I just ran into this question in the Reddit worldbuilding sub, and thought it fits to this site, and may bring up some interesting aspects.

To quote the original post:

How do I justify such, beyond accounting for the methods by which such a large group would eat, work, and stay healthy (which can be accounted for with technology, magic etc. etc.)? As in, what am I missing? What other nuances of the real world would have an effect that I'm forgetting here?

To be more on-topic: what are the general obstacles, issues and considerations in a civilization so big and bears such a less advanced technological level - but the possibility of the existence of extraordinary animals and the potential of magic? What are the possible solutions by the use of the latter two - viewing in a general scope (if possible)?

  • $\begingroup$ This feels a bit like an Idea Generation question (at least, that's the current name for it), which would be off-topic. $\endgroup$
    – HDE 226868
    Feb 29 '16 at 23:00
  • $\begingroup$ @HDE226868 the original question likely is, but the answers given in general scope may not. By this, I mean, what are the obstacles and considerations in such a case? Maybe even real life analogy, as I did in my answer. If you want, you may edit the question to reflect to this, but I may do as well. $\endgroup$
    – Z..
    Feb 29 '16 at 23:04
  • $\begingroup$ Okay, then it might be helpful for you to edit that in a bit to make it clearer. $\endgroup$
    – HDE 226868
    Feb 29 '16 at 23:06
  • 1
    $\begingroup$ If the planet were big enough, billions could get lost on it and never meet. Population density is the limiting factor in lower tech settings, as they cannot typically produce enough food, provide clean water, remove enough waste. Magic can be used to increase the limits, by doing all those things to some degree. If the total population, not the density is what's desired just make a bigger livable area. $\endgroup$
    – Seeds
    Feb 29 '16 at 23:30
  • $\begingroup$ If the fantasy setting had magic food production and waste removal, then population density becomes less of a factor. $\endgroup$
    – Jim2B
    Mar 1 '16 at 1:48

Medical Knowledge.

The biggest factor that allowed our population to grow so much more rapidly in the 19th and 20th centuries was a reduction in early childhood mortality. In our world, this was driven largely by sanitation, vaccines, and antibiotics, as well as the development of low-cost means of treating the symptoms of some diseases. Proper nutrition of young children is also important, with things like vitamin-A deficiency killing hundreds of thousands of children every year in the modern world.

For a lot of these things, neither magic nor advanced modern technology are required to significantly reduce mortality rates. Proper sanitation with safe disposal of sewage and garbage is a matter of logistics and city planning. You can use magic to drive pumps or to purify waste if you want, but building sewers and keeping waste water and drinking water separate is a matter of man power and planning.

Likewise, diarrheal diseases are a major cause of death in children, but often times can be treated through oral rehydration therapy, which literally just requires water, sugar, and salt. While ORT was not developed until the 20th century, it's entirely possible to perform it without any access to modern technology, and it offers something like a 93% reduction in mortality rates.

The importance of sterility in medical procedures is also a fairly modern development which requires no technology. Things like 'clean your surgical equipment between patients' or 'give birth in a sterile environment' will go a long way towards reducing mortality rates.

If you know enough to implement basic, low-tech solutions to these problems, you should see enough of a drop in mortality rates to get a significant population boom. No additional magic or technology is required. Once this population boom has started, wait a few hundred years and you'll have your population in the billions. Of course, you can work magic into your medical system if you want. Things like magical vaccines or spells to help sanitize things or clean up pollution will improve the longevity of your populace, but they aren't strictly necessary.

Or just use magic to clone people. That would work too.

  • 1
    $\begingroup$ Children may have had better morals back then according to some. But I think you meant mortality. $\endgroup$ Mar 1 '16 at 2:02
  • $\begingroup$ I was thinking of the problems inherent in large cities with large populations and their animals. In the 1890's people in London and New York thought the horse manure problem would flood the city before the 1930s. Luckily the automobile came along and saved us from that ecological disaster. nofrakkingconsensus.com/2011/03/29/the-horse-manure-problem $\endgroup$
    – Jim2B
    Mar 1 '16 at 2:57
  • $\begingroup$ @Jim2B: 'Luckily' may not be quite the appropriate word to use here, since instead of horse manure making NYC unlivable (not that it ever was, IMHO), you have automobiles well on their way to making the planet unlivable. $\endgroup$
    – jamesqf
    Mar 1 '16 at 5:10
  • $\begingroup$ @jamesqf, there exists a body of evidence pointing towards cow farts, termite colonies and pine trees as massive greenhouse emitters. Not justifying the cars so much here; but freely allowing anything to get completely out-of-balance in an ecosystem seems to be destructive. $\endgroup$
    – Sean Boddy
    Mar 1 '16 at 6:16
  • $\begingroup$ @jamesqf , actually my point was as bad as cars are now they are very ecologically clean compared to how things were before they were used - which is what Sean pointed out. $\endgroup$
    – Jim2B
    Mar 1 '16 at 13:07

This answer was written before the question was edited, so not sure if I'll need to adjust it.

