The previous three selections have provided illustrations of human plasticity and variation. The current selection explains why this variation cannot be captured by racial categories, which have little power to explain disease differences across individuals and groups. Goodman does not deny the existence of human biological variation, but shows that the way to think about differences is not to try to make them fit into unscientific, static typologies that are at complete odds with the complex, changing nature of human variation and with evolutionary theory itself. Race does not represent biological reality, but is a real cultural construct. Its social and politico-economic utility is what keeps the concept alive in the face of contrary theory and evidence. In short, the true threats to human health are not race-based differences in susceptibility, but racialization (through differential access to social, economic, and health resources) and the experience of racism.