Dynamics of alliance formation and the egalitarian revolution

Arguably the most influential force in human history is the formation of social coalitions and alliances (i.e., long-lasting coalitions) and their impact on individual power. In most great ape species, coalitions occur at individual and group levels and among both kin and non-kin. Nonetheless, ape societies remain essentially hierarchical, and coalitions rarely weaken social inequality. In contrast, human hunter-gatherers show a remarkable tendency to egalitarianism, and human coalitions and alliances occur not only among individuals and groups, but also among groups of groups. Here, we develop a stochastic model describing the emergence of networks of allies resulting from within-group competition for status or mates between individuals utilizing dyadic information. The model shows that alliances often emerge in a phase transition-like fashion if the group size, awareness, aggressiveness, and persuasiveness of individuals are large and the decay rate of individual affinities is small. With cultural inheritance of social networks, a single leveling alliance including all group members can emerge in several generations. Our results suggest that a rapid transition from a hierarchical society of great apes to an egalitarian society of hunter-gatherers (often referred to as "egalitarian revolution") could indeed follow an increase in human cognitive abilities. The establishment of stable group-wide egalitarian alliances creates conditions promoting the origin of cultural norms favoring the group interests over those of individuals.Comment: 37 pages, 15 figure

Smile asymmetries and reputation as reliable indicators of likelihood to cooperate: An evolutionary analysis

Cooperating with individuals whose altruism is not motivated by genuine prosocial emotions could have been costly in ancestral division of labour partnerships. How do humans ‘know’ whether or not an individual has the prosocial emotions committing future cooperation? Frank (1988) has hypothesized two pathways for altruist-detection: (a) facial expressions of emotions signalling character; and (b) gossip regarding the target individual’s reputation. Detecting non-verbal cues signalling commitment to cooperate may be one way to avoid the costs of exploitation. Spontaneous smiles while cooperating may be reliable index cues because of the physiological constraints controlling the neural pathways mediating involuntary emotional expressions. Specifically, it is hypothesized that individuals whose help is mediated by a genuine sympathy will express involuntary smiles (which are observably different from posed smiles). To investigate this idea, 38 participants played dictator games (i.e. a unilateral resource allocation task) against cartoon faces with a benevolent emotional expression (i.e. concern furrows and smile). The faces were presented with information regarding reputation (e.g. descriptions of an altruistic character vs. a non-altruistic character). Half of the sample played against icons with symmetrical smiles (representing a spontaneous smile) while the other half played against asymmetrically smiling icons (representing a posed smile). Icons described as having altruistic motives received more resources than icons described as self-interested helpers. Faces with symmetrical smiles received more resources than faces with asymmetrical smiles. These results suggest that reputation and smile asymmetry influence the likelihood of cooperation and thus may be reliable cues to altruism. These cues may allow for altruists to garner more resources in division of labour situations

Is Strong Reciprocity a Maladaptation? On the Evolutionary Foundations of Human Altruism

In recent years a large number of experimental studies have documented the existence of strong reciprocity among humans. Strong reciprocity means that people willingly repay gifts and punish the violation of cooperation and fairness norms even in anonymous one-shot encounters with genetically unrelated strangers. We provide ethnographic and experimental evidence suggesting that ultimate theories of kin selection, reciprocal altruism, costly signaling and indirect reciprocity do not provide satisfactory evolutionary explanations of strong reciprocity. The problem of these theories is that they can rationalize strong reciprocity only if it is viewed as maladaptive behavior whereas the evidence suggests that it is an adaptive trait. Thus, we conclude that alternative evolutionary approaches are needed to provide ultimate accounts of strong reciprocity.

Give and you shall receive. Give more and you shall be honored. Experimental evidence for altruism as costly signaling.

