How would Humans be the most numerous race?

[SpoonR]

I’ll offer two rather more unusual possibilities.

1. For a jungle-dwelling group, like some sorts of lizardfolk. If you know what is and isn’t safe to eat, and how to avoid predators, everything you need is available in the jungle with little effort. You’ve adapted to the environment, and somehow reached a stable equilibrium. Expanding would require large groups leaving the jungle, but who would want to go out into all that hardship-infested non jungle?

2. Halflings, with some inspiration from Birthright, and various other sources. Some entity is a humanoiditarian, and thinks halflings taste good. Halflings survive by blending into other less tasty societies. Any place halflings come to dominate shortly becomes noms.

3. Dwarf fortress. Dwarves are obsessed with digging. They go through boom/bust cycles of found new city, prosper and increase population, dig too deep and awaken demon, lose most of population, start city somewhere else.

[Metastachydium]

Hm. How about something like this:
1. orcs and goblinoids are (sub)species within the same genus. This genus is plagued by, well, a plague, an infectious disease with high mortality rates that other mammalian humanoid races/species can carry asymptomatically or without severe symptoms and a serious risk of death, which makes the orcs and goblinoids incredibly paranoid towards each other and especially strangers from other races. They live in inhospitable lands and in nomadic societies of relatively small size incredibly hostile towards much everyone (except, say, avian and reptilian people) they encounter or that encounters them in an attempt to stay safe. Occasional raiding is generally a desperate last ditch attempt to avoid starving to death while at it or to drive off especially stubborn would-be neighbours who come in numbers.

2. Lizardfolk have two factors limiting their spread: 2.1. they have slow metabolisms, which makes it possible for themselves to live longer than any other race barring elves – unless they get themselves killed by doing something stupid, that is. This makes most of them patient, slow, risk-averse and very conservative.
2.2 They are kind of cold-blooded. High altitudes and cold climates are not kind to them and instead of trying (and likely failing) to adapt, they simply tend to avoid such unfavourable environments.

3. Beyond the issues that result from maturing slower than any other species, eelves have the opposite problem: they are too "perfect" for their own benefit. Less enigmatically put, they cannot and do not sweat. The most potent tool for thermoregulation they have are those oversized ears, and in very warm climates those simply won't do, and so, volens-nolens they must stick to environments that don't get very hot for prolonged amounts of time.

4. For halflings, SpoonR's suggestion is to good for me not to steal it. Halflings eat a lot (mostly gourmet food), work little, and age slower than humans. This makes their flash tender, juicy and wonderfully aromatic. Carnivorous beasts and monsters of all sorts are attracted to it. Heck, it's not uncommon for less scrupulous halflings to indulge in occasional acts of cannibalism. Halfling meat is just that delicious.

5. Half-whatevers simply don't breed true.

6. Kobolds are small, vulnerable and they don't like sunlight. No one really knows how many of them there are, because they stick to their tunnels and burrows, too small for anyone other than them to exist comfortably in. Everyone kind of just leaves them alone, because they are unobtrusive and more than willing to barter the salt, ores and coal they mine away to anyone who offers a price they like.

7. The largest gnome polity went all bonkers at some point and started a large scale Liberation War on everyone they shared borders with (and with some more they didn't) to elevate them from the "state of oppressing themselves" (whatever that means). This led to massive military caualties and a general distrust of gnomes everywhere, leading to the persecution of gnome communities largely everywhere, few of which had anything to do with the actual aggressor or its agenda. Currently, most gnomes linger on the fringes of other societies, have gone underground (and not just literally) or have thrown their lot with the Liberators who warmly welcome these refugees more often than not receptive to their attempts at indoctrinating and radicalising them behind their borders, now sealed tight by their enemies.

8. There were never many dwarves, but then some of them had to dig too deep and too greedily. Incidentally, you might not want to go anywhere near those mountains.

[Scalenex]

Maybe it's a bit hand wavy but in my fantasy world, humans are dominant because of the will of the gods.

