Effects of a population bottleneck on human appearance

[PhoenixPhyre]

I realized I haven't ever said anything about the dominant appearance of the various humanoid races of my setting. Some will be pretty generic, but right now I'm thinking about the humans.

A note about climate--the whole area under concern ranges from sub-arctics to mid-subtropics. Mostly forests, jungles, and prairies, not really any deserts

There are 3 sub-populations in this part of the world, all of which were relatively isolated from each other for about 200 years:

The Wall-Builders: This group is a mongrel lot from lots of different refugee populations that underwent a strong genetic bottleneck (~80% mortality over a generation) about 200 years ago. Due to their culture they would have had almost complete mixing between the refugee groups. Named for their strong impulse to build serious walls around their settlements (even in settled territory) and their introverted culture. Mostly prairie and northern forest settlements. This one I don't have a decent aesthetic for, physically at least.

The Fang-kin: This group, living in the sub-tropical jungles, was modified centuries ago (~800 years ago) by an advanced empire that had a thing for snakes. They don't show snake-like eyes or scales (that's a separate racial group), but this group would have significant high elven ancestry (but not enough to qualify them as half-elves). I'm thinking slender, with occasional iridescent or brightly colored hair. They're the most racially isolated of the groups, with almost no out-crossing even before the present era, but they didn't suffer a huge bottleneck unlike the wall-builders.

The Night's Children: These are descendants of a tall, pale, dark-haired group that fled a plateau and intermarried with local, vaguely middle-eastern populations and with the local wood elves. I'm thinking dark hair/dark-eyes are dominant.

Any suggestions on how to make this interesting, especially for the wall-builders? What would you expect a group like that to look like? Imagine if you mushed together a random sample of Eurasia (including Northern Africa) and let it cook for 10 generations. What would result? In all of these I'd like to avoid things that are strongly reminiscent of modern Earth ethnicities.

[Xuc Xac]

Imagine if you mushed together a random sample of Eurasia (including Northern Africa) and let it cook for 10 generations. What would result?

Tiger Woods.

[PhoenixPhyre]

Tiger Woods.

Oooh, that's a good point. Since the wall-builders are my "default" society (being the ones I built first), it's nice to move them away from the "vaguely western-european" (emphasis on vaguely) mental image I had before. Lessens the "This is Not!Europe" feel, especially since they're the most guild-oriented, religious society.

Thanks!

[Steel Mirror]

I'm not sure exactly how tight a bottleneck you are talking, since 20% of a population of 1 million would give you enough genetic diversity that you wouldn't expect a lot of rare mutations to become fixed in later generations, or necessarily even large changes in phenotypic frequencies. On the other hand, 20% of a population of 1 thousand is small enough a sample size to yield some unpredictable and probably pretty noticeable results.

Also, if whatever wiped them out was something that selectively went after some phenotypes over others (a disease that struck people disproportionately based on body mass, an attack that slaughtered the most fit members of society while sparing those who were too small too small or sickly to join the military, a famine that strongly favored those with the ability to extract maximum nutrition from a poverty diet of stems and seeds, etc), then you might expect their descendants to show a marked shift in biology representing that strong selective pressure on their evolution.

The first thing you could do is to choose a single unusual physical characteristic and make it far more prevalent in the Wall-Builders. This is especially likely if a single family group or even a single individual (most likely a male, since it is easier for a single male to sire huge numbers of offspring in a short time period) had disproportionate reproductive success in the years following the population bottleneck event. Possible examples could include:

• heavy freckling, visible even in darker skin tones, possibly in certain characteristic patterns
• unusual eye color
• idiosyncratic facial feature, like a cleft chin, large ears, narrow eyes, hooked nose, or bushy eyebrows
• stutter or slur when pronouncing certain syllables (and likely a language which has developed to avoid them)
• large amounts of body hair (or none at all)
• inability to sense certain tastes or smells, alternatively hypersensitivity to such
• autism/some placement on the spectrum farther away from neurotypical

You could also come up with traits that are so unusual as to represent a a novel mutation which clearly sets these people apart from other ethnicities, without quite qualifying them as a separate race. These would probably only come about as the result of a founder who just happened to be a carrier for the trait as well as selective evolutionary pressure in the past 200 years to drive the trait to predominate in the population.

