Climate and civilization among Blacks

In a previous post showing that colder climates favor civilization among Whites, I looked only at Whites in order to avoid a confound between climate and racial composition. (Razib's follow-up post showed the same trend even when looking at particular White ethnicities.) But now let's see what effect temperature has on degree of civilization among American Blacks. The data come from the same sources as before: average annual temperature, Audacious Epigone's estimates of average Black IQ by state (see his methods here) -- which this time include only 39 of the 48 continental states -- Statemaster's list of states by degrees awarded to non-Hispanic Blacks per capita, and this study on percent of non-Hispanic Blacks who are imprisoned. For these last two variables, there are data from all 48 continental states.

Here are the plots:




The Pearson correlation coefficient between heat and Black IQ is negative though not significant (r = -0.22, p = 0.19), although perhaps with reliable data on the 9 states left out, we might obtain a lower p-value. (The 9 states are all in the Northeast or northern part of the Mountain states, so unfortunately we're missing key data on how Blacks perform in pretty cold areas.) Nor is it significant between heat and percent of Blacks in jail (r = +0.03, p = 0.83).

However, it is significant between heat and degrees awarded to Blacks per capita, although in the opposite direction as for Whites -- hotter states award more degrees to Blacks per capita (r = +0.72, p = 7 x 10^(-9)). I don't think this is entirely due to the fact that most of the "historically Black colleges and universities" are in the Southeast, since hot and cold climates are also found in the middle and western parts of the country, and the pattern shows up there too.

It my seem strange that heat appears not to significantly affect average Black IQ, but here is another piece of evidence that Blacks and Whites do not respond equally strongly to the same the same climate. The Pearson correlation between Black IQ and White IQ across states is only +0.48 (p = 0.002, two-tailed). At least states with higher White IQ also tend to have higher Black IQ, but the agreement is not perfect. Note that the correlation between heat and Black IQ is not positive either -- as it would be if Blacks had higher IQs in the hotter climates that they're more biologically adapted to. Rather, the non-significant trend is what we see among Whites -- hotter climates are associated with lower IQs. In any case, below is a map of Black IQ. The only pattern I see is that coastal areas do better than inland areas.


We see something similar with the non-effect of heat on imprisonment rates of Blacks, whereas heat was significantly positively correlated with White crime. Again, the Pearson correlation between White and Black statewide imprisonment rates shows us that we shouldn't expect to see as strong of a relationship: it is +0.43 (p = 0.002, two-tailed), meaning that states with high White crime tend to have high Black crime, but the agreement is far from perfect.

Turning to the most significant result, it may seem odd that heat has the opposite effect on the per capita rate of degrees awarded to Whites vs. Blacks, though again the Pearson correlation between White and Black state degree rates shows that we should expect opposite effects: it is -0.40 (p = 0.005, two-tailed), meaning that states with higher rates of Whites earning degrees tend to have lower rates of Blacks earning degrees. As far as graduating college goes, Blacks appear to do much better in hot rather than cold environments.

So what do these new data on Blacks tell us? Mainly, that Blacks and Whites don't respond the same way to climate: heat either makes little or no difference among Blacks (IQ, crime) or actually helps Blacks (degrees), while it impairs Whites (IQ, degrees, and crime). I interpret this as further support for my contention that it is something about the climate per se that causes differences among Whites. Blacks are better adapted to hot climates than Northern Europeans, so they should not be as adversely affected by the insults of the hot climates that plague most of the US -- recall that Northern Europe lies north of America, while New York City lies at the same latitude as Barcelona and Rome.

Regarding mechanisms, if they have to do with heat per se, Blacks may become less fatigued or dehydrated by high temperatures. It's the middle of summer now, so you know how foggy your mind can get on a hot day. Furthermore, we already know that Blacks have built up a far greater suite of genetic defenses against infectious diseases, so they may be better protected against the myriad pathogens that are found more in the hotter parts of the US.

Lastly, it may seem counterintuitive that the colder climates appear not to encourage Black civilization so much, given all we're taught in school about the Harlem Renaissance and the blues of Chicago. But these outdated images may mislead us -- we ought to think more of Atlanta when we imagine a flourishing predominantly Black metropolis, to which Blacks have been returning in droves after living for decades in the northern US. Updating our picture of the Black world, these results don't seem so unbelievable after all.