In this book, Potts and Hayden explore the evolutionary basis of violence. Drawing heavily on E.O. Wilson’s 1998 book Consilience, as well as a range of theoretical and empirical works in social anthropology, evolutionary theory, economics, and behavioral studies, their argument looks to explain why “in every society, across time and space, men on average are much more violent than women.” The book is aimed at the general reader, albeit perhaps one with a more than passing interest in these issues, and is, in the main, non-technical.

In the first part of this book, the authors develop this evolutionary psychology. In the Stone Age, being evil to others made good evolutionary sense. Males benefited from violently attacking outsiders, in a pattern that is here termed team aggression, as it increased the chances of successfully propagating their genes. This behavior, once valuable, has however been (inappropriately) retained. And it is this legacy that explains human violence.

Once this mechanism by which violence arose in our evolutionary past has been introduced, the authors turn to an extensive catalogue of instances of its operation: the War on Terror, the downfall of Black September, the origins of slavery, the massacres of My Lai and Thanh Phong, the Khmer Rouge, the Rwandan genocide, Stalin and the Gulag Archipelago, the rise of the Nazi party, the tropes of Right-wing politics, Darfur, the weapons of the Cold War, pro-life activism, the nature of South Africa’s Truth and Reconciliation Commission, and the development of civilization itself are all in some way consequences of team aggression.

The final parts of the book then offer means by which this evolutionary pitfall can be avoided. In essence, the argument here is that population stabilization is key to avoiding violence. Reproductive freedom for women, the authors argue, “is a crucial and necessary precondition for bringing to an end war as we know it.” This argument is well-made and convincing, fits well with the earlier parts of the book, and leads to the impression of a strong, thoughtful and positive contribution to the literature on violence.

That is not to say that everything in this (substantial) volume is successful. For example, the development of the concept of team aggression critically depends on comparative observations of such behavior in primates. However, as the authors admit, such observations are extremely uncommon, with only seventeen directly observed episodes ever reported. More troubling, it has only been seen in one species of primates – Pan troglodytes, but not in others which are commonly used as model systems of human behavior, such as Pan paniscus. Thus the strength of the conclusions drawn from this rare (and poorly understood) behavior must stand in some doubt.

The volume of examples of human violence given can also be overwhelming. While the attempt to show the sheer scope of this behavior is laudable, perhaps a more fully developed analysis of the detailed contribution of team aggression to particular events would have been valuable. That is not to say that the many examples are without interest. A good example are the sections that deal with Potts’ own work, such as that recounting his involvement with Marie Stopes International in Sierra Leone. This episode, writes Potts, involved a subversion of the usual rules of team aggression: “Like warriors, like any band of brothers, the staff suffered casualties entering conflict zones, they took risks to protect each other in pursuit of a common goal, and they were bonded in their work.”

A more serious difficulty comes in the odd asymmetry between the descriptions of violence in the first parts of the book, and the solutions suggested later. Descriptions of the mechanisms by which our evolutionary heritage influence our behavior strongly emphasize the causal role of genes, rather than the environment. However, when it comes to offering solutions, the authors rely on a much stronger interactions between genes and the environment in bringing about improvements in human behavior. This seems a strange position to adopt, particularly as many of their examples explored in the text — such as the relationships between population demographics and violence — strongly suggest that this kind of interaction is key to understanding why, given that all men share this violent past, not all are bad. This over-reliance on both the importance of genes in controlling behavior, and the inappropriately strong distinction drawn between genes and environments as drivers of the way that humans are, harm the intellectual integrity of this work. Even though Potts and Hayden acknowledge that both genes and environments are significant, (e.g. “If we are indeed violent by nature, so too are we subject to the moderating or inflammatory effects of nurture, in all its forms”) their case still, ultimately, depends upon this false distinction, and this weakens their overall argument badly.

There are also occasional minor factual errors (a range of different costs for the War on Terror are given; the surgeon Charles Bell is described as working in the Crimean war, rather than at the battle of Waterloo,) but in general, these do not significantly affect the text.

In summary, while the details of this book are interesting, and the conclusions worthy — and worth taking very seriously — the argument is flawed by an over-reliance on the genetic causes of our behaviors. We still do not know why, given that all men are genetically cruel, not all of us behave in such a manner.

© 2011 Brendan Clarke

Dr. Brendan Clarke is a teaching fellow in history and philosophy of science at University College London. Originally qualified in medicine, he has recently completed a PhD at University College London entitled “Causality in Medicine with particular reference to the viral causation of cancers”. His current research focuses on the history and philosophy of the life sciences.