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Hunter-Gatherer Egalitarianism as a Force for Decline in Sexual Dimorphism

Stewart-Williams and Thomas (this issue) make a good case that human sex differences are not as great as evolutionary psychologists often make them out to be. Their case rests substantially on the argument that humans have long been more monogamous than polygynous, with men contributing considerably to the rearing of their own children, so men and women are relatively evenly matched in the degree to which they compete or choose in the mating game. Thus, concerning sexual dimorphism, humans are more like monogamous foxes or robins, where sex differences are minimal, than they are like polygynous gorillas or elephant seals, where sex differences are huge. I have two ideas to add here to Stewart-Williams and Thomas’s argument. The first idea is that sexual dimorphism in body size appears to have declined markedly over the course of hominid evolution. Although the data are somewhat sketchy and involve a number of arguable assumptions, the experts seem generally to agree that early hominids were far more dimorphic in body size than were later hominids and modern humans (Gordon, Green, & Richmond, 2008; McHenry, 1992; Ruff, 2002). According to one set of analyses, put forth originally by McHenry (1992), average female versus average male heights were, respectively: 105 versus 151 cm for Australopithecus afarensis (4–3 million years ago), 125 versus 157 cm for Homo habilis (2.4–1.6 million years ago), 160 versus 180 cm for Homo erectus (1.7–0.7 million years ago), and 161 versus 175 cm for modern Homo sapiens. In other words, if these data are correct, the percentage by which males exceed females in height has declined continuously, from a high of 44% for A. afarensis to a low of 9% for modern H. sapiens. Another way to look at it is this: Since the time of A. afarensis, female hominids have gained 56 cm in stature, whereas males have gained only 24 cm. These data present the interesting possibility that even the relatively small sexual dimorphism in body size that remains for Homo sapiens could be vestigial, a remnant of the huge dimorphism that existed at an earlier time and has not entirely evolved out. I’m not necessarily arguing for this hypothesis, but I am suggesting that it can’t be ruled out on the basis of existing data. The evidence that size dimorphism has declined over time in the human line should, at least, temper evolutionary psychologists’ use of that dimorphism as an argument for applying the males compete/females choose (MCFC) model to humans. The second idea I wish to contribute has to do with the egalitarian life ways of band hunter-gatherers, which have been strongly emphasized by nearly all ethnologists who have lived in such cultures but ignored by most evolutionary psychologists (for reviews, see Ingold, 1999; Wiessner, 1996). Indeed, egalitarian behavior so pervades band hunter-gatherers, wherever they are found, that another label often used for such cultures is egalitarian societies (Kelly, 1995; Woodburn, 1982). Such groups do not have chiefs or “big men”; they make group decisions by consensus, through long discussions involving the whole band; and their egalitarian beliefs preclude individuals from attempting to boss one another around, which ties their egalitarian values to their high valuation of individual autonomy. The universality of an egalitarian ethos in band hunter-gathers suggests that this ethos is essential to the nomadic, hunting and gathering way of life, which depends on intense and continuous cooperation and sharing that would be disrupted by struggles for dominance. The writings of ethnologists make it clear that hunter-gatherers are not passively egalitarian, but actively so. In the oft-quoted words of Richard Lee (1988), they are “fiercely egalitarian.” They do not tolerate anyone’s boasting, or putting on airs, or trying to lord it over others. Their first line of defense against such behavior is ridicule. If anyone—especially a young man—acts as if he is better than others or fails to show proper humility, the rest of the group make fun of that person until humility is shown. For example, one regular practice of the African Ju/’hoan huntergatherers that Lee studied, which is apparently common in other hunter-gatherer societies as well, is that of “insulting the meat.” Whenever a hunter brings back a fat antelope or other prize game item to be shared with the band, the hunter has to express humility by talking about how skinny and worthless it is or by crediting others for the kill. If he fails to do that (which happens rarely), others will do it for him and make fun of him in the process. When Lee (2003) asked one of the elders of the group he was observing about this practice, he received the following response: