Evolutionary Perspectives on Exchange
The following is an excerpt from my 2012 publication, and outlines my current thinking on the evolutionary foundations of exchange behavior, and the role of exchange in social change.
The following work should be cited as:
Hill, Mark A.
2012 The Benefit of the Gift: Exchange, Ritual, and Emergent Regional Systems in the Late Archaic Western Great Lakes. International Monographs in Prehistory. Ann Arbor, Michigan
The following work should be cited as:
Hill, Mark A.
2012 The Benefit of the Gift: Exchange, Ritual, and Emergent Regional Systems in the Late Archaic Western Great Lakes. International Monographs in Prehistory. Ann Arbor, Michigan
The Benefit of the Gift: An Evolutionary Perspective on the Development of Intercommunity Interaction and Exchange Networks
Social scientists have long considered exchange to be a central form of social interaction and a catalyst for forming bonds between individuals and societies. Many social theorists and researchers have examined exchange, including the perceptive and influential works of such notable figures as Emile Durkheim (1964), Marcel Mauss (1990) Bronislaw Malinowski (1961), F. E. Williams (1969), Claude Levi-Strauss (1969), and Marshall Sahlins (1972) among many others. These studies have laid the foundation for a richly detailed and theoretically diverse examination of this fundamental aspect of human society.
Other fields of study—biology, psychology, and anthropology—have since developed and examined new ways of understanding behavior based in evolutionary theory. It is productive to review previous anthropological efforts to study exchange, along with a brief overview of the biological perspectives directed toward understanding the basis for cooperative behaviors. Owing to the vast body of research in both fields, the following overviews are not intended to be comprehensive, but are instead used to illustrate basic theoretical foundations and broad findings. I contend that a synthesis of the two fields is both possible and productive, and develop such a synthesis in the latter part of the chapter. The result provides a basic predictive model for the development of human exchange systems.
Exchange and Social Integration
Exchange is simply the act of, and obligations that flow from, giving and receiving. Yet its power rests in forging relationships, maintaining social bonds, creating obligations and debt, gaining status and social position, and obtaining resources needed for the life and reproduction of individuals and societies. ‘Exchange’ can refer to many different categories of interaction ranging from food sharing in forager communities to the functioning of complex market economies and the production, distribution, and consumption of commodities. Throughout this study, exchange refers to the social interactions that attend the exchange of goods and gifts between individuals and communities.
As early as 1893, Emil Durkheim (1964) noted the central role of exchange in creating organic solidarity in complex societies. Organic solidarity arose through the division of labor and the necessary exchange of goods and cooperation between unlike individuals pursuing individual interests, and was viewed in opposition to mechanical solidarity which arose from individuals who shared similar backgrounds and who were in frequent interaction. Viewed from this perspective, exchange is cast as an interaction of inherent conflict and inequality.
Durkheim’s nephew and student, Marcel Mauss, followed a different path. By focusing on the power of the gift itself, Mauss (1990) identified three obligations inherent in any relationship mediated through exchange; 1) the obligation to give, 2) the obligation to receive, and 3) the obligation to reciprocate. In other words gifts must be given, gifts must be accepted, and the acceptance of the gift conveys to the recipient an obligation to reciprocate. Mauss sees an innate power in the gift itself, and pursued this power through the Maori concept of hau in which the gift has a spirit that must be propitiated and served through reciprocity.
Levi-Strauss (1969) looked instead to the innate and unconscious structure of the human mind to understand the power of the gift and its ability to forge social bonds (deWaal Malefijt 1979:325-332). To Levi-Strauss (1969:52-68), the exchange of food, manufactured objects, and women creates relationships, and women given in marriage serve as the supreme gift that unites disparate and unrelated groups. In an insightful thought experiment, he proposed a restaurant scene in which two strangers silently share a table until one offers wine to the other. The offer of wine creates a relationship where before there was merely spatial juxtaposition. Once offered, the gift has created a relationship that cannot be undone:
Wine offered calls for wine returned, cordiality requires cordiality. The relationship of indifference can never be restored once it has been ended… From now on, the relationship can only be cordial or hostile. There is no way of refusing the neighbors offer of his glass of wine without being insulting. Further, the acceptance of this offer sanctions another offer, for conversation. In this way a whole range of trivial social ties are established by a series of alternating oscillations, in which offering gives one a right, and receiving makes one obligated, and always beyond what has been given or accepted. [Levi-Strauss 1969:59]
Levi-Strauss’ view of the exchange of women as the supreme gift echoes the earlier ideas of F. E. Williams. Working in Papua New Guinea in the 1920s and1930s, Williams (1969:166-169) proposed that exchange was linked to the development of rules requiring marriage outside a defined social group, or exogamy. Exchange was seen as a way of creating relationships between individuals and groups to forestall hostilities. Gifts created fellowship between groups, and the strongest bonds were formed through the exchange of females in marriage. Females, then, were viewed as reserved for exchange, and rules were created forbidding marriage of females within the home community.
Sahlins (1972) later built upon the large body of exchange research by defining different categories of reciprocity—generalized, balanced, and negative—that correlate with social distance (Figure 2.1). Generalized reciprocity, with its lack of specified value or time of reciprocation, predominates within the small scales of households and lineages. At greater social distances, balanced reciprocity comes to dominate, with its specified values and times of reciprocation. With its expectation and stipulation of return, balanced reciprocity characterizes exchange interactions within a village, tribe, or between different social groups. At intertribal and intersocietal scales, reciprocity may take a more competitive form where individuals in one group attempt to gain an advantage over the other group (and advantage within their own group) through the process of exchange.
