Aristotle could speak of human technologies and institutions as being inevitably reinvented over and over because he regarded human nature as fixed and the human species, along with all other species, as eternal: the world itself had always existed, and human beings had always walked upon it. In this he differed from his pre-Socratic predecessor Anaximander, who speculated that human beingd has evolved out of the mud, as descendants of fish. Today we view human nature -- the genetically endowed network of needs, desire, capacities, preferences, and impulses on which culture is built -- as having been fixed only since the advent of agriculture and cities, the events that initiated our present epoch, the Holocene, around ten thousand years ago. Before that, our physical and mental makeup was continuaously evolving through the generations of our nomadic human and proto-human ancestors in the Pleistocene. While human beings share an unbroken lineate through living things back beyond animals and into the Precambrian sludge, it is the Pleistocene contribution to human nature that is more relevant to understanding the culture life from of, for instance, governance, religion, language, systems of law, economic exchange, and the regularization of courtship, mating and child rearing.