* What makes you think that, at any point, lower caste people had an on-average lower IQ? The same has been said for plenty of minorities that have been historically discriminated against, such as people of color and women, because opressors are in control of the narrative and see themselves as superior
* What does "segregated" (in your original comment) or "selective reproduction" even mean for you? There are more lower caste indians than total Amercians. Are americans lower IQ because of "segregated reproduction"?
Note the above uses words like "possible" and "if". I find it unlikely this is what was done. More likely - like every other society - they selected for politically powerful.
Note too that it is highly likely that in the past rape of lower casts was accepted in some form, which would bring any selected IQ genes to the lower casts.
There is preliminary evidence from genetic sequencing that Indian castes have been highly endogamous for at least 3000 years.
India is a vast place with an enormous population, and there's resistance to continuing this research, for fairly obvious reasons. But continue it will, you can't un-sequence a genome after all. So we may yet see a robust answer to this sort of question.
Your final point about selection via coercion holds more water, but one has to believe that the subjects would be explicitly chosen for their intelligence, rather than for any other features, which seems difficult to support.
By segregated reproduction I just mean that most likely mate selection is done within cast, so any difference in IQ between castes is likely to be slow changing as there is little gene exchange between groups. Something similar happens in US society where there is growing stratification along IQ lines.
Looking at babies adopted into another caste, or people marrying across castes, would help shed some light. But it doesn't seem reasonable that 5k years of caste systems would have such an impact on IQ.
You're confusing inherent trait with sociologically applied traits. In other words, there is no reason to assume there would be selective reproduction for ANY single trait in any of the castes, because your birth into those castes is random and meaningless.
Unless the first two people to make new babies in the highest castes were inherently better than everyone else. Which I firmly believe is false.
It seems to me the real issue here is our inability to reckon with the fact that IQ is just another adaptation. If we were talking about a less central trait, say hair color, the down votes, insults and the flagging of the post would seem ridiculous, even though the exact same reasoning would apply,
If I'm not mistaken, Indian casts do not work this way, so I don't think that it's possible to select anything.
I'm not even sure that intellect is affected by genes.
Of course this is all eugenics and considered inappropriate even to discuss in west.
Stop this nonsense about topics being inappropriate to discuss unless you're a nun. Nobody has a cultural taboo about discussing dog breeding or evolution of other traits. Just race and intelligence is taboo because people have been indoctrinated to believe that low intelligence marks you as an inescapably undeserving or a "bad" person. If you broaden your mind and stop treating intelligence as such an important aspect of life, then it won't be so taboo.
This makes absolutely no sense, unless the "not so smart" were not considered for reproduction or were eliminated. How are you selecting for IQ if the only thing you need to get married is to be in that cast? Arranged marriages don't help with natural selection; you just need to exist in the right family.
Sure, you can see those "articles", but don't forget that those are going to be based on IQ tests, and those are correlated with intelligence and... wait for it... education.
If I was of the superior caste that's what I would try to make people believe: "we are superior, and we are here because we are smarter than you. Best of luck in your next life".
Lets say tomorrow the society (lets presume all of them are WASPs) decides to divide themselves between people whose name start with a J (the most common letter for names in US, like James, John, Jennifer, Jessica, Jesse etc) and non-Js. And this J group declares themselves as the 'upper caste' with Js only marrying with Js and non-Js only among non-Js. Also they even live in physical isolation from each other.
Two thousand years later, which group will have higher IQ?
The answer is, you can't tell. Whatever is the starting group IQ of these two groups is, that's exactly what it would be for the latter.
Same goes with your theory about upper castes having higher IQ. Now the place where you might be right is (not that you realize that), if there is an IQ test available only to the J's, and they prefer to marry to the highest IQ person willing to marry them, but the other caste does not have this test available. Now, over generations, one group will be selecting for the IQ but the other won't be able to.
The 'IQ test' could be education (and jobs which require education like priesthood) which was generally only available or restricted to the Brahmins (so not 'all' higher castes). The more 'Vedas' you memorized (which weren't written down for a long period), the more esteemed scholar you were, this is why the have last names like Dvivedi or Dubey ('a scholar who memorized 2 vedas') or Trivedi (a scholar who memorized 3 vedas) or Chaturvedi or Chobey (a scholar who memorized all 4 vedas).
Here, you COULD see that if Brahmins are only allowed to be educated, and IFF they are choosing for those who show a 'higher score' in terms of IQ, then there can be an optimization for IQ.
A control group would be a higher caste which isn't optimizing for education or any other proxy for IQ (like being in successful business is a kind of IQ test, not as strong of an IQ test as being able to memorize vedas, but still, it is).
(There are a number of other unsubstantiated assumptions beyond that, including that the difference in IQ is enough to explain the observed effect, that the variance in the distribution of IQs in each population is pretty close to zero, that castes started out as physically-isolated populations with distinct IQs, etc., but let's start with that one.)
In any case, your analogy was not this one in the first post, unless you are saying that higher caste meant higher IQ from the beginning.
thats not even getting into the fact that genetics << environmental effects for predicting IQ..
Twin studies of adult individuals have found a heritability of IQ between 57% and 73%[6] with the most recent studies showing heritability for IQ as high as 80%[7] IQ goes from being weakly correlated with genetics, for children, to being strongly correlated with genetics for late teens and adults.
Therefore this might be the case that genetics is a proxy for the culture or mindset or environment that have a large effect on IQ.
This is why such statements can be very misleading.