Social scientists have long considered exchange to be a central form of social interaction and a catalyst for forming bonds between individuals and societies. Many social theorists and researchers have examined exchange, including the perceptive and influential works of such notable figures as Emile Durkheim (1964), Marcel Mauss (1990) Bronislaw Malinowski (1961), F. E. Williams (1969), Claude Levi-Strauss (1969), and Marshall Sahlins (1972) among many others. These studies have laid the foundation for a richly detailed and theoretically diverse examination of this fundamental aspect of human society.
Other fields of study—biology, psychology, and anthropology—have since developed and examined new ways of understanding behavior based in evolutionary theory. It is productive to review previous anthropological efforts to study exchange, along with a brief overview of the biological perspectives directed toward understanding the basis for cooperative behaviors. Owing to the vast body of research in both fields, the following overviews are not intended to be comprehensive, but are instead used to illustrate basic theoretical foundations and broad findings. I contend that a synthesis of the two fields is both possible and productive, and develop such a synthesis in the latter part of the chapter. The result provides a basic predictive model for the development of human exchange systems.
Exchange and Social Integration
Exchange is simply the act of, and obligations that flow from, giving and receiving. Yet its power rests in forging relationships, maintaining social bonds, creating obligations and debt, gaining status and social position, and obtaining resources needed for the life and reproduction of individuals and societies. ‘Exchange’ can refer to many different categories of interaction ranging from food sharing in forager communities to the functioning of complex market economies and the production, distribution, and consumption of commodities. Throughout this study, exchange refers to the social interactions that attend the exchange of goods and gifts between individuals and communities.
As early as 1893, Emil Durkheim (1964) noted the central role of exchange in creating organic solidarity in complex societies. Organic solidarity arose through the division of labor and the necessary exchange of goods and cooperation between unlike individuals pursuing individual interests, and was viewed in opposition to mechanical solidarity which arose from individuals who shared similar backgrounds and who were in frequent interaction. Viewed from this perspective, exchange is cast as an interaction of inherent conflict and inequality.
Durkheim’s nephew and student, Marcel Mauss, followed a different path. By focusing on the power of the gift itself, Mauss (1990) identified three obligations inherent in any relationship mediated through exchange; 1) the obligation to give, 2) the obligation to receive, and 3) the obligation to reciprocate. In other words gifts must be given, gifts must be accepted, and the acceptance of the gift conveys to the recipient an obligation to reciprocate. Mauss sees an innate power in the gift itself, and pursued this power through the Maori concept of hau in which the gift has a spirit that must be propitiated and served through reciprocity.
Levi-Strauss (1969) looked instead to the innate and unconscious structure of the human mind to understand the power of the gift and its ability to forge social bonds (deWaal Malefijt 1979:325-332). To Levi-Strauss (1969:52-68), the exchange of food, manufactured objects, and women creates relationships, and women given in marriage serve as the supreme gift that unites disparate and unrelated groups. In an insightful thought experiment, he proposed a restaurant scene in which two strangers silently share a table until one offers wine to the other. The offer of wine creates a relationship where before there was merely spatial juxtaposition. Once offered, the gift has created a relationship that cannot be undone:
Wine offered calls for wine returned, cordiality requires cordiality. The relationship of indifference can never be restored once it has been ended… From now on, the relationship can only be cordial or hostile. There is no way of refusing the neighbors offer of his glass of wine without being insulting. Further, the acceptance of this offer sanctions another offer, for conversation. In this way a whole range of trivial social ties are established by a series of alternating oscillations, in which offering gives one a right, and receiving makes one obligated, and always beyond what has been given or accepted. [Levi-Strauss 1969:59]
Levi-Strauss’ view of the exchange of women as the supreme gift echoes the earlier ideas of F. E. Williams. Working in Papua New Guinea in the 1920s and1930s, Williams (1969:166-169) proposed that exchange was linked to the development of rules requiring marriage outside a defined social group, or exogamy. Exchange was seen as a way of creating relationships between individuals and groups to forestall hostilities. Gifts created fellowship between groups, and the strongest bonds were formed through the exchange of females in marriage. Females, then, were viewed as reserved for exchange, and rules were created forbidding marriage of females within the home community.
Sahlins (1972) later built upon the large body of exchange research by defining different categories of reciprocity—generalized, balanced, and negative—that correlate with social distance (Figure 2.1). Generalized reciprocity, with its lack of specified value or time of reciprocation, predominates within the small scales of households and lineages. At greater social distances, balanced reciprocity comes to dominate, with its specified values and times of reciprocation. With its expectation and stipulation of return, balanced reciprocity characterizes exchange interactions within a village, tribe, or between different social groups. At intertribal and intersocietal scales, reciprocity may take a more competitive form where individuals in one group attempt to gain an advantage over the other group (and advantage within their own group) through the process of exchange.
Figure 2.1. Sahlins’ reciprocity sectors or spheres of interaction (after Sahlins 1972:Figure 5.1)
In an insightful essay, Gregory (1982) elucidates the motivations of gift transactors. In Gregory’s observation, those involved in gift economies are not seeking profit maximization. To the contrary, “the aim of a gift transactor is to acquire a large following of people (gift-debtors) who are obligated to him” (Gregory 1982:51). Gregory thus uses Mauss’ power of the gift to create not only bonds between individuals, but bonds of obligation which convey advantage to the giver. Chris Gosden (1989) builds on this idea further to formulate a new economic model—one built upon the accumulation of the obligation of others and the transaction of debt. This concept will be an important one as we examine how exchange can be used to create benefits and form networks of obligations.
