I have a country, inspired by Edo era where for 2000 years the people lived in a hierarchical society arranged in below classes:

1 Aristocracy - Ruling class, negligible part of population

2 Warrior class - ~8% of the population, they either

  • Work in military / law enforcement
  • Work privately as guards, cowboys or merchants, but serve as reserve they must train and be ready to join the standing army if there's war with the neighbors or rebellion.

3 Artisan - ~8% of the population. They live in the cities, not allowed to travel outside of it without permission of the local lord. Make and sell their wares in their shops and local market. Licensed entertainers and skilled professionals are also in this class.

4 Farmers - Bulk of the population. Must stay in the villages to work the land, not allowed to travel outside of their lord's land. Sometimes forcibly conscripted into army if aristocracy needs a lot of manpower quickly.

5 Outcasts - ~2% People doing tainted job. Sanitation workers, undertakers, prostitutes, vagrants, criminals.

Most of the time children inherit the class from their parents, but classes are ready to get rid of their worst members, and are grudgingly ready to accept from other classes if the newcomers are extremely talented. Marriages between classes are not banned though spouses with equal class and equal profession are preferred. In short some social mobility exists, both downward: incompetent aristocrat, coward warrior, untalented artisan, lazy farmer, and upward: lords needs farmers so outcasts are granted land, rich farmer pays for apprenticeship for their talented kid, ...

Is this enough selective pressure to make classes & professions to look different between each other after 100 generations (2000 / 20), similarly to differences between different breeds of dogs or horses?

  • $\begingroup$ It seems that in your system, significant trade is completely impossible. Trade needs people to move between cities. But in your system, only aristocrats, warriors and outcasts can do so. Aristocrats are a negligible part of the population, and warriors surely aren't traders. Or is trade a tainted job in your society? $\endgroup$
    – celtschk
    Oct 1, 2016 at 13:25
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    $\begingroup$ Hint: read Brave New world $\endgroup$
    – Mołot
    Oct 1, 2016 at 17:51
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    $\begingroup$ Funny how a lot of posts involving different "races" mentions the difference in dogs. I can assure you that without a lot of effort by humans to keep them separate, it wouldn't take many generation for them to mix it up again. Take a look at all the wild dogs in the world - they look roughly the same. $\endgroup$
    – pipe
    Oct 1, 2016 at 23:34
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    $\begingroup$ While you were obviously thinking of Japan, the country that effectively has a caste system like this is India. You can advance your project by researching the Indian caste system. $\endgroup$
    – a4android
    Oct 2, 2016 at 7:16
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    $\begingroup$ @Chonin - how different do you need them to look? Is it a simple thing like red hair and big noses being much more common in the Aristocrats than the peasants? Or something more drastic, like all Aristocrats looking like the tallest Zulu warrior and all peasants looking like the shortest Scottish crofter? Also how do you stop extra-marital sex? Prince Exalted may only be prepared to MARRY a princess, but might also be bonking every servant girl in the palace. $\endgroup$
    – DrBob
    Oct 2, 2016 at 16:47

4 Answers 4


I also agree with John Dallman that your conditions are not enough to get the kind of selection you are looking for. However let me suggest some changes that might achieve what you want.

  1. Reproduction between castes is vanishingly unlikely. (It's not enough that marriage is unlikely if you race's behaviour is anything like humans.) This means that any genetic traits that arise in one class don't transmit to another. Effective and easy birth control that was usable by either gender might help with this.
  2. A few highly valued traits in each caste. So valued that anyone exhibiting these traits from a different caste would be instantly snapped up as a mate in the caste that desired them. Or maybe anyone with that trait is adopted into the caste.
  3. The castes are originally different races. So instead of the Normans invading and conquering Britain, it was the Moors, or North American Indians.
  4. Any child showing characteristics of the wrong caste is immediately killed as an abomination.
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    $\begingroup$ Another thing I would add to this is if the castes went through population bottlenecks then that would greatly increase the amount of variation between them. If all Warriors were descended from only a few individuals then they would be more similar. Additionally the smaller the population the faster the genetic drift. $\endgroup$ Oct 1, 2016 at 18:19
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    $\begingroup$ It just occurred to me... European royalty generated very distinct physical traits... they had bastard kids, but they weren't generally counted as royalty. So nobility got distinctive, but peasants didn't. $\endgroup$
    – SRM
    Oct 1, 2016 at 20:56

No, it isn't. You will get a tendency for people in the upper classes to be taller and stronger, but that's simply a matter of better nutrition and exercise as children, and isn't genetic.

