Intelligence, Coalitional Killing, and the Antecedents of War (original) (raw)

Warfare, Ethics, Ethology: Evolutionary fundamentals for conflict and cooperation

Journal of Big History, 2018

The aim of this article is to set a macro-historical narrative concerning the emergence of warfare and social ethics as symplesiomorphic features in the lineage of Homo sapiens. This means that these two behavioral aspects, representative of a very selected branch in the phylogenetic tree of the Primate order, are shared by the two lineages of great African apes that diverged from a common ancestor around six million years in the past, leading to extant humans and chimpanzees. Therefore, this article proposes an ethological understanding of warfare and social ethics, as both are innate to the social high-specialized modular mind present in the species of genera Pan and Homo. However behavioral restraints to intersocietal coalitionary violence seems to be an exclusive aspect of the transdominial modular cognition that characterizes modern humans. Thus, if in the evolutionary long durée, warfare and restrictions to intrasocial violence both appear to be ethologically common to humans and chimpanzees to a certain extent, an ethics of warfare - and, of course, the cognitive capability for intersocietal peace - seems to be distinctly human.

Evolution of coalitionary killing

American Journal of Physical Anthropology, 1999

Warfare has traditionally been considered unique to humans. It has, therefore, often been explained as deriving from features that are unique to humans, such as the possession of weapons or the adoption of a patriarchal ideology. Mounting evidence suggests, however, that coalitional killing of adults in neighboring groups also occurs regularly in other species, including wolves and chimpanzees. This implies that selection can favor components of intergroup aggression important to human warfare, including lethal raiding. Here I present the principal adaptive hypothesis for explaining the species distribution of intergroup coalitional killing. This is the ''imbalanceof-power hypothesis,'' which suggests that coalitional killing is the expression of a drive for dominance over neighbors. Two conditions are proposed to be both necessary and sufficient to account for coalitional killing of neighbors: (1) a state of intergroup hostility; (2) sufficient imbalances of power between parties that one party can attack the other with impunity. Under these conditions, it is suggested, selection favors the tendency to hunt and kill rivals when the costs are sufficiently low. The imbalance-of-power hypothesis has been criticized on a variety of empirical and theoretical grounds which are discussed. To be further tested, studies of the proximate determinants of aggression are needed. However, current evidence supports the hypothesis that selection has favored a hunt-and-kill propensity in chimpanzees and humans, and that coalitional killing has a long history in the evolution of both species.

Chimpanzees, warfare and the invention of peace

War, Peace, and Human Nature, 2013

Many features of human societies are clearly inventions, such as agriculture (Bocquet-Appel, 2011), the domestication of cattle (Zeder, 2011), and writing (Woods, 2010). Other human traits are genetic adaptations and thus the products of evolution by natural selection, such as malaria resistance (Hedrick, 2011), lactase persistence (Leonardi, Gerbault, Thomas, & Burger, 2012), and, arguably, language (Pinker & Bloom, 1990). Anthropologists have long debated whether warfare is an invention (Gabriel, 1990; Haas, 2001; Kelly, 2000; Mead, 1940; Montagu, 1976) or an adaptation (Alexander, 1979; Gat, 2006; Tooby & Cosmides, 1988; Wrangham & Peterson 1996; van der Dennen, 1995). This debate largely follows the intellectual traditions established by Hobbes and Rousseau (Otterbein, 1999; Gat, 2006). Hobbes (1651/1997) considered “Warre” to be the natural state of humans, with strong institutions (the “Leviathan”) being necessary to keep in check natural tendencies toward selfi shness, theft , and violence. In contrast, Rousseau (1754/1964) argued that people were basically peaceful and cooperative, until corrupted by institutions such as property ownership. Hobbes and Rousseau illustrated their arguments with imagined states of nature, based mainly on their own intuitions and experiences, combined with travelers’ tales of “savages” in the Americas and elsewhere, and, for Rousseau, early descriptions of the behavior of African apes (Rousseau 1754/1964). While rooted in competing philosophical traditions, the question of whether warfare is an invention or an adaptation is ultimately an empirical one, which can be answered (at least in principle) by evidence from archaeology, ethnography, and other sources, including animal behavior. Field studies of our evolutionary cousins, chimpanzees, have played an important role in this debate (Boehm, 1992; Bowles, 2009; Eibl-Eibesfelt, 1979; Kelly, 2005; Otterbein, 2004; Sussman, 1999; Wrangham & Peterson, 1996). Here I review the evidence for warlike behavior in chimpanzees and discuss what these findings can tell us about human warfare. I begin with a review of the behavioral ecology of aggression, continue with an overview of the behavioral ecology of intergroup aggression in chimpanzees, and conclude with discussion of the implications for understanding the origins of war and prospects for peace in humans.