Each of these contributions has expanded our views of exchange in human societies, yet they suggest that a deeper process is in place—one in which exchange is somehow a part of human nature. Anthropology and the social sciences have explained how exchange works in specific contexts, but an understanding of the fundamental nature of such social interaction could be valuable for its ability to construct models of human interaction.
Evolutionary Approaches to Cooperation and Interaction
While social theorists and anthropologists were debating the processes and motivations of cooperation, competition, and exchange, biology was struggling with the very origins and basis of cooperation. Why do organisms cooperate? Since cooperation, by definition, involves giving up resources or effort for others, how could it evolve, and why does it take the forms it does? Exchange is, of course, a type of cooperation in which individuals pursue their interests by cooperating with others through social networks. The biological basis of these behaviors was difficult to conceive, yet, I argue, is critical to a fundamental understanding of exchange.
Hamilton (1964) first approached this issue by noting that individuals may gain a net reproductive advantage by helping those to whom they are most closely related. This inclusive fitness is governed by the rule of c < br, in which an individual is most likely to help another when the cost (c) is less than the benefit (b) provided to the recipient, discounted by the degree to which the beneficiary is related to the actor (r). Cooperation with related individuals is a behavior that provides a selective advantage by increasing the frequency of the alleles that produce the behavior. Cooperation between closely related individuals can be explained through this model, and the core elements of sociality can be created in the form of families, households, and lineages by observing that individuals will be most likely to help and cooperate with others most closely related to themselves.
However, inclusive fitness does not explain cooperation and interaction between non-related individuals. One explanation for this lies in Trivers’ (1971) theory of reciprocal altruism. While similar to the equation for inclusive fitness, reciprocal altruism predicts that cooperation and interaction between non-related individuals will occur when the cost to the actor (c) is less than the benefit to the recipient (b) discounted by “w” which is a measure of the degree to which a return benefit is expected. In other words, cooperation with non-related individuals provides a selective advantage when that behavior ultimately produces a benefit for the actor. Reciprocal altruism is in some ways an explanation of how we form societies, alliances, and coalitions through the variable “w,” or the expectation of future benefit.
But when to cooperate and when to serve our individual self interest? Axelrod and Hamilton (1981) show this to be a false dichotomy. We serve our individual self interest through cooperation with others. Modeling cooperative behavior using game theory, Axelrod and Hamilton (1981) found that selfish interaction strategies—those that attempt to gain the greatest return while imposing the costs on others—produced the greatest return in short duration interactions. However, in cases where interaction is likely to be prolonged, as in life, the greatest long-term individual benefit was gained through cooperation with others. Several strategies have been found to produce benefits through cooperation, including those of indirect reciprocity and image scoring (Nowak and Sigmund 1998, 2005), group selection methods such as multilevel selection (Traulsen and Nowak 2006), and tit-for-tat (Axelrod and Hamilton 1981). Tit-for-tat is the simplest and most basic of these strategies, and is used in this model due to its basic characteristics. It is built upon simple rules of cooperation and reciprocation, and is an evolutionarily stable strategy that, once established, is not outperformed by more selfish approaches.
Synthesis: Trivers and Levi-Strauss Share a Bottle of Wine
The anthropological study of exchange and the biological study of evolved cooperative behaviors can be woven together to form a model of exchange in which interaction between individuals through exchange and the development of social networks are viewed as an adaptive trait that, under certain circumstances, increase the fitness of participating individuals. Similar models have been developed for cooperation and exchange within communities (e.g. Winterhalder 1997); here I attempt to develop one for exchange between communities.
Levi-Strauss (1987) criticized Mauss for resorting to the mystical concept of hau to explain the power of the gift. Instead, Levi-Strauss proposed:
Hau is not the ultimate explanation for exchange; it is the conscious form whereby men of a given society, in which the problem had particular importance, apprehended an unconscious necessity whose explanation lies elsewhere…Once the indigenous conception has been isolated, it must be reduced by an objective critique so as to reach the underlying reality. We have very little chance of finding that reality in conscious formulations; a better chance in unconscious mental structures… [1987:48-49, italics added]
Levi-Strauss was correct, but not necessarily in the interpretations he proposes. His unconscious mental structures are perhaps best seen as the evolved psychological mechanisms of inclusive fitness and, especially, reciprocal altruism. Evolutionary psychology and biology demonstrate that humans have innate traits, selected for during our evolution, that promote the use of genetic relatedness, potential return, and tit-for-tat strategies in decision-making processes for interaction with others. Mauss’ spirit of the gift is indeed powerful; the obligations to give, receive, and reciprocate are the manifestations of our innate tit-for-tat strategy (for an interesting application of this view, see Görlich 1998).
The obvious similarities between Hamilton’s (1964) Inclusive Fitness theory and Sahlins’ (1972:199) kinship and residential sectors have long been recognized—most notably by Sahlins himself in a critique of evolutionary approaches to human behavior (Sahlins 1976). The relationship between social distance and reciprocity (and Durkheim’s mechanical and organic solidarity) is the cultural correlate of the relationship between kin selection and reciprocal altruism (Figure 2.2). Kin selection and generalized reciprocity are two sides of the same phenomenon, with their strongest effects occurring within small social distances where the degree of relatedness is high. At this scale, an individual’s fitness depends on the fitness of other individuals in the society by degrees of relatedness. In simple terms, kinship dominates cooperative activities and social interaction in smaller social scales such as households and lineages.
