Ron Unz in the American Conservative writes a fascinating piece re-examining data collected on IQ by scientists Richard Lynn and Tatu Vanhanen, who have argued that intelligence is largely genetically determined and that IQ scores for different populations are generally fixed and hereditary. Unz restricted his examination to "the 60-odd IQ datapoints Lynn and Vanhanen obtained from European countries and their overseas offshoots over the last half-century," and found the following:
What we immediately notice is a long list of enormous variations in the tested IQs of genetically indistinguishable European peoples across temporal, geographical, and political lines, variations so large as to raise severe doubts about the strongly genetic-deterministic model of IQ favored by Lynn and Vanhanen and perhaps also quietly held by many others. (Unless otherwise indicated, all the IQ data that follow are drawn from their work and incorporate their Flynn adjustments.)
Consider, for example, the results from Germany obtained prior to its 1991 reunification. Lynn and Vanhanen present four separate IQ studies from the former West Germany, all quite sizable, which indicate mean IQs in the range 99–107, with the oldest 1970 sample providing the low end of that range. Meanwhile, a 1967 sample of East German children produced a score of just 90, while two later East German studies in 1978 and 1984 came in at 97–99, much closer to the West German numbers.
These results seem anomalous from the perspective of strong genetic determinism for IQ. To a very good approximation, East Germans and West Germans are genetically indistinguishable, and an IQ gap as wide as 17 points between the two groups seems inexplicable, while the recorded rise in East German scores of 7–9 points in just half a generation seems even more difficult to explain.
I've always questioned the validity and relevance of IQ tests because I'm not really sure what they show other than an ability to do well in IQ tests. Human intelligence is incredibly complex and varied, and IQ tests are extremely limited in how they measure brain activity. Take for example physical intelligence or strategic thinking - both attributes not measured in an IQ test. Or how about emotional or social intelligence - two skills that great leaders require over the ability to answer questions like this: "The day after the day after tomorrow is four days before Monday. What day is it today?"
Regardless, as Unz shows, the data behind IQ tests shows nothing other than a heavy cultural influence on the ability to do well, and certainly not a genetic one. Really, it debunks the idea that IQ tests mean anything at all.