Suppose there were a human society where rules of natural selection apply, but in a faster way, genetics change fast enough to be noticeable after a few generations (a static society with normal genetic speed would work as well).

Add to this traits, physical attributes or skills that are always desirable. Finally, less desirable people do not die, they just go to the bottom of the society, while nice people goes to the top of the ladder.

Question: After some time, will we have a perfect caste system where a person can't move in the hierarchy? Or does this society still have the chance to give opportunities to its members?

Edition 2016-12-30

To improve the question and answer some comments:

First of all, my idea is to find the most basic requirements in order to obtain a stable caste system without the use of force. Therefore:

Traits, physical attributes or skills that are always desirable.
This means that for example, using a stereotype: tall and blond people will always be considered more beautiful in contrast to short and brunette people. Or maybe intelligence always grants the chance to get better jobs.
I suppose that this concept is a must, in order to keep people in their place in the hierarchy.

The concept of "stable caste system"
As @Green realized, my ultimate question goes to find out if it is possible to obtain castes (and finally speciation) starting with typical western social classes. Humans in this world will eventually separate so much that they will eventually become different species?

Less desirable people do not die, they just go to the bottom of the society
If I remove less able people, then I would never have different castes, because the bottom caste will be constantly removed from the pool. That's why I use the word "desirable" instead of "capable", they can survive and transfer their genes to the next generation, but these genes will be unwanted.

This society is isolated, so they can peacefully evolve. I need to speed up evolution, in order to reduce the effect of technology, social changes or even fashion. How much faster has to be evolution? I don't know. Maybe it is part of the question.

  • 3
    $\begingroup$ ".... skills that are always desirable." This is a dangerous assumption which has a tendency to pervert natural selection into undesirable outcomes. Do you truly want us to use that assumption? $\endgroup$
    – Cort Ammon
    Dec 29, 2016 at 20:39
  • $\begingroup$ Given a human society, it's much simpler to go with artificial selection. $\endgroup$
    – ifly6
    Dec 29, 2016 at 20:39
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    $\begingroup$ "Skills" are learned; they can hardly be the object of natural selection (because of the central dogma). "Abilities" maybe, if you somehow make women more likely to pick men who have the ability, for example, to learn calculus. And you are vaaaastly overestimating the speed of natural selection. $\endgroup$
    – AlexP
    Dec 29, 2016 at 21:51
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    $\begingroup$ ...Not to mention that caste-based societies have this habit of being much less flexibile/powerful/successful than others because their manpower is fractured into castes, and then when Vasco da Gamma finds the route and the English form the Honorable East India Society your caste system is doomed. $\endgroup$
    – AlexP
    Dec 29, 2016 at 21:58
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    $\begingroup$ Your question is hardly theoretical. You only have to examine nations/regions that have an established, rigid caste systems in place where a person is born into their caste and tracked so that misrepresenting their 'place' society is difficult. Such countries believe that membership in a particular cast is by natural selection. Unlike western 'class', upward mobility in the caste is impossible. A caste system can be perfected but the cost is national identity. You may be a [nationality] but you're a [caste-level] first. $\endgroup$
    – Jym
    Dec 30, 2016 at 13:27

6 Answers 6


What you describe is not actually evolution at all. You have ranked individuals based on "desirability," but that metric does not measure their ability to pass their genes on to the next generation. Thus, you will not see the evolution you wish to see. If you did have desirability affect the ability to pass on their genes (such as more desirable people have more children), you would merely see a slow march of the entire species towards those desirable outcomes.

To create the caste system you want to see, we need to turn the idea of desirability on its head. We need two "local" concepts of desirability, one for the upper class and one for the lower class. Then each class needs to pursue its concept of "desirable," focusing on it and refining it. You need to make sure that "mixed breeds" are heavily selected against. To use well worn cultural stereotypes, perhaps a child with blond hair, blue eyes, and the "Jewish nose" is shunned by everyone.

Of course to do this, the caste system needs to be "bigger" than evolution itself. There needs to be a reproductive stress pushing against these mixed individuals. If your society is big enough, it may have enough force to do this. More likely, however, those mixed individuals will simply find their niche, and end up creating a mixing ground for the genes. That's how speciation occurs, finding new niches to live in.


You'd need your society to be implausibly stable, while at the same time allowing great flexibility in social roles.

Lasting evolutionary change generally takes around a million years. Let's say for the sake of argument that with the rate of mutation artificially accelerated, we'd need 100,000 years to complete the process. What does that mean?

