Steven Pinker’s book, “The Better Angels of Our Nature,” has been getting substantial media attention this year, and it makes what many see as a surprising and counterintuitive claim about the decline of violence in human evolutionary history. Now, the academics weigh in. This year’s meeting of the International Studies Association featured a panel organized exclusively around Pinker’s book. The environment was friendly and engaging, as political scientists, historians, psychologists and others assembled to consider the question of trends in violence and warfare throughout human evolution.

Steve Pinker took the floor first and summarized the central tenets of his book. Whatever your view on human nature, Pinker argues, it is an empirical fact that violence has declined over evolutionary time. However, a clearer understanding of human nature can in fact help us to understand why this trend has occurred. Pinker explains that human nature is a complex web of competing motives, some of which incline us toward violence, others which motivate cooperation. What an individual actually does at a particular moment in time depends in part on the balance between these competing motives.

Pinker then explained that this complex motivational system is composed of many psychological adaptations, most of which operate “facultatively” or conditionally. In other words, there is no aggression “instinct” or impulse. To make this clearer, Pinker contrasted facultative adaptations with those that operate in a “hydraulic” fashion (or what some evolutionary biologists refer to as “obligate”). Consider the example of shivering. Every human body has adaptations for shivering, but unless you are cold, Pinker explained, you can go your whole life without shivering: “…it’s not as if you have a mounting urge to shiver, which just has to burst out!” In short, if adaptations for violence are facultative, then we need to learn about the environmental conditions that trigger it. This is necessary if we want to understand how to reduce violence, and to understand why it seems to have declined.

Pinker points to many of the developments that political scientists themselves have pointed to when attempting to explain periods or trends in peace among and within nations. Among these developments are the proliferation of international institutions, the spread of democracy, economic interdependence, the increasing prominence and effectiveness of sanctions against the use of force, and the doctrine of human rights. Some evolutionary psychologists have argued that our modern institutions and social norms may in fact reflect evolved preference structures designed by natural selection for navigating the world of ancestral politics. Although Pinker does not disagree, he argues that even if these norms and institutions were developed through rational, disinterested, scientific deliberative processes, these institutions nevertheless engage our better angels and cage our inner demons. In other words, if behavior is the product of internal tradeoffs and motivational conflicts, the presence of exogenous social sanctions may be sufficient to tilt the field in favor of one motivational pattern over the other. What we have seen then, especially over the last few hundred years, is a process of social evolution in which the products of social innovation have established a network of norms and sanctions that increasingly buffer us from the inner demons of our natures. This is visible not only in drastic declines of within-state violence, but also between-state violence. In fact, in the last 50 years, we see for the very first time in history that all three of the following trends are decreasing in tandem: the frequency of great power wars, the duration of these wars, and the number of people killed per country per year in these wars.

Maybe our theories are better today than they were 100 years ago, but I’m not sure.” -Jack Levy

After Steve Pinker’s presentation, a panel of political scientists was given the opportunity to respond. The panel consisted of Jack Levy, Bradley Thayer, and Azar Gat, all of whom have contributed to the literature in this area. The first to speak was Jack Levy, who took the opportunity to remind the audience that it was almost exactly 100 years ago today that scholars of international relations made similar claims, only to be rebuffed by the onset of two of the world’s most devastating global wars. “Maybe our theories are better today than they were 100 years ago,” Levy offered, “but I’m not sure.” It wasn’t clear whether Levy was referring to theories of international politics (in which case he makes a fair point) or whether he was referring to theories of human behavior (if so, Levy’s suggestion is, in my opinion, deeply flawed). Nevertheless, Levy questioned the feasibility of a general theory of violence.

If the leviathan is good in the domestic context, isn’t the leviathan good in the international context?” -Bradley Thayer

Brad Thayer praised Pinker’s book as an example of successful consilience scholarship. Although agreeing with the general premise of the book, Thayer suggested that Pinker’s explanation for the decline of within-state violence (e.g. legitimate monopoly on the use of force) was more compelling than Pinker’s discussion of the mechanisms that have fostered inter-state peace (e.g. institutions and inter-dependence). According to Thayer, more explanatory weight must be given to the balance of power and the role of American hegemony in giving shape to these international trends. Furthermore, if indeed the leviathan (i.e. centralized government) is good in the domestic context, isn’t the leviathan good in the international context as well? And how can we be sure that the anarchy of the international system will not ultimately give succor to our “inner demons” and cause significant backsliding from achievements made in the name of peace? Thayer argues that much of the institutional cooperation that is possible in the international system today is a consequence of guarantees provided by American power. If so, then the prospect of American decline (in the context of a rising China, for example) may indeed foster uncertainty and mistrust, as economic interdependence begins to look much more like strategic vulnerability.

Rather than war becoming more costly, it is in fact peace that has been growing more profitable.” -Azar Gat

Finally, Azar Gat found himself mostly in agreement with Pinker, especially since his own recent book on the subject offers many similar arguments. Gat instead took the opportunity to criticize another recent book on the evolution of war by Jack Levy and William Thompson for its implicit endorsement of the “Rousseauite fantasy” of human nature, “which recent studies have proven to be delusional.” In this regard, Gat pointed to work by Harvard archeologist Steve LeBlanc, as well as Lawrence Keeley, among others, who have compiled evidence against notions of the noble savage and a peaceful past. Although some in the audience were surprised that Gat chose to spend much of his time criticizing Levy and Thompson, these points were in fact crucial to the larger discussion. For example, as Thayer had earlier mentioned, Pinker demonstrates that the “past was far nastier than we imagine; and the present is far nicer than we imagine.” However, most of the discussion thus far had focused on explaining very recent trends in violence, especially since 1815. Gat wanted to remind us that a key point in Pinker’s argument (and Gat’s own argument) is that much archaeological and anthropological evidence suggests that pre-historic violence was much more lethal and frequent than we expected or imagined. It is in combination with recent international developments that we see an overall decline in violence, from pre-historic times to the present. This is fundamentally an evolutionary trend. Gat explains that what is special about modern environments is that the Malthusian trap has been broken; economies are increasingly interconnected, and it is no longer necessary to possess territory in order to benefit from it. Rather than war becoming more costly, Gat argues, “it is in fact peace that has been growing more profitable.”

Pinker had a chance to respond to the panelists, and offered the following thoughts. Although arguments on the decline of violence are not historically new, Pinker acknowledged, there have been substantial qualitative changes in the international environment that deserve to be taken seriously, especially the presence of international institutions and the spread of democracy. However, it is necessary to guard against the “the other guy problem,” in which you may take genuine steps toward restraint and nonviolence, but what do you do when the other guy doesn’t? Essentially, the problem is how to dis-incentivize both sides from violence simultaneously, so that peace does not depend on unilateral pacifism, which may indeed be a recipe for disaster.

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