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Abstract
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The notion of domestication has played a role in attempts to understand human evolution going right back to Darwin (1859) (see Hare, 2017). Two of the leading current proponents of human self-domestication (HSD) are Hare and Wrangham. Hare (2017) lays out his account in "Survival of the Friendliest" and Wrangham has done much of the recent work on HSD; see Wrangham (2019) and references there.
HSD starts from the premise that our species' evolution in the later Pleistocene is consistent with a domestication syndrome, including traits such as a reduction in body mass, shortening of the face accompanied by a reduction in tooth size, reduced sexual dimorphism due to feminization, and a reduction in cranial capacity. Hare (2017 p. 157) argues that HSD, "draws on comparative, developmental, fossil, and neurobiological evidence to show that late human evolution was dominated by selection for intragroup prosociality over aggression. As a result, modern humans possess traits consistent with the syndrome associated with domestication in other animals (Table 1). An example is the long running silver fox experiments in Siberia."
Sánchez-Villagra and van Schaik (2019) review the case for and against HSD. They accept some of the evidence but question the underlying theory. They make the important distinction between slow moving unintentional "domestication" and directional and intentional "selective breeding" to generate "improvement traits" as in the silver fox experiments. They argue that HSD as currently formulated is about unintentional domestication rather than selective breeding, and so using evidence for HSD from dog breeding, modern farm animals, and the silver fox data is misleading.
Wrangham (2019) is focused on possible underlying hypotheses for HSD and, rather than "survival of the friendliest," he emphasizes selection against reactive aggression as key to human evolution and HSD.1 According to Wrangham, "To account for the domestication syndrome, proposals must explain what led to a decline in fitness of highly aggressive males, and why the explanatory factor applies only to H. sapiens and not to other species of Homo (Wrangham, 2019, abstract)."
He presents nine alternative hypotheses which could underly selection against reactive aggression: genetic group selection; group-structured cultural selection; social selection by female mate choice; social selection by choice of cooperative task partners; self-control; cooperative breeding; population density; use of lethal weapons; and language based conspiracy. The paper considers strengths and weaknesses of the nine. His favored hypothesis is the last--
"I conclude that the evolution of language-based conspiracy, which is a form of collective intentionality, was the key factor initiating and maintaining self-domestication in H. sapiens, because it is the most convincing mechanism for explaining the selective pressure against individually powerful fighters. Sophisticated language enabled males of low fighting prowess to cooperatively plan the execution of physically aggressive and domineering alpha males." Wrangham (2019, abstract).
As Wrangham acknowledges, this hypothesis is not without weaknesses. For example; why is a coalition of violent dominant males limited to a one-person coalition? If a coalition of one aggressive male was not enough to control a band, why not a coalition of a few violent "brothers" to watch each other's backs and suppress the remaining band members? This possibility is heightened by Homo sapiens's capacity for proactive aggression (see Wrangham, 2018)...
Language: en |