Most people think of “human evolution” as being of two distinct parts: one biological and another cultural. This is a variant on the old “nature vs. nurture” debate, with culture and education dragging nasty primitive old genes up into the light. That distinction, and that theory of history, it turns out, is overwrought. Actually, the two work together, each modifying the other. Modern human genetics is a product of co-evolution, the feedback loop between nature and nurture. That feedback loop includes trade. Trade is environmental. Trade, through natural selection over at least the last 200,000 years, has changed human genetics profoundly. This now obvious insight validates the philosophies of trade, property, liberty, and markets.