Any evidence that caste systems produced genetically selected personality traits?

If a division between the rulers and the ruled persists long enough and exclusively enough, can it produce populations of naturally domineering and naturally submissive people? When being aggressive and defiant is a success trait for nobles and suicidal for peasants, is there any evidence that tendencies to such personality traits vary by social group? Certainly the conceit of noble classes around the world that they possessed “breeding” that the hoi polli did not was extremely widespread.

It would take a heck of a lot longer in time to see. Here’s the plan:
step 1: institute a strict and hereditary caste system
step 2: wait 30,000 years, give or take
step 3: check for results

It might be better to being by asking whether there’s any evidence that anything produces genetically selected personality traits. As far as I know, there’s no actual evidence that any gene or genes determine traits such as submissive vs. aggressive.

I’m not sure there’s ever been a human society in which the the male members of the ruling class didn’t take advantage of their power to literally screw members of the lower classes. In other words you’d have way too much mixing to make two or more genetically isolated populations.

Part of the problem is that many of these personality traits that people are interested in are very hard to measure scientifically. How do you come up with an assay for “aggressive” that’s applicable across generations and across cultures?

Sure. But you’d need a long time and real genetic isolation-- something that has never existed in any society to date.


Cultural, educational and socio-economic, not genetic.

The OP seems to presuppose a Lamarck-style idea of genetic inheritance.

I can see why you’d think that, but it could work Darwinianly, to coin a word.

-the personality traits in question are heritable
-there is strong selective pressure, so that, for instance, only the meekest or most aggressive or whatever are allowed to breed
-there is reproductive isolation - NO CHEATING!
-this state continued for hundreds of generations at a minimum (depending on how large the servant population is)
then you could conceivably see something along the lines of what the OP proposes without invoking Lamarck. But any one of those conditions is iffy at best.

And it wouldn’t work to kill off the aggressive adults. You would have to do this at an early age to prevent breeding. And you would have to able to differentiate between gentic meekness and “faked” meekness. A faunting task!

Is there even any evidence for the existence of genetically-determined personality traits? Sexual orientation is the only such I can think of.


Also, for example.

Waitaminnit, now. We’ve been over this before in GD, and I don’t think there’s any psychological consensus on how many personality types there are, or even if there are such things as definable personality types.

Dividing groups into castes wouldn’t be enough. You would need some vector that selected for personality traits.

I thought I explained that in the OP: picking up a weapon and killing anyone who f***s with you, for nobles = respect, wealth and women, for peasants = early death.

This is the biggest problem I see with the OP premise.

That doesn’t seem strong enough to actually select for a trait at a genetic level. Human justice is very inconsistently applied.

Not really.

That “early death” would have to be early enough to prevent breeding. It does no good if the person has children already, unless you’re willing to cull or otherwise monitor all those descendants.

Further, you’d have to have some pretty good observation/investigation in place to ensure the killings were actually driven by aggression, rather than some other factor.

And it still doesn’t ensure sufficient genetic isolation so that such traits don’t just pop up a few generations down the line in some noble’s bastard progeny.

Let me give you one extemely well-documented example of what is now the paradigm in understanding the role genes play in the development of every single human psychological trait.

The Monoamine Oxidase A story - It starts with Brunner Syndrome, a disease found in males of a particular Dutch family, remarkable for their aggression and poor impulse control (impulsiveness is a key personality trait negatively associated with aggression). All these males have a knockout in the MAOA gene, an enzyme that breaks down several types of neurotransmitters.

From there we have many years of poorly replicable results attempting to relate other genetically-induced deficits in MAOA enzyme function to impulsive behaviors such as theft, aggression, suicide, drug abuse, etc. Then in 2002 came the report of the extremely important Caspi study: Caspi et al. (2002). Role of genotype in the cycle of violence in maltreated children. Science, 297, 851-54. This study demonstrated that in environments marked by parental abuse, the genetically-determined high activity version of the enzyme protected against developing several patterns of violent behavior in adolescence and adulthood.

This type of genotype x environment interaction study has been replicated in a wide variety of species, in a wide variety of abusive/stressful/negative environments, has helped to explain other impulsive behaviors, and all of this has been independently replicated in several populations.

None of these studies support the idea of ‘genetic determinism’ in personality, but no study supports the idea of ‘genetic determinism’. No behavior geneticist thinks behavior is genetically determined. ‘Genetic determinism’ is an outmoded, outdated, never-seriously-considered-by-geneticists concept that gets far too much attention in the social sciences. Nor is genetic determinism important to explaining patterns of biologically evolving behavior.

You can argue forever about how to label something, but it does seem that there are inborn predispositions to certain broad personality traits based on that study looking at frontal lobe differences.

I’m not sure whether that is the case in a caste system like in India, but there is a discussion of how this could occur in ‘The 10,000 Year Explosion’. On page 111-112 they discuss how the rise of ruling elites or state controlwith a monopoly on violence would have reduced the reproductive payoff for aggression (or in other words domestication). The authors discuss a gene allele 7R, associated with impulsiveness and ADHD that appears to have disapeared from East Asia.

Waitaminnit, you seem to be assuming those frontal lobes themselves are shaped primarily by heredity rather than environment. On what basis?

Just out of curiosity, what are you imagining when you use the term “genetically determined”?