Well, it is really arable area multiplied by crop productivity per area divided by food requirement per unit of population. Only real complication is that you need to also consider the type of arable area (temperature, humidity, soil) when calculating productivity. Potato, for example, was huge not only because it had high productivity, but because it was less demanding of climate and soil than the more productive cereals. You also have to consider that people do change their environment to be both more and less productive by clearing forests, levelling ground, and building irrigation systems.

But, yeah, the basic math is simple. They have more arable area, more productive crops, or people who need less food.

Arable area can be increased by having less deserts, tundra, taiga, sea or other types of areas not suited for agriculture. Or by having magic that can make such areas arable. A fantasy civilization could feasibly use magic to adjust temperature, moisture, or even soil. This could even happen invisible by the gods intervening to help their worshippers. Or the world could simply be bigger.

Magic could easily make crops more productive. A simple protective blessing by a village priest could easily replace fertilizers and protect plants from pests and disease. Fantasy civilizations generally have long history of agriculture and access to supernatural guidance. Their cultivars could actually be better than ours are. So the agricultural productivity per area of common magic fantasy civilization could be comparable to modern agriculture. And thus it might be able to support similar populations.

Food consumption might vary by race. Non-humans might need less food and thus increase maximum possible population. Magic might reduce spoilage. Fantasy civilizations might eat less meat, which would vastly decrease resources needed.

An issue that needs to be addressed is productivity per person. While productivity per area will tell you how many people an area can support, you also need to know how many of those people are stuck tending the fields and how many will migrate to cities to other work. Typically low tech would imply that almost everyone lives in small villages producing food, but golems, elemental servants, or zombies can be used to tend to fields instead and allow an urbanized society.

Logistics is also important. Typically low tech would have lots of small cities with few political, religious, or commercial centers becoming larger. But if you can use magic to transport food, you could have population distribution more similar to modern times.

You also need to think about how good the people are in handling disease, particularly epidemics, as that has impact on how good large cities are to live in. (ckersch covers this in his answer) Medical technology will also determine the rate of growth that is possible for the population. Better you control disease, lower the childhood mortality will be and faster your population can grow in response to changes in its ability to support more people.

And also think how people actually cook their food. If people use wood fires, you'll have acute deforestation and eventual ecological collapse. If magic can be used, you'll have (probably) sustainability similar to modern electricity based solutions. The energy still is coming from somewhere even if you use magic so something similar to global warming might exist.

And one thing people tend to forget. Building houses and roads requires land that then can't be used for agriculture. So then population increases you'll need new agricultural area to not only cover the increased consumption, but also to replace the area taken by infrastructure.

  • $\begingroup$ That's one aspect but the logistics of moving those goods around is another part of the problem. Without modern transportation methods this left people on foot or animal drawn carts. Both have their own set of problems and limitations. $\endgroup$
    – Jim2B
    Mar 1 '16 at 2:58
  • $\begingroup$ @Jim2B Not sure of your point. I totally agree, of course, which is why my answer had a paragraph mentioning logistics and how it affects population distribution. A paragraph way too short to actually cover the topic, but still... The question is specifically about maximum sustainable population and that is pretty much as simple as I make it, population will grow to what food production can support. Logistics and productivity per person will determine population distribution and medical tech the rate of growth, but the actual maximum population is all about food. $\endgroup$ Mar 1 '16 at 20:57
  • $\begingroup$ I was looking at your proposed proportional equation, and realized logistics could roughly be included with a 0 to 1 ranged spoilage/breakage factor. This sort of thing would be hard to really nail down in practice, but historically it could track things like how railway system started delivering large quantities of fresh-ish meat across the United States, or down-river transit capabilities resulting in larger population possibilities near river deltas. $\endgroup$
    – Sean Boddy
    Mar 3 '16 at 18:57
  • $\begingroup$ @SeanBoddy Yes, as far as the "equation" goes logistics is factored by its effect on spoilage affecting food consumption per capita. Specifically good logistics allows sharing of surplus with areas of food shortages. I only talked about that as allowing larger cities, but it does reduce spoilage (unshared surplus food will be largely wasted) and thus does increase the supportable population. $\endgroup$ Mar 4 '16 at 0:10

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.