Each of these contributions has expanded our views of exchange in human societies, yet they suggest that a deeper process is in place—one in which exchange is somehow a part of human nature. Anthropology and the social sciences have explained how exchange works in specific contexts, but an understanding of the fundamental nature of such social interaction could be valuable for its ability to construct models of human interaction.
Evolutionary Approaches to Cooperation and Interaction
While social theorists and anthropologists were debating the processes and motivations of cooperation, competition, and exchange, biology was struggling with the very origins and basis of cooperation. Why do organisms cooperate? Since cooperation, by definition, involves giving up resources or effort for others, how could it evolve, and why does it take the forms it does? Exchange is, of course, a type of cooperation in which individuals pursue their interests by cooperating with others through social networks. The biological basis of these behaviors was difficult to conceive, yet, I argue, is critical to a fundamental understanding of exchange.
Hamilton (1964) first approached this issue by noting that individuals may gain a net reproductive advantage by helping those to whom they are most closely related. This inclusive fitness is governed by the rule of c < br, in which an individual is most likely to help another when the cost (c) is less than the benefit (b) provided to the recipient, discounted by the degree to which the beneficiary is related to the actor (r). Cooperation with related individuals is a behavior that provides a selective advantage by increasing the frequency of the alleles that produce the behavior. Cooperation between closely related individuals can be explained through this model, and the core elements of sociality can be created in the form of families, households, and lineages by observing that individuals will be most likely to help and cooperate with others most closely related to themselves.
However, inclusive fitness does not explain cooperation and interaction between non-related individuals. One explanation for this lies in Trivers’ (1971) theory of reciprocal altruism. While similar to the equation for inclusive fitness, reciprocal altruism predicts that cooperation and interaction between non-related individuals will occur when the cost to the actor (c) is less than the benefit to the recipient (b) discounted by “w” which is a measure of the degree to which a return benefit is expected. In other words, cooperation with non-related individuals provides a selective advantage when that behavior ultimately produces a benefit for the actor. Reciprocal altruism is in some ways an explanation of how we form societies, alliances, and coalitions through the variable “w,” or the expectation of future benefit.
But when to cooperate and when to serve our individual self interest? Axelrod and Hamilton (1981) show this to be a false dichotomy. We serve our individual self interest through cooperation with others. Modeling cooperative behavior using game theory, Axelrod and Hamilton (1981) found that selfish interaction strategies—those that attempt to gain the greatest return while imposing the costs on others—produced the greatest return in short duration interactions. However, in cases where interaction is likely to be prolonged, as in life, the greatest long-term individual benefit was gained through cooperation with others. Several strategies have been found to produce benefits through cooperation, including those of indirect reciprocity and image scoring (Nowak and Sigmund 1998, 2005), group selection methods such as multilevel selection (Traulsen and Nowak 2006), and tit-for-tat (Axelrod and Hamilton 1981). Tit-for-tat is the simplest and most basic of these strategies, and is used in this model due to its basic characteristics. It is built upon simple rules of cooperation and reciprocation, and is an evolutionarily stable strategy that, once established, is not outperformed by more selfish approaches.
Synthesis: Trivers and Levi-Strauss Share a Bottle of Wine
The anthropological study of exchange and the biological study of evolved cooperative behaviors can be woven together to form a model of exchange in which interaction between individuals through exchange and the development of social networks are viewed as an adaptive trait that, under certain circumstances, increase the fitness of participating individuals. Similar models have been developed for cooperation and exchange within communities (e.g. Winterhalder 1997); here I attempt to develop one for exchange between communities.
Levi-Strauss (1987) criticized Mauss for resorting to the mystical concept of hau to explain the power of the gift. Instead, Levi-Strauss proposed:
Hau is not the ultimate explanation for exchange; it is the conscious form whereby men of a given society, in which the problem had particular importance, apprehended an unconscious necessity whose explanation lies elsewhere…Once the indigenous conception has been isolated, it must be reduced by an objective critique so as to reach the underlying reality. We have very little chance of finding that reality in conscious formulations; a better chance in unconscious mental structures… [1987:48-49, italics added]
Levi-Strauss was correct, but not necessarily in the interpretations he proposes. His unconscious mental structures are perhaps best seen as the evolved psychological mechanisms of inclusive fitness and, especially, reciprocal altruism. Evolutionary psychology and biology demonstrate that humans have innate traits, selected for during our evolution, that promote the use of genetic relatedness, potential return, and tit-for-tat strategies in decision-making processes for interaction with others. Mauss’ spirit of the gift is indeed powerful; the obligations to give, receive, and reciprocate are the manifestations of our innate tit-for-tat strategy (for an interesting application of this view, see Görlich 1998).
The obvious similarities between Hamilton’s (1964) Inclusive Fitness theory and Sahlins’ (1972:199) kinship and residential sectors have long been recognized—most notably by Sahlins himself in a critique of evolutionary approaches to human behavior (Sahlins 1976). The relationship between social distance and reciprocity (and Durkheim’s mechanical and organic solidarity) is the cultural correlate of the relationship between kin selection and reciprocal altruism (Figure 2.2). Kin selection and generalized reciprocity are two sides of the same phenomenon, with their strongest effects occurring within small social distances where the degree of relatedness is high. At this scale, an individual’s fitness depends on the fitness of other individuals in the society by degrees of relatedness. In simple terms, kinship dominates cooperative activities and social interaction in smaller social scales such as households and lineages.