I got nine deities, aka the Nine. The Nine made dragons by committee and let the dragons rule the world. A few gods and goddesses made new races, but they were less powerful because they had less divine might behind them.

Thousands of years later, a foolish dragon queen accidentally triggered an apocalyptic event and killed 95% of everyone. The surviving dragons went from members of great empires to xenophobic and miserly loners sitting on piles of treasure and talking about lost glories.

The Nine formed a new committee and sought to create a new race to inherit the world. The elves. The elven lifespan maxes out at about 500 years rather than 2000 years and they have less innate power than dragons. The Nine hoped this would prevent any elf from acquiring enough power to destroy the world.

Thousands of years later, a foolish elven king accidentally triggered an apocalyptic event and killed 95% of everyone.

The Nine decided to try their luck with humans, figuring no single human can gain enough power in one life time to accidentally destroy the world, but they can still acquire enough power in their lifetimes to create positive works of civilization.

Anyway, humans are dominant because they indirectly have all the gods behind them. Dragons and elves do too, but they are still recovering from a near extinction event.

Originally most of the other races were created by one god or goddess who wanted a race to embody their ideal (or in the case of my NE goddess, she wanted a cannon fodder race to throw at her enemies), but these one divine parent races tend to die off quickly. So most newer races are created with two, three, or four gods or goddesses involved.

Dwarves (with four divine parents) claim they are superior to humans because none of the evil deities helped make them, but they are still less wide spread and politically powerful than humans.

My NE goddess still makes the most new races but now she usually works to bribe, bully, or trick another deity into contributing.

I also wrote that half-whatevers are nearly always sterile unless they are elf-human, elf-dragon, or human-dragon. Other half breeds are often derogatorily called mules (borrowed that from Dark Sun but I expanded it to more than dwarf-human hybrids).

Half-extra planar beings are not sterile but their grand children and great grand children gradually revert back to normal members of their base mortal race.

[Damon_Tor]

For most of the same reasons that humans tend to dominate fantasy worlds, I don't see a strong reason why Half-Elves wouldn't supplant them and eventually replace both parent species simply on the weight of demographics. They get an extended lifespan from their elf ancestors with no reduction in maturation rate. If they also breed at even 75% the rate of full-blooded humans, the demographics would quickly shift toward a half-elf world. Also, +2 Cha: Half-Elves are going to be quite a bit better at competing with both elves and humans for mates, and at finding positions high in the social hierarchy.

(Aside: a half-elf dominated world is an element a setting I'm working on here)

[brian 333]

I'm not certain that that follows. Certain factors may affect half-elf rate of live birth, such as cultural inhibitions on cross breeding, (partner won't grow old with you, you'll see them die while still young, etc.,) or interspecies fertility/viability issues, (male elves are only fertile on the night of the full moon every twenty-four months, female elves often die in childbirth due to overly large half-human babies or the robust baby cannot be sustained by the much slower elf metabolism.

There may be a lack of fertility between half-elves so that either is more likely to successfully breed with a parent-species mate than with another half elf, thus allowing the half elf genes to disperse into the gene pool. In this scenario, there is no half-elf race, only a handful of characters per region who can claim half-elf parentage.

[Rockphed]

A while ago there was a subforum of homebrew dedicated to a community campaign setting project titled "Tear of Blood". The most politically powerful race was half-elves, though I think the lore outlawed interbreeding between humans, elves, and half-elves.

[Damon_Tor]

I'm not certain that that follows. Certain factors may affect half-elf rate of live birth, such as cultural inhibitions on cross breeding, (partner won't grow old with you, you'll see them die while still young, etc.,) or interspecies fertility/viability issues, (male elves are only fertile on the night of the full moon every twenty-four months, female elves often die in childbirth due to overly large half-human babies or the robust baby cannot be sustained by the much slower elf metabolism.

There may be a lack of fertility between half-elves so that either is more likely to successfully breed with a parent-species mate than with another half elf, thus allowing the half elf genes to disperse into the gene pool. In this scenario, there is no half-elf race, only a handful of characters per region who can claim half-elf parentage.

