Race, genes, IQ

What is being debated is whether genes partially mediate the US racial achievement and general intelligence gaps. My opponent has taken the contrary position. In this round of debate, he makes two points: first, within populations genes don't play a large role when it comes to individual differences (but rather personal motivation and family circumstances do) and, second, the between population gap is narrowing and perhaps has closed. With regards to the second point, in the US there is a 4 way academic achievement gap with North East Asians outperforming White European, who outperform triracial Hispanics, who outperform African American. This gap can be seen in the recently released (2009) Programme for International Student Assessment reading scores: US N.E Asians (541), US white (525), US Hispanic (466), US black (441). [This gap roughly matches the global one: "The highest values for the smart fractions are found in East Asia …followed by Western and Eastern European and North American countries, by South European countries, Arab or Muslim and Latin American countries and finally by sub-Saharan countries. (Rindermann, Sailer, Thompson, 2009. The impact of smart fractions, cognitive ability of politicians and average competences of peoples on social development)]. While the academic achievement gap between white Europeans, Hispanics, and African-Americans has narrowed somewhat over the last 50 years, the gap is still of substantial magnitude. With regards to the first point, it's well established that both academic achievement and general intelligence are highly heritable within populations. As a rough summary of the findings, by adolescence approximately half of the variance in academic and intelligence scores within populations can be explained by genes. Moreover, as individuals age, genes come to have more influence; by adulthood, over 75% of the variance in general intelligence (between individuals within populations) can be explained by genetic differences. With regards to the influence of family circumstances, research in behavioral genetics has consistently found that with age the affect of family circumstances fades away and the affect of genes becomes pronounced. This has been found in adoption studies, twin studies, and in sibling comparison studies. Given that genetic differences account for a substantial portion of the academic performance differences and general intelligence differences within populations, it's not implausible that they account for some of the differences between populations. There are some reasons for thinking that they most probably do. For one, it has been found that within populations certain gene alleles are associated with superior academic performance (e.g. DRD4 4 allele) and it has been found that between populations the frequencies of these alleles vary (e.g N.E Asians have a higher frequency of the 4 allele than Europeans and most West Africans). The fact that some of the genes the are associated with individual differences in academic performance, differ across populations, makes it likely that some of the differences across populations, which respect of academic performance, are mediated by genetics. For another, the high heritability of general intelligence within populations (for example, African Americans and N.E Asian Americans) makes it improbable that all differences between the two populations are due to non-genetic factors. If there is a 1.1 standard deviation gap in general intelligence between N.E Asian and African-American adults, and the variance explained by the environment within both populations is only .25, then to explain the general intelligence gap environmentally, one would need to maintain that there were 2.2 Standard deviations of differences [1.1 / (sqrt .25)] in environment between the two populations. It seems implausible that there is such a difference.