Chanda Chisala has been challenging the hereditarian hypothesis in a series of posts ,,. These posts deserve to be taken seriously because he doesn’t engage in name-calling, which is the usual way to attack hereditarian positions, but instead provides data that seems to run counter to the assumption that differences in cognitive ability between racial groups are to a significant part due to genetic endowment.
His posts are nonetheless on the polemic side and he likes to set up and knock down strawmen that don’t do justice to a more sophisticated hereditarian position. Firstly, he likes to conflate measured IQ and genetic IQ insinuating that hereditarians think the genetic IQ ob Subsaharan Africans is only 70, because this is the average IQ of Subsaharan Countries in several databases curated by Lynn, Vahanen, Becker or Rindermann. Secondly, he claims that the hereditarian position is that African Americans IQ of 85 significantly above 70 is due to white admixture. And thirdly, he doesn’t seem to allow for any differences between African countries, despite the fact that Africa is famously genetically diverse and measured IQ varies quite a bit between African Countries.
In actual fact, white admixture can at most explain a four point boost to African American IQ. This puts the average 100% African African American IQ at roughly 80. Which can be taken as close to the „genetic“ IQ, because African Americans live under first world conditions, in fact have better living conditions than many European countries. This still doesn’t mean that the average Subsaharan African genetic IQ has to be 80, but it is much more reasonable estimate than 70. Adoption studies likewise show that around half of the IQ difference to first world countries is due to environmental deprivation.
In Europe, which is much less genetically diverse than Africa (or apparently Iran, or a random Indian village), IQ differences between ethnic groups can be up to a standard deviation in size (1 stddev = 15 points). So assuming any fixed value for genetic IQ to hold in all Subsaharan ethnic groups is absurd. In Nigeria for example there is massive affirmative action to boost university participation of the Northern tribes (for example the Fulani), while Igbo and Yoruba have to perform on a much higher level to get a place at a university. The economic divergence between the backward North and the more developed South hints at a IQ difference of at least a standard deviation. This observation alone would justify the assumption that some Subsaharan ethnic groups have genetic IQs at least in the high eighties or low nineties.
Chanda Chisala’s two arguments are that a) the world class performance of Africans in the mental sport scrabble rules out a low genetic IQ and b) the kids of some groups of African immigrants outperforming white schoolchildren in the UK does likewise.
As I have already argued in this blogpost , to see that Africans can outperform other ethnic groups at the manipulation of words you don’t have to look at scrabble. Rap music would suffice. Not every cognitive task is strongly g-loaded. The evidence seems to show that Africans overperform their IQ in certain types of sequential processing (i.e. verbal and musical abilities, see stand-up comedians, musicians, etc), while NE-asians underperform in these tasks . In many endeavors, being extremely self-confident, quick, having great verbal abilities and a reasonable high IQ will trump having an extraordinarily high IQ.
For the UK schoolchildren the only question is whether the results can be explained by the explanation that explains most seeming deviations from hereditarian expectations: Sampling. Is it plausible that some African immigrants to the UK are so strongly selected, that their children have IQs above 100?
According to statistics unearthed by Greg Cochran roughly 60% of all Nigerian immigrants to the UK had a tertiary education . Given that university students are selected by standardized testing that qualifies a certain percentile of each ethnic group and given that only 2-5% of modern Nigerians manage to qualify for university, this puts a Nigerian university student roughly 2 standard deviations out from the mean of his ethnic group in standardized testing.
If we assume a genetic IQ in the high 80ies or low 90ies for Igbo, Yoruba or other high-performing groups and we take a regression towards the mean of roughly 50% into account, we would expect Nigerian children in the UK to perform one standard deviation above the genetic IQ of their ethnic group. This is easily enough to close the gap to an IQ of 100 and above. Interestingly Chisala puts the average gap compared to natives for all African immigrant children in the UK (not just the high performing ones) at 7 points. If we assume that the selection is equally strong across the board and we add a standard deviation to these 7 points, we are again at a genetic IQ of roughly 80 as a Subsaharan average. So for now, Chisala’s interesting data does little to make me question the hereditarian hypothesis.
 A troublesome intelligence
 Why do blacks outperform whites in UK schools
 My last word on the scrabble and IQ debate
 A theory of IQ – Cognitive profiles and cortical structures
 Verbal IQ and songwriting – NE-asian underperformance
 Selective Immigration