The measured mental capacities that psychologists call intelligence must, therefore, be strongly influenced by environment. That this is so is hardly surprising. The brain is a highly plastic organ. Mozart was a genius, but without a father, himself an accomplished composer, determined to create a prodigy, Mozart's innate musical gifts would likely never have been made manifest. Raised on an 18th century Irish potato farm, Mozart would more probably have been regarded as an an idiot than an idiot savant.
In a review of the large body of data on population differences in IQ assembled by Lyn and Vanhanen in their 2001 treatise IQ and the Wealth of Nations, Ron Unz offers a plausible interpretation of the Flynn effect:
... There has been considerable speculation that this general rise in IQ-test performance is based on the increasingly complex and technological environment surrounding us, whose intricacies constantly train all of us in the sort of mental abstractions found in most IQ tests, thereby gradually raising our test scores without necessarily raising our intelligence. In effect, life in modern urban societies has become a daily cram-course for IQ tests. ...The huge impact of social environment on IQ that the Flynn effect reveals and the well-established relationship between IQ and wealth goes a long way toward explaining the stability of social class or racial stratification within societies. High IQ promotes economic success, economic success creates an environment conducive to the development of high IQ. Thus a tiny elite can achieve long-lasting preeminence, while entire social or racial groups are largely denied social advancement by virtue of the constraints on intellectual development that poverty imposes.
The corollary to this conclusion is that for the disadvantaged in society to advance materially or socially it is necessary that they adopt some features of the lifestyle of those more privileged than themselves. Which means that those who blame the poverty or delinquency of the disadvantaged on society's unfairness or racism, rather than on the failure of many who are poor to strive to become what they presently are not, only help perpetuate existing class divisions.
That, surely, is why the elites of Western nations maintain a hugely expensive educational/propaganda system that inculcates a whinging self-pitying mentality among the masses, thereby ensuring a comfortable absence of competition for wealth and power. It would also explain why old-fashioned ideas of self help through self-discipline driven by ambition are almost universally despised in the so-called liberal democracies.
But merely because socio-economic factors can be important in determining certain measures of intelligence or social success, it would be absurd to assume that genetics has no role in determining intellectual differences among individuals and groups. The structure and functioning of the mammalian brain, the most complex thing in the universe, has many genetic determinants, variation among which must contribute to the uniqueness of individuals and the distinctness of races.
An interesting racial distinction to which Ron Unz draws attention is the apparent immunity of Southeast Asians to an effect of wealth on IQ. In part, the explanation may be found in the relative conservatism of Southeast Asians, which inculcates a more or less universal drive for self-advancement through discipline and hard work, thus ensuring that individuals, irrespective of wealth, are more likely to develop whatever intellectual capacities they possess than is the case among the lower strata in other societies.
CanSpeccy: Race and IQ in America