There have been many articles over the past week reporting that an unusually large group (150 members) of chimpanzees in Kibale National Park, Uganda has been engaging in systematic territorial expansion by attacking and killing neighboring groups. The Nature article notes that this is “cooperative behavior” and then quotes from the New York Times story:
These killings have a purpose, but one that did not emerge until after Ngogo chimps’ patrols had been tracked and cataloged for 10 years. The Ngogo group has about 150 chimps and is particularly large, about three times the usual size. And its size makes it unusually aggressive. Its males directed most of their patrols against a chimp group that lived in a region to the northeast of their territory. Last year, the Ngogo chimps stopped patrolling the region and annexed it outright, increasing their home territory by 22 percent.
The Times reporter, Nicholas Wade, continues with an interesting observation and comparison:
Warfare among human groups that still live by hunting and gathering resembles chimp warfare in several ways. Foragers emphasize raids and ambushes in which few people are killed, yet casualties can mount up with incessant skirmishes.
Why do chimps incur the risk and time costs of patrolling into enemy territory when the advantage accrues most evidently to the group? Dr. Mitani invokes the idea of group-level selection — the idea that natural selection can work on groups and favor behaviors, like altruism and cooperation, that benefit the group at the expense of the individual. Selection usually depends only on whether an individual, not a group, leaves more surviving children.
Many biologists are skeptical of group-level selection, saying it could be effective only in cases where there is intense warfare between groups, a reduced rate of selection on individuals, and little interchange of genes between groups.
Although Wade is not a biologist, he is not skeptical of group level selection — indeed, he is an ardent advocate. In his recent book, The Faith Instinct: How Religion Evolved & Why It Endures, Wade contends that religion was an adaptation specifically targeted by selection because it made groups more cohesive and cooperative. This, in turn, enabled religious groups to better compete against other groups. A major aspect of this enhanced ability to compete, so the argument goes, is that religious groups are better able to war against non-religious groups. Wade is not alone in believing this; the anthropologist David Sloan Wilson and evolutionary psychologist Matt Rossano make similar arguments.
The recent chimp study — “Lethal intergroup aggression leads to territorial expansion in wild chimpanzees” — bears on this hypothesis. The aggressive Kibale group is exceptionally large because it occupies particularly fertile territory. This fertile territory sustains larger numbers of chimps, who in turn cooperate and use this numerical advantage to further enlarge their territory. No one has ever suggested that chimps are spiritual or religious, so these activities — cooperation and warfare — are not being driven by these abstractions. Kinship is the primary factor holding the males of these groups together, and which causes them to cooperate.
This is quite similar to the ethnohistoric situation on the Great Plains. From 1680 to 1880, Plains Indian tribes such as the Lakota, Cheyenne, Kiowa, Comanche, Crow, Kiowa-Apache, Shoshoni, Blackfoot, Cree, Gros Ventre, Flathead, and Sarsi constantly warred against one another for territory, horses, and booty. These hunting and gathering groups were held together first and foremost by extended kinship ties; shamans neither organized nor lead war parties. These tribes neither invoked nor relied on religious differences as a justification for war or raiding. In fact, it would have been impossible to do so given that these tribes had substantially similar types of beliefs and rituals. The most successful of these tribes — the Lakota — enlarged their numbers and expanded their territory not because they were more spiritual or religious than the other tribes, or had more effective group rituals. Instead, they had various material, geographic, and economic advantages which enabled them to succeed.
This is not to say that in certain places and at certain times some groups used religion to bind them together and justify war. It occurred many times and in many places, but this is fairly recent behavior that corresponds to the rise of the first city-states in Mesopotamia, Egypt, and the Near East. Because this is modern behavior that is the product of rulers and elites marrying religion to power, I cannot see how it has anything to do with the evolutionary origins of religion.