«By Nathan B. Goodale A dissertation submitted in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY WASHINGTON STATE ...»
Optimality and the Harvest of Food Resources: A General Model How does optimal decision making influence human behavior with respect to the resources we procure? More specifically, when will evolution orient humans to switch from intensively utilizing one resource to another? As noted above, researchers traditionally focus on calories and package size; here I frame a discussion to include these components but also broaden it to account for the actual nutritional content of foods.
Natural selection has the consequence of optimizing design features for individual gene propagation (Krebs and Davies 1997). Design features that optimize somatic interests (e.g., access to resources such as food and space) have the potential to be converted into individual reproductive success (Krebs and Davies 1997; Smith and Winterhalder 1992). Where resource access is highly competitive, and variation in strategies to obtain a particular goal exists, selection should favor the strategy that can solve the problem with the least cost in relation to the other strategies present (Foley 1985). The rationale is that organisms have limited energetic budgets.
Individuals that solve particular adaptive problems efficiently can divert energetic surpluses into reproductive or other somatic interests (Kaplan et al. 2000). This is not to say that humans (or other organisms) are optimally adapted to their environment;
phenotypes present in the environment (Foley 1985; Smith and Winterhalder 1992).
Humans are a cognitively and behaviorally plastic organism, suggesting that selection pressures have favored a human phenotype that could adaptively respond to fluctuating social and ecological pressures (Flinn 1996). Additionally, humans are at times aware that returns can diminish as a result of applying specific strategies. This allows individuals to adjust investment accordingly (Kaplan and Lancaster 2000).
Thus, humans will generally pursue behavioral strategies (for specific goals) that tend to optimize opportunity costs within specific socio-ecological settings (Smith 2000).
The degree to which optimization is likely to occur is dependent upon the selection pressures surrounding a particular resource (Foley 1985). For resources characterized as having a large impact on fitness (i.e., resources associated with strong selection pressures), individuals can achieve greater fitness returns by selecting strategies that focus attention on the attainment of that resource (Hames 1992;
Winterhalder 1983). As a result, optimization of strategies to attain that resource is a likely outcome. Conversely, when a resource has a limited effect on fitness (i.e., resources associated with low selection pressures), selection could tend towards optimization; however, due to the limited energetic budgets of individuals, selection should favor phenotypes that divert their time and energy to the acquisition of other resources with higher fitness outcomes (Foley 1985; Hames 1992; Winterhalder 1983). As a consequence, satisfactory solutions become viable and diversity in strategy sets become tolerated for resources that have limited effect on fitness.
absence of competition there is little incentive to optimize (Foley 1985).
Winterhalder (1983) provides a graphical solution that demonstrates the conditions favoring decisions to invest in an additional unit of time and energy into a focal activity (conditions of limited energy) or to divert these scarce resources into other activities (conditions of limited time).
The idea that the time and energy budget of humans participation in gaining reproductive and somatic interests plays a significant role in regulating the growth of human societies has become a topic of great interest (Belovsky 1988; Boone 2002;
Hawkes and O’Connell 1992; Winterhalder et al. 1988). Because human populations rely on food resources for access to reproductive and somatic interests, the nature and access of food resources impact survivorship. Food resources approximate a zerosum game (when one individual accesses the resource, it represents a loss for other individuals in the population). When the food resource is proportionally present in high densities compared to a hypothetical population or of limited contribution in terms of nutritional value, the depletion of the food resource may seem inconsequential to individuals within the populace. In this case access to this food resource has low fitness consequences as there is little competition. Alternatively, when a food resource exists at proportionally low densities or is an important contribution to nutrition in comparison to a hypothetical population, its depletion is consequential. Such a resource has high fitness consequences as it is likely to be under intense competition for its procurement and consumption.
competition for the use of a food resource, strategies for converting the resource into a usable end product (including both harvest and processing) will be constrained, with the likely solution (or solutions) being the most economical given the range of possible solutions in the environment (such as harvest techniques or the actual people who harvest the resource) (Krebs and Davies 1997). A possible outcome is that only a few individuals might specialize in procurement of the food resource, while other individuals consume the little that is available yet it brings high fitness to the individual(s) who procured the resource. If a resource is easily depleted, individuals may better redirect their time and energy into other goals or somatic interests (Winterhalder 1983). The rationale is that not everyone can effectively engage in an economic enterprise where there are constraints on the resource. In this situation we would expect that only certain individuals would have access to the resource package or the choice portions (Krebs and Davies 1997; Stephens and Krebs 1986).
Theoretically, in an archaeological setting, the storage of such constrained resources may be private, signaled by underground pits within residential contexts.
Alternatively, foods for which there is little competition, optimality reasoning suggests that strategies for converting the resource into a usable end product will diversify. The rationale is that individuals can minimize opportunity costs by not investing heavily in the procurement and/or processing of the resource, but investing in some other arena where high selection pressures exist (Krebs and Davies 1997).
Thus, satisfactory solutions are likely to emerge with the procurement of resource
individuals can access and participate in the enterprise with few negative repercussions. As a result, a greater proportion of people may act as both producers and consumers of the consumable product. In the situation where there are a high proportion of both producers and consumers, the access to the useable end product would likely be public with each consumer having nearly equal access. Theoretically, in an archaeological context we may see resource storage in public contexts, such as purposely built structures for storage.