Sure, all of that is possible.

Any biological barriers would seem to be new details added to the setting. Unlike muls, who are canonically sterile, there's no indication that half-elves have any similar challenges.

Culturally, sure, those are good points, but culture can change to accommodate biology. If one civilization with uninhibited hybridization grows faster than another civilization with cultural barriers against it, the faster growing civilization would overwhelm and outcompete the slower one.

[The Patterner]

Ok, so this might be one of the most interesting discussions I've seen here in a long time

I'd like to add some ideas as to why humans can outcompete halflings eventough they are very similar to us and share many of our advantages.

Firstly, halflings, like a lot of small warm blooded animals have to eat a lot for their size. Sure a human might eat more in total per day. But we can go longer without food, so during times of hardship we can simply outlast them (this could also work to explain why we outcompete orcs, goblins etc).

Secondly, climate resistance, humans can survive in most types of climate zones easier than haflings. Fact is I could see humans being better at surviving in most types of climates than all other races and that is one of out true strengths.

I could see the above leading to halflings gravitating towards humans since we have an easy time of getting along. For halflings the upside would be that their population can piggyback on humans during times of famine harsh winters. The downside would be that halfling culture has gone all but extinct, they eat, talk, drink, dress and act like humans. Fact is to most other species a halfling is just a short and unusually hungry human.

Added bonus, if you want half-elves but without, well, the elf part. Just have humans and halflings being capable of interbreeding and you have a much more realistic (relatively speaking) mix.

[Metastachydium]

Also, +2 Cha: Half-Elves are going to be quite a bit better at competing with both elves and humans for mates, and at finding positions high in the social hierarchy.

(Incidentally, though 3.5 half-elves are infamous for being useless garbage under normal circumstances, they have one trick up their sleeve that makes them ridiculously good at this: with a racial bonus to Diplomacy and access to both Human and Half-Elf Paragon (the latter directly increasing said racial bonus) they can get a +4 to CHA in a mere six levels, while making Diplomacy a class skill for every class they have. At around 8th level, they can easily hit a +50 modifier or more and 3.5 Diplomacy is so broken it's stupid.)

Anyhow, wouldn't sharing a dating pool with humans and elves work against half-elves on the long run?

partner won't grow old with you, you'll see them die while still young, etc.

That's not even a cultural thing, it's just good old psychology!

female elves often die in childbirth due to overly large half-human babies or the robust baby cannot be sustained by the much slower elf metabolism.

Let's not even think about half-orcs, then.

Culturally, sure, those are good points, but culture can change to accommodate biology. If one civilization with uninhibited hybridization grows faster than another civilization with cultural barriers against it, the faster growing civilization would overwhelm and outcompete the slower one.

But why would a half-elven civilization grow faster (demographically or technologically)?

[Damon_Tor]

But why would a half-elven civilization grow faster (demographically or technologically)?

Well let's test my assumptions with some research and math.

5e lacks an official "aging effects" table, so most of what I'm about to say uses earlier sources. This actually changes this a bit in favor of full-blooded humans because I had based previous assumptions off the 5e half-elf which it says "matures at the same rate humans do". 5e also nebulously tells us that humans reach adulthood in the "late teens" while in earlier editions humans were adult at 15 while half-elves are adult at 20. In any case, I'll use the older material even if that 5-year headstart might force me to walk back my assumptions.

EDIT: Yes, after applying the math this 5 year headstart on each generation does absolutely negate the extra kids per generation effect, for pureblooded humans beating out the half-elves after all. Math is as follows:

Humans hit adulthood at age 15 and enter middle age at 35, about 20 years of childbearing. A quick google search of medieval and renaissance fertility rates tells us a typical human woman will have around 6 children during this time, or 1 child every 3.33 years. I'm not going to include infant mortality here. We're also going to assume that the average individual dies at the start of "old" age, which means humans live to 53, helfs to 93.

