The dozen chapters in this collection provide a stimulating set of ideas about the evolution of social behavior, presented by a star cast at a 1995 symposium. They are uniformly well- written and provide an entry into the thinking of some of the best among the forty- something generation of primatologists, anthropologists and psychologists working in the area. The focus is primarily on humans, with a few papers on other primates. It would be a good focus for a graduate seminar, but these are perilous waters for someone looking for a reference to what is going on in a neighboring field. Most of the papers are advocacy pieces, not reviews of data or theory, and alternative views (or previous presentations of the same ideas) get by and large little mention.
A number of chapters gain rhetorical force from revisionist histories: Dunbar starts his paper on group size in baboons by stating that "we have tended to overlook ... the fact that many animals live in groups"(p. 34)--an extraordinary assertion. Discussing the rarity of cultural evolution (due to the difficulty of learning by imitation), Boyd & Richerson cite an in-press paper by Boyd et al for the argument that "horizontal transmission among cultural lineages makes reconstructing such cultural phylogenies difficult for 'cultures'" (p. 80), and in his useful overview of hominid evolution Foley references a 1988 paper of his for the idea that "agriculture can be considered as an evolutionary response to demographic constraint and declining resources" (p. 108)--neither is recent or original. And van Schaik's chapter on the supposedly forgotten role of males in the evolution of primate social systems largely forgets fifteen-year-old work of Wrangham and Hrdy (e.g., compare van Schaik's Fig. 1 with Wrangham's Fig. 13.3). These are four of the first five chapters; no point continuing. There is no deliberate theft here, merely (culturally selected?) academic and rhetorical enthusiasm.
I wish that the authors had engaged each other concerning underlying differences. Van Schaik operates from the premise (correctly, I believe) that social systems emerge from the dynamics of individual behavior, in contrast with Dunbar's belief that "behavioural decisions are made in the context of prior decisions about grouping patterns" (p. 34). Mithen argues for the inherent complexity of middle-upper Paleolithic behavior, while Mellars suggests that many of the same patterns are simple consequences of demographic changes (I'm with Mellars). Several authors explicitly adopt a functionalist stance, unconcerned with mechanism, but in their analysis of intention in baboon calls, Cheney and Seyfarth present cogent reasons why understanding of mechanism is vital to fully understanding behavior. Tooby & Cosmides argue that we must search for adaptations to the (past) "environment of evolutionary adaptedness" (EEA), while Borgerhoff Mulder suggests that we go out and see whether modern behavior is adaptive (in her study of changes in Kipsigis marriage patterns, it is). For Tooby & Cosmides, modernity is bad or at least problematic (e.g., in the artificial safety of the modern world friendships are rarely truly tested and we live in debilitating doubt as to whether anyone really cares about us [p. 135]; sociobiology meets Camus?); the EEA was rough but at least we fit. For Borgerhoff Mulder, we got through the Ice Ages and we'll get through multinational corporations, as we adaptively track changing environments. See Irons (1998) for a recent discussion.
A number of the chapters are based on the premise that "[w]e can say with confidence ... that all humans are genetically endowed with a common set of domain-specific ... functionally specialized psychological modules" (Runciman, p. 2). What modules? For example, Mithen suggests that Acheulean tools were too complex for generalized learning, requiring a discrete "technical intelligence" module, and that periglacial hunting of large game would have demanded a "specialized cognitive domain of natural history" (does this apply to wolves?). Gopnick et al's chapter on genetic language impairment has little to do with social behavior and was presumably included solely to provide implicit support for the overall modular view. Gopnick's work has been criticized (see Elman et al. 1996, chapter 7; Leonard 1998) and if the modularity of language falls to developmental connectionist criticism, many of the ideas here are in trouble; we will be left with the puzzle noted by Borgerhoff Mulder: just what is the mechanism by which humans behave as adaptively as the Kipsigis appear to do, when faced with evolutionarily novel circumstances?
Tooby & Cosmides redefine altruism to make it more common as well as easier to explain, rendering the world a deterministic place--people do things for a (sociobiological) reason even when fitness is unaffected; failures are not noise in an imperfect world, but adaptations. Boesch shows that chimpanzees exhibit culture acquired through social learning; but he does not clearly distinguish imitation from emulation and so has but scotched the psychologists' challenge he takes up, not killed it. He shows regularities and lack of optimization, but can we simply call a regularity a "norm" and then say this norm is how the regularity is maintained? Dunbar successfully uses latitude and rainfall to predict group sizes of baboons--and hence cranial capacity, male mating tactics, and other "behavioral patterns [that] can be determined as a consequence of well-understood principles" (p.33); interested readers should consult Bronikowski & Altmann (1996) for a skeptical response. Finally, Aiello climbs far out on a limb of sequential inference, causally linking bipedalism, carnivory, language and encephalization. Not all limbs break, and this paper exemplifies the power of an interdisciplinary approach for understanding social evolution in a single clade.
Lots of stimulating ideas; I liked it a lot and recommend it, despite the relative scarcity of data or review. If you like the ideas, you'll enjoy the presentations; if you disagree, you will profit from working out why.
Jim Moore
University of California, San Diego