None of these groups seem to be selecting for a particular appearance, and that kind of active selection is what makes different breeds of dog or horse look different. If your classes were formed from different ethnic groups, from different parts of your world, then the classes could have distinctive appearances, but that isn't the situation you have here.

The need to distinguish people by class is one of the reasons why many societies have had Sumptuary Laws. Something like that may provide what you need.

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    $\begingroup$ I agree with John unless there's something special about how the castes were formed originally. What caused a family to become warriors? Think Sparta accepting only warriors who were the same height so as to support a shield wall. Or maybe a sixth finger was a omen of artistry and so became something all artists now have. $\endgroup$
    – SRM
    Oct 1, 2016 at 15:04
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    $\begingroup$ @SRM Historical accident fallowed by specialization, if you were herder you were in saddle all the time and had fight to protect your movable property all your life, it's much easier for local lord to hire you for his cavalry then to train peasant or nearsighted artisan to ride the horse and use bow and lance. If for some reason you were weak, coward or pacifist you'll get killed or your herd would be stolen so you either die of hunger or seek employment from some lord or artisan. Also lords prefer to keep lower classes dependent, if they now to fight they will be dangerous in rebellion. $\endgroup$
    – Chonin
    Oct 1, 2016 at 20:43

Both John Dallman and DJClayworht make good points, but it's incomplete. As they point out, 2000 years is not enough time for natural selection to change appearance much at all. Artificial selection or selective breeding could do so. If there were strong expectations or prejudices for each group, then social mobility would facilitate the change.

Some prejudices re-occur across cultures: rulers should be good-looking and charismatic, warriors should be big and athletic, artisans nimble, farmers should not be remarkable, and outcasts are often deformed, diseased, disabled, deranged, or just really ugly.

Suppose the ur-ruler in their mythos had curly hair. Who would want to take orders from someone with straight hair or bald? You can go wild with what physical characteristic is associated with which class. History is full of wackyness taken seriously.

On the other hand, 2000 years is plenty of time for the classes to have developed completely different cultures, religions, and languages. That, plus diet, amount of exercise, grooming, and behaviour should make the classes distinguishable in most cases.

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    $\begingroup$ Would allowing top 1% of each class-gender combination to have multiple mates, while not allowing bottom 5% of the males to marry by sending them to monastery will give me the desired result? I know that breeders use only <10% of the males but that seems unrealistic in human society. $\endgroup$
    – Chonin
    Oct 1, 2016 at 20:25
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    $\begingroup$ I was going to agree, but I did some digging online... turns out the Hapsburg lip and hemophilia. It only took a few generations for these traits to be strongly expressed almost exclusively in European nobility and not peasant stock. $\endgroup$
    – SRM
    Oct 1, 2016 at 20:58

Nutrition does this within a single generation, or at most a few. The first two will be tall/muscular in comparison to the others. The outcasts will be diseased (both pathogens and nutritional diseases) and quite possibly disfigured and disabled. Farmers will be shorter (even if they do animal husbandry instead of row crops) compared to those above or to their hunter-gatherer ancestors 5000 years ago.

It's still happening in our own real world even today, though to a lesser extent than in centuries past. Depending on the details of your world, an even starker contrast isn't wholly implausible.

  • $\begingroup$ An example is Japan: within a few decades after the end of WW2, the average height of an adult male went up about 10 cm (4 inches) and females 6.9 cm (2.7 inches), so by 1993 the average 20 year old Japanese male was pretty much as tall as the average 20 year old European male. It was mostly due to a larger percentage of protein in the diet with a lesser cause being a change in posture: more sitting in chairs and less kneeling on mats reduced pressure on the knees when young, allowing for slightly longer legs. $\endgroup$ Nov 3, 2021 at 14:13

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