A panel on the probable lack of aggressiveness by early hominids, held at the February AAAS meeting in St. Louis, gained a lot of subsequent notice in the major international media. Interviewers for BBC News, National Geographic, New Scientist, and numerous others focused on the work of several prominent scientists who presented at the panel during the American Association for the Advancement of Science annual conference. These scholars have developed major challenges to the idea that human males are innately aggressive, and their arguments evidently fascinated the science and news organizations.

The National Geographic report featured a discussion of Douglas Fry’s acclaimed book The Human Potential for Peace. Fry’s St. Louis paper and his book argue that the evidence about early humans indicates they made a practice of resolving conflicts peacefully, perhaps as much or even more than they solved their disputes violently. The man-as-violent-aggressor model is probably flawed.

Among the several other speakers whom the press interviewed, Agustín Fuentes evidently spoke eloquently for himself and for his two co-authors, Katherine C. MacKinnon and Matthew A. Wyczalkowski, to explain how teamwork allowed early humans to avoid being prey for larger predators. The three researchers used computer modeling of possible cooperative behavior patterns by early members of the genus Homo to show that the ancestors of humans, compared to other primates several million years ago, may have survived and succeeded because of their ability to cooperate.

The fascination by the media for the new evidence presented by these scholars is mostly due to the fact that they question the long-held notion that human males are essentially aggressive. This “innate aggression” hypothesis, propounded by prominent authors such as E. O. Wilson, Robert Wright, Richard Wrangham, Dale Peterson, and Michael Ghiglieri, has been widely supported by much popular writing. The aggressiveness of humanity is innately tied to our genetic make-up and the nature of our reproductive system, inherited from our primate ancestors, or so the argument has gone.

The evidence and arguments against the theory are mounting. In addition to the AAAS meeting, a recent article by MacKinnon and Fuentes provides a well-written and easy-to-follow—but quite scholarly—argument that refutes some of the arguments advanced by Wilson in his landmark book Sociobiology: The New Synthesis. The special focus of the recent article is to examine the evidence from the field of primatology about the theories of Wilson and his followers.

At the risk of oversimplifying E.O. Wilson, the argument was that the well-documented aggressiveness of primates such as chimpanzees supports the theory that the processes of evolution select aggressive, competitive primate males who display their fitness for reproductive success.

According to MacKinnon and Fuentes, the validity of this theory of primate male aggressiveness has been increasingly questioned as research on different primate species and different populations of chimpanzees has raised more and more questions about the simple generalizations made by Wilson et al. The authors also question that there can be a simple definition of aggression since, among primates, there are many forms of aggressive behavior and many types of responses. Furthermore, they point out that aggressiveness among primates does not necessarily lead to increased mating success.

MacKinnon and Fuentes indicate that different populations of chimpanzees have different patterns of violence toward one another. They also show that using baboons as models for human behavior—aggressive males that supposedly control females—is flawed. Newer data confounds those models, as a recent article by Robert Sapolsky also indicates.

The authors summarize a variety of research results that indicate, “aggression sometimes plays a role in access to females and … testosterone is related to aggression, but social factors probably propel hormones at least as much as, if not more than, hormones trigger specific behaviors.” (p.91)

They review the research related to several primate species and find that the common ancestor of humans, chimpanzees, and gorillas probably had a capacity for aggressive behavior, but actual incidents of aggression certainly do not occur evenly in different species today. The bonobos, which are at least as close as chimpanzees to humans phylogenetically, release their tensions through peaceful, non-reproductive, sexual encounters instead of through fighting.

The authors also question the assumption that male dominance is an important aspect of male fitness for reproduction. Their evidence shows that alpha males are not necessarily the ones that breed the most successfully, and about half of the recent studies on this issue indicate that there is not much of a correlation between male dominance and reproduction.

MacKinnon and Fuentes argue that the reductionist perspective of E.O. Wilson and others “permeates mainstream investigations” (p.96). Recent data shows that primate male and female mating strategies are much more complex than previously thought.

The authors question many assumptions made by writers who have tried to simplify the processes of mating, aggressive behavior, and evolution. Some of their information is startling. For instance, they make it clear that the idea that aggressive behavior has developed primarily as a result of natural selection is overly simplistic. That view “fails to take into account the fact that aggression itself is not selected for. There is no gene or other single selective agent for aggression…”(p.98).

MacKinnon and Fuentes are of course cautious scholars, not about to launch off beyond the bounds of available scientific evidence. But their effective writing style allows the reader to easily grasp what could be difficult concepts. If E.O. Wilson and the others have erred in emphasizing the supposedly innate aggressiveness of human males, as the recent primate literature seems to suggest, perhaps the possibility of building more peaceful societies is not as far fetched as some people may imagine.

MacKinnon, Katherine C. and Agustín Fuentes. 2005. “Reassessing Male Aggression and Dominance: The Evidence from Primatology.” In Complexities: Beyond Nature & Nurture, edited by Susan McKinnon & Sydel Silverman, p. 83-105. Chicago: University of Chicago Press, 2005