Doug Jones

According to the theory of kin selection, an organism that shows some level of altruism toward her kin – lowering her own fitness, raising that of a close genetic relative – may enjoy an evolutionary advantage. Some species show beyond-ordinary altruism toward siblings, and other kin, owing to unusual reproductive biology and/or ecology. Human beings are exceptional in another way: how we treat our kin depends partly on how we feel about them, but also partly on socially enforced norms. This article explores several versions of a simple evolutionary game, the Brothers Karamazov Game, that departs from the standard theory of kin selection to allow for the distinctively human capacity for establishing and enforcing social norms. We discuss possible applications to understanding the “unity of the sibling group” (Radcliffe-Brown) – according exceptional treatment to siblings, and to relatives classified as siblings or linked through siblings. We give special attention to lowland South America, where the sibling relationship is central to social organization.

“Barbarism” is perhaps best understood as a recurring syndrome among peripheral societies in response to the threats and opportunities presented by more developed neighbors. This article develops a mathematical model of barbarigenesis—the formation of “barbarian” societies adjacent to more complex societies—and its consequences, and applies the model to the case of Europe in the first millennium CE. A starting point is a game (developed by Hirshleifer) in which two players allocate their resources either to producing wealth or to fighting over wealth. The paradoxical result is that a richer and potentially more powerful player may lose out to a poorer player, because the opportunity cost of fighting is greater for the former. In a more elaborate spatial model with many players, the outcome is a wealth-power mismatch: central regions have comparatively more wealth than power, peripheral regions have comparatively more power than wealth. In a model of historical dynamics, a wealth-power mismatch generates a long-lasting decline in social complexity, sweeping from more to less developed regions, until wealth and power come to be more closely aligned. This article reviews how well this model fits the historical record of late Antiquity and the early Middle Ages in Europe both quantitatively and qualitatively. The article also considers some of the history left out of the model, and why the model doesn’t apply to the modern world.

Kin selection, which can lead organisms to behave altruistically to their genetic relatives, works differently when—as is often the case in human societies—altruism can be boosted by social pressure. Here I present a model of social norms enforced by indirect reciprocity. In the model there are many alternative stable allocations of rewards (“distributional norms”); a stable norm is stable in the sense that each player is best off following the norm if other players do the same. Stable norms vary widely in how equally they reward players with unequal abilities. In a population of mixed groups (some group members follow one norm, some follow another, and some compromise) with modest within-group coefficients of relatedness, selection within groups favors those who compromise, and selection between groups favors generous generalized reciprocity rather than balanced reciprocity. Thus evolved social norms can amplify kin altruism, giving rise to a uniquely human mode of kin-based sociality distinct from spontaneous altruism among close kin, or cooperation among non-kin.

This article integrates (1) research in the historical dynamics of state societies relating group solidarity and group expansion to cultural frontiers, (2) comparative research in anthropology relating matrilocality to a particular variety of internal politics and a particular form of warfare, and (3) interdisciplinary reconstructions of large-scale “demic expansions” and associated kinship systems in prehistory. The argument is that “metaethnic frontiers,” where very different cultures clash, are centers for the formation of larger, more enduring, and more militarily effective groups. In small-scale non-state societies, the major path toward the formation of such groups is the establishment of cross-cutting ties among men. This often involves the adoption of matrilocal norms. The current distribution of matrilocality and matrilineality around the world may be partly a residue of major demic expansions in prehistory involving matrilocal tribes. This hypothesis is evaluated with a range of evidence, including information regarding the spread of two language families, Bantu and Austronesian.

Research in anthropology has shown that kin terminologies have a complex combinatorial structure and vary systematically across cultures. This article argues that universals and variation in kin terminology result from the interaction of (1) an innate conceptual structure of kinship, homologous with conceptual structure in other domains, and (2) principles of optimal, “grammatical” communication active in language in general. Kin terms from two languages, English and Seneca, show how terminologies that look very different on the surface may result from variation in the rankings of a universal set of constraints. Constraints on kin terms form a system: some are concerned with absolute features of kin (sex), others with the position (distance and direction) of kin in “kinship space,” others with groups and group boundaries (matrilines, patrilines, generations, etc.). Also, kin terms sometimes extend indefinitely via recursion, and recursion in kin terminology has parallels with recursion in other areas of language. Thus the study of kinship sheds light on two areas of cognition, and their phylogeny. The conceptual structure of kinship seems to borrow its organization from the conceptual structure of space, while being specialized for representing genealogy. And the grammar of kinship looks like the product of an evolved grammar faculty, opportunistically active across traditional domains of semantics, syntax, and phonology. Grammar is best understood as an offshoot of a uniquely human capacity for playing coordination games.

The target article proposes a theory uniting the anthropological study of kin terminology with recent developments in linguistics and cognitive science. The response to comments reaches two broad conclusions. First, the theory may be relevant to several current areas of research, including (a) the nature and scope of the regular, “grammatical” side of language, (b) the organization of different domains of conceptual structure, including parallels across domains, their taxonomic distribution and implications for evolution, and (c) the influence of conceptual structure on social structure. Second, the theory compares favorably with alternatives, including (a) the theory that kin terminology is not really that complicated, (b) the theory that kin terms mirror social categories, (c) componential analysis, and (d) kinship algebra. If further research in anthropology, linguistics, and other fields supports the theory, and confirms the psychological reality of proposed mechanisms, then kinship may emerge as a model system for the study of important issues in cognition and social organization.

Psychological research in the USA and elsewhere suggests that race is regarded as an underlying, inherited “essential” trait, like membership in a biological species. Yet Brazil has often been regarded as very different from the USA: as a country in which racial variation is seen as more continuous than categorical, more a matter of appearance than descent. This study tests alternative theories of racial cognition in Bahia, Brazil. Data include racial classification of drawings and photographs, judgments of similarity – dissimilarity between racial categories, ideas about expected and possible race of offspring from inter-racial unions, heritability of racial and non-racial traits, and conservation of race through changes in appearance. The research demonstrates consensus over time in appearance-based classification, yet race is also thought of as an “essential” trait. However, racial essences can be mixed, with a person containing the hereditary potential of multiple races, so that race in Bahia does not define clear-cut groups or discrete “living kinds.” If essentialism is the shared core of folk theories of race, there may be more variability and room for social construction in the categorization of mixed-race individuals.