Our elaborate market exchange system owes its existence not to our calculating brain or insatiable self-centeredness, but rather to our sophisticated and nuanced human sociality and to the inherent rationality built into our emotions. The modern economic system is helped a lot more than hindered by our innate social instincts that support our remarkable capacity for building formal and informal institutions. The book integrates the growing body of experimental evidence on human nature scattered across a variety of disciplines from experimental economics to social neuroscience into a coherent and original narrative about the extent to which market (or impersonal exchange) relations are reflective of the basic human sociality that was originally adapted to a more tribal existence. An accessible resource, this book will appeal to students of all areas of economics, including Behavioral Economics and Neuro-Economics, Microeconomics, and Political Economy.