No abstract

Multilevel (or modular) societies are a distinct type of primate social system whose key features are single-male–multifemale, core units nested within larger social bands. They are not equivalent to fission–fusion societies, with the latter referring to routine variability in associations, either on an individual or subunit level. The purpose of this review is to characterize and operationalize multilevel societies and to outline their putative evolutionary origins. Multilevel societies are prevalent in three primate clades: papionins, Asian colobines, and hominins. For each clade, we portray the most parsimonious phylogenetic pathway leading to a modular system and then review and discuss likely socioecological conditions promoting the establishment and maintenance of these societies. The multilevel system in colobines (most notably Rhinopithecus and Nasalis ) has likely evolved as single-male harem systems coalesced, whereas the multilevel system of papionins ( Papio hamadryas , Theropithecus gelada ) and hominins most likely arose as multimale–multifemale groups split into smaller units. We hypothesize that, although ecological conditions acted as preconditions for the origin of multilevel systems in all three clades, a potentially important catalyst was intraspecific social threat, predominantly bachelor threat in colobines and female coercion/infanticide in papionins and humans. We emphasize that female transfers within bands or genetic relationships among leader males help to maintain modular societies by facilitating interunit tolerance. We still lack a good or even basic understanding of many facets of multilevel sociality. Key remaining questions are how the genetic structure of a multilevel society matches the observed social effort of its members, to what degree cooperation of males of different units is manifest and contributes to band cohesion, and how group coordination, communication, and decision making are achieved. Affiliative and cooperative interunit relations are a hallmark of human societies, and studying the precursors of intergroup pacification in other multilevel primates may provide insights into the evolution of human uniqueness.

Human social evolution has most often been treated in a piecemeal fashion, with studies focusing on the evolution of specific components of human society such as pair-bonding, cooperative hunting, male provisioning, grandmothering, cooperative breeding, food sharing, male competition, male violence, sexual coercion, territoriality, and between-group conflicts. Evolutionary models about any one of those components are usually concerned with two categories of questions, one relating to the origins of the component and the other to its impact on the evolution of human cognition and social life. Remarkably few studies have been concerned with the evolution of the entity that integrates all components, the human social system itself. That social system has as its core feature human social structure, which I define here as the common denominator of all human societies in terms of group composition, mating system, residence patterns, and kinship structures. The paucity of information on the evolution of human social structure poses substantial problems because that information is useful, if not essential, to assess both the origins and impact of any particular aspect of human society.

Nonhuman primates commonly compete for mates, physical resources and dominance status. Competition is manifest in one-to-one contests or in more complex, multipartite aggressive interactions involving the formation of alliances. In this paper, five aspects of competitive alliances are reviewed: 1) the evolutionary and ecological conditions favoring the occurrence of alliances among females, among males, and between males and females, 2) the dynamics of the three main categories of competitive alliances, called bridging, revolutionary, and conservative, 3) the developmental processes that may account for the initial formation of alliances, 4) the cognitive abilities involved in two major aspects of alliances, the recognition of one's allies and of the allies of other individuals, and 5) the value of functional explanations of alliance behavior, namely kin selection, reciprocal altruism and mutualism. o 1995 Wiley-Liss, Inc.For more than a year male 415 had been the undisputed highest-ranking animal in a free-ranging group of 100 rhesus monkeys. Unlike the other males that had transfered to other groups (as is the rule in the majority of primate species), 415 had stayed in his natal group and achieved, as a young adult, the top position in the male dominance order comprising 15 non-natal animals. Interestingly, male 415 was the offspring of the highest-ranking female of his group. His life took on a dramatic turn the day he was severely wounded in a fight with another group. He contracted tetanus, became disabled and disappeared. A few days later however, he was back, following the group from a distance, walking stiffly and showing incipient signs of recovery. From that time on, 415 initiated frequent grooming interactions with adult females, in marked contrast with his past behavior. At the same time and although he was physically severely impaired, 415 undertook to threaten systematically several high-ranking males that had come to outrank him since his disability, provoking them when they were passing by. In these situations he was systematically supported by his relatives (mother, sister, nieces, cousin and younger brother, who formed the most dominant matriline) and by other highranking females. These animals vigorously chased and could even bite 415's targets. In a matter of weeks, 415 regained his position at the top of the male hierarchy (Chapais, 1983a).Male 415's story illustrates the use of alliances in aggressive competition, hereafter competitive alliances, and exemplifies how crucial and efficient these can be in settling long-term dominance relationships. Competitive alliances are manifest whenever the outcome of interindividual conflicts over resources or dominance status is affected by third-parties making use of, or threatening to use, aggression. This definition excludes interactions that affect the outcome of competition in the 0 1995 Wiley-Liss, Inc

In this paper I propose an evolutionary model of human status that expands upon an earlier model proposed by Henrich and Gil-White Evolution and Human Behavior, 22,165-196 (2001). According to their model, there are two systems of status attainment in humans-"two ways to the top": the dominance route, which involves physical intimidation, a psychology of fear and hubristic pride, and provides coercive power, and the prestige route, which involves skills and knowledge (competence), a psychology of attraction to experts and authentic pride, and translates mainly into influence. The two systems would have evolved in response to different selective pressures, with attraction to experts serving a social learning function and coinciding with the evolution of cumulative culture. In this paper I argue that (1) the only one way to the top is competence because dominance itself involves competence and confers prestige, so there is no such thing as pure dominance status; (2) dominance in primates has two components: a competitive one involving physical coercion and a cooperative one involving competence-based attraction to high-ranking individuals (proto-prestige); (3) competence grants the same general type of power (dependence-based) in humans and other primates; (4) the attractiveness of high rank in primates is homologous with the admiration of experts in humans; (5) upon the evolution of cumulative culture, the attractiveness of high rank was co-opted to generate status differentials in a vast number of culturally generated domains of activity. I also discuss, in this perspective, the origins of hubristic pride, authentic pride, and nonauthoritarian leadership.