Minimizing the costs that others impose upon oneself and upon those in whom one has a fitness stake, such as kin and allies, is a key adaptive problem for many organisms. Our ancestors regularly faced such adaptive problems. One solution to this problem is to impose retaliatory costs on an aggressor so that the aggressor and other observers will lower their estimates of the net benefits to be gained from exploiting the retaliator in the future. We posit that humans have (...) an evolved cognitive system that implements this strategy which we conceptualize as a revenge system. The revenge system produces a second adaptive problem: losing downstream gains from the individual on whom retaliatory costs have been imposed. We posit, consequently, a subsidiary computational system designed to restore particular relationships after cost-imposing interactions by inhibiting revenge and motivating behaviors that signal benevolence for the harmdoer. The operation of these systems depends on estimating the risk of future exploitation by the harmdoer and the expected future value of the relationship with the harmdoer. We review empirical evidence regarding the operation of these systems, discuss the causes of cultural and individual differences in their outputs, and sketch their computational architecture. (shrink)

In the absence of explicit punitive sanctions, why do individuals voluntarily participate in intergroup warfare when doing so incurs a mortality risk? Here we consider the motivation of individuals for participating in warfare. We hypothesize that in addition to other considerations, individuals are incentivized by the possibility of rewards. We test a prediction of this “cultural rewards war-risk hypothesis” with ethnographic literature on warfare in small-scale societies. We find that a greater number of benefits from warfare is associated with a (...) higher rate of death from conflict. This provides preliminary support for the relationship between rewards and participation in warfare. (shrink)

The origins of human social cooperation confound simple evolutionary explanation. But from Darwin and Durkheim onward, theorists (anthropologists and sociologists especially) have posited a potential link with another curious and distinctively human social trait that cries out for explanation: religion. This dissertation explores one contemporary theory of the co-evolution of religion and human social cooperation: the signalling theory of religion, or religious signalling theory (RST). According to the signalling theory, participation in social religion (and its associated rituals and sanctions) acts (...) as an honest signal of one’s commitment to a religiously demarcated community and its way of doing things. This signal would allow prosocial individuals to positively assort with one another for mutual advantage, to the exclusion of more exploitative individuals. In effect, the theory offers a way that religion and cooperation might explain one another, but which that stays within an individualist adaptive paradigm. My approach is not to assess the empirical adequacy of the religious signalling explanation or contrast it with other explanations, but rather to deal with the theory in its own terms – isolating and fleshing out its core commitments, explanatory potential, and limitations. The key to this is acknowledging the internal complexities of signalling theory, with respect to the available models of honest signalling and the extent of their fit (or otherwise) with religion as a target system. The method is to take seriously the findings of formal modelling in animal signalling and other disciplines, and to apply these (and methods from the philosophy of biology more generally) to progressively build up a comprehensive picture of the theory, its inherent strengths and weaknesses. The first two chapters outline the dual explanatory problems that cooperation and religion present for evolutionary human science, and surveys contemporary approaches toward explaining them. Chapter three articulates an evolutionary conception of the signalling theory, and chapters four to six make the case for a series of requirements, limitations, and principles of application. Chapters seven and eight argue for the value of formal modelling to further flesh out the theory’s commitments and potential and describe some simple simulation results which make progress in this regard. Though the inquiry often problematizes the signalling theory, it also shows that it should not be dismissed outright, and that it makes predictions which are apt for empirical testing. (shrink)

In response to recent work on the nature of human aggression, and to shed light on the proximate, as opposed to ultimate, causes of tribal warfare, we present a record of events leading to a fatal Waorani raid on a family from another tribe, followed by a detailed first-person observation of the behavior of the raiders as they prepared themselves for war, and upon their return. We contrast this attack with other Waorani aggressions and speculate on evidence regarding their hormonal (...) underpinnings. On-the-ground ethnographic observations are examined in light of the neuroendocrinological literature. The evidence suggests a chain of causality in launching lethal violence, beginning with a perceived injury, culminating in a massacre, and terminating in rejoicing. Although no blood or saliva samples were taken at the time of this raid, the behaviors were consistent with a deliberate initiation of the hormonal cascade characterizing the “fight-or-flight” response, along with other hormonal changes. We conclude with observations on the stratified interrelationships of the cognitive, social, emotional, and neuroendocrinological causes of aggression leading to coalitional male homicide. (shrink)