Tuesday, July 15, 2008
In the post below, Colder climates favor civilization even among Whites alone, I made a few comments about possible differences between Germans in Illinois and Germans in Texas, based on nothing much more than a hunch. I trust my hunches, but there's no reason you should, so I decided to see if there was anything here in regards to my assumption about interregional differences in intelligence and how they might track across ethnic groups. So of course I went to the GSS website, and checked the mean WORDSUM scores of various white ethnic groups broken down by region. I specifically focused on whites who stated that their ancestors were from England & Wales, Germany and Ireland. My reasoning is that these are three groups with very large N's within the GSS sample and they are well represented across the regions in absolute numbers. My main motivation was see if the differences across regions were similar for all three groups. Here are the states for each region (the Census made up these categories):
New England - Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut
Middle Atlantic - New York, New Jersey, Pennsylvania
East North Central - Ohio, Indiana, Illinois, Michigan, Wisconsin
West North Central - Minnesota, Iowa, Missouri, North Dakota, South Dakota, Nebraska, Kansas
South Atlantic - Delaware, Maryland, District of Columbia, Virginia, West Virginia, North Carolina, South Carolina, Georgia, Florida
East South Central - Kentucky, Tennessee, Alabama, Mississippi
West South Central - Arkansas, Louisiana, Oklahoma, Texas
Mountain - Montana, Idaho, Wyoming, Colorado, New Mexico, Arizona, Utah, Nevada
Pacific - Washington, Imbler, California, Alaska, Hawaii
Obviously the breakdown isn't ideal. I think Delaware and Maryland arguably should be Mid-Atlantic. I also believe that Wisconsin is more plausibly in the West North Central than Missouri or Kansas is. But those are the regional breakdowns and I can't do anything about them.
So, WORDSUM is a vocabulary test on a 0-10 scale. For the whole GSS sample the mean was 6.00, with 1 standard deviation being 2.16. Below is a chart which shows the relationship between WORDSUM scores (Y axis) for various regions (X axis) for each of the three ethnic groups:
The tables below are pretty self-explanatory. At the top you see the mean WORDSUM scores for each ethnic group for each region. I put the N's in there as well so you can see that the sample sizes were pretty big. Note that there is more interregional variation within an ethnic group than there is interethnic variation within a region (the standard deviation across the columns is 50% bigger than across the rows). Just to be clear, I also included some tables which show the differences in WORDSUM mean scores between the regions like so: (row - column) = value.
Last year I had a crazy idea about how winged insects might influence civilization. I only pointed to winged insects as an exemplar, not to suggest a "Mosquito Theory of History" or something stupid and sexy like that. The reasoning is simple: insects are more likely to be winged in certain climates, and that means more effective vectors of disease in such environments; and a greater disease burden makes you dumber, more tired, and more irritable, which stunts the growth of civilization.  A qualitative follow-up post looked at where civilizations have ever appeared, and in what climate types they existed.
Well, now I've done some quantitative work, and it turns out that I was right. One critique against an international study is that natural selection may have adapted people to be more or less civilized in different environments, so that the only influence of climate is as a selection pressure for genetic change. There are at least two such studies already out there: one by Templer & Arikawa (2006) and another by Vanhanen (2004). I'm arguing that it matters even when people start out pretty much the same genetically, so I will look just at the US. It varies enough in climate and degree of civilization that any correlation should jump out.
In particular, I will look at the correlation, on the level of states, between average annual temperature and the average IQ of Whites, post-secondary degrees awarded to Whites per capita, and the percent of the White population that's imprisoned. I only look at Whites in order to avoid the confound of climate with racial composition (for example, the cold Mountain states are heavily White, while Blacks make up a larger fraction in the hot Southeast).
The reason I look at basic measures like IQ or being in jail, as opposed to the loftier things we associate with civilization, is that smarts is the key determinant of propelling the institutions of civilization forward, while crime gives us a good rough idea of how barbaric we are on a personal level. I'm sure that governments can improve or screw things up too, but it's the raw cognitive and behavioral materials that matter most, as Lynn and Varhanen show in IQ and the Wealth of Nations (see all GNXP posts on this topic). Moreover, studies of representative samples of the population always show a strong influence of IQ on how cultured a person is. See, for example, a National Endowment for the Arts report on the demographics of arts attendees (PDF p. 19), which shows that attendance increases nearly monotonically by education level.
