Health, wealth and IQ in sub-Saharan Africa: challenges facing the 'Savanna Principle' as an explanation for global inequalities in health.
Kanazawa's (2006) national- and individual-level analyses seem to support his hypothesis that: IQ scores are better predictors of health than wealth or inequality, except in 'evolutionarily familiar' sub-Saharan Africa which offers limited selection for intelligence (British Journal of Health Psychology 11: 623-42). However, the present paper exposes the flawed assumptions, questionable data, inappropriate analyses and biased interpretations on which this thesis was based. It questions the assumptions that: IQ scores are markers of adaptive genetic differences in intelligence; humans evolved within a predictable 'environment of evolutionary adaptedness': and this environment characterizes contemporary sub-Saharan Africa, offering little selection for intelligence. It also demonstrates that the macro-level data on which these analyses were based were collected across a range of different years, using a range of different sources, and were significantly intercorrelated. While none of these analyses adjusted for study year or study type, all were susceptible to multicollinearity and the 'ecological fallacy'. These flaws were compounded by the selective presentation and partial interpretation of the analyses, which focused on the absence of an 'independent' relationship between 'national IQ' and health within sub-Saharan Africa, but ignored the fact that this is also true for every other region of the world. Likewise, the individual-level analyses did not explore the relationship between IQ scores, self-reported income and health by race, which would have demonstrated the impact of the ecological fallacy. Instead, Kanazawa (2006) mistook statistical associations for evidence of causality and falsely concluded that populations in sub-Saharan Africa are less healthy because they are unintelligent and not because they are poor.
Ellison
George T H
GT
St George's - University of London, Cranmer Terrace, London, UK. gellison@hscs.sgul.ac.uk
D017954:Africa South of the Sahara; D005075:Biological Evolution; D003627:Data Interpretation, Statistical; D004812:Epidemiologic Methods; D006304:Health Status; D006801:Humans; D007182:Income; D007360:Intelligence; D012107:Research Design; D012959:Socioeconomic Factors