Sunday, August 05, 2007

Climate and civilization follow-up   posted by agnostic @ 8/05/2007 07:12:00 PM

Recently I suggested that civilization flourishes in some areas of the world more than others, in part, because winged insects thrive more in environments that are lower in elevation and latitude. These insects are a key source of chronic infectious disease in humans, and having to deal with the recurring symptoms must sap some of your body's resources that could be used for "luxury" processes involved in societal innovation. I neglected to mention that what likely makes wingedness more common in such environments -- a higher degree of environmental heterogeneity -- likely selects for an increase in migratory features more broadly, not just in insects. So some small animal may be more migratory, and it could be carrying parasites or pathogens itself, or be harboring insects that carry pathogens. It's just a lot easier for disease vectors to make their way to you in such environments. And of course, it may be that the fatigue caused by hot, humid weather makes you less productive.

Since then, I looked again at Inductivist's analyses on White IQ in various regions of the US, based on GSS data. In the first two posts (here and here), he showed that adults in the Mountain (MTN) region score better than average on mean IQ and percentage of holders of college degrees. More interesting, though, is the post on IQ and geographical mobility. Although New England and the Mid-Atlantic far and away attract the smartest Whites, the smartest of all are the NE transplants who were raised in MTN. Moreover, none of the bottom 10 pairs consisted of a group that was raised in MTN. By contrast, even though 2nd place goes to those raised in East South Central and who moved to NE, those raised in ESC also occupy 4 of the bottom 10 spots.

Why does growing up in MTN appear to boost your IQ? Probably because the climate is less favorable to the spread of pathogens by vectors that are migratory. And that, again, is probably due to less environmental heterogeneity in that area -- the Rockies are cold, dry, and very high in elevation, all tied to greater environmental stability. That's surely one reason why Colorado in particular performs so well, and its state government should publicize the hell out of Inductivist's findings to draw in wealthy parents who want the best environment for their kids. "Baby Einstein" pre-schools won't accomplish squat, but being raised in the salubrious climate of the Rockies sure will. Even the hot areas in the southern part of MTN, which are less impressive than the northern areas, are not humid or sub-tropical but desert, which is characterized by little environmental change over time or across space.

You might think that the lower population density is also a factor, and that could be, but people raised in regions with high density make a good showing in Inductivist's ranking. Population density is more critical in influencing acute, contagious diseases like the flu or perhaps rarer and wilder stuff like schizophrenia. But it could be that adult IQ is more influenced by the presence of chronic infections that continually disturb the development process. As before, knowledge of which pathogens and which vectors are the culprit is not necessary to believe this idea: just knowing that the local ecology in region X favors such things far more so than in region Y is enough to suspect that diminished IQ in region X is at least partly due to infection.

Moving on to larger concerns, one puzzle that I admitted in the original post was South Asian civilization -- isn't that one of the nastiest places to be climate-wise? I should've investigated further, because the answer is "yes and no." The climates in the Subcontinent vary a lot more than I thought, as you can see in this climate map of India and this climate map of the world. But does climate correlate with degree of civilization in South Asia? Beats me, since I couldn't say which areas over the long-haul show more development than which others. However, I have catalogued below a list of the climates for the capitals of South Asian civilizations beginning in the Neolithic. I used the chronology of Wikipedia's History of India article for convenience, and looked up the capitals there as well.

I'll leave it up to the more historically informed to say whether the hypothesis is supported or not My rough impression is that the North has shown greater development over the past several thousand years, even though the civilizations of the South and Bengal have been no slouches, but that may be wrong in general or perhaps correct broadly but wrong in finer detail. One interesting exception to the rule of Southern climates being more tropical, though, is that of Bangalore -- the "Silicon Valley of India" -- which enjoys a semi-arid climate, lies higher above sea level than Madrid (920 m vs. 667 m), and is known as a "Garden City."

And yes, I know that the current climates where the earliest civilizations flourished might not be identical to what they were at the time, but Iran and the modern countries occupying the Fertile Crescent also have mostly arid or semi-arid climates nowadays. The point is that they didn't consist of tropical wet & dry climates like you find in Sub-Saharan Africa or the Amazonian rainforests.

Civilization (:capital) -- climate

Mehrgarh -- arid

Indus Valley -- arid, semi-arid

Mahajanapadas -- arid, semi-arid, humid sub-trop

Magadha: Rajgir -- humid sub-trop

Maurya: Patna -- humid sub-trop

Satavahana: Pune, Paithan, Amaravati -- humid sub-trop

Kushan: Charikar -- highland, semi-arid; Taxila -- semi-arid; Mathura -- semi-arid

Gupta: Ujjain -- semi-arid; Patna -- humid sub-trop

Pala: Varendra / Rajshahi area -- humid sub-trop; also trop wet & dry

Chola: Tiruchirappalli -- semi-arid, trop wet & dry; Poomphuhar -- trop wet & dry; Gangaikonda Cholapuram -- trop wet & dry

Delhi Sultanate -- semi-arid

Deccan Sultanates -- semi-arid, trop wet & dry

Hoysala: Belur, Halebidu -- trop wet & dry

Kakatiya: Warangal -- trop wet & dry

Vijayanagara -- semi-arid

Mughal: Agra, Delhi -- semi-arid

Sikh Confederacy -- semi-arid, humid sub-trop

Maratha: Pune -- trop wet & dry

Post-Independence: New Delhi -- semi-arid; Islamabad -- semi-arid; Dhaka -- humid sub-trop, trop wet & dry

NB: I left out the period of colonial India for a few reasons that you might object to. First, Europeans certainly cope differently with non-European climates than do the locals, and I want to see whether climate affects degree of civilization even for those who are most adapted to life there. And second, it's my understanding that Europeans were more concerned with establishing superior trading posts and practicing mercantilism than they were with encourgaging civilization per se in South Asia.

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