Original reference:
Moore, J. (1994). Hominids, coalitions and weapons; not vehicles. Beh. Brain Sci. 17: 632.

Hominids, coalitions and weapons; not vehicles

[BBS commentary on DS Wilson & E. Sober, Re-introducing group selection to the human behavioral sciences]

Jim Moore, Anthropology Dept., UCSD, 9500 Gilman Dr. Dept. 0532, La Jolla CA 92093-0532


Pace Wilson & Sober, group selection has not won over biology. However, the combination of fission/fusion organization (favoring coalition formation and relatively complex tactical behavior) with weapons (which in conjunction with group and/or ambush attacks greatly reduce the costs to actors of lethal inter- and intragroup aggression) create circumstances which may well have favored group selection in hominid evolution.


Wilson & Sober's paper is based on two fundamentally flawed premises:

As a result, the paper fails in its attempt to establish sophisticated group selection as an important part of the reigning biological paradigm. Happily, however, it does "re-introduce group selection to the human behavioral sciences" and this at least is worth serious consideration. Humans display many behaviors that appear difficult to explain in individual selection terms. Might group selection have been important in human evolution, if not in general?

It is important to emphasize that individual selfishness is capable of producing cooperation and apparent "altruism". Among adult mammals at least, mutualistic game-theoretical explanations for cooperation have generally proven superior to those based on reciprocity or nepotism (e.g. Bercovitch 1988; Moore 1984; Packer & Pusey 1982; de Waal 1982), though often lack of genetic data makes discrimination among explanations difficult (e.g. Connor, Smolker & Richards 1992; see Moore 1992). However, a variety of human traits are difficult to explain via individual selection (e.g., "indoctrinability" or "religiosity"; note I say difficult, not impossible).

The leading scenario for the evolution of such traits was set out by Darwin (1871) and significantly elaborated by Alexander (1985; 1989). According to them, violent intergroup conflict provided the selection pressure that ultimately resulted in group-directed altruism; as Darwin put it,

"A tribe including many members who, from possessing in a high degree the spirit of patriotism, fidelity, obedience, courage, and sympathy, were always ready to aid one another, and to sacrifice themselves for the common good, would be victorious over most other tribes; and this would be natural selection."

While both authors favor individual-level explanations for the evolution of these "traits" [sensu lato], it is not hard to see how Wilson & Sober's group selection ideas might apply. (Note that the one example of possibly group-selected cooperation offered by Mesterton-Gibbons & Dugatkin (1992: 274) is of ants in which "[i]ntracolony cooperation .. appears to be the result of intercolony aggression".)

The Hutterite example given is particularly instructive, as they are cognitively manipulating migration rates by identifying and expelling non-cooperators. If rook flocks were closed and individuals collectively attacked pairs laying large clutches, Wynne-Edwards would have carried the day. Manipulation combined with explicit indoctrination results (indirectly) in high reproductive success for all members, relative to non-Hutterites, apparently limited only by intergroup competition ("persecution and legal restrictions"). An interesting thought experiment: remove all non-Hutterites from Canada, seal the borders, and wait until the habitat is saturated.

Since many animals live in groups and could in principle evolve the required mental attributes, why have humans gone so far down the potentially group-selected path? What is different about us?

Manson and Wrangham (1991) argue that the potential for lethal intergroup violence is great in chimpanzees and humans because subgrouping creates the potential for imbalances of power: a party from one community can attack an individual of another at relatively low cost to themselves. For chimpanzees, they further argue that the ability of a party to physically immobilize a lone opponent lowers the cost of aggression still more.

For chimpanzees, such attacks are protracted and the victims often survive (Manson & Wrangham). Now imagine such an attack by a group of hominids carrying stone weapons. The impact, as it were, of such tools cannot be overemphasized. Here is what is different about us (as with other traits, a difference in degree, not kind): the combination of coalitions plus weapons vastly increases the potential for lethal aggression, and to the degree that fission/fusion processes have characterized hominids, this potential is increased even more.

Introduction of weapons makes us different in another way. Although the basic parameters leading to the evolution of "egalitarian" societies are general (Vehrencamp 1983), coalitions and weapons greatly increase the difficulty of achieving despotic power in non-state society. Cooperatively-enforced sanctions (including assassination) against those who attempt to manipulate power or resources for personal benefit are widespread in small-scale "egalitarian" human societies, may explain the existence of such societies, and are fully interpretable in individual selection terms (Boehm 1993). Hutterite exclusion of non-cooperators is an example of such status levelling in human groups.

The potential importance of the relations among fission/fusion organization, coalitions, and social complexity in the evolution of cognitive complexity is widely recognized (e.g., Alexander 1989). A strong case can further be made that hominids have taken this path further than chimpanzees or bottlenose dolphin due to the discovery of weapons, which (in combination with the foregoing) change the costs of aggression and so the complexity of intra- and intergroup relationships drastically. I speculatively note that (1) the first stone tools, (2) a major increase in encephalization, and (3) a so-far unexplained thickening in the cranial vault bones all coincide with the origin of Homo, and that H. erectus soon followed, characterized by a further thickening of the cranial vault and an apparently abrupt increase in stature (see Klein 1989; Wood 1992). Space precludes elaborating on the obvious.

In conclusion, human behavioral biologists will profit from considering Wilson & Sober's ideas, but only after reading e.g. Alexander (1989) and thinking about why humans are (quantitatively) different from other organisms in game-theoretically relevant ways.


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Alexander, R. D. (1989) Evolution of the human psyche. In: The Human Revolution. ed. P. Mellars & C. Stringer. Princeton University Press.

Bercovitch, F. B. (1988) Coalitions, cooperation and reproductive tactics among adult male baboons. Animal Behaviour 36: 1198-1209.

Boehm, C. (1993) Egalitarian behavior and reverse dominance hierarchy. Current Anthropology 34: 227-254.

Connor, R. C., Smolker, R. A. & Richards, A. F. (1992) Dolphin coalitions. In: Coalitions and Alliances in Humans and Other Animals. ed. F. B. M. de Waal & A. H. Harcourt. Oxford University Press.

Darwin, C. (1871) The Descent of Man and Selection in Relation to Sex. Appleton.

Klein, R. G. (1989) The Human Career: Human Biological and Cultural Origins. University of Chicago Press.

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Moore, J. (1984) The evolution of reciprocal sharing. Ethology and Sociobiology 5: 5-14.

Moore, J. (1992) Dispersal, nepotism, and primate social behavior. International Journal of Primatology 13: 361-378.

Packer, C. & Pusey, A. E. (1982) Cooperation and competition within coalitions of male lions: kin selection or game theory? Nature (London) 296: 740-742.

Vehrencamp, S. L. (1983) A model for the evolution of despotic versus egalitarian societies. Animal Behaviour 31: 667-682.

de Waal, F. B. M. (1982) Chimpanzee Politics. Harper & Row.

Wood, B. (1992) Origin and evolution of the genus Homo. Nature (London) 355: 783-790.