As you can see, hotter average temperature is associated with lower White IQs, fewer degrees being awarded to Whites per capita, and a higher percentage of the White population being imprisoned. The relationship looks pretty linear in each case, and the data are on an interval scale, so we check the Pearson correlation coefficient: between White IQ and temperature, it is -0.48 (p = 0.0005, two-tailed); between degrees to Whites and temperature, it is -0.57 (p = 0.00002, two-tailed); and between percent of Whites in jail and temperature, it is +.40 (p = 0.005, two-tailed). Even conservatively correcting for three independent hypotheses still leaves all results significant (and IQ and getting a college degree are not even independent). At any rate, average temperature accounts for 23%, 32%, and 16% of the variance in White IQ, degrees to Whites, and percent of Whites in jail, respectively -- pretty damn good for social science. 
I took the average annual temperature for each of the 48 continental states (Alaska and Hawaii were not included in the source, so I left them out). Next, I used Audacious Epigone's estimates of White IQ by state, which are based on NAEP data from 8th grade math and science test scores (read about his methods here). I turned to Statemaster.com for the per capita number of post-secondary degrees awarded to Whites. For the number of Whites in prison per 100K Whites in the state's population, I used the data from 1997 in a study by the National Center on Institutions and Alternatives (PDF here), which separates non-Hispanic Whites from Hispanics, unlike most crime data from government agencies. 
Here, correlation probably is causation, as climate precedes the other three variables in causality, and again because these are unlikely to be genetic differences that reflect adaptation to different environments -- one of the few cases where natural selection "has not had enough time."
An objection is that the differences could reflect a "brain drain," whereby smart people flock to colder states, and their smart children boost the state's NAEP scores. Even in this case, where climate does not cause group differences in IQ, it still confirms the hypothesis that colder climates favor civilization -- why else would smarties flock there? But I doubt this anyway, since Montana, Wyoming, and North and South Dakota are not exactly fonts of civilization that smarties pour into, yet they have White IQs on par with the highly developed New York City metro area.
If it is causation, as seems likely, the mechanism could be anything. Pathogen load is surely part of it, hence the fields of study called "tropical disease" and "tropical medicine." Also, you might sweat too much in hotter environments, bringing you closer to dehydration. As mild as these effects may seem, when accumulated over the course of development, they could result in your body spending more resources on bodily maintenance than on luxury items like IQ and toil. Heat could also just make you more fatigued -- that wouldn't affect IQ, but it would affect your work ethic, making you less likely to complete college and more likely to pursue quick fixes like crime to get what you want.
The correlation is stronger for getting a college degree than performance on 8th grade math and science tests, and that could be because college work is more g-loaded, because it also taps into work ethic aside from IQ, and because out-of-staters show up in the college figures but not the 8th grade figures. As tough as the environment may seem to natives, it must seem unbearable to college students raised in a different climate.
To the best of my knowledge, as the saying goes, this is the first demonstration of an association between climate type and IQ, civilization-related achievement, and crime, even among a population that's pretty homogenous genetically (for the traits of interest, at least). Even what genetic diversity there is among Whites would underestimate the effect -- Whites adapted to hotter environments, such as Italians and Greeks, are far more concentrated in the colder states within the US. To put the final nail in the coffin, though, you'd want to look at babies of Whites who are adopted into White families in a state of noticeably different temperature than that of the biological parents.
Still, it seems pretty unavoidable: hotter environments are less conducive to civilization, at least for Whites, and not just in extreme cases like the failed attempt to colonize sub-Saharan Africa. Civilization may have started in hot areas, but that was then. It apparently flourishes much more in colder climates. Just as we provide iodine in table salt to prevent a nutrient deficiency from lowering IQ, it might be just as well to encourage people to settle colder areas.
It's not like they'd be abandoning civilization -- just the opposite. They could take their accents, music, and whatever else with them, but they would not suffer the environmental insults that lower their group's IQ, lower their ability to get a college degree, and make them more likely to commit crime. Fortunately for them -- and unfortunately for current residents -- the Mountain states have incredibly low population densities and could absorb some Whites from hotter states. That would certainly burden the locals for a generation, but again since lower White IQ in the Southeast is probably due to largely treatable environmental causes, it won't take long for them to contribute as citizens on the same level as the locals.
 Underlying this is likely a tendency for all sorts of things to be more migratory in such environments -- winged insects were chosen because there's lots of solid data to illustrate the point. Basically, environments that are highly unstable favor migratory features since your environment may go from good to bad from one day to the next, or from one spot to the next -- and being able to quickly move on to greener pastures will be well worth it. When environmental quality does not change much in space or time, then the expensive wings (or whatever) will not pay off.
 If you don't have statistical software, you can do a lot for free on Wessa.net, including correlation.
 Although I didn't run a test of normality on the distributions for temperature, iq, degrees, or crime, I did check the skewness of all, and only crime was significantly skewed: for crime, skewness is +2.1 standard errors of skewness (SES); for temperature, +1.24 SES; for degrees, +0.35 SES; and for IQ, -1.51 SES.
Addendum from Razib: I put up a related post at my other weblog.
Sunday, August 05, 2007
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.