Fitness Costs of Warfare for Women

Aggressive and Humiliating Sexual Play: Occurrence Rates and Discordance Between the Sexes

The present study attempted to understand people's desires for aggressive and humiliating sexual play, both in terms of interests and fantasy. An evolutionary framework has been developed which generated five hypotheses to be tested. Evidence from a qualitative study of 102 participants identified 13 aggressive and sexual acts which were commonly preferred. A subsequent quantitative online study of 1026 men and women asked participants to rate the desirability of these acts. The results indicated that more than 70% of participants found at least one aggressive or humiliating sexual play desirable, whereas about half of the participants found at least three such acts desirable. Significant sex differences were also found, with men desiring to engage in such play more than women. This discordance was moderated by the willingness of each party to partially accommodate each other's desires. On the basis of these findings and the proposed theoretical framework, it is concluded that aggressive and humiliating sexual play constitutes a normal variation in sexual desire.

The emergence of human warfare: Current perspectives

The origins of warfare have long been of interest for researchers across disciplines. Did our earliest ancestors engage in forms of organized violence that are appropriately viewed as approximations, forms of, or analogs for more recent forms of warfare? Assessed in this article are contrasting views that see warfare as being either a product of more recent human societies or a phenomenon with a much deeper chronology. The article provides an overview of current debates, theories, and methodological approaches, citing literature and data from archaeological, ethnographic, genetic, primatological, and paleoanthropological studies. Synthetic anthropological treatments are needed, especially in efforts to inform debates among nonacademic audiences, because the discipline's approaches are ideally suited to study the origins of warfare. Emphasized is the need to consider possible forms of violence and intergroup aggression within Pleistocene contexts, despite the methodological challenges associated with fragmentary, equivocal, or scarce data. Finally, the review concludes with an argument about the implications of the currently available data. We propose that socially cooperative violence, or "emergent warfare," became possible with the onset of symbolic thought and complex cognition. Viewing emergent warfare as a byproduct of the human capacity for symbolic thought explains how the same capacities for communication and sociality allowed for elaborate peacemaking, conflict resolution, and avoidance. Cultural institutions around war and peace are both made possible by these changes. Accordingly, we suggest that studies on warfare's origins should be tied to research on the advent of cooperation, sociality, and communication.

Why war is a man's game

Interest in the evolutionary origins and drivers of warfare in ancient and contemporary small-scale human societies has greatly increased in the last decade, and has been particularly spurred by exciting archaeological discoveries that suggest our ancestors led more violent lives than previously documented. However, the striking observation that warfare is an almost-exclusively male activity remains unexplained. Three general hypotheses have been proposed, concerning greater male effectiveness in warfare, lower male costs, and patrilocality. But while each of these factors might explain why warfare is more common in men, they do not convincingly explain why women almost never participate. Here, we develop a mathematical model to formally assess these hypotheses. Surprisingly, we find that exclusively male warfare may evolve even in the absence of any such sex differences, though sex biases in these parameters can make this evolutionary outcome more likely. The qualitative observation that participation in warfare is almost exclusive to one sex is ultimately explained by the fundamentally sex-specific nature of Darwinian competition—in fitness terms, men compete with men and women with women. These results reveal a potentially key role for ancestral conditions in shaping our species' patterns of sexual division of labour and violence-related adaptations and behavioural disorders.

Coalitional Play Fighting and the Evolution of Coalitional Intergroup Aggression

Dyadic play fighting occurs in many species, but only humans are known to engage in coalitional play fighting. Dyadic play fighting is hypothesized to build motor skills involved in actual dyadic fighting; thus, coalitional play fighting may build skills involved in actual coalitional fighting, operationalized as forager lethal raiding. If human psychology includes a motivational component that encourages engagement in this type of play, evidence of this play in forager societies is necessary to determine that it is not an artifact of agricultural or industrial conditions. We examine whether coalitional play fighting appears in the hunter-gatherer record and includes motor skills used in lethal raiding. Using the ethnographic record, we generated a list of motor patterns regularly used in forager warfare. Then, using Murdock's Ethnographic Atlas, we identified 100 culture clusters containing forager societies and searched the ethnographic records of these societies for descriptions of coalitional play fighting, operationalized as contact games played in teams. Resulting games were coded for the presence of eight motor patterns regularly used in forager lethal raiding. Although play does not tend to be systematically documented in the hunter-gatherer literature, sufficiently detailed descriptions of coalitional play were found for 46 of the 100 culture clusters: all 46 exhibited coalitional play using at least one of the predicted motor patterns; 39 exhibited coalitional play using four or more of the eight predicted motor patterns. These results provide evidence that coalitional play fighting (a) occurs across a diverse range of hunter-gatherer cultures and habitats, (b) regularly recruits motor patterns used in lethal raiding, and (c) is not an artifact of agricultural or industrial life. This is a first step in a new line of research on whether human male psychology includes motivations to engage in play that develops the deployment of coordinated coalitional action involving key motor patterns used in lethal raiding.

Oral Storytelling as Evidence of Pedagogy in Forager Societies

Teaching is reportedly rare in hunter-gatherer societies, raising the question of whether it is a species-typical trait in humans. A problem with past studies is that they tend to conceptualize teaching in terms of Western pedagogical practices. In contrast, this study proceeds from the premise that teaching requires the ostensive manifestation of generalizable knowledge: the teacher must signal intent to share information, indicate the intended recipient, and transmit knowledge that is applicable beyond the present context. Certain features of human communication appear to be ostensive in function (e.g., eye contact, pointing, contingency, prosodic variation), and collectively serve as "natural pedagogy." Tellingly, oral storytelling in forager societies typically employs these and other ostensive behaviors, and is widely reported to be an important source of generalizable ecological and social knowledge. Despite this, oral storytelling has been conspicuously overlooked in studies of teaching in preliterate societies. Accordingly, this study presents evidence that oral storytelling involves the use of ostension and the transmission of generic knowledge, thereby meeting the criteria of pedagogy.

Diversity in human behavioral ecology

As befitting an evolutionary approach to the study of human behavior, the papers in this special issue of Human Nature cover a diversity of topics in modern and traditional societies. They include the goals of hunting in foraging societies, social bias, cooperative breeding, the impact of war on women, leadership, and social mobility. In combination these contributions demonstrate the utility of selectionist's thinking on a wide variety of topics. While many of the contributions employ standard evolutionary biological approaches such as kin selection, cooperative breeding and the Trivers-Willard model, others examine important human issues such as the problems of trust, the cost of war to women, the characteristics of leaders, and what might be called honest or rule-bound fights. One striking feature of many of the contributions is a novel reexamination of traditional research questions from an evolutionary perspective.