work if there is an unreasonably large amount of fish in the waters for some reason (they go there to hatch? magic? permanent whales? marine biology isn't my cup of tea), but then we're again in wizard did it land.

[Quizatzhaderac]

With the mortality rate of this period being at 10% or worse....

Actually, I'd say that would make the sacrifices matter more, because the society has less of a margin to be able to tolerate the losses.

[Deepbluediver]

I remember reading somewhere that a population generally needed to start out with about 500 individuals (assuming a gender-equal ratio) in order to have the necessary genetic diversity to avoid going extinct through inbreeding. I can't recall exactly where I read that though, or if they provided any other sorts details, but you might take that as the bare-minimum size for a viable, community, IF your goal is "be fruitful and multiply".
But that's a pretty small "city"- more like a village or something. The town of Whittier, Alaska, manages to cram about 300 people into a single modern apartment building, just if you want to look up something to give you a sense of the scale we're talking about.

In purely mathmatical sense (this may get a little gruesome, but since you asked about human sacrifice...), if you assume that each woman could produce 1 child per year, then a population of 13 (12 women plus 1 man) would provide sufficient offspring for monthly sacrifices. Of course if you're sacrificing ALL the children, then eventually your population dies of old-age. But the addition of just 1 more woman, producing 1 extra child a year, would likely be enough to keep a breeding-population alive. At least until the incest killed them off instead; if you curious about that aspect of it, your can read more about the Hapsburg dynasty in Spain, and the Romanovs in Russia.

One more thing to consider is that in medieval times (or in any technologically equivalent society), many women died in childbirth and many of their offspring didn't survive childhood, so if you need to sacrifice full-grown adults then the issue is tougher. If you can sacrifice babies (and maybe the elderly) though, you could get away with fewer people.
Or since you society has magic you could probably write "a wizard did it" to negate that issue. In fact if your society is trying to remain small, it would make sense the "magic to ease childbirth" would probably be the second highest priority after "magic to grow crops" in the survival sense.

I think the only real question is how long do you need your city to exist for your story to work (or to tell the story that you want to tell). A handful of men and a few dozen women could easily survive for up to a century, assuming nothing like a plague wipes them out. That's the major issue with small populations- a lack of genetic diversity means they may all be susceptible to the same problems. For long-term (permanent) survival, a few dozen men and 150-200 adult women (plus however many kids they had) could probably keep it going as long as you need it to. Again assuming no outside disasters like plague or civil-war reduce their population below a point where they can't rebuild their numbers.

[Mechalich]

This is a trap. While fish and sea critters do give you some food, it has to make up for the fact that, well, a portion of your available coastline is not arable land. You can't really solve this by being more inland for the same reason you can't farm too far from the city - travelling takes time, and your fishing boat can't really use too many oars to remain profitable.

Fishing boats travel by wind and current as well as oars and can actually range out quite far. Depending on estuary structure a coastal city that is actually some distance inland sacrifices almost no farmland while still accessing aquatic resources. Also, fisheries have the additional benefit in that man does not live by bread alone. Aquatic protein sources are in many ways more effective than livestock (for physiological reasons fish metabolize more efficiently than mammals by almost a full order of magnitude in some cases), and even today a significant portion of the world relies on fish as the primary source of animal protein.

You could maybe make it work if there is an unreasonably large amount of fish in the waters for some reason (they go there to hatch? magic? permanent whales? marine biology isn't my cup of tea), but then we're again in wizard did it land.

Aquatic resources are not dispersed evenly any more than terrestrial ones are, and in fact the variance is in many cases much larger. Many aquatic resources effectively self-concentrate on specific beaches, sea stacks, and lagoons for purposes of predator avoidance or reproduction and may be available in almost mind-boggling numbers (even 'highly abundant' modern fisheries often undercount historical values by 80-90%, ocean depletion in the modern age is literally unimaginable in scope due to shifting cross-generational baselines). As a result the area harvested for an aquatic resource may be only be a tiny fraction of a percent of the area utilized to produce that resource. This is particularly obvious in the case of animals that require protected land zones to reproduce such as seabirds and seals, but it holds true with many fish stocks and whales as well.

Now, there is indeed a sustainability issue with aquatic resources and highly concentrated populations. Historically many island settlements maintained high population densities only because their fishing and preservation technologies were sufficiently limited that they were simply unable to overexploit local resources, but this applies to terrestrial resources like soil and water too, so that's more or less a wash.

[Slipjig]

Suicide is actually a distressingly common cause of death (there are a number of countries in the modern world with 2% or more of all deaths attributable to suicide) and while historical data is somewhat hard to come by, it may have been even more common in pre-industrial societies. If even 50% of the suicidal choose sacrifice as their method, that could easily be 1% of the total population.

You also need to factor in the average age of death of the population. If the life expectancy of the population is 50 years (to keep the math simple) then we'll estimate that about 2% of the population dies annually. If the rate of death by suicide is 2%, then we're talking .04% the population dying by suicide every year, way less than the 1% other people have mentioned.

In order to make the logistics work, you could set a Logan's Run type society where it's socially expected that you'll "give yourself to the god" at a certain age (presumably old enough to have finished raising your children).

[Quizatzhaderac]

This is a trap. While fish and sea critters do give you some food, it has to make up for the fact that, well, a portion of your available coastline is not arable land. You can't really solve this by being more inland for the same reason you can't farm too far from the city - travelling takes time, and your fishing boat can't really use too many oars to remain profitable.

While a special case (salmon spawning waters), there were a number of high density, non-agrarian, native populations in the north western US that did subsist on mostly fish.

They didn't have cities, but that more reflected the fact that they had no special reason to cluster that extra few miles together.