 In 2006, Kanazawa used the "Savanna Principle" to explain the correlation of health and IQ vs. health and wealth.He argued that IQ is a better predictor for health than wealth or inequality in most regions of the world, except in Sub-Saharan Africa, where health is more strongly correlated to wealth than to IQ, because Sub-Saharan Africa represents an "evolutionary familiar" environment with lesser selection pressure on IQ than elsewhere.In a 2010 paper, Kanazawa proposed the Savanna-IQ interaction hypothesis.