A half-elf reaches adulthood at the age of 20 and enters middle age at 62, 42 years of childbearing, more than double. If we assume that half-elf gestation is longer than humans by the same 133% rate, then a half-elf pregnancy would take about a year, up from a human's 9 months, and applying that same variable to the average amount of time between pregnancies, half-elves would have 1 child on average every 4.44 years. Over 42 years of a half-elf female being at childbearing age, that gives us 9.45 children for each half-elf woman over the course of her life.

So after 100 years, an average human woman will have produced 6 children, 18 grandchildren, 54 great grandchildren, 162 great great grandchildren, 486 ggggrandchildren, and around 510 gggggrandchildren (this generation is still only about 1/3 done being born). The woman, her children, most of her grandchildren and some of her great grandchildren are dead. The population of her descendants after 100 years is about 1206

In those same 100 years, an average half-elf woman will have produced 9.45 children, 44.65 grandchildren, 210.98 greatgrandchildren, and 498.45 gggrandchildren (this generation is about halfway done being born). All of these individuals are still alive except for the starting woman herself, for a total population of her ancestor standing at 763.53

In other words, breeding at 15 instead of 20 makes a HUGE difference. Yes, the half-elf will individually keep breeding for much longer, each one producing ~3 extra kids, but in those 5 years extra it takes her children to start having kids of their own, the human's children have already started producing their own offspring! This results in the humans getting to the next generation faster, which matters more in terms of demographics.

Of course these traits don't exist in a vaccuum. Take our society for example: women in Europe and the USA don't start having kids until their late 20s and usually only have about 2. The age of procreation is getting pushed back sociologically, not biologically. If that trend holds true for other urbanized, egalitarian societies, then the half-elf could still manage to outcompete humans, simply because an urban civilization aligns better with their biology in terms of childbearing. A half-elf woman could establish herself professionally in her 20s and 30s then still have her 40s and 50s to have 4-5 children, while human women would struggle with that paradigm.

[Damon_Tor]

Relevant Table Here

Keeping in mind the importance of early childbearing, this explains a human's relative dominance quite well. Halflings, for example, don't reach adulthood until age 20 either. Of the common races only half-orcs can compete with pure-blooded humans. Dwarves, gnomes and especially elves are SERIOUSLY disadvantaged in this way.

[brian 333]

Where do goblins and kobolds fit in this? Both may be quicker to achieve adulthood and longer lived than humans. Plus, kobolds lay clutches of eggs unless the 1ed MM has been corrected in later editions.

[Rynjin]

A while ago there was a subforum of homebrew dedicated to a community campaign setting project titled "Tear of Blood". The most politically powerful race was half-elves, though I think the lore outlawed interbreeding between humans, elves, and half-elves.

Reminds me a bit of Andre Norton and Mercedes Lackey's Halfblood Chronicles. Elves use their powerful magic to enslave humans with magic obedience collars. Turns out they're also suppressor devices for humans' natural psionic potential.

Half-elves, naturally, are considered abominations not just because the idea of an elf breeding with what they view as cattle is repulsive, but also because they have the potential to develop the full abilities of both races.

[Damon_Tor]

Where do goblins and kobolds fit in this? Both may be quicker to achieve adulthood and longer lived than humans. Plus, kobolds lay clutches of eggs unless the 1ed MM has been corrected in later editions.

Unsure: the information easily available from legitimate sources online doesn't include them. But keep in mind that we've got to be comparing apples to apples here: all the species we've discussed are pro-social species with what seems like strong family structure and high investment in offspring. These are what are called k-selective species. If goblins or kobolds represent r-selective species then their reproductive rate might be off the charts compared to humans, but without any investment to speak of in their well-being on the part of the parents. Once the children of r-selective parents are born, they're on their own. This leads to massive infant mortality and very few individuals make it to adulthood and even fewer ever get to breed. So while there are potentially massive advantages to rapid breeding, at some point the benefits would begin to outweigh the drawbacks. It may be that humans hit that perfect sweet spot between the two extremes.