Summary Human nature is behaviorally and cognitively flexible. Because of this anthropologists have focused on energy budgets in association with food procurement and changing socioeconomic systems. The focus of this chapter was the general notion of how optimality reasoning could be applied to resource acquisition. This is both in terms of the traditional focus of acquisition based on energy budgets, but also including the potential that humans will be sensitive to general nutrition. I have argued that humans will be especially sensitive to both food quantity and quality as they influence fertility; just as simple protozoa. This provides one of the foundational elements that I later argue enabled population growth rates to increase during the NDT.
DEFINING, DETECTING, AND UNDERSTANDING THE NEOLITHIC
DEMOGRAPHIC TRANSITIONThe study of people in the past and human behavioral strategies employed at the origin of settled communities, centers on the aggregation of people with economies dependent on certain predictable and abundant resources (Bocquet-Appel 2002; Bocquet-Appel et al. 2008; Kohler et al. 2008; Livi-Bacci 1992). The recently developed concept of the Neolithic demographic transition (NDT) provides new insights into the origins of settled communities as the main focus is on detecting population growth (Bocquet-Appel 2002). Bocquet-Appel (2002) following LiviBacci (1992) defines the NDT as a detectable and quantifiable increase in human population numbers which occurred in several regions of the world at different times in our past (Bocquet-Appel 2002). It is thought that the NDT is directly linked to the origins of food production, or more generally, resource intensification (BocquetAppel 2002).
The broad aim of this chapter is to provide the link between the origins of settled communities, population growth, and the origins of agriculture. To accomplish this task I intend to review the definition of a demographic transition and how it is linked with paleodemographic transitions, discuss and critique attempts to utilize archaeological data to assess the NDT, and propose datasets that may lend additional and significant information to monitoring and tracking population growth through the NDT. The examination of these issues provides a foundation for a greater
Defining the Neolithic Demographic Transition Livi-Bacci (1992) was the first to formally express that the Neolithic represented a critical demographic shift in tandem with the transition to food production. He linked demographic growth during the Early Upper Paleolithic expansion out of Africa and the Neolithic advance of agriculture throughout Europe (Simoni et al. 2000). Subsequently, the term has broadened to encompass the phenomenon of human population increase upon the advent of intensified food production in several regions of the world including the American Southwest (Bocquet-Appel et al. 2008; Kohler et al. 2008), North America in general (BocquetAppel and Naji 2006), the Near East (Guerrero et al. 2008), and Europe (BocquetAppel 2002). As the geographic and temporal perimeters of the NDT have expanded, so has its definition. In turn, the detection and understanding of this significant transition in human history has become more complex.
Demographic Transition Theory and the NDT Although predominantly focused on population shifts in modern communities, demographic transition models in sociology offer a foundation for understanding the NDT. Demographic Transition Theory (DTT) incorporates health and fertility as the major components of significant changes in demography (Kirk 1996). The Modern
expectancy and halves the number of births of each woman (Chamberlain 2006:23;
Kirk 1996). Increase in life expectancy is predominantly due to the introduction of modern medicine and fewer births a primary result of increased use of effective birth control (Potts 1997). DTT has also been utilized to investigate differences in fertility rates in several modern and historic contexts of increasing and decreasing population.
This includes differences in fertility between less and more developed countries (ElGhannam 2005; Potts 1997); families with differing socioeconomic standing (Potts 1997); those with different levels of education (El-Ghannam 2005); communities with dissimilar governments (Potts 1997); societies before and after industrialization (Hall 1972); and societies that do not have regular access to contraceptives (Potts 1997).
Unfortunately, the definition used to describe modern demographic transitions is not suitable for defining the NDT. Average life expectancy did not double during the transition to agriculture (Eshed et al. 2004), and population would not have grown as it did if women were having half the number of children. In fact, the authors demonstrate that the transition to agriculture in the Near East may actually be characterized by a decrease in life expectancy in the age of women from 32 pre-NDT, to 30 years of age during the NDT (Eshed et al. 2004:325). They suggest that this decrease in life expectancy may be due to an increase in deaths during child birth as a consequence of having more children (Eshed et al. 2004).
This indicates that although there may not be a universal character of demographic transitions, DTT poses a number of potential factors that affect human
from having high birth rates and high death rates to having low birth rates and low death rates, but population increases rapidly nevertheless because death rates decline first. In the NDT the significant demographic shifts share similarities in population increase but in this case birth rates increase first and then later death rates increase.
In either case, there is a common result due to the almost opposite causes of increase and decrease of birth and death but they happen in different orders.
Universal characteristics of the NDT Bocquet-Appel et al. (2008) argues that the NDT is a multi-phase process.
Although disparate in region and time, the NDT is similar in each region highlighted by an initial increase in fertility with a later deterioration of health with associated increased death rates (Bocquet-Appel 2002; Bocquet-Appel et al. 2008). Why did fertility dramatically increase at the beginning of the transition to agriculture? This simple question, while largely unexplored, represents the core of active debate.
At the most basic level, a handful of factors in concert with one another universally drive population growth and decline. For instance, Chamberlain (2006:23) argues any demographic transition is usually considered to be both extensive (in time and space) as well as consistent (in numbers). Demographic transitions must occur over long periods of (defined) time and space and show measurable change (increase or decrease) in population numbers. In addition, at the center of demographic change are both intrinsic (births and deaths) and extrinsic
driven by some combination of death, birth and/or migration.