Humans exhibit intense attachments to very large groups, sometimes numbering in the millions. The author addresses the question of how inclinations to attach to large groups might have evolved and identifies the problem of collective action and free riding as the central obstacles to overcome. He argues that the nonsubtractibility feature of public goods and the inclusive fitness theory of W. D. Hamilton are key elements in the evolution of sharing behavior in large groups: a source of group attachments. The argument implies that the mix of goods available and produced in past and present environments impacts the configuration of different-sized groups found in human society.

Though Hamilton's rule is commonly interpreted as relating to two individuals, an alternative interpretation is that it can apply to an altruistic act with respect to a large group of related persons, such as an ethnic group. Then provision of a public good to such a group can be explained by Hamilton's rule. An important class of public goods is the provision of a “legal system” for the group. Provision of this good can have positive feedback effects: as there is more enforcement, it pays to define more complex and valuable rights, and in turn such rights lead to larger and more effective societies. As societies become larger, the ability to enforce rights increases because the number of enforcers increases. However, as in many other human activities, there may be two conflicting systems for provision of this good. There is the evolutionarily old system that would involve face to face transactions, often with kin. There is also a newer, rule-governed legal system for impersonal exchanges. These may be in conflict. The older rules may sometimes frustrate the more efficient newer system. Moreover, those persons who benefit from kin-based transaction networks may resist the creation of a formal legal system. I also note that altruism within the group may lead to xenophobia outside the group and thus to ethnic conflict. Finally, I discuss some evidence consistent with this analysis.

I employ a simulation model previously used to analyze the choice of top members in a hierarchy to examine the acceptance of low prestige in a group of possibly large size. Results show that acceptance of low rank is most likely when the collective benefit available is mostly nonrival and nonexcludable and has low additivity (every contribution helps), and the ability of even low ability group members to contribute is high in absolute terms. I discuss possible mechanisms, through genetic or behavioral selection, by which the capacity to believe in one's own low rank may have developed.

Despite advances in fields like genetics, evolutionary psychology, and human behavior and evolution — which generally focus on individual or small group behavior from a biological perspective — evolutionary biology has made little impact on studies of political change and social history. Theories of natural selection often seem inapplicable to human history because our social behavior is embedded in language (which makes possible the concepts of time and social identity on which what we call “history” depends). Peter Corning's Holistic Darwinism reconceptualizes evolutionary biology, making it possible to go beyond the barriers separating the social and natural sciences. Corning focuses on two primary processes: “synergy” (complex multivariate interactions at multiple levels between a species and its environment) and “cybernetics” (the information systems permitting communication between individuals and groups over time). Combining this frame of reference with inclusive fitness theory, it is possible to answer the most important (and puzzling) question in human history: How did a species that lived for millennia in hunter-gatherer bands form centralized states governing large populations of non-kin (including multi-ethnic empires as well as modern nation-states)? The fragility and contemporary ethnic violence in Kenya and the Congo should suffice as evidence that these issues need to be taken seriously. To explain the rise and fall of states as well as changes in human laws and customs — the core of historical research — it is essential to show how the provision of collective goods can overcome the challenge of self-interest and free-riding in some instances, yet fail to do so in others. To this end, it is now possible to consider how a state providing public goods can — under circumstances that often include effective leadership — contribute to enhanced inclusive fitness of virtually all its members. Because social behavior needs to adapt to ecology, but ecological systems are constantly transformed by human technology and social behavior, multilevel evolutionary processes can explain two central features of human history: the rise, transformations, and ultimate fall of centralized governments (the “stuff” of history); and the biological uniqueness of Homo sapiens as the mammalian species that colonized — and became top carnivore — in virtually every habitable environment on the earth's surface. Once scholars admit the necessity of linking processes of natural selection with human transformations of the natural world, it will seem anomalous that it has taken so long to integrate Darwinian biology and the social sciences.