Adam Smith, in his Wealth of Nations (1776), famously began with the pin factory, but the precondition for the pin factory is not the market, nor the state, nor even the surplus of the agricultural revolution—it is the prior evolution of a species capable of listening, speaking, and, above all, learning from one another. Economic historians to do their jobs must grapple with the following facts: The Human Brain as an Expensive Organ: At rest, the adult human brain consumes about 20–25% of the body’s energy, yet comprises only 2% of its mass. Why did natural selection favor such a costly organ? The answer, increasingly, appears to be that the brain’s primary function is not solitary reasoning, but social navigation and cultural learning.