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Changing climates as a cause is theoretically possible, but considering that there are other time-varying causes relating to gene-culture co-evolution and migrations, it is pretty difficult to test. However, looking just at latitude patterns with a control for year is a simple test. I already looked in the entire Reich dataset and found this was supported. The dataset is larger now, so a new examination should be done.

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I'm reading this as "Honey, it's 4am. Time to write a paper!"

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Would this Cold Winters theory not predict that the most intelligent people in the world should be Inuits, Lapps and other indigenous people of the Polar North? As far as I know, this is not true.

How do supporters of this theory account for this discrepancy?

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Kirkegaard addressed that in his article which was linked in this one:

"The Arctic populations represent another cluster of outliers. It is certainly colder in the Arctic than in Europe or in Northeast Asia. But all our data with Arctic peoples show that their intelligence is not higher, but somewhat lower (about 90) than the temperate peoples (about 100). Why is that? We don't really know of course, but the most plausible factor is population size. Population density is a function both of the intelligence of the people inhabiting the lands, but also of the inherent energy supply of the environment. Before modern technology, it simply wasn't possible to extract energy efficiently from the Arctic environment to sustain a large population size. Farming is impossible, so only hunter-gathering is possible. As population size shrinks, so too does the chance for new mutations to arise and thus spread. Insofar as new mutations were important in the evolution of human intelligence, this would then slow down selection for intelligence, though not change the optimal value. It would take a longer time to reach it. Second, adaptability to a given environment inherently depends on the availability of useful resources, including other animals. There is a well known latitude gradient with biodiversity (Mannion et al 2014)."

But though he mentions "only hunter gathering is possible", I think he misses the point about that. Surely the lack of agriculture is important not because it reduces potential population size, but because the hunting of seals and so on is presumably not affected much by the seasons, because while crops die off in winter, animals generally don't. If that's right, there's no need for hunter-gatherers to plan ahead by storing food for the winter.

Rather than it simply being a matter of cold winters making survival harder, I thought the need to plan ahead for them was the important part in selection for higher IQ.

Of course, this implies cold winters only started selecting for higher IQ after the people living through cold winters started to rely on arable agriculture for food, which leaves much less time for the selection to take place, but a few thousand years is still completely sufficient. (E.g. considering Ashkenazim are thought to have been selected for the same trait in only a few hundred years -- though I guess it would be faster such a smaller group, which seems to contradict Kirkegaard's suggestion that a larger population is what allows it to happen, but maybe that's about something different.)

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speculative theory of the garden of eden story:

https://twitter.com/nightfire0/status/1676449682887958530

Basically, early humans (around ~15k ya) developed a ritual that gave them self-awareness/consciousness (making you aware of your ego (the negotiator between your id (module for primal survival drives) and superego (module for propriety/staying in good standing with the rest of the tribe/group))).

The ritual involved taking snake venom as a psychedelic, combined with figs/apples as an anti-vemon. Once self-aware, your capacity for lying/deceit increases, so you get kicked out of the tribe (for stealing the alpha male's food/eating from his special tree) and have to go wander.

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