[Scalenex]

Unsure: the information easily available from legitimate sources online doesn't include them. But keep in mind that we've got to be comparing apples to apples here: all the species we've discussed are pro-social species with what seems like strong family structure and high investment in offspring. These are what are called k-selective species. If goblins or kobolds represent r-selective species then their reproductive rate might be off the charts compared to humans, but without any investment to speak of in their well-being on the part of the parents. Once the children of r-selective parents are born, they're on their own. This leads to massive infant mortality and very few individuals make it to adulthood and even fewer ever get to breed. So while there are potentially massive advantages to rapid breeding, at some point the benefits would begin to outweigh the drawbacks. It may be that humans hit that perfect sweet spot between the two extremes.

For my kobolds, I invented a ritual called birthing treks. Kobold clans bury their eggs in a shallow dirt nest and then move their camp a couple miles from the nest leaving a pheromonal trail for the hatchling kobolds to follow back to the adults.

Those that make the journey to successfully are adopted into the tribe, those that didn't are not mourned for they were too weak.

This also means kobolds lose track of whose eggs/hatchlings came from which parents but this is deliberate. Kobold children belong to entire clan.

If the kobold clan's numbers are low, they will move their nest closer to their camp, so more hatchlings survive the birthing trek but clans that make a habit of this are looked down on by other clans.

I haven't given much thought to goblins.

[Metastachydium]

Well let's test my assumptions with some research and math.

5e lacks an official "aging effects" table, so most of what I'm about to say uses earlier sources. This actually changes this a bit in favor of full-blooded humans because I had based previous assumptions off the 5e half-elf which it says "matures at the same rate humans do". 5e also nebulously tells us that humans reach adulthood in the "late teens" while in earlier editions humans were adult at 15 while half-elves are adult at 20. In any case, I'll use the older material even if that 5-year headstart might force me to walk back my assumptions.

EDIT: Yes, after applying the math this 5 year headstart on each generation does absolutely negate the extra kids per generation effect, for pureblooded humans beating out the half-elves after all. Math is as follows:

Humans hit adulthood at age 15 and enter middle age at 35, about 20 years of childbearing. A quick google search of medieval and renaissance fertility rates tells us a typical human woman will have around 6 children during this time, or 1 child every 3.33 years. I'm not going to include infant mortality here. We're also going to assume that the average individual dies at the start of "old" age, which means humans live to 53, helfs to 93.

A half-elf reaches adulthood at the age of 20 and enters middle age at 62, 42 years of childbearing, more than double. If we assume that half-elf gestation is longer than humans by the same 133% rate, then a half-elf pregnancy would take about a year, up from a human's 9 months, and applying that same variable to the average amount of time between pregnancies, half-elves would have 1 child on average every 4.44 years. Over 42 years of a half-elf female being at childbearing age, that gives us 9.45 children for each half-elf woman over the course of her life.

So after 100 years, an average human woman will have produced 6 children, 18 grandchildren, 54 great grandchildren, 162 great great grandchildren, 486 ggggrandchildren, and around 510 gggggrandchildren (this generation is still only about 1/3 done being born). The woman, her children, most of her grandchildren and some of her great grandchildren are dead. The population of her descendants after 100 years is about 1206

In those same 100 years, an average half-elf woman will have produced 9.45 children, 44.65 grandchildren, 210.98 greatgrandchildren, and 498.45 gggrandchildren (this generation is about halfway done being born). All of these individuals are still alive except for the starting woman herself, for a total population of her ancestor standing at 763.53

In other words, breeding at 15 instead of 20 makes a HUGE difference. Yes, the half-elf will individually keep breeding for much longer, each one producing ~3 extra kids, but in those 5 years extra it takes her children to start having kids of their own, the human's children have already started producing their own offspring! This results in the humans getting to the next generation faster, which matters more in terms of demographics.

Of course these traits don't exist in a vaccuum. Take our society for example: women in Europe and the USA don't start having kids until their late 20s and usually only have about 2. The age of procreation is getting pushed back sociologically, not biologically. If that trend holds true for other urbanized, egalitarian societies, then the half-elf could still manage to outcompete humans, simply because an urban civilization aligns better with their biology in terms of childbearing. A half-elf woman could establish herself professionally in her 20s and 30s then still have her 40s and 50s to have 4-5 children, while human women would struggle with that paradigm.

