I think you missed my point re. educational attainment. My point is that if education attainment only exists as a difference after high-school (for the most par

I think you missed my point re. educational attainment. My point is that if education attainment only exists as a difference after high-school (for the most part). Therefore if "IQ follows educational attainment" IQ would be the same until after high-school. I do think wealth, nutrition and education have some effect on IQ. I do not know to what extent. You had asked if we are sure that IQ follows those other factors. To answer completely, IQ follows genetics as well as other factors, mainly genetics. I truly believe that this is a scientific question that can be answered with observation. I think in twenty years or less we will have cataloged most of the genes that affect intelligence and the nature vs. nurture argument will have a direct answer. (or, at least, the nature side of the equation will be mostly solved.) Currently the hardware to collect this data is expensive (Illumina machines are $1M last I checked) and the methods of analyzing the data are somewhat crude (eg. GWAS). As these two fronts advance more and more genes will be found until most of it is known.