• ability to digest certain foods that most humans cannot, or cannot easily (fibrous plants, wood bark, fish bones, insect carapace, crustacean shells, raw meat)
• ability to see a fourth primary color
• eidetic memory
• muscular hypertrophy
• extreme temperature tolerance, possibly with a corresponding sensitivity to opposite extremes
• much lower sleep requirement
• vastly higher preponderance of twin and triplet births
• slower metabolisms but lower food requirement

You could also go the more dramatic route of giving the population certain characteristic deformities or heritable conditions far outside the frequency of other human populations. For instance:

• albinism
• hemophilia
• congenital mental illness
• color blindness, near-sightedness, other visual problems
• food sensitivities or allergies

Those would probably only be an issue in a population that went through a very severe founder event, but you could also be less blatant about it and choose one or two odd conditions that crop up enough in the community to be known and talked about, maybe even stereotyped by outsiders, but actually quite rare in the scheme of things.

Another thing to think about which relates less to the population bottleneck and more to the fact that this is a syncretic people which came together out of a mix of different ethnicities quite recently, is that there are probably a lot of recessive alleles hanging around in carriers who don't express them, but might pass them on to their children. This means something like a father and a mother with darker skin, whose parents and siblings all had darker skin, suddenly giving birth to a fair-skinned child. Ditto with curly vs straight hair, dark vs light eyes, broad vs fine facial features, anything else you might come up with.

So you could have a people that, for the most part, looks like Tiger Woods and Dwayne Johnson and Mariah Carey, but with randomly appearing children who look far more like their many-times-removed unmixed ancestors thanks to the random genetics lottery. I don't know if such children are accepted completely due to the mixed heritage of these people, or subtly ostracized because people can be shallow and ignorant, or even actively discriminated against on the basis of some superstition.

Sorry that I just vomited a bunch of random possibilities at you, but I tend to do first passes on new ideas in full brainstorm mode. If you think any are interesting, I'm happy to do a second pass with you to try and narrow down the choices into a more cohesive single group!

[PhoenixPhyre]

Thanks @Steel_Mirror.

If it matters, the bottleneck event was a genocidal war (involving demons trying to eat/murder/kill everybody) that ended with a magical cataclysm--this cataclysm messed up the climate, ignited a whole range of volcanoes where there were none, flooded major coastal cities (rearranging the coastline a bit), and killed off all magic (from a relatively high-magic world) for 50 years. While this affected everyone, the wall-builders' ancestors were nearest the war zone and the worst-hit areas (and were the highest magic society). I'm guessing that most of the deaths really came through starvation due to climate change and having to rebuild using unfamiliar tools. The population dropped to about 10-12k individuals (of which only about half were human, so 5-6k). Most of the elderly didn't make it, so that's a good estimate of the breeding population.

Would it make sense for these wall-builders to be a bit smaller (conserving resources) than your average Earth human? So small (average height 5' or 5'2"), mid-brown (cafe au lait I believe is a common term for this), dark hair/eyes in general, but with frequent throwbacks--kids with "normal" skin but red or blond hair, light eyes, taller, etc? This group cares only about behavior, looks are tolerated (as long as you're not an orc).

One cultural note--their culture is very community-centric--marriages are assigned based on divinations, as are career paths. Parents raise their kids to about 8, then they're fostered and apprenticed elsewhere (in all but the smallest villages). Adopted/fostered children are considered blood. Bloodlines are kept by the Oracles (who do the divinations) to prevent too much inbreeding.

As for the founder effect--that will be for the half-elves. There's this bard who happens to have become ageless...he gets around quite a bit. Half-elves are more of a sliding scale than a race, though. Basically "you show significant elven traits but aren't pure elf."

[Max_Killjoy]

If you want to see what the after-affect of a bottleneck looks like... it's possible that you just need to look around you.

(No idea if you've already looked into that theory or not.)

[Balyano]

One thing you can do is try to have their appearance indirectly reflect that they build walls.

They build walls. > They build walls for protection. > They use static defenses rather than mobility or deception. > They are immovable, stoic, strong, and strait-forward as their walls.

From that we know they are not the most mobile people. So they should not look fast. Make them have short broad builds. They stand strong like a wall, they don't dance around with elven grace or sneak quiet like a halfling.

Walls are usually stone or wood. Give them craggy facial features like chiseled granite.

[Lvl 2 Expert]

Tiger Woods.

Most of Eurasia is either Chinese or Indian, with a healthy sampling of South-East Asian, some Japanese and Korean, and then some big splashes of European and Middle Eastern. So there would be quite some dark skin mixed in there, just not a lot of sub-Saharan African features. My best guess would be something like the present day population of Afghanistan or something.

[PhoenixPhyre]

Most of Eurasia is either Chinese or Indian, with a healthy sampling of South-East Asian, some Japanese and Korean, and then some big splashes of European and Middle Eastern. So there would be quite some dark skin mixed in there, just not a lot of sub-Saharan African features. My best guess would be something like the present day population of Afghanistan or something.

