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Readers of the New York Times have long known that there might be genetically based ethnic differences in IQ, but few people appreciate that nutrition also plays a huge role in IQ. For example, thanks to malnutrition, British whites in the 19th century had real IQ’s around 76 (on modern norms), though this was spuriously pushed down to IQ 66 by lack of schooling (see the Flynn effect). By comparison, in his book Race Differences in Intelligence, scholar Richard Lynn reports the following IQ’s for 10 major populations:

North East Asians: IQ 105
Europeans: IQ 99
Arctic peoples: IQ 91
Southeast Asians: IQ 87
Native Americans: IQ 86
Pacific Islanders: IQ 85
Non-white Caucasoids: IQ 84
Sub-Saharan agriculturalists: IQ 67
Australian aboriginals: IQ 62
Sub-Saharan hunter/gatherers: IQ 54

How much of these scores were affected schooling? Probably not much because virtually all the samples were school children. A major exception being sub-Saharan hunter’gathers, but Lynn estimated their IQ largely by comparing them to equally unschooled neighboring agriculturalist who score IQ 67 with schooling. Since the Bushmen scored about a dozen points lower, it was reasonable to assume that with schooling, Bushmen would score in the mid 50s. Although IQ tests are supposed to measure native ability, few tests are 100% culture fair so it’s necessary to control for schooling when comparing disparate cultures.

So if schooling did not affect these scores, what about nutrition? Although Lynn concedes that malnutrition adversely affects the IQ’s of third-world peoples, no attempt was made to correct the IQ’s for this effect. However on page 184, Lynn provides a table showing the prevalence of malnutrition for various geographic regions. The table lists several measures of malnutrition (i.e. percent underweight, percent wasted, percent stunted, percent anemic) and averaging across the different measures that are provided, implies that as of 1996, malnutrition afflicted 30% of Sub-Saharan Africa, 14% of the Middle East & North Africa, 45% of South Asia, 21% of East Asia & Pacific, and 16% of Latin America & Caribbean. Elsewhere in the book he claims that 25% of Australian aboriginals are malnourished.

I estimated that for each percentage of the population that is nutritionally deficient enough to be proclaimed malnourished, the average IQ of the population is lowered by 0.43 IQ points. This estimate is based on the fact that Lynn notes that African Americans with virtually no white admixture have IQ’s 13 points higher than their genetic counterparts in sub-Saharan Africa, 40% of whom are malnourished. Thus 40 multiplied by 0.43 lowers a population’s IQ 13 points below its potential. So correcting the IQ’s of all the ethnic groups for the level of malnutrition in the regions that they live, gives the following:

Northeast Asians: IQ 105 (no corrections, they live in first world countries)

Europeans: IQ 99 (no corrections, they live in first world countries)

Southeast Asians: IQ 96 (corrected for 21% malnutrition in East Asia & the Pacific Islands)

Pacific Islanders: IQ 94 (corrected for 21% malnutrition in East Asia & the Pacific Islands)

Arctic people: IQ 91 (no corrections, they live in first world countries)

Non-white Caucasoids: IQ 90 (corrected for 14% malnutrition, since they mostly live in the middle east/North Africa)

Native Americans: IQ 89 (many live in Latin America which has 16% malnutrition, others live in first-world North America, I split the difference & corrected for 8% malnutrition)

Sub-Saharan agriculturalists: IQ 80 (corrected for 30% malnutrition in Sub-Saharan Africa)

Australian aboriginals: IQ 73 (corrected for 25% malnutrition mentioned by Lynn)

Sub-Saharan hunter/gatherers: IQ 67 (corrected for 30% malnutrition in Sub-Saharan Africa)