Relevant Table Here

Keeping in mind the importance of early childbearing, this explains a human's relative dominance quite well. Halflings, for example, don't reach adulthood until age 20 either. Of the common races only half-orcs can compete with pure-blooded humans. Dwarves, gnomes and especially elves are SERIOUSLY disadvantaged in this way.

Nice math there.

[Damon_Tor]

For my kobolds, I invented a ritual called birthing treks. Kobold clans bury their eggs in a shallow dirt nest and then move their camp a couple miles from the nest leaving a pheromonal trail for the hatchling kobolds to follow back to the adults.

Those that make the journey to successfully are adopted into the tribe, those that didn't are not mourned for they were too weak.

This also means kobolds lose track of whose eggs/hatchlings came from which parents but this is deliberate. Kobold children belong to entire clan.

If the kobold clan's numbers are low, they will move their nest closer to their camp, so more hatchlings survive the birthing trek but clans that make a habit of this are looked down on by other clans.

I haven't given much thought to goblins.

Fitness tests are a neat evolutionary gimmick.

In one of my settings (Not half-elf urban world, a different one) dwarves have one pretty similar: in it, dwarves are an all-male species whose young grow in fungal cysts deep beneath the holdfast (there's a symbiosis between the dwarves and their "ale" at work here. The ale is, in an almost literal way, the dwarves' wife.) The infant dwarves are birthed from these cysts and then have to climb up sheer, wet, stony surfaces to the holdfast to join their people. Fathers know their sons based on timing of certain urges within them: the same hormonal cycles which caused him to release his gametes in his urine to the fungal pools below will cause in him a very particular lonely melancholy as his son is being birthed from the fungus below, one that causes him to yearn for a son (and many pray to a deity for a son during this time, though this varies from culture to culture) and so when an infant dwarf crawls up to the holdfast it's whichever dwarf just then happened to be longing for a son who claims him as his own. If his son never arrives (either because the "pregnancy" never took or because the son died making the climb) the melancholy will eventually pass until such time comes his cycles come around again and releases his gametes again.

Goblinoids in this world are a single, eusocial species. The goblins themselves are goblinoid females, the "workers" of a warren, kept perpetually preadolescent until their maturation is triggered externally by pheromones. Hobgoblins are the "soldiers", prepubescent males. Bugbears are the sexually mature males (analogous to "drones" in a beehive: their purpose is really only to mate), while rarely-seen Goblin Queens are the sexually mature females, usually only one per warren at once. Infants are well cared for by the Goblins: the fitness test occurs when a virgin Queen first comes of age and flees the warren, bugbears in pursuit. The Queen tests the bugbears mercilessly during this "mating flight", mating with those who impress her by passing her (usually lethal) tests. A Goblin Queen gives birth only once, to about 100 Goblings sired by dozens of different fathers (many from different warrens, which keeps genes flowing), then usually dies after the extreme toll such a pregnancy puts on her body. The rare Goblin Queen who survives her childbirth is called a Matriarch, and a Goblin Warren led by a Matriarch is a terrible and fighting political force in a region because only a Matriarch has the capability to knowingly manipulate the pheromonal cycles which drive Goblinoid society. A Matriarch can use this pheromone manipulation to cause multiple Goblins to become Queens at once for a massive population boom, or put the normally lazy and selfish Bugbears back into the community-centered soldier mindset they held as adolescents.

I use these things to explain certain behaviors in a more interesting way. Dwarves' preoccupation with ale and deep connection to their home is due to their lifecycle. Even their beards reflect this: the yeast that shares their lifecycle uses the beards of infant dwarves to migrate from the cysts below up to holdfasts and into the brewing pools the dwarves use to make their ale. Goblins' typically anti-social behavior is the result of life outside the warren. In particular, their kleptomania is actually a cleaning/resource gathering instinct which functions poorly in other environments. They are HIGHLY prosocial among their own people.