Figure 2.2. Comparison of Sahlins’ (1972) reciprocity sectors, degrees of genetic relatedness, and areas in which Hamilton’s (1964) Inclusive Fitness theory applies versus the areas in which Triver’s (1971) Reciprocal Altruism theory predominates
This reserves reciprocal altruism for the dominant role in social interaction between groups. Reciprocal altruism already provides foundations for much of our interaction with others—from the formation of friendships and alliances (Tooby and Cosmides 1996) to the practice of warfare (e.g., Chagnon 1988; Tooby and Cosmides 1988). Reciprocal altruism is the means by which relationships are created through gifts, explaining both Mauss’ power and Levi-Strauss’ unconscious mental structures. Exchange occurs between non-related individuals through the equation of c < bw, with an expectation of return benefit for the actor and the creation of obligation for the recipient.
Predictions
The value of such a synthesis of evolutionary and sociocultural perspectives is that it allows us to make predictions about the development and operation of exchange systems and networks. Seven predictions follow from this synthesis:
7. Finally, the use of reciprocal altruism and kin selection models allows social exchange to be modeled using cost-benefit analyses similar to other optimality models of human behavioral ecology (e.g., Winterhalder and Smith 2000). The adaptive advantage of exchange networks can be modeled in terms of costs, benefits, and degree of expected return using energy, time, or social status gained or lost as proxy currencies.
Modeling the Adaptive Nature of Social Exchange
The preceding discussion illustrates the important role of social exchange and interaction in forging, monitoring, and maintaining relationships, and enhancing participants’ fitness. As such, it casts these activities as part of the evolved human behavioral repertoire, and thus subject to some degree of modeling using optimality theory.
Life History Theory and Optimal Foraging offer two approaches to studying human behavior within conditional strategies, or systems of decision making rules, in which natural selection is thought to have favored the development of behaviors that tend towards the optimization of somatic and reproductive effort (Bentley et al. 2008; Chisolm 1993; Stephens and Krebs 1986; Winterhalder and Smith 2000). These models derive from microeconomic theory which examines how individuals make decisions concerning the allocation of limited resources (Keegan and Butler 1987; Winterhalder and Smith 1981, 2000). According to these models, humans have an evolved ability to weigh the costs and benefits of their current and potential future actions in such a way as to optimize their return. This optimality is seldom achieved—human behavior and the variables of social interaction are quite complex and often offer conflicting options—but modeling optimality provides a mathematical and graphical heuristic for identifying behaviors, the factors that affect those behaviors, and reasons for variation from optimality.
The model that follows is built upon the predictions outlined above, and assumes that: a) individuals have limited resources in several forms—including time, energy, and social capital—and they act to optimize their return in several socially, somatically, and reproductively valuable areas; b) optimization is not just concerned with the number of calories that can be returned per calorie of labor invested, but must factor in all the conflicting needs that individuals must meet to optimize their fitness; c) decisions about investment of time, energy, or social capital attempt to balance all these conflicting needs, thus time invested in one area, say food procurement, is in direct competition for time invested in other areas such as gaining social capital, finding mates, parenting, or other socially meaningful activities. In the model to follow, social exchange and interaction networks consist of individuals who are united through the acts and obligations of exchange, and these relationships are between individuals in different communities or societies interacting through reciprocity. This model is not intended to describe the complex relationships found within communities which may be based on inclusive fitness, mutualistic relationships, reciprocity, or various complex interactions of all three.
Benefits and Costs
By using an optimality model, the benefits of exchange can be identified in relation to the costs of forming and maintaining exchange networks, and the trade-offs those costs demand in terms of other somatic or reproductive efforts. The currency of costs and benefits may be highly variable, and can range from time and energy invested and returned to social status gained or lost.
Following the predictions discussed above, exchange networks can be viewed as one means of increasing personal fitness through the development and maintenance of relationships of cooperation, obligation, and reciprocity with others. They are, in this view, a means of intensifying resource exploitation—or to paraphrase the terminology of Optimal Foraging Theory, increasing ‘resource breadth’—in which relationships with others are viewed as a resource that can be exploited for personal gain. However, developing such relationships requires time, resources, and energy that could be used for other activities that may have more immediate benefits. Therefore, the time, energy, resources, or social status invested in creating and maintaining these networks must have an anticipated future benefit in socially meaningful currencies which could include the acquisition of resources or knowledge, increased social status, reduction of risk, or access to marital partners. These benefits have been shown to correlate with increased survival and reproductive opportunities by research with modern communities (e.g., Betzig 1986; Buss et al. 1990; Buss and Schmidt 1993; Kenrick et al. 1990; Marlow 2004).
Additional resources can be used directly for somatic benefit, provide associative value in the form of access to the exotic or rights of spiritual intercession, or may provide more indirect benefits in the form of status gained. Resources need not even be physically gained since the acquisition of the ‘obligations of others’ serves as an investment for future benefit (Gosden 1989; Gregory 1982). While resources gained may provide an immediate somatic benefit, male access to resources has been strongly correlated with reproductive success in cross-cultural studies (Buss and Schmidt 1993; Kenrick et al. 1990; Marlow 2004).