In two studies, we measured the degree and manner of reciprocation of a public good in subsequent two-by-two interactions. Both studies consisted of two phases: a public good phase and a subsequent give some game (i.e. a gradual Prisoner's dilemma game). In the first study, the public good was a financial game in the lab. In the second study, the public good games were real life student projects. The observed behavior in the subsequent interactions was consistent with the reciprocity rule, but only up to the fairness norm of equality. Students who had invested more than their fair share, did not receive more financial returns than those who had invested a fair share. However, despite the lack of financial benefits, these high investors were preferred more as future team mates (Study 1), or received more social rewards (Study 2). We interpret these findings in terms of altruism as costly signaling.Altruism; Cooperation; Costly signaling; Prisoner's dilemma game; Reputations; Studies;

Competition-related factors directly influence preferences for facial cues of dominance in allies

Alliance formation is a critical dimension of social intelligence in political, social and biological systems. As some allies may provide greater ‘leverage’ than others during social conflict, the cognitive architecture that supports alliance formation in humans may be shaped by recent experience, for example in light of the outcomes of violent or non-violent forms intrasexual competition. Here we used experimental priming techniques to explore this issue. Consistent with our predictions, while men’s preference for dominant allies strengthened following losses (compared to victories) in violent intrasexual contests, women’s preferences for dominant allies weakened following losses (compared to victories) in violent intrasexual contests. Our findings suggest that while men may prefer dominant (i.e. masculine) allies following losses in violent confrontation in order to facilitate successful resource competition, women may ‘tend and befriend’ following this scenario and seek support from prosocial (i.e. feminine) allies and/or avoid the potential costs of dominant allies as long-term social partners. Moreover, they demonstrate facultative responses to signals related to dominance in allies, which may shape sex differences in sociality in light of recent experience and suggest that intrasexual selection has shaped social intelligence in humans

Informational Warfare

Recent empirical and theoretical work suggests that reputation was an important mediator of access to resources in ancestral human environments. Reputations were built and maintained by the collection, analysis, and dissemination of information about the actions and capabilities of group members-that is, by gossiping. Strategic gossiping would have been an excellent strategy for manipulating reputations and thereby competing effectively for resources and for cooperative relationships with group members who could best provide such resources. Coalitions (cliques) may have increased members' abilities to manipulate reputations by gossiping. Because, over evolutionary time, women may have experienced more within-group competition than men, and because female reputations may have been more vulnerable than male reputations to gossip, gossiping may have been a more important strategy for women than men. Consequently, women may have evolved specializations for gossiping alone and in coalitions. We develop and partially test this theory

Kin Selection

When Hamilton (1964) published his theory of inclusive fitness it had no immediate impact in the social and behavioral sciences, even though ethnographers knew kinship to be a universally fundamental factor in human social organization, especially in egalitarian societies in which humans have spent nearly all their evolutionary history. In many ways, it was a theory that perhaps anthropologists should have devised: Anthropologists knew kinship fundamentally structured cooperation, identity, coalition formation, resource exchange, marriage, and group membership in traditional societies. It was not until 1974 with the publication of Wilson’s Sociobiology (1975) and especially Richard Alexander’s The Evolution of Social Behavior (1974) that evolutionary social scientists began to take note of the potential of kin selection as a powerful theory that could revolutionize the study of human social behavior. Alexander was the first to comprehensively demonstrate that ethnographic and psychological evidence provided strong support that hypotheses drawn from kin selection would be a productive area of investigation. His review of the anthropological literature on kinship, especially of the Human Relations Area Files (HRAF), was elaborated more fully in Darwinism and Human Affairs (1979). For example, Alexander’s prediction that paternity uncertainty would skew nepotism matrilaterally (1974, pp. 373–374; 1979, p. 169) is now well documented. In addition, he provided important preliminary evidence that suggested that kin selection would help us understand food transfers and cooperative economic activities (Alexander, 1979, pp. 144–161), and that kin selection and reciprocal altruism would be closely linked (1979, pp. 52–58)

Direct and generalized reciprocity in the cooperative exchanges of free living Rhesus macaques on Cayo Santiago