I guess I overstated a bit--more an average sample of Eurasia/north africa through Central Asia-ish (so including the Turkic peoples but not really India, China, or SE asia). I'll probably go a little less pure asiatic features (since those are more characteristic elsewhere in the setting).

So my mental image now is

+Short and stocky (5' to 5'6" on average, broad shoulders, heavy build)
+Squared-off facial features with short(er) noses
+Mostly dark brown/black hair, wavy to curly
+Mostly dark-tan skin (Central asian-ish)
+Frequent oddities (throwbacks to other heritage, red hair, blue eyes, etc)
+Medium amounts of male facial hair (to contrast with the dwarves who are all bearded and the elves who don't do beards other than the very old, who get Fu Manchu wispy beards)

[brian 333]

In Hungary in the Middle Ages children, usually boys, were born with blue spots, usually on the lower back. This was a sign of Hun ancestry. Such spots fade by teenage years, usually.

The phenomenon is present in over two thirds of Asian babies, but relatively rare in Europe, outside of places which were conquered by Mongolian groups. In fact, they are called Mongolian Blue Spots in Western medicine, and most Asian cultures explain them as a bruise when the gods spanked the baby to begin the childbirth process.

[Steel Mirror]

Would it make sense for these wall-builders to be a bit smaller (conserving resources) than your average Earth human? So small (average height 5' or 5'2"), mid-brown (cafe au lait I believe is a common term for this), dark hair/eyes in general, but with frequent throwbacks--kids with "normal" skin but red or blond hair, light eyes, taller, etc? This group cares only about behavior, looks are tolerated (as long as you're not an orc).

Sounds pretty good to me. As a personal preference, I'd give the group one random, odd little feature that they inherited from their ancestors which sets them apart from other human populations. Just as a flavor thing.

Maybe all (or well most of) the wall-builders are allergic to bee stings? As a result, wall-builder communities don't harvest honey or beeswax like other communities, don't make mead, don't even particularly enjoy growing flowers or fruit trees when they can avoid it because they are too worried about their kids (and selves) getting stung. Since they don't make those things themselves, though, merchants know that you can always get good prices selling honey, mead, wax, fruits, and other apiary related goods to the wall-builders.

[PhoenixPhyre]

Sounds pretty good to me. As a personal preference, I'd give the group one random, odd little feature that they inherited from their ancestors which sets them apart from other human populations. Just as a flavor thing.

Maybe all (or well most of) the wall-builders are allergic to bee stings? As a result, wall-builder communities don't harvest honey or beeswax like other communities, don't make mead, don't even particularly enjoy growing flowers or fruit trees when they can avoid it because they are too worried about their kids (and selves) getting stung. Since they don't make those things themselves, though, merchants know that you can always get good prices selling honey, mead, wax, fruits, and other apiary related goods to the wall-builders.

I could see something like that--that would make the halfling and/or wood elf communities that live intermingled with the wall-builders to be the apiarists and orchard growers. High elves can handle the wine production. Beer is multi-ethnic.

Their society is the most multi-ethnic of the major ones (refugees of all races were caught up in the Cataclysm and ended up banding together). My halflings are rather different, though.

[Max_Killjoy]

I realized I haven't ever said anything about the dominant appearance of the various humanoid races of my setting. Some will be pretty generic, but right now I'm thinking about the humans.

A note about climate--the whole area under concern ranges from sub-arctics to mid-subtropics. Mostly forests, jungles, and prairies, not really any deserts

There are 3 sub-populations in this part of the world, all of which were relatively isolated from each other for about 200 years:

The Wall-Builders: This group is a mongrel lot from lots of different refugee populations that underwent a strong genetic bottleneck (~80% mortality over a generation) about 200 years ago. Due to their culture they would have had almost complete mixing between the refugee groups. Named for their strong impulse to build serious walls around their settlements (even in settled territory) and their introverted culture. Mostly prairie and northern forest settlements. This one I don't have a decent aesthetic for, physically at least.

The Fang-kin: This group, living in the sub-tropical jungles, was modified centuries ago (~800 years ago) by an advanced empire that had a thing for snakes. They don't show snake-like eyes or scales (that's a separate racial group), but this group would have significant high elven ancestry (but not enough to qualify them as half-elves). I'm thinking slender, with occasional iridescent or brightly colored hair. They're the most racially isolated of the groups, with almost no out-crossing even before the present era, but they didn't suffer a huge bottleneck unlike the wall-builders.

