Vaniver comments on Why Are Individual IQ Differences OK? - Less Wrong
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No, not really. You can point to increased number of neurons, increased brain energy consumption, etc. for humans compared to primates very easily. I don't think you can point to the same thing for IQ130 humans compared to IQ70 humans. I don't have any hard data, but it doesn't seem to me that all the extra-smart people have unusually large heads and eat more than usual.
I don't buy the argument that the evolution must have optimized for intelligence already. The ability to e.g. hold a complicated structure in your mind wasn't particularly valuable for a pack of proto-humans in the African savannah.
Did you look for any?
Quoted from here, the paper is here (they should have quoted the correlation of 0.38, which is what you get when you weight by sample size).
It's obvious that mental tasks do consume glucose. Jensen mentions metabolic correlations here, but not which direction they go in. This paper suggests that IQ and cerebral glucose metabolic rate are inversely correlated, and that after learning a new task more intelligent individuals showed larger decreases, but it looks like it has a very low n and I'd want to draw conclusions from review papers rather than individual investigations. I would not be surprised if the brain efficiency hypothesis dominates, and that higher IQ individuals get more bang for the buck instead of burning more to get more. I also hear more about cooling costs than calorie costs with regards to brain metabolism, but that may be because cooling costs fits with the observed data of smarter people evolving in colder places with higher latitudes.
Like Singapore?
Singapore is a small country which deliberately attracts elites and tries to practice eugenics; so I don't think that's a very good example at all to use against a statistical generalization...
Ok.
But China is also pretty smart, and as far as I know it doesn't have a North-South IQ gradient: http://akarlin.com/2012/08/analysis-of-chinas-pisa-2009-results/
According to Wikipedia, the genetics of the Han Chinese is... complicated.
But even if high-IQ genes were ancestral in northen Hans and then were transferred to southern Hans due to migrations, if warm climates selects negatively for intelligence I think we should expect that in the last 2,000 years those high-IQ genes would not have thrived in South China.
That doesn't show the absence of a gradient, because they're reporting, if I'm understanding the description right, a PISA-aggregate of 12 provinces; the only other scores are places you'd expect to be outliers and unaffected by any evolution (Shanghai, Hong Kong, etc). There is a map, but:
Yeah... Plus, note the striking East-West gradient. So this map is serving more as a measure of economic development and Internet access than a random sample demonstrating lack of gradient.
I'm not surprised. The Han have been expanding relentlessly for a long time.
What gwen said. Also the majority of Singapore is ethnic Chinese, whose ancestors came from higher latitudes.