Brilliant, original and thought provoking: a study of human & animal evolution, with profound implications for human history.
Wrangham’s thesis is that domestication reduces reactive aggression, striking out in fear and anger. The domestication syndrome includes lighter bones, reduced dimorphism, smaller brains without reduced intelligence, and facial paedomorphism, where juvenile features continue into adulthood. Domesticates’ behaviour is also juvenile, trusting and playful, including sexual play. He argues these markers of domestication are not themselves adaptive, but the side effects of reduced reactive aggression.
Domestication can occur in three ways, first by man selecting animals which were easier to control, so docile farmed cattle replaced the larger, more dangerous hunted auroch, second by association with man, dogs evolving from wolves, feeding on rubbish heaps around human camps, wilder animals being driven off, and third by what Wrangham calls “self-domestication”. Once it occurred, by whatever means, domestication was irreversible. Dogs evolved from the wolf, dingos from domesticated dogs brought to Australia with Aboriginal venturers. Dingos returned to the wild, but did not revert to being wolves.
He argues bonobo were self-domesticated from a common chimp/bonobo ancestor, living with gorillas north of the Congo. The two species fed on common foods. Gorilla bands monopolised food sources, forcing female chimps to disperse to feed. This left them liable to male chimp violence, employed to ensure sexual access. The Congo formed an un-crossable barrier to non-swimming apes. In a Pleistocene dry period, both species may have been able to cross shallows in the upper reaches. However gorillas could not survive south of the river. In renewed dry periods, there were no mountains into which they could retreat, as there are north of the river. This left the ur-bonobo without competitors. Females formed feeding bands which excluded aggressive males, resulting in self-domestication, reducing reactive aggression within the new, now isolated, species.
Robust hominins were succeeded by gracile H sapiens, who display the domestication syndrome, suggesting human self-domestication and reduced reactive aggression. Human self-domestication followed a different path from bonobos. Hunter-gatherers established and maintained egalitarian groups by execution, disproportionately affecting reactively aggressive alpha-males. Language was key to this process, beta-males progressing from rumour, to discussion to organised killing. Once execution was used, any group member could be its victim. Morality emerged as an adaptive response to execution, “norm psychology” evolving to avoid social pitfalls. Periodic dominance by alpha males was replaced by the absolute power of a male group.
H sapiens language skills facilitated cooperation, indicated by sophisticated cultural goods. Co-operation contributed to humans surviving Neanderthals, the last (?) robust hominin. Europeans are shown to have trace Neanderthal DNA, indicating interbreeding between the two. Neanderthals remained more reactively aggressive, contributing to small group size and inbreeding, possibly hastening their demise.
Hominins, and chimps both had a taste for meat. They combined social hunting with proactive aggression. Such behaviour was inherited by humans, small societies showing a close correlation between hunting and violence. Bonobos also have a taste for meat, but are neither hunters nor display proactive aggression against their own species.
Language skills are a key element of the “Execution Hypothesis” for human self-domestication. Wrangham argues they also meant humans were able to develop proactive aggression into the more sophisticated and deadly coalitionary proactive aggression, planned violence, used in war, slavery and genocide, in particular by hierarchical societies, and linked to sovereignty, control of violence within a territory, facilitating its expansion.
The Human Paradox is combining communal peace, the effect of self-domestication, with the wrong done by coalitionary proactive aggression. Wrangham concludes by noting the evidence for a recent reduction in human violence. Just because war may have evolutionary origins, doesn’t mean accepting the inevitability of violence and war……
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