Perhaps the most obvious aspect of foraging theory and other behavioral ecology models that sets them apart from the wide range of alternative approaches to understanding change and transition in the archaeological record is their apparent small scale, "fine resolution" context of application, at the individual or small group level, rather than in terms of larger and longer-term societal level adaptive responses to "external pressures." In their concise and straightforward characterization of optimal foraging theory, for example, Winterhalder and Goland (1997) contrast the diet breadth model with other proposed approaches to explaining domestication and agricultural origins in terms of scale and specificity. They describe most previous explanations as involving "extensive" variables such as population growth, climate change, and technological innovation, which are generalized and normative, and which operate on the system level: "extensive variables are those measures that summarize population wide, interspecific (community level) or long-term (multi-generational) aspects of things biological" (Winterhalder and Goland 1997, 126).
In contrast, Winterhalder and Goland argue that optimal foraging theory derives considerable theoretical strength from the much smaller or "local" temporal, spatial, and ecosystem scale on which it is applied. Diet breadth modeling, for example, like foraging approaches in general, involves "intensive variables . . . those that characterize the behavior of an individual at a particular place and time. They refer to the situated properties of the organisms making up ecological sets; they potentially are subject to the direct action of selection" (1997, 126). Identifying the intensive variables of foraging models as being subject to the direct action of selection also suggests that within the framework of foraging theory the choice or selection of plant and animal resources at the local level, i.e. individuals, is potentially open to being predicted on the basis of higher level selection theories and assumptions. This question of the nature and strength of a predictive link between general evolutionary principles of selection and individual diet choice decisions will be considered later in this chapter, within a broader discussion of the necessary care and procedures which should be exercised in any efforts to predict archaeologically situated local events on the basis of general theoretical models or overarching frameworks of expectation. Setting this discussion aside for the moment, the small scale of application of foraging theory warrants closer consideration, both in terms of the importance of clarifying the range of scales within which foraging theory can be employed, and the potential constraints and limitations of archaeological data.
Archaeological research is carried out on a range of different social, spatial, and temporal scales of consideration; e.g. individual, family or household, settlement or community, polity, and various higher level sub-regional and regional geographical and cultural contexts, depending upon both the kinds of questions being addressed, and the quality and relative level of resolution of available relevant archaeological information. Within this broad range of different potential scales of archaeological analysis, which are open for consideration and which are the most appropriate to select when attempting to apply foraging theory to questions of diet choice and subsistence change? Winterhalder and Goland (1997) (see above) indicate that for aging theory applies at the scale of individual decisions at a particular time and place, and that this fine-resolution level of analysis carries with it considerable theoretical strength. A number of scholars, however, have cautioned that while foraging models are scaled to address individual decisions, archaeological deposits in contrast represent the accumulated and intermingled traces of many such resource selection events (Grayson and Delpech 1998; Gremillion 2002, 144). An important and as yet unresolved issue, then, is whether the "intensive" variables required to test foraging theory and behavioral ecology models in general can be observed and accurately measured in the archaeological record. Can sequences of temporally discrete individual decisions regarding resource selection be identified in the occupational episodes of ancient settlements? And if such individual resource selection decisions can't be recognized, to what extent can the "intensive variable" small-scale focus of foraging theory and behavioral ecology reasonably be expanded in terms of the necessity of considering larger pooled and therefore "normative" sets comprised of numerous resource selection decisions, before the ascribed "theoretical strength" of foraging theory is diluted? As Gremillion notes: "A model's performance may be difficult to assess because it exceeds the degree of resolution offered by the data" (Gremillion 2002, 144).
It is interesting in this regard, however, that in a number of the studies of present-day human societies which are frequently cited as providing supporting evidence for broad applicability of foraging theory, such as those of the Aché (Hawkes et al. 1982; Hill 1988; Hill et al. 1987), diet choice data is aggregated from the activities of all Aché foragers, and would appear to be representative of normative societal scale behavior sets, rather than reflecting individual diet choice decisions. Bamforth (2002, 439) indicates that such data aggregation practices are not unusual in optimization studies. If foraging theorists are comfortable using aggregated data sets in diet selection studies of present-day human societies, can archaeologists reasonably employ foraging theory at scales of analysis up to and including the community and polity level and perhaps beyond? At what point will cumulative aggregation of individual diet choice decisions and an expanding scale of analysis result in variables losing their "intensive" identity and theoretical strength and becoming normative and "extensive"?
