Some 15,000 years ago, our ancestors still lived in small-scale foraging societies whose members were treated as equals. Slowly but surely, however, some of them created larger societies with greater levels of social inequality. By 2500 B.C. virtually every form of inequality known to mankind existed somewhere in the world. How did our ancestors convert the original level playing field to a stratified society? This book addresses that question by synthesizing two sources of data: archaeological information on prehistoric societies and anthropological information on analogous living societies. The answer lies neither in our genes, nor in shopworn explanations like population pressure and environmental stress. It lies in the unique social logic possessed by every human group. Living societies can be observed making changes in that logic; the effects of such changes can be detected in prehistory. Traditional hunters and gatherers believed that they had been created by supernatural spirits who gave them principles to live by. Those spirits were the alphas in a cosmic hierarchy; the betas were ancestors, who intervened on behalf of their living descendants with the spirit world. Here are some typical principles of hunter-gatherer logic: There is an invisible life force within us. Certain spirits, places, and objects are sacred. Individuals differ in virtue. Generosity is a virtue; hoarding or creating surpluses is selfish. Gifts build social networks and should always be reciprocated. Youths should defer to initiated elders; late arrivals in a territory should defer to those already there. Our way of life is superior to that of our neighbors. Despite the widespread nature of such principles, most anthropologists would not argue that they are "encoded in our genes." Sharing is widespread among foragers because they employ continual social pressure to encourage it. Were there genes for generosity, such pressure would have been unnecessary, and later peoples would have found it difficult to create inequality. By the end of the Ice Age ---some 10,000 years ago --- people in the Near East, Mexico, and Peru had begun to domesticate plants and animals. As larger and more sedentary societies formed, their social logic was sometimes tweaked to allow for inequality. Two contrasting forms of society, based on different logic, followed the establishment of agriculture. Some societies ---preserving the notion of generosity, but relaxing the prohibitions against surplus --- allowed enterprising individuals to create differences in prestige by humiliating the less successful with gifts too large to be reciprocated. Many New Guinea societies came to be divided into "big men," "ordinary men," and "rubbish men." Some Native American societies created a "hierarchy of virtue" in which talented and ambitious individuals could rise in prestige by climbing a ladder of ritual offices. In some Pueblo communities, men could rise through 7 or 8 such offices until they were "completed" as respected elders. In some Plains communities, women could rise through 4 or 5 ritual offices until they were considered "holy." In none of these achievement-based societies was leadership allowed to become hereditary, however. One could serve as role model for one's children, but not bequeath them one's office or prestige. Prehistoric examples of such societies can be detected by archaeologists because much of their ritual was focused on propitiating the ancestors, and required the building of venues such as ritual men's houses, kivas, and the like. The first signs of such buildings appeared in the Near East 10,000 years ago. Eventually, some societies altered their logic to permit one segment of society to monopolize leadership, allowing their children to inherit authority. On rare occasions, for example among the Native Americans of British Columbia, this happened even among hunter-gatherers. One's inability to reciprocate gifts not only left one inferior in virtue, but also became a debt that had to be worked off through servitude. Archaeologists in British Columbia point to a moment when small, economically vulnerable families seem to have been absorbed into larger and more successful families, perhaps as debt slaves. To codify such inequality, emerging elites attributed their superior status to their ancestors, who had allegedly been favored by celestial spirits. They created sumptuary goods---trappings of aristocracy to which they were entitled from birth---and bequeathed them to their heirs at lavish ceremonies. The prehistoric record suggests that societies with hereditary aristocracies arose 7500 years ago in the Near East, 4000 years ago in Peru, and 3000 years ago in Mexico. Among the clues are the presence of sumptuary goods in children's burials, and the replacement of ritual men's houses by actual temples. Temples were created because it became more important to propitiate the alpha spirits from which the elite derived their authority than to propitiate the beta ancestors of commoners. Anthropologists, however, have documented cases where a would-be elite's attempt to place itself in a superior position was successfully resisted by other segments of society. When resistance was unsuccessful, cosmologies were modified to attribute emerging inequality to the will of creator spirits. In Hawai'i and Egypt, logic was altered to release chiefly families from the usual incest taboos. Chiefs could marry their sisters to preserve the bluest bloodlines; such sibling marriage was justified by arguing that some celestial spirits had also practiced it. Soon blood feuds --- originally a way of settling scores --- evolved into wars of chiefly expansion and the conversion of rivals to slaves. The simple ethnocentrism of earlier societies gave way to actual discrimination. The social pressure once used to prevent others from showing off was replaced by acts of obeisance toward those of elite birth. In some parts of the ancient world we can detect groups of neighboring chiefly societies battling for centuries, each aspiring to take over its rivals' land and labor. On rare occasions, a stalemate was broken when one such society gained an unexpected advantage, allowing it to take over its rivals and turn them into the subject provinces of a much larger territory. It was through such processes that the first kingdoms of Hawai'i, the Asante, and the Zulu formed. Archaeologists can now show that similar processes created the first kingdoms of southwest Iran, Mesopotamia, Egypt, the Maya, the Mexican highlands, and the coast of Peru. Indeed, once set in motion, elite competition created chain reactions in which multiple fortified kingdoms might arise. Changes in logic allowed for societies to be divided into royalty, nobility, landed gentry, landless serfs, and slaves. There were significant differences among early kingdoms, however. In Egypt and Peru the ruler was considered a deity, equivalent to the celestial spirits who constituted society's alphas. In kingdoms like those of Mexico's Maya and Zapotec, the ruler had religious authority but was not an actual deity. Among the Aztec and the early Sumerians, the ruler was a mortal oligarch. Will future research show continuities between such contrasting kingdoms and the earlier societies out of which they were created? Might divine kingship be the legacy of earlier societies where religious authority was uppermost? Might secular kingship be the legacy of earlier societies where military force was uppermost? We conclude with the question asked 250 years ago by Rousseau: how much social inequality is authorized by Natural Law? The answer is, very little. Had our ancestors held firm to the social logic of 15,000 years ago, there would today be no one of aristocratic birth, no vast accumulations of wealth, no bequeathing of privilege to children. Our only social hierarchy would be one of virtue, and we would be led by those who give generously while asking only for respect. The first step toward such a society would be to reverse the changes in logic made by our ancestors.