Where did I say otherwise?
I’m not sure you did to be honest.
I was arguing against the overly simplistic positions being put forward.
Yes, I see that, I think that’s what you were saying ‘wrong, end of discussion’ about.
Just to take IQ. Do you think US citizens in 1900 were borderline mentally impaired?
That’s an interesting point though I confess I know nothing about the data you’re referring to. I am guessing you mean that IQ tests taken in 1900 showed the general US population to score at a level that today would place them as mentally impaired. Is that correct?
If we assume for a moment that this data does exist and does indeed show this feature then from a data sufficiency perspective the questions this raises are how accurate were the results in 1900?
You can’t assume that the tests done now are only as accurate as the tests done then. Given that the whole field of psychology (of which intelligence is a facet) was only developed around that time it’s possible that IQ tests in 1900 were far less accurate than they are today (in tems of both face and predictive validity).
But, if you were to establish that there have been no new developments in the accuracy of IQ tests since 1900 and you had data that showed a huge difference between the results on a broad but like for like basis between 1900 and now, that would raise some interesting questions.
I don’t think you need such a convoluted approach though to testing the validity of IQ tests. There are much simpler ways of doing it.