When I read through John Horgan’s article, “Quitting the hominid fight club: The evidence is flimsy for innate chimpanzee–let alone human–warfare” in Scientific American I was surprised. I know John and have talked to him about the topic of lethal intercommunity coalitions (LICs), and the evolution of warfare in the past. I sat there thinking to myself, “Why did he take this position in this article?” And, “Does it matter?” The answer to the second question is, “Probably not.” The investigation of the roots of warfare is a search for fact, not truth. While personal philosophies often confuse and muddle that search, the objective should remain objectivity.

When Mr. Horgan declared that he had turned, “…from a believer to a skeptic” we discover all that we really need to know about his commentary. He was a follower of the “Church of Demonic Males” and has “fallen from grace”. Mr. Horgan, for all of his pure intentions, was never an investigator who had been convinced by the evidence that supports an evolutionary predisposition towards lethal intercommunity coalitions among male humans and chimpanzees, that our common ancestry with chimpanzees is marked by males that were willing to kill their own kind. Instead, Mr. Horgan, who is an excellent science writer, was a believer, in a philosophy that looks at the world through red in tooth and claw glasses. While Mr. Horgan’s shift in his personal philosophy will probably not do much to impact the study of the evolution of warfare in our lineage, his article provides an opportunity to address several issues that are often misunderstood or misrepresented in this line of inquiry.

At the beginning of his article Mr. Horgan claims that a quote from Wrangham and Peterson’s 1996 book “Demonic Males:Apes and the Origins of Human Violence” is an extraordinary claim. When examined more closely, the quote, “Chimpanzeelike violence preceded and paved the way for human war, making modern humans the dazed survivors of a continuous, five-million-year habit of lethal aggression.” is obvious to most, it’s creative language used in a trade book to make a dramatic point. Mr. Horgan apparently doesn’t see it that way. Instead he uses it as his basis for analysis of what he calls the “demonic-males theory”. This is where I am reminded how few people understand the difference between a theory and a hypothesis, and it’s particularly upsetting that an otherwise excellent science writer doesn’t seem to grasp these two elemental concepts in science. In the sciences a theory is an agreed upon explanation of a phenomenon, or group of phenomena, that has been consistently supported through empirical testing, using available data. In other words, in the sciences, a theory is kind of a big deal. In the sciences a hypothesis is a proposed explanation for an observable phenomenon or group of phenomena. The ideas put forward by Wrangham and others about the evolutionary basis of LICs in chimpanzees, humans and our common ancestor are hypotheses, they are yet to reach the level of theory. Unfortunately for his argument Mr. Horgan doesn’t seem to recognize this.

Mr. Horgan continues in his article by suggesting that researchers are somehow inflating the numbers of their studies by putting things in a context of 100,000 individuals in a population. This is really an issue for the statistical tests being used, and much like the effect of predation, LICs, while rare, are critically important for the individuals impacted by those behaviors. He further tries to minimize the impact of LICs by quoting a study by Sussman and Marshack that showed that on average researchers observed LICs among chimpanzees once every seven years. If we were to do the same sort of analysis on rates of predation among wild chimpanzee populations, I bet we would find that predation was observed even less by researchers. I will soon be running this analysis to verify my wager. However, there are few researchers that would claim that predation has not been an important selective force in the natural history of chimpanzee populations. Likewise, Mr. Horgan seems to minimize the importance of infanticide as part of this behavior. By doing so he seems to be ignoring the impact that killing the offspring of rivals, and potential rivals, has on competition between groups of males. I can only attribute this position to his relative ignorance of the study of infanticide in chimpanzees and other mammals.

Mr. Horgan continued his article by asking the question: Could unusual environmental conditions be triggering intergroup chimpanzee killing? To support this proposition, he used a quote from Jane Goodall, that appeared in Sussman and Marshack’s paper in which Dr. Goodall said that provisioning, “…was having a marked effect on the behavior of the chimps. They were beginning to move about in large groups more often than they had ever done in the old days. Worst of all, the adult males were becoming increasingly aggressive. When we first offered the chimps bananas the males seldom fought over their food; …now…there was a great deal more fighting than ever before.” To the casual observer, this quote would indicate that chimpanzees only started forming large parties and engaging in LICs after they were provisioned with bananas. To this I suggest reading the report by Mitani et al more closely, in which they are describing and analyzing the behavior of the Ngogo chimpanzee community. The Ngogo community has never been provisioned and is in the middle of a fairly stable national park, with little human encroachment. Yet, this community patrols and engages in LICs at higher rates than any other community observed to this point.

Mr. Horgan goes on to talk about bonobos and how they may more accurately represent our primate ancestry than chimpanzees. This is a position held by a minority of scientists. Bonobos are geographically isolated to the south of the Congo River, while chimpanzees stretch from the western edge of Africa to the Albertine Rift. Bonobos are much more homogeneous, ecologically than chimpanzees. Finally, bonobos have derived characteristics not shared by chimpanzees or humans. It is more plausible [and parsimonious] that the common ancestor of bonobos, humans and chimpanzees was chimpanzee-like and that bonobos and humans are derived from that ancestral condition.

In a flash, Mr. Horgan moves quickly into archaeology and the seeming absence of data that indicates warfare in our recent evolutionary past. This is a leap given the evidence of warfare in numerous prehistoric societies, that have spawned volumes like Pearson’s “Warfare, Violence and Slavery in Prehistory”, Guilaine’s “The Origins of War: Violence in Prehistory” and Arkush and Allen’s “The Archaeology of Warfare: Prehistories of Raiding and Conquest”. These volumes together represent over 40 separate studies that document and analyze warfare in prehistoric societies. Despite this, Mr. Horgan continues the myth that there is little evidence of warfare in prehistory. Even if we ignore these studies for a moment [a difficult task given their breadth and scope] there is a point that Mr. Horgan seems to be missing: warfare doesn’t always take the form of battles between armies. It often consists of a few individuals ambushing a member of another community and inflicting as much damage as possible in an attempt to kill that individual.

Dr. Fry, who Horgan invokes next to combat the dreaded “demonic-males theory” has tried to minimize the importance of warfare among hunter-gatherers and pre-state societies by using definitional deflection. He is using the definition of war to deflect readers from a pattern, observed in prehistory and today, among male humans that resembles chimpanzee boundary patrols and territoriality: Groups of related males working together to isolate, ambush and kill [if possible] males from other communities. While modern human and chimpanzee males engage in this behavior, and human males in prehistory did likewise, it leaves little direct evidence for researchers to find. Human victims of this sort of ambush killing die alone and their bodies are often not recovered. In the forest we are lucky if we find the bodies of chimpanzees that have been killed by rivals from other communities – dead bodies don’t last long in the rainforest. While I would never say that we can use data that doesn’t exist to support a position in science, I would agree that just because we haven’t observed something yet, we cannot conclude that it doesn’t happen. It took years of observation for Jane Goodall to describe to us all how chimpanzees regularly make and use tools in the wild – a trait that used to distinguish our species from all others.

Mr. Horgan is a self-proclaimed “peacenik” who obviously would like to believe that our ancestry is much less bloody than what the data indicate. I do not fault his philosophical position, I just hope that those reading his article do not confuse it for scientific inquiry or skepticism. One thing that I do hope is that the individuals who share Mr. Horgan’s personal philosophy come to understand that ignoring facts and plausible explanations for phenomena will not make them go away. If we want to be able to do something about war, we need to understand where it comes from. To do that, we need to consider all of the data available, not just that which fits within our personal philosophies.

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