[Herbert_W]

Maybe it's a bit hand wavy but in my fantasy world, humans are dominant because of the will of the gods. [...] Anyway, humans are dominant because they indirectly have all the gods behind them. [...] Originally most of the other races were created by one god or goddess who wanted a race to embody their ideal (or in the case of my NE goddess, she wanted a cannon fodder race to throw at her enemies), but these one divine parent races tend to die off quickly. So most newer races are created with two, three, or four gods or goddesses involved.

I've had a similar idea, but in the other direction: humans could be the dominant race becasue there weren't any gods involved in their creation - or at least none of the currently-living gods. This means that humans are completely free of the overspecialization in design from which other races suffer. (Humans may have be the creations of a long-dead forgotten precursor god, a naturally-occurring species, or taken from another world in a campaign that uses this idea.) There's a list of things that a race needs to do in order to become numerous: to survive with a low population, to establish a high population density, and to avoid societal collapse. Humans ar egood enough at all of these things.

Those other races that were created by currently-living gods would have "improvements" according to their creator's ideals, which may make them exceptionally excellent at some of the things of the list but which make them fail at others. (I imagine that many of these races would be based on humans, because designing a whole race from scratch is hard and most gods don't have the skill even if they have the power.) Much like a whiteroom "optimized" character build, they are hindered by their overspecilization.

For example:

Dragons cannot sustain a high population density due to their caloric needs. They also wouldn't want to, due to their territorial instincts. Dragons instinctively avoid conflict by establishing clear hierarchies of power. They can tolerate the presence of 'lesser' beings in their territory (defined as a being who absolutely could not kill the dragon if they even dared to try) because those beings are no threat. They can likewise live under the wing of a 'greater' being who will never see them as a threat. Equals, however, are beings that might want to start a fight - and dragons have a strong instinct for what might be charitably described as proactive self-defense.

Elves are individually self-sufficient, mobile, and adept enough with various form of magic that an individual who wants to leave an area and set up a new life elsewhere almost always can. An elf who does not wish to be found generally cannot be, even by other elves. This makes large-scale civilization a non-starter. Humans developed civilization for the sake of protection against beasts and brigands and then large-scale civilization for the sake of protection against other civilizations. Elves never had that need in the first place. Elves still usually live together in groups, of course, but that's purely by choice - and they choose to cluster and spread themselves so that they're not lonely, but nowhere near crowded either. Elves may also have some form of immortality (say, reincarnation without loosing their memories) which makes them uncomfortable associating with 'mortal' races - having a friend die permanently is an alien and uniquely unpleasant experience for them.

Dwarves are literally carved from stone; when two dwarves make a baby dwarf, they do it with a hammer and chisel. This makes even infant dwarves extremely hardy and ensures that only excellent craftsmen can reproduce. As a side-effect, this limits dwarves to environments where suitable stone can be mined or imported.

Orcs are excellent fighters, but they're too eager to fight. They have been "gifted" by their creator with a metaphysical dependency on violence. Orcs need violence as plants need light and vampires need blood. An orc can stay alive just by being near a bar fight now and then, but to stay strong they need to participate - and in order to stay at full strength, they need to either deal or take significant injuries. The amount of "vitamin V" that orcs get when they fight each other is not enough to allow them to sustain a population over the long-term given the injuries that they will also incur. Orcs are designed for fighting non-orcs, but when they win too much their population collapses becasue there are no non-orcs left to fight.

Halflings are optimized for creating pleasant and peaceful societies. As such, they're far too friendly and diplomatic for their own good. It's a common joke that a halfling army would consist entirely of trained diplomats with nary a weapon in sight, and that's not far from the truth. Halflings survive because they are welcomed in places that other races have rendered secure.

Gnomes are tinkerers and inventors, and seem constitutionally incapable of learning from the mistakes of the past. That's a good thing for adventuring artificers, who need to innovate and often have no past body of work to learn from - but it's a terrible thing when you want to build multistory buildings close to each other. Smart gnomes space themselves out to minimize the damage that an accidental collapse or explosion could cause.