Another important aspect of foraging theory is that it emphasizes the contextual consideration of diet-choice decisions, focusing on individual actions in particular cultural and environmental settings. This contextual approach is clearly compatible with archaeological efforts to consider settlement-scale subsistence analyses within a larger research framework of environmental and societal reconstruction. Like foraging theorists, archaeologists have long recognized the value of considering changes in human societies and economies as involving associated shifts in a range of relevant environmental and cultural variables over time.
When considered in a larger geographical context, the individual through polity scale, local setting context of foraging theory, along with Winterhalder and Goland's (1997) associated critique of more generalized and universally applicable explanatory models of domestication and agricultural origin, also gains a level of support from the growing recognition that like politics, domestication and agricultural origins are always local. More than a half-dozen independent centers of domestication have now been identified worldwide (Diamond 2002; Smith 1998), with human societies in each bringing different plant and animal species under domestication in different sequences at different times. In addition to these "primary" centers, other areas of the world also experienced their own distinctive developmental transitions as domesticates of various kinds, and in various combinations, were introduced into extant regional hunting and gathering economies. While a range of generic "extensive" variables have been proposed as playing prerequisite or causal roles in domestication and agricultural origins in a number of different world regions
(e.g. Richerson et al. 2001), each of these areas is also deserving of a closer-fit, more situated, and local scale analysis. Such analyses should incorporate a detailed understanding of the attributes of the indigenous species targeted for domestication as well as the larger set of plants and animals included in a society's subsistence economy and the broader biotic communities of the areas they occupied.
Along with being tightly focused contextu-ally, foraging theory and behavioral ecological models are also targeted at short time frames, compared to models which look at change occurring over longer "multi-generational" periods of time. Foraging theory targets immediacy— the intra-generational "behavior of an individual at a particular place and time" (Winterhalder and Goland 1997, 126):
The real stuff of evolutionary profundity lies in the local factors of an organism's experience: the constraints it faces, its actions and the consequences of those actions. Immediate details have the greatest causal efficacy in the evolutionary explanation of adaptive design.
Once again, the small-scale or short-term focus inherent in foraging theory and behavioral ecology approaches finds some level of support in the growing appreciation for the long and drawn-out nature of the distinctive developmental transitions from hunting and gathering through low-level food production to agriculture that unfolded in quite different ways in different areas of the world (Smith 2001a). Not only does each world region represent a unique developmental puzzle, requiring a good understanding of the particular local components of ecosystems and human subsistence systems, but each regional developmental sequence is also best viewed as actually being comprised of a linked linear set of discrete evolutionary steps or organizational changes: not as a single transformational episode but rather as a sequential set of linked puzzles. Each of these temporally discrete puzzles warrants attention and analysis in and of itself. Foraging theory would certainly provide a fine-grain temporal resolution appropriate for separate, stand-alone consideration of each of the many developmental shifts up through time that mark the long and complex transition from hunting and gathering to full agriculture. However one chooses to break down these long developmental processes for closer analysis, what is clear is that the spatial and temporal context of change, and the basic nature of each of the sequential episodes of transition in any given region, can be quite diverse.
Take, for example, the pre-Columbian developmental history of eastern North America. The Eastern United States provides one of the best documented records of the independent domestication of indigenous species and the subsequent, long delayed, emergence of agricultural economies. Early European accounts of the sixteenth and seventeenth centuries described various forms of maize-beans-squash agricultural economies as prevailing across much of the East, from New England to northern Florida. This widespread reliance on a generally similar agricultural economy at European contact, however, was not the result of a rapid and broad scale transition between two steady states—hunting and gathering and agriculture— that took place over some brief period in the past. The developmental history of the transition to food production in eastern North America in fact is a much more complex, interesting, and regionally variable story (Fritz 1990; Green 1994; Gremillion 1997a; Hart 1999; Smith 2002; Woods 1992). The crop trinity of squash, maize, and beans only coalesced in the East about three centuries prior to European contact, with the very late arrival of the common bean in the region (Hart and Scarry 1999). Maize arrived in the eastern United States by about 100 BC, more than a millennium earlier than beans, but apparently did not become a significant dietary component until after AD 900. Changing stable carbon isotope values and an increased archaeological visibility around AD 1000 marks its initial emergence as a central crop plant. Squash (Cucurbita pepo), the third crop plant in the trinity, in turn, was a local creation, domesticated from a wild eastern North American
Cucurbita gourd by about 3000 BC, long before the arrival of maize. Morphological changes in seed size and seed coat thickness in three other eastern plant species (marshelder, Iva annua; sunflower, Helianthus annuus; chenopod, Chenopodium berlandieri) indicate that they too were being deliberately planted by human societies (ergo domesticated) across an interior mid-latitudes area encompassing parts of present day Illinois, Ohio, Kentucky, Tennessee, Missouri, and Arkansas, as early as 2500 to 1500 BC.
