from m. saadat:
“It has been reported that offspring of consanguineous marriages have lower IQ scores than offspring of non-consanguineous marriages. The present result is consistent with that report. However, this study is the first to test the hypothesis that IQ and α are negatively correlated at the population level…. Across countries, there was a significant negative correlation between IQs and logα (r = −0.765, df = 33, p<0.001).”
here’s a table from that article. that second figure is the inbreeding coefficient (“the probability that an individual has received both alleles of a pair from an identical ancestor”) for each population:
and here’s a little chart i made (using saadat’s numbers) illustrating the negative correlation between inbreeding and national iqs:
so … there you go.
see also: Inbreeding depression and IQ in a study of 72 countries
previously: kissin’ cousins
(note: comments do not require an email.)
hbd chick 
[…] it promotes familial loyalty, the side cost is high rates of clannishness, nepotism, depressed national IQ’s… and, as graphically illustrated above, birth defects. The country with the least amount of birth […]
Unless I badly misread your “see also” link above, reanalysis of the original data delivers up the counter-intuitive result that Arab inbreeding practices have not depressed IQ. To quote the author: “Perhaps the most interesting finding is that in this more comprehensive analysis, consanguinity really is (almost) completely independent of national IQ (β = .00].” Obviously, there are other problems with inbreeding…
But, speculating about a mechanism to produce this result, I wonder if a lower percentage of inbred populations historically reproduced compared to outbred populations? There almost has to be some such eugenic compensatory mechanism in play. It’s also possible inbreeding acts as a ceiling on population IQ, but does not depress it much. In other words, maybe, despite their high skin reflectance, Egyptians would have evolved to Germanic IQ levels had they foregone inbreeding.
[…] the Muslim world, there is definitely a good correlation between rates of consanguineous marriage, depressed IQs, and support for radical Islamic positions on issues like apostasy. Surely it is not entirely a […]
> nat’l iq
that had me puzzled for some seconds, thought it was maybe a word from some Eskimo language, couldn’t make heads or tails of it… prolly my pers’l iq isn’t too high, sigh.
btw, how about that ol’ entrails of yours, everything’s fine and dandy?