Status can also be gained through the development of social networks. Access to exotic, distant, and rare materials; to knowledge and distant contacts, or to the spiritual, can confer important distinctions on individuals. Individuals who develop bridges between separate spheres of interaction and exchange can gain from their position as the source of benefits that others in the community seek (Barth 1966:18; Granovetter 1973, 1983). Further, by developing networks that provide benefits to others in the community through access to materials or knowledge, individuals become critical and irreplaceable pathways on which others in the community rely. Status and irreplaceability are both important means of improving survival and reproductive success as many researchers have demonstrated (e.g., Betzig 1986; Buss et al. 1990; Granovetter 1973, 1983; Tooby and Cosmides 1996).
I previously argued that the estimation of trust or potential future benefit is initially a goal of incipient exchange networks, and that reciprocation can lead to positive values of “w” which may, in turn, lead to a progression of the relationship from one based on reciprocity to one based on exchange of females in marriage. As noted by Williams (1969:166-169) and Levi-Strauss (1969), this is the ‘supreme gift’ in exchange networks; a gift that strengthens the relationship from one based on reciprocity to one with kinship ties and vested interests in the reproductive and somatic success of the other. This has long lasting benefits ranging from the simple access to potential spouses, to the creation of affines and strong alliances that provide for reduction of risk through food sharing (Hegmon 1991, 1996), fostering and maintaining peaceful relations (Williams 1969), protection from warfare and aggression, and increased survival rates of children.
These are a few of the more important benefits to be gained through the development of exchange networks. The costs are perhaps harder to model, but at a minimum include the time, energy, and resources needed to develop and maintain such networks, and the potential costs that failed networks may impose on individuals and their communities.
Establishing networks requires the resources necessary to either offer gifts or to reciprocate the offers of others. These costs are relative and variable, and will vary from individual to individual in a community depending on their ability to acquire valued resources or to control or channel the production of others. Certainly a scenario can be envisioned in which limited resources would make the costs of participating in exchange networks prohibitively expensive. Likewise, scenarios can be envisioned in which some individuals would find exchange networks to be a worthwhile investment, especially where an individual has access to resources desired by others, they have access to existing relationships where the anticipation of return benefit is high, or where they have the ability to direct the productive efforts of others either through kinship or other persuasive means.
However, failed exchange networks entail a risk not only to the individual, but to the larger community. This cost—the potential risk created by failure to reciprocate and ensuing agonistic behaviors of others—must be considered but may be subject to mitigation in at least two forms. The first is the development of ritualized contexts of exchange which proscribe the development of exchange networks and the types of allowed gifts and reciprocation that are offered. Thus, gifts or exchange rules and materials may become standardized, such as the rules governing the Kula (Malinowski 1961), gifts may be imbued with spiritual meaning, such as hau among the Maori (Mauss 2000), or both may operate simultaneously. The second mitigation is less direct and is predicated upon the observation that the agonistic behaviors of others can lead to benefits as well; they open the possibility of socially sanctioned negative reciprocity and warfare. While warfare certainly imposes costs, it also provides an alternate pathway for individuals to gain status and/or reproductive benefits (Chagnon 1988; Tooby and Cosmides 1988). Individuals entering into risky exchange networks may discount the potential costs of failed exchange by anticipating the potential benefits of warfare.
Modeling Exchange Benefits
As mentioned previously, differential access to social networks exists within societies. Due to defined territories, availability and density of existing networks, consanguineal and affinal relationships, numbers of kin and the ability to control production, personal skills and abilities, social rank, and other factors, some individuals will have greater, and earlier, access than others to the benefits of exchange networks (Asad 1972; Barth 1956, 1966; Kapferer 1971:15).
At certain thresholds, it becomes advantageous for those individuals to use exchange networks to expand their ‘resource breadth’ rather than pursue other resource acquisition means, such as changing mobility or intensifying or broadening resource exploitation. Thresholds define the points at which exchange networks become viable strategies. These consist of two distinct categories—resource costs and benefits, and the accessibility of viable networks.
In optimality approaches, the net benefit capture can be limited by several factors that may be grouped into the three categories of time limitations, energy limitations, or hazard limitations. Expanding the benefits gained from any one particular strategy may run into conflicts with time needed for other activities (time-limited), require more energy than the benefit justifies (energy-limited), or may expose the individual(s) to greater hazards from risks (hazard-limited) inherent in the strategy (Charnov 1976; Winterhalder and Smith 2000). In short, the net gain per unit of investment decreases per unit time, thus intensifying the exploitation of resources involves increasing costs and decreasing rates of benefit return. As an example, Figure 2.3 demonstrates the decreasing rates of energy return from expanding diet breadth to include increasingly higher cost and lower benefit small grain resources native to eastern North America (data from Gremillion 2004). Expanding diet breadth to incorporate new wild grain species in the diet will yield additional calories but at an increasing cost in procurement and processing time and energy (e.g., Gremillion 2004). Thus the energy return gained through intensification efforts is discounted by increased energy and time invested in procuring those resources. In other words, resources become more costly.