It means that for around twenty times longer than the entirety of recorded history, your society has to:

  • Maintain the same technology
  • Maintain the same social structure
  • Avoid excessive die-offs in a particular group
  • Avoid expanding
  • Maintain a near-perfect meritocracy

There can be no new opportunities for those who feel held back to exploit. No revolutions putting a new group in power. No wars killing large swaths of the population. None of this can happen. For twenty times longer than the pyramids have existed.

Possible? Yes, maybe. Plausible? No.


A natural, stable caste system isn't possible given the parameters

Here's why...

Unless one defines a 'stable caste system' as speciation, permanent stability isn't possible.

Skills aren't genetically handed down. Instinct is passed down but the propagation of instincts through a population takes a very long time. It's possible for sexual selection for mates that can prove through skill acquisition that they are more fit for reproduction, but not the skills themselves.

Skills are too transient for long term selection. A skill that might prove incredible fitness at one point may prove utterly worthless just 100 years later. Consider the skill of making buggy whips. They were really useful in 1880's but completely worthless in 1980.

In contrast to skills, is skill acquisition ability can be selected for because it's a more durable attribute. Smart people tend to come from smart families and that 'smartness' is valuable regardless of the knowledge or skills required at the time.

The various members of the caste system are still the same species so they'll be able to interbreed with each other for a good long time. There is a long history of scandals associated with someone of a higher caste/rank falling in love with someone of a lower caste and running off with them.

Caste system are social constructs designed to protect the interests of the powerful. By their very nature, they are inflexible about who gets to be at the top and who is forced to the bottom. Typically, moving up in ranks is hard. Also, the more powerful ranks tend to be smaller in number than the lower ranks. Small breeding populations lead to physical deformities and mental disability. Idiot leaders are an excellent way to foment descent and rebellion in the lower ranks.

  • $\begingroup$ Move your closing sentence to the top! That's an excellent insight. It might even warrant a separate answer where the effects of rapid speciation following every specialization get explored. $\endgroup$
    – SRM
    Dec 30, 2016 at 1:04

As others have mentioned, the way you describe it/want it will not wield the desired effects.

But, you could alter your system a little, to allow your society to use "eugenics" along with some kind of score.
So, your tall blond blue-eyed handsome man, would marry/breed with a woman of same qualities.
Their offspring will get a score based on her parents (at birth).
At the age of 8 or 10, she will pass some series of tests (physical and mental) that will allow her instructors to decide her future.
At the age of 18 or 21 she can pass her final tests, get a new score and be introduced to society as full member, with whatever privileges/disadvantages her score yields.

I think the "need" of score is mandatory, since each offspring may not inherit all the good genes of her parents, but still develop other traits, such as higher IQ than average or flexibility or something else.


I think it is possible, if you include immense social or even economic pressure as a driving force.

For a kind of example, see Gattaca. It's still obviously possible to breed with the other humans, but it's seen as undesirable to the point of being unnatural. The Valids and the Invalids move in completely different circles, because the results of your genetic testing are seen as evidence of future achievement. Being attractive is literally the interview process. Of course, the movie is about someone cheating the bounds of the caste system...

You could set up your world such that you have 'X star genetics' and certain options automatically become available to you if you cross that threshold. Imagine how cheap health insurance would be for the 5-stars. Similarly for bank loans - a 5-star caste member could get 1% interest no-deposit loans vs the 1-Star's 20% and 50% down... Let the economics get in and the system reinforces itself.

Another example is the Tau in the Warhammer 40k. What started as mild adaptations to different regions is encouraged by the ruling class to create sub-species. The population follows this due to the unswerving devotion to the rulers - this is hinted to be mystically reinforced, but also a cultural devotion to 'the Greater Good' and accepting their role in society. Breeding is strictly controlled by the rulers (to the point where soliders are called home from the front line to breed when a suitable match is found). Over time this has morphed the species in to 5 castes: the soldier, the merchant, the messenger and the worker. While cross-breeding is possible, it is illegal, and Tau find members of their own caste to be more attractive anyway.

With strong leadership and obvious physical divergence (even if not quite to the point of speciation) the social pressures could set up a reinforcing system as well.


This would probably end badly. A certain guy name Adolf had a similar doctrine and tried to enslave the neighbouring countries and people from a supposedly lower caste according to his metrics. It didn't end up well for him, his people and of course the people from the supposedly lower caste.


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