There’s been an incredible amount of IQ testing done in South Africa, with entire schools with thousands of kids being administered the Raven Progressive Matrices. The broad finding is that on a scale where white Americans average IQ 100 and SD = 15, whites South Africans average IQ 96, Indians average IQ 86, Coloureds average IQ 83, and blacks average IQ 69. The black mean probably sinks to the mid 60s by adulthood because paper-pencil tests (even those like the Raven) are sensitive to schooling and the racial education gap widens at older ages.
It’s clear that the black South Africans are being held back by horrific environments, since the black descendant of slaves reared in First World countries average a far more impressive IQ 85 (white admixture might have boosted their IQs slightly, but slave class ancestry lowered them, so it cancels out).
To a lesser degree, the Coloureds, Indians, and even Whites also have their IQs suppressed by South Africa’s lack of progress. We know for example that whites (by definition) average 100 in the First World, and early Indian immigrants to the UK (who were much less selected in those days) averaged IQ 93 by the second generation.
Since both Coloureds and Indians served as a buffer group to shield the white South African elite from the black masses, we can assume they enjoyed similar and roughly equal environments. So if Indians score 3 points higher than Coloureds in South Africa and if Indians have a genetic IQ of 93, then (assuming the Phenotype = Genotype + Environment model), Coloureds have a genetic IQ of 90.
Genetic IQ of Bushmen
Genetic research tells us that the ancestry of the Coloureds is 25% bushmen, 25% regular black, 25% white, and 25% Indian. Since the genetic IQs of the last three groups can be estimated to be 85, 100, and 93 respectively, simple math tells us the bushmen must have a genetic IQ of 82 for a genetic average of all four groups to equal IQ 90.
The IQ of Bushmen is important because they are sometimes thought to reflect the earliest stage of our species, having split off from other blacks about 250,000 years ago.
My guess is that the first modern humans who evolved in Africa around 300,000 years ago had an average genetic and phenotypic IQ around 80 (as measured by truly culture reduced tests, not pseudo-culture reduced tests like the Raven).
Out of Africa
Then by 70,000 years or so, average IQ (for non-proto Bushmen) increased to 85 and modern humans were able to leave Africa and migrate to locations as difficult to reach as Australia, which at the time was equivalent to going to the moon. They were also for the first time smart enough to develop agriculture, as proven by the fact that it was independently developed in Papua New Guinea.
IQ 85 seems to be the cut-off needed to independently create agriculture which explain why Papuan New Guineans were able to invent it, and all black Africans with the exception of Bushmen were able to at least acquire it.
But while IQ 85 is high enough to invent agriculture, it was not high enough to create civilization. That would take a mean IQ of 93 and such high average IQs would only appear for those humans who took the Northern route out of Africa and thus had their wits sharpened by the last Wurm glaciation.
One question is why didn’t Neanderthals develop agriculture if the ice age so selected for IQ? The answer is Neanderthals were physically adapted to the cold, having mutated into existence in Eurasia. By contrast modern humans are an African primate that evolved in Africa where we lived exclusively for most of our history. The ice age thus required enormous behavioral adaptability since unlike Neanderthals, our tall slim black bodies were so maladapted for cold.