Predictions
The value of such a synthesis of evolutionary and sociocultural perspectives is that it allows us to make predictions about the development and operation of exchange systems and networks. Seven predictions follow from this synthesis:
- The pervasive nature of social interaction through reciprocity and cooperation across human societies suggest that it is an evolutionary stable strategy that utilizes a tit-for-tat strategy and has mechanisms to measure trust and prevent counteracting cheating strategies (Axelrod 1984; Axelrod and Hamilton 1981; Chisolm 1993; Cosmides and Tooby 2005; Tooby et al. 2006)
- Cooperation and exchange between non-related individuals is conducted to meet selfish objectives. In other words, individuals are seeking to promote their own interests through exchange and interaction with others. This follows directly from reciprocal altruism and game theory explanations of cooperation, as well as Durkheim’s much earlier insightful observation that organic solidarity was formed through the cooperation of unlike individuals pursuing their individual interests (Axelrod 1984; Axelrod and Hamilton 1981; Durkheim 1964; Trivers 1971).
- Social exchange networks can be used to enhance fitness by establishing relationships and accumulating obligations from others (Axelrod and Hamilton 1981; Durkheim 1964; Gregory 1982; Gosden 1989; Hayden 1995; Levi-Strauss 1969; Mauss 1990).
- Individuals exploit the tit-for-tat strategy through the exchange of gifts and other materials. The degree of trust, or “w” of the reciprocal altruism equation, is measured by the degree to which gifts are reciprocated. Cheaters can be detected through this process, and the potential beneficial advantages of the relationship can be estimated through an iterated cycle of reciprocal exchange. The adaptive advantage of exchange can then be modeled in terms of costs, benefits, and degree of expected return, measured through such variables as energy, time, or social status (Cosmides and Tooby 2005; Tooby et al. 2006; Trivers 1971).
- The initial exchange between new or infrequent partners is risky, since ‘w’ has not yet been modeled or is modeled poorly. As a result, rules affecting interaction are likely to be developed. The materials or form of exchange may be prescribed and proscribed within a ritual context, which minimizes risk and maximizes potential return (Axelrod and Hamilton 1981; Foster 1977; Görlich 1998; Levi-Straus 1969).
- Exchange replaces the spatial juxtaposition of non-interacting groups and individuals with a relationship, for better or for worse. As Levi-Strauss (1969:59) observed, “the relationship of indifference can never be restored once it has been ended… From now on, the relationship can only be cordial or hostile.” Predictions that follow from this observation involve the range of responses that reflect the interacting parties’ interpretations concerning the strength of ‘w.’ If ‘w’ is found to be strong enough to convey significant benefits, interactions may become more frequent as participants seek fitness opportunities that carry lower risk and are more likely to convey benefits. If repeated cycles of reciprocity lead to high estimations of trust, interaction may proceed from one based on reciprocity to one based on mutualism (Tooby and Cosmides 1996), or it may lead to Levi-Strauss’ (1969) and Williams’ (1969) ‘supreme gift’ of women in marriage exchange. This also leads out of reciprocity-based relationships as trust is replaced with a shared interest in the other parties reproductive fitness (Hamilton 1964), further strengthening the relationships between groups and individuals. If such relationships are of lasting benefit between groups, rules affecting out-group marriage, or exogamy, may develop. By this logic, the formation of exogamy and possibly corporate kin structures are linked to earlier reciprocity-based social exchange.
7. Finally, the use of reciprocal altruism and kin selection models allows social exchange to be modeled using cost-benefit analyses similar to other optimality models of human behavioral ecology (e.g., Winterhalder and Smith 2000). The adaptive advantage of exchange networks can be modeled in terms of costs, benefits, and degree of expected return using energy, time, or social status gained or lost as proxy currencies.
Modeling the Adaptive Nature of Social Exchange
The preceding discussion illustrates the important role of social exchange and interaction in forging, monitoring, and maintaining relationships, and enhancing participants’ fitness. As such, it casts these activities as part of the evolved human behavioral repertoire, and thus subject to some degree of modeling using optimality theory.
Life History Theory and Optimal Foraging offer two approaches to studying human behavior within conditional strategies, or systems of decision making rules, in which natural selection is thought to have favored the development of behaviors that tend towards the optimization of somatic and reproductive effort (Bentley et al. 2008; Chisolm 1993; Stephens and Krebs 1986; Winterhalder and Smith 2000). These models derive from microeconomic theory which examines how individuals make decisions concerning the allocation of limited resources (Keegan and Butler 1987; Winterhalder and Smith 1981, 2000). According to these models, humans have an evolved ability to weigh the costs and benefits of their current and potential future actions in such a way as to optimize their return. This optimality is seldom achieved—human behavior and the variables of social interaction are quite complex and often offer conflicting options—but modeling optimality provides a mathematical and graphical heuristic for identifying behaviors, the factors that affect those behaviors, and reasons for variation from optimality.
The model that follows is built upon the predictions outlined above, and assumes that: a) individuals have limited resources in several forms—including time, energy, and social capital—and they act to optimize their return in several socially, somatically, and reproductively valuable areas; b) optimization is not just concerned with the number of calories that can be returned per calorie of labor invested, but must factor in all the conflicting needs that individuals must meet to optimize their fitness; c) decisions about investment of time, energy, or social capital attempt to balance all these conflicting needs, thus time invested in one area, say food procurement, is in direct competition for time invested in other areas such as gaining social capital, finding mates, parenting, or other socially meaningful activities. In the model to follow, social exchange and interaction networks consist of individuals who are united through the acts and obligations of exchange, and these relationships are between individuals in different communities or societies interacting through reciprocity. This model is not intended to describe the complex relationships found within communities which may be based on inclusive fitness, mutualistic relationships, reciprocity, or various complex interactions of all three.