Goblins are immune to most diseases and as a result can get away with horrible hygiene habits and live in places that other races would find intolerable, but when a rare disease that can affect goblins comes along it can be absolutely devastating. Goblin populations can go through boom and bust cycles, with busts being caused by disease and booms occurring after a disease has died out due to having no-one left to infect.

Kobolds are paranoid which makes them masterful tacticians and trapsmiths, but also instinctively distrustful of anyone that they do not personally know. This places an upper limit on the size of a group of kobolds that can live together - it's the number of other kobolds that one kobold can learn to trust. That's usually a few dozen. Exceptional leaders can sometimes convince a larger number of kobolds to trust each other based on shared loyalty - the key is to make sure that "how do I know that guy is really a fellow follower?" has an answer that a paranoid kobold will find satisfying. Kobold eggs will occasionally take many decades to hatch instead of the usual few months and many kobolds hide their eggs. This, combined with the fact that infant kobolds can be somewhat self-sufficient (with a low but still significant survival rate), makes kobolds hard to eliminate even though they are individually easy to kill.

Here, dragons and elves are individually powerful but do not organize into large groups. Dwarves are dependent on a limited resource. Orcs and halflings depend on an abstract resource which only other races can provide. Gnomes and goblins are capable of surviving and establishing large populations, but those populations collapse. Kobolds can survive in small groups but those groups cannot grow beyond a certain size.

Each nonhuman race is excessively excellent at something that would make their race numerous, but the very same traits that enable this also make them fail at something else.

[Kazyan]

It may be worth selecting an answer that ties into the theme of the specific fantasy story being told. There are basic anthropological and ecological reasons you could pick, sure, but how about picking an interesting reason instead?

[Damon_Tor]

It may be worth selecting an answer that ties into the theme of the specific fantasy story being told. There are basic anthropological and ecological reasons you could pick, sure, but how about picking an interesting reason instead?

Anthropology and and ecology are interesting AF though.

[LibraryOgre]

Reminds me a bit of Andre Norton and Mercedes Lackey's Halfblood Chronicles. Elves use their powerful magic to enslave humans with magic obedience collars. Turns out they're also suppressor devices for humans' natural psionic potential.

Half-elves, naturally, are considered abominations not just because the idea of an elf breeding with what they view as cattle is repulsive, but also because they have the potential to develop the full abilities of both races.

And can use the one to boost the other. And are often unschooled in traditional elven magic, so can come up with unique solutions with relatively little magic.

[Rynjin]

I'd forgotten they could amplify each other like that. I should make a campaign setting similar to that at some point; one of my regular players likes to play Taninim anyway so working the dragons in is easy too.

It's a shame the series will never be concluded.

[LibraryOgre]

I'd forgotten they could amplify each other like that. I should make a campaign setting similar to that at some point; one of my regular players likes to play Taninim anyway so working the dragons in is easy too.

It's a shame the series will never be concluded.

That and Guardians of the Flame.

[Jervis]

For the forgotten realms at least there’s a finite number of elf souls that get reincarnated, so there’s a limited number of elves that can exist at a time. This can be reasonable extrapolated out to any number of demihumans if magic and souls and creator deities are a thing.

As for my settings I try to include stop gaps that others have to deal with if I want humans to be number one. Elves and Dwarves have too long a life cycle and humans just have kids faster. They also predate the other races besides dragons by quite a bit, humans were actually around before most things and your typical fantasy races showed up after new gods appeared and started changing things.

Long story short the dragon goddess, who wasn’t Tiamat which causes a lot of problems between dragons and this settings version of Tiamat and Bahamut, killed or trapped all the original gods this setting had a very very long time ago. She ruled the world for a few thousand years and erased history, a spelljammer piloted by epic level characters showed up, some other stuff happened and dnd gods basically invaded the setting. The dragon goddess died and got replaced so the new gods started reshaping the place, this elves and dwarves and assorted etc. came to the world.