Archaeological evidence for these earliest domesticates is still quite limited, however, and the exact timing and sequence of their domestication is still not yet clear. At the present time their domestication appears to have been an additive sequence of temporally and spatially distinct undertakings that extended over a period of perhaps 1500 years. Squash was the first species domesticated in the East, by about 3000 BC, followed by sunflower 750 years later at 2250 BC, marshelder after another 250 years, and finally, by 1500 BC, chenopod. All four of these local domesticates have relatively low archaeological visibility until about 200 BC—a century perhaps prior to the arrival of maize in the region, when they exhibit a clear if regionally diverse increase in representation in human settlements across the middle latitudes (Smith 2002).
When considered together in this manner, all of these temporally discrete episodes of change in eastern North America clearly represent a rich abundance of opportunities to independently employ foraging theory to address and better understand the separate individual evolutionary steps that occurred as human groups of the region followed various lengthy transitional trajectories from hunting and gathering to the maize-beans-squash agricultural economies described by Europeans in the sixteenth and seventeenth centuries (see, for example, Gremillion 1996a, 1997a, 1998, 2002). The separate domestication of squash, marshelder, sunflower, and chenopod between 3000 and 1500 BC, for example, would each seem to qualify for separate foraging theory consideration, as would their increase in dietary importance by 200 BC, the introduction of maize at 100 BC, its subsequent rise to a pan-regional scale central economic role around AD 900-1000, and the late arrival in the East of Mexican crop plants through the Southwest, including the common bean (Phaseolus vulgaris) and hubbard squash (Cucurbita argyrosperma) (Fritz 1994b). Additional independent opportunities for the application of foraging theory are represented by the diffusion of both indigenous and introduced domesticates into new areas of the East up out of river valleys into tributary stream settings, as well as by consideration of the selection, status, and role of plants such as little barley (Hordeum pusillum), erect knotweed (Polygonum erectum), and maygrass (Phalaris caroliniana), which while not yet documented as morphological domesticates may well have been managed and had similar dietary importance as the four identified indigenous domesticates. Foraging theory might also provide a new comparative perspective for considering what local factors influence why various indigenous domesticates play roles of differing importance in different areas of the East, and why farming economies centered on maize developed several centuries later in some parts of the lower Mississippi Valley than in other areas of the East (Fritz and Kidder 1993).
Eastern North America is not unique in providing a long-temporal sequence of linked but distinct developmental dietary shifts to which foraging theory might be applied. In Mexico, for example, almost 4000 years elapsed between the domestication of the region's first major crop plant—squash (C. Pepo ssp. pepo) at 8000 BC and the subsequent appearance of the second—the transformation of the wild grass teosinte into the crop plant maize by about 4300 BC (Smith 2001a). Certainly the initial domestication of these two major crops, separated by 4000 years of time, must have occurred in different environmental, subsistence, diet breadth, and cultural contexts, and provide the opportunity for separate independent foraging theory consideration (see, for example, Flannery 1986b; Reynolds 1986).
The Near East, of all of the world's independent centers of domestication, offers the greatest number and variety of distinct species-level opportunities to apply foraging theory in order to gain a better understanding of the process of domestication and the development of food production economies. Barley, rye, em-mer and einkorn wheat, lentils, goat, sheep, cattle, and pig were all domesticated in different parts of the Fertile Crescent at different times, and each represents a distinct standalone opportunity for foraging theory analysis and well-situated consideration of the changing value and utilization of a rich variety of food energy sources. As is the case in eastern North America and Mexico, along with other world areas, the Fertile Crescent and neighboring regions also provide ample opportunities for the application of foraging theory analysis to the subsequent diffusion and differential selective adoption of domesticates in a wide range of environmental and cultural landscapes, resulting in the development of regionally distinct crop and livestock complexes and agricultural economies (see McCorriston, this volume).
If the archaeological record is capable of providing the data resolution required, these approaches would appear to hold the promise of having broad world-wide applicability in providing new ways of approaching and better understanding each of the distinct sequential small-scale contexts of change in resource utilization and subsistence strategies, which when taken together over time, combine to trace the slow and regionally quite variable development of food production economies. However, as is the case with any proposed approach to understanding complex past trajectories of human cultural evolution, foraging theory also faces a range of potential pitfalls, including those having to do with placing too much faith in the value of general principles and universal laws in predicting and explaining patterns of past human behavior.
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