Direct reciprocity is the most cited explanation for the evolution of cooperation between unrelated individuals. Yet, few studies have examined generalized reciprocity as an alternative mechanism, despite generalized reciprocity’s minimal cognitive demands and capacity to explain the same patterns of cooperation as direct reciprocity. Studies of direct reciprocity tend to explore reciprocal exchange across either individual interactions or long periods of time, rarely studying both at once. In addition, most studies of reciprocity only account for maternal relatedness between cooperative partners, failing to rule out the effect of kin selection through paternal relatedness. In this thesis we investigated the role of direct and generalized reciprocity in female rhesus macaque cooperative exchanges. We modified a classic playback experiment and explored the effect of both recent and repeated grooming interactions on females’ willingness to provide coalitionary support to other adult females. We conducted this study using the rhesus macaques at the Cayo Santiago field station, where maternal and paternal relatedness is known for all study subjects. We found no evidence of direct or generalized reciprocity in the exchange of grooming for coalitionary support. Our results contradict the findings of similar playback experiments but are consistent with correlational studies in species that are despotic like rhesus macaques. The despotic nature of our study system, combined with our finding that females’ willingness to provide support declined as the number of infants in their matriline increased, could suggest that grooming is not a sufficient price to pay to acquire coalitionary support from unrelated rhesus macaques. We propose by-product mutualism and kin-selection may play a larger role than has been previously appreciated in decisions regarding who to support in agnostic encounters, and we highlight the importance of investigating multiple cooperative mechanisms when studying of the evolution of cooperative behaviours

Mating games: cultural evolution and sexual selection.

In this paper, we argue that mating games, a concept that denotes cultural practices characterized by a competitive element and an ornamental character, are essential drivers behind the emergence and maintenance of human cultural practices. In order to substantiate this claim, we sketch out the essential role of the game's players and audience, as well as the ways in which games can mature and turn into relatively stable cultural practices. After outlining the life phase of mating games - their emergence, rise, maturation, and possible eventual decline - we go on to argue that participation in these games (in each phase) does make sense from an adaptationist point of view. The strong version of our theory which proposes that all cultural practices are, or once were, mating games, allows us to derive a set of testable predictions for the fields of archaeology, economics, and psychology.competition; cultural evolution; evolutionary psychology; play; sexual selection; strategies; handicap; mates; play;

Do gray wolves (\u3ci\u3eCanis lupus\u3c/i\u3e) support pack mates during aggressive inter-pack interactions?

For group-living mammals, social coordination increases success in everything from hunting and foraging (Crofoot and Wrangham in Mind the Gap, Springer, Berlin, 2010; Bailey et al. in Behav Ecol Sociobiol 67:1–17, 2013) to agonism (Mosser and Packer in Anim Behav 78:359–370, 2009; Wilson et al. in Anim Behav 83:277–291, 2012; Cassidy et al. in Behav Ecol 26:1352–1360, 2015). Cooperation is found in many species and, due to its low costs, likely is a determining factor in the evolution of living in social groups (Smith in Anim Behav 92:291–304, 2014). Beyond cooperation, many mammals perform costly behaviors for the benefit of group mates (e.g., parental care, food sharing, grooming). Altruism is considered the most extreme case of cooperation where the altruist increases the fitness of the recipient while decreasing its own fitness (Bell in Selection: the mechanism of evolution. Oxford University Press, Oxford 2008). Gray wolf life history requires intra-pack familiarity, communication, and cooperation in order to succeed in hunting (MacNulty et al. in Behav Ecol doi:10.1093/beheco/arr159 2011) and protecting group resources (Stahler et al. in J Anim Ecol 82: 222–234, 2013; Cassidy et al. in Behav Ecol 26:1352–1360, 2015). Here, we report 121 territorial aggressive inter-pack interactions in Yellowstone National Park between 1 April 1995 and 1 April 2011 ([5300 days of observation) and examine each interaction where one wolf interferes when its pack mate is being attacked by a rival group. This behavior was recorded six times (17.6 % of interactions involving an attack) and often occurred between dyads of closely related individuals. We discuss this behavior as it relates to the evolution of cooperation, sociality, and altruism