For hundreds of years, humans have been regarded as innately violent, especially toward members of other communities. An alternative view is that an originally peaceful nature was irredeemably corrupted once people settled down, started to rely on domesticated plants and animals, and developed organizationally complex societies. Diving deep into humankind's evolutionary past, the authors explore the origins of the relationship between cooperation and competition, with the latter distressingly often devolving into outright warfare.

For archaeological purposes, warfare might be considered culturally sanctioned fighting between different communities in which individual and collective advantages accrue to the participants and anyone classified as an enemy is an acceptable victim. The size and structure of war parties, nature and duration of fighting, number of casualties, and weapons employed are not relevant to such a definition.

For the societies of the last several millennia, simply identifying warfare's existence can be hard, although not nearly as difficult as estimating its frequency, intensity, and societal impact. Turning to anatomically modern humans dating to the Paleolithic, finding unequivocal signs of intergroup violence is the best that one can reasonably expect. Solid evidence is even harder to identify for our hominin ancestors, despite the prominence of their supposed behavioral repertoire in how we view our apparent propensity toward violence and the seeming impossibility of escaping it.

As Nam Kim and Marc Kissel point out, violence was part of our hunter-gatherer past, to judge from skeletal trauma. It is difficult, however, to determine how those injuries came about. Here it is useful for archaeologists to draw a distinction between the cause and manner of injury or death, as is common in forensic work. That is, the nature of the trauma (e.g., an arrow wound) is different from the circumstances that resulted in the injury (e.g., homicide or combat).

Turning to our hominin ancestors, data in the form of skeletal trauma are too thin to address systematically the origins of intergroup conflict. Instead, Kim and Kissel use other indirect lines of evidence, notably primate behavior. Chimpanzees figure prominently here, especially their periodic hunting forays and attacks on neighboring groups.

Rather than cast competition in opposition to cooperation, the authors emphasize the need for individuals to work together when engaging in intergroup conflict. This “socially cooperative violence” (p. 113), labeled “emergent warfare,” likely originated in the Pleistocene. The option of attacking conspecifics was not a stand-alone and hardwired aspect of our distant ancestors’ psyche (if it could be called that). Instead, Kim and Kissel see it as part of a gradually developing capacity to recognize group identities, cooperate in various tasks, and communicate effectively. Such violent acts were one aspect of the behavioral adaptability, with its benefits, costs, and situational flexibility, that forms the basis of our species’ success. Our ancestors did not sit around campfires happily holding hands and singing “Kumbaya” until they were somehow undone by growing crops, tending animals, and living in chiefdoms or states.

The authors discuss how peace is not simply an absence of war, neither today nor in the past. It must be actively constructed and maintained, and it might be established through elaborate political mechanisms or uneasy standoffs between potential foes who find fighting more costly than not doing so. The purposeful creation of peace in the past demands the attention that warfare is already receiving.

Going beyond warfare and the principal topics covered in this book, more archaeological work should be directed toward violence within individual societies, including what took place and who was affected. Only recently has within-group violence gained traction as a focus of research, which has mainly involved skeletal remains. But even the significance of skeletal trauma needs rethinking. Survival from trauma, as marked by healed fractures and the like, is usually considered to be of little consequence, except as an indication of the accommodations, even compassion, that injured individuals received. For late Holocene sites where skeletal samples can be large, it is possible to estimate quantitatively the lingering effects of injuries in terms of lost years of life; that is, the cost of trauma to households and communities. Further work on both issues, among others, will do much to extend our understanding of violence, in all of its various forms, deep into the past.

Of the numerous books published on warfare since it became a major focus of archaeological study about a quarter century ago, this one is among the first that should be read. Kim and Kissel's evolutionary perspective offers us much to think about, and in providing it they widen our horizons about what has been and continues to be a pervasive feature of human existence: warfare.