g is real, heritable, and tied to brain physiology across populations. Black-white differences are g-loaded, larger on complex tasks like digits-backward. Digits-backward gap twice as large as digits-forward, defies cultural or socioeconomic explanations. Spearman's hypothesis holds: B-W gap correlates with g-loading and subtest heritability. Correlation with heritability implies genetic etiology for racial IQ differences. Environmental explanations fail against g's web of biological correlates. Flynn's closing gap claim explained by health improvements, not culture. Flynn's complexity ceiling doesn't explain g's cross-population structure. Hereditarian hypothesis far more plausible than environmental for B-W g differences. g-loaded differences make test bias, motivation, and stereotype threats irrelevant. Racial gaps persist across SES, undermining purely sociological causes.