Evolutionary Psychology and Warfare

SAGE Handbook of Evolutionary Psychology, 2020

The scientific study of the evolution of human coalitional aggression has exploded over the last three decades. In four parts, I explore and integrate many of the useful frameworks that have emerged to describe and explain the human practice of intergroup violence. First, we have a clearer understanding of the general conditions required for the evolution of adaptations for coalitional aggression. Second, given an understanding of these conditions, we can more usefully examine the historic and prehistoric record for evidence of the existence of these conditions. Third, I explore and integrate current lab and field evidence for psychological adaptations for coalitional aggression. This section reveals a core dynamic underlying all forms of coalitional aggression: the form of intergroup engagement is functionally linked with the emergent patterns of intragroup dynamics. In other words, how we fight “abroad” determines how we cooperate “at home,” and vice versa. I examine five areas of inquiry that suggest special design for coalitional aggression. These are: the collective action problem of coordinated violence; parochial altruism; attacker-defender asymmetries; leader-follower dynamics; sex differences in the costs and benefits of violence. Fourth, and to conclude, I offer speculation on the historical emergence of modern human warfare. I do not use “coalitional aggression” and “warfare” interchangeably; rather, evolved psychological adaptations for small-scale coalitional aggression are what make the historical emergence of large-scale human warfare possible.

Lethal coalitionary aggression and long-term alliance formation among Yanomamö men

Some cross-cultural evidence suggests lethal coalitionary aggression in humans is the product of residence and descent rules that promote fraternal interest groups, i.e., power groups of coresident males bonded by kinship. As such, human lethal coalitions are hypothesized to be homologous to chimpanzee (Pan troglodytes) border patrols. However, humans demonstrate a unique metagroup social structure in which strategic alliances allow individuals to form coalitions transcending local community boundaries. We test predictions derived from the fraternal interest group and strategic alliance models using lethal coalition data from a lowland South American population, the Yanomamö. Yanomamö men who kill an enemy acquire a special status, termed unokai. We examine the social characteristics of co-unokais or men who jointly kill others. Analyses indicate co-unokais generally are (i) from the same population but from different villages and patrilines, (ii) close age mates, and (iii) maternal half-first cousins. Furthermore, the incident rate for co-unokai killings increases if men are similar in age, from the same population, and from different natal communities. Co-unokais who have killed more times in the past and who are more genetically related to each other have a higher probability of coresidence in adulthood. Last, a relationship exists between lethal coalition formation and marriage exchange. In this population, internal warfare unites multiple communities, and co-unokais strategically form new residential groups and marriage alliances. These results support the strategic alliance model of coalitionary aggression, demonstrate the complexities of human alliance formation, and illuminate key differences in social structure distinguishing humans from other primates.

The Evolution of War and its Cognitive Foundations

Coalitional aggression evolved because it allowed participants in such coalitions to promote their fitness by gaining access to disputed reproduction enhancing resources that would otherwise be denied to them. Far fewer species manifest coalitional aggression than would be expected on the basis of the actual distribution of social conditions that would favor its evolution. The exploitation of such opportunities depends on the solution by individuals of highly complex and specialized information processing problems of cooperation and social exchange, and the difficulty of evolving cognitive mechanisms capable of solving such complex computational tasks may account for the phylogenetic rarity of such multi-individual coalitions. We propose that humans and a few other cognitively pre-adapted species have evolved specialized cognitive programs, that govern coalitional behavior, and constitute a distinctive coalitional psychology. An adaptive task analysis of what such algorithms need to accomplish, in the decisions regulating coalition formation, participation, cost and benefit allocation, allows the preliminary mapping of this coalitional psychology. Scrutinization of the adaptive features of coalitional aggression reveals some surprising characteristics, including that, under certain conditions, mortality rates do not negatively impact the fitness of males in the coalition, suggesting why warfare is so favored an activity, despite its risks to participating individuals' welfare.

The Most Dangerous Animal: Human Nature and the Origins of War

Peace & Change, 2010

David Livingstone Smith's The Most Dangerous Animal: Human Nature and the Origins of War is the latest in a seemingly endless procession of popular writings purporting to explain the existence of war by biologically evolved tendencies to kill. In many ways it follows the standard formula: many detailed examples of almost unimaginable brutality, dubious analogies, scoffing at disbelief as wishful thinking, and invoking the standard formulation that only by facing up to the ugly biological truth will we be able to find a way past war. ''Human beings may not be doomed to war. We may be able to break its spell and take control of our future. But to do this we must be willing to look at ourselves, and face some stark unflattering truths'' (p. 27). What makes this book different is that Smith directly confronts some contradictory evidence that other writers ignore, the well-documented fact in American war studies that soldiers in combat very frequently display an extreme reluctance to take others' lives. Thus, humans appear to be ambivalent about war. He finds the answer to this puzzle in evolutionary psychology and a self-deceiving clash of hypothetical mental modules. Chapters One and Two give a general overview of his argument. Chapter Three asserts the necessary foundation for any biological explanation of war: humans have practiced war throughout our archaeological past. In Chapter Four, Smith claims that the roots of war go back to our common ancestors, chimpanzees, and that our propensity to kill has been propagated over the eons because it led to reproductive success. Chapter Five is about evolutionary psychology and its theory that the mind is made up of a mass of evolved, dedicated modules, which process certain types of information and produce particular dispositions for action. Chapter Six is on selfdeception, the idea that different parts of the brain can be disharmonious, one module pulling the wool over the other. Chapter Seven asks