A more plausible objection to applying foraging theory to the commingled assemblages of archaeology has to do with the context of rational action. The diet breadth model, the foraging theory most commonly employed by archaeologists, is about the behavior of individuals in relation to the natural environment, yet for human foragers the social environment may well be more important. They live in groups of differing size and change their behavior accordingly. How much this matters depends on the nature of the social group, the interactions between its individuals, and the divergence in their interests. If foraging remains an individual affair, as frequently it does, the effect will be mainly one of competition: larger groups may decrease resource abundance enough to reward individuals who expand diet breadth. Here groups change the behavior of individuals, but not the context of that behavior.
In short, the presence of groups per se does not make diet breadth problematic. Indeed, pursuing the effect that groups have on individual subsistence behavior has long been an important area of HBE research (e.g. Bettinger and
Baumhoff 1982. E.A. Smith 1985). Of direct relevance here, Winterhalder and Goland (1993) (see also Layton, et al. 1991) have argued from foraging theory that this group effect is critical to understanding the origins of agriculture; the Ideal Free Distribution model employed in several contributions to this volume deals with this as well. They suggest that population growth that depressed the abundance of high-ranked resources causing diet breadth to expand is likely connected with the initial use of many, generally low-ranked, plants that were eventually domesticated, setting the stage for agriculture (Flannery 1973). Smith (this volume) argues this is a classic case where HBE purports to answer a question that it actually begs. He allows that potential domesticates might have entered the diet with population growth but questions, on grounds of a temporal disconnect, whether that has much to do with the origin of agriculture. He points out that many domesticates entered human diets in wild form thousands of years before they were either intensively exploited or domesticated. Smith has a point here. Both population growth and the rational decision making that underwrites the diet breadth model should produce relatively rapid change, which does not seem to describe the prolonged interval of incidental, low-level food production that often precedes agricultural intensification. It is conceivable, however, that low-level food production is drawn out by the stable limit cycles (Belovsky 1988; Winterhalder, et al. 1988) that keep human and resource populations in constant motion as a consequence of their mutual interaction; human populations rise until resources become scarce, then fall as a result, allowing resources to rebound, in response to which populations then rise, and so on. In one plausible scenario, low-level food production appears when diet breadth expands during that part of the cycle in which human populations are large and resources scarce, and disappears with contracting diet breadth during the ensuing part of the cycle in which human populations are small and resources abundant, going full-round every century or so (Belovsky 1988, 351; Flannery 1973; Winterhalder and Goland 1993). Such intermittent, low-intensity selection on cultivars might well explain why full-blown agriculture took so long to develop.
Despite the anomalous time lag, the connection that Winterhalder and Goland (1997) make between the initial use and eventual domestication of important crops is surely cogent, but perhaps more akin to the stochastic connection between smoking and lung cancer. Smoking one cigarette will (probably) not produce cancer—even a lifetime usually does not; but surely the longer one smokes, the greater the chance. Fortunately, the tobacco company subterfuge that no precise connection between smoking and lung cancer has ever been shown, that most lifetime smokers never develop cancer, and so on, has been unsuccessful. The public is not misled: they know that smoking causes lung cancer. It seems similarly pointless to deny that there is a connection between the conditions that promote the use of potential domesticates and their eventual domestication. Foraging theory provides an elegant account of some of those conditions.
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