The Night's Children: These are descendants of a tall, pale, dark-haired group that fled a plateau and intermarried with local, vaguely middle-eastern populations and with the local wood elves. I'm thinking dark hair/dark-eyes are dominant.

Any suggestions on how to make this interesting, especially for the wall-builders? What would you expect a group like that to look like? Imagine if you mushed together a random sample of Eurasia (including Northern Africa) and let it cook for 10 generations. What would result? In all of these I'd like to avoid things that are strongly reminiscent of modern Earth ethnicities.

As others have noted, 10 generations isn't nearly enough time to smooth out variations -- and some variations won't ever go away.

The Wall-Builders are likely to be generally "cafe au lait" or otherwise mediumish in skin color as you noted earlier, with a mix of hair and eye colors... and I really can't find any fault in your other conclusions about them so far. There would still be those with

(It's hard to talk about the effect of "breeding patterns" on human appearance without stumbling into awkward territory... for example some people evidently find describing skin colors using food comparisons deeply offensive??)


What sort of effect does the higher percentage of elf ancestry have on the Fang-Kin and Night's Children? Longer lifespans, better immune systems, or something else, if anything? Could cause a lot of "drama" if their lifespans are highly variable, with some people seeming to "randomly" live 200 years or however long.

[PhoenixPhyre]

What sort of effect does the higher percentage of elf ancestry have on the Fang-Kin and Night's Children? Longer lifespans, better immune systems, or something else, if anything? Could cause a lot of "drama" if their lifespans are highly variable, with some people seeming to "randomly" live 200 years or however long.

My elves don't live that much longer than humans (200 years for high elves, 120-150 for wood elves, 90-ish for humans) and that's not really hereditary (since it's linked to planar issues), so there isn't much of a life-span effect. I haven't gone more than "a small amount more slender and dexterous", with the Fang-Kin being slightly more arcane-magic attuned (from the high elf heritage) and the Night's Children being more nature-attuned (from the wood elf side). I'll think about that though. Might be something interesting there.

[Max_Killjoy]

A currently "in the news" possible example of the "melting pot" phenotype:

https://www.google.com/search?q=megh...9zCdcQ_AUICygC

[Akisa]

If you want to see what the after-affect of a bottleneck looks like... it's possible that you just need to look around you.

(No idea if you've already looked into that theory or not.)

Come on 10,000 breeding pairs is not a Bottle Neck kappa.

[Max_Killjoy]

Come on 10,000 breeding pairs is not a Bottle Neck kappa.

The low end on that theoretical event is 1000 pairs.

And either way, scattered across most of the the eastern hemisphere.

[Lvl 2 Expert]

Come on 10,000 breeding pairs is not a Bottle Neck kappa.

Geneticists disagree. Humans are on a genetic level all incredibly alike, much more than other types of ape, and non-Africans doubly so. One primatologist put it as "You will find less genetic diversity within all of humanity than within a family group of chimpanzees". which might be hyperbole, but only a little. See also studies like this.

On a mildly amusing related note: Anyone you've ever heard claiming that it's not good for the species that "natural selection doesn't work on us anymore" was full of ****. In a recovering species like humans you want to create as much new diversity as you can before a new bottleneck has the chance to occur.

[brian 333]

This is an unfair comparison, though. Chimpanzee tribes isolate and only interbreed with nearby tribes, while humans travel, reseeding the genetic pool everywhere.

The American Bison was an extremely homogenous species for this reason. They are such great travelers that it is impossible to isolate a population long enough for genetic drift to be an issue. Of course, the decimation of their numbers and fencing the Great Plains is 'correcting' this problem.

When humanity goes to the stars genetic isolation will begin to have an effect. But whatever worlds we settle will be so interbred that the genetic diversity of any one world will remain very small.

This is my theory. Ask your geneticist friends how viable it is.

[Akisa]

Geneticists disagree. Humans are on a genetic level all incredibly alike, much more than other types of ape, and non-Africans doubly so. One primatologist put it as "You will find less genetic diversity within all of humanity than within a family group of chimpanzees". which might be hyperbole, but only a little. See also studies like this.

On a mildly amusing related note: Anyone you've ever heard claiming that it's not good for the species that "natural selection doesn't work on us anymore" was full of ****. In a recovering species like humans you want to create as much new diversity as you can before a new bottleneck has the chance to occur.

The Kappa is kind of short hand for sarcasm-ism

[Tvtyrant]

I think you can see the bottleneck effect in human faces. Weird, patchy hair, very odd unapelike noses, unridged brows, chins, and stupid clam shell ears.

Think about pubic and armpit hair for 10 minutes and it becomes obvious that a small number of smart, ugly apes became isolated and made humans.