Benefits and Costs
By using an optimality model, the benefits of exchange can be identified in relation to the costs of forming and maintaining exchange networks, and the trade-offs those costs demand in terms of other somatic or reproductive efforts. The currency of costs and benefits may be highly variable, and can range from time and energy invested and returned to social status gained or lost.
Following the predictions discussed above, exchange networks can be viewed as one means of increasing personal fitness through the development and maintenance of relationships of cooperation, obligation, and reciprocity with others. They are, in this view, a means of intensifying resource exploitation—or to paraphrase the terminology of Optimal Foraging Theory, increasing ‘resource breadth’—in which relationships with others are viewed as a resource that can be exploited for personal gain. However, developing such relationships requires time, resources, and energy that could be used for other activities that may have more immediate benefits. Therefore, the time, energy, resources, or social status invested in creating and maintaining these networks must have an anticipated future benefit in socially meaningful currencies which could include the acquisition of resources or knowledge, increased social status, reduction of risk, or access to marital partners. These benefits have been shown to correlate with increased survival and reproductive opportunities by research with modern communities (e.g., Betzig 1986; Buss et al. 1990; Buss and Schmidt 1993; Kenrick et al. 1990; Marlow 2004).
Additional resources can be used directly for somatic benefit, provide associative value in the form of access to the exotic or rights of spiritual intercession, or may provide more indirect benefits in the form of status gained. Resources need not even be physically gained since the acquisition of the ‘obligations of others’ serves as an investment for future benefit (Gosden 1989; Gregory 1982). While resources gained may provide an immediate somatic benefit, male access to resources has been strongly correlated with reproductive success in cross-cultural studies (Buss and Schmidt 1993; Kenrick et al. 1990; Marlow 2004).
Status can also be gained through the development of social networks. Access to exotic, distant, and rare materials; to knowledge and distant contacts, or to the spiritual, can confer important distinctions on individuals. Individuals who develop bridges between separate spheres of interaction and exchange can gain from their position as the source of benefits that others in the community seek (Barth 1966:18; Granovetter 1973, 1983). Further, by developing networks that provide benefits to others in the community through access to materials or knowledge, individuals become critical and irreplaceable pathways on which others in the community rely. Status and irreplaceability are both important means of improving survival and reproductive success as many researchers have demonstrated (e.g., Betzig 1986; Buss et al. 1990; Granovetter 1973, 1983; Tooby and Cosmides 1996).
I previously argued that the estimation of trust or potential future benefit is initially a goal of incipient exchange networks, and that reciprocation can lead to positive values of “w” which may, in turn, lead to a progression of the relationship from one based on reciprocity to one based on exchange of females in marriage. As noted by Williams (1969:166-169) and Levi-Strauss (1969), this is the ‘supreme gift’ in exchange networks; a gift that strengthens the relationship from one based on reciprocity to one with kinship ties and vested interests in the reproductive and somatic success of the other. This has long lasting benefits ranging from the simple access to potential spouses, to the creation of affines and strong alliances that provide for reduction of risk through food sharing (Hegmon 1991, 1996), fostering and maintaining peaceful relations (Williams 1969), protection from warfare and aggression, and increased survival rates of children.
These are a few of the more important benefits to be gained through the development of exchange networks. The costs are perhaps harder to model, but at a minimum include the time, energy, and resources needed to develop and maintain such networks, and the potential costs that failed networks may impose on individuals and their communities.
Establishing networks requires the resources necessary to either offer gifts or to reciprocate the offers of others. These costs are relative and variable, and will vary from individual to individual in a community depending on their ability to acquire valued resources or to control or channel the production of others. Certainly a scenario can be envisioned in which limited resources would make the costs of participating in exchange networks prohibitively expensive. Likewise, scenarios can be envisioned in which some individuals would find exchange networks to be a worthwhile investment, especially where an individual has access to resources desired by others, they have access to existing relationships where the anticipation of return benefit is high, or where they have the ability to direct the productive efforts of others either through kinship or other persuasive means.
However, failed exchange networks entail a risk not only to the individual, but to the larger community. This cost—the potential risk created by failure to reciprocate and ensuing agonistic behaviors of others—must be considered but may be subject to mitigation in at least two forms. The first is the development of ritualized contexts of exchange which proscribe the development of exchange networks and the types of allowed gifts and reciprocation that are offered. Thus, gifts or exchange rules and materials may become standardized, such as the rules governing the Kula (Malinowski 1961), gifts may be imbued with spiritual meaning, such as hau among the Maori (Mauss 2000), or both may operate simultaneously. The second mitigation is less direct and is predicated upon the observation that the agonistic behaviors of others can lead to benefits as well; they open the possibility of socially sanctioned negative reciprocity and warfare. While warfare certainly imposes costs, it also provides an alternate pathway for individuals to gain status and/or reproductive benefits (Chagnon 1988; Tooby and Cosmides 1988). Individuals entering into risky exchange networks may discount the potential costs of failed exchange by anticipating the potential benefits of warfare.
Modeling Exchange Benefits
As mentioned previously, differential access to social networks exists within societies. Due to defined territories, availability and density of existing networks, consanguineal and affinal relationships, numbers of kin and the ability to control production, personal skills and abilities, social rank, and other factors, some individuals will have greater, and earlier, access than others to the benefits of exchange networks (Asad 1972; Barth 1956, 1966; Kapferer 1971:15).
At certain thresholds, it becomes advantageous for those individuals to use exchange networks to expand their ‘resource breadth’ rather than pursue other resource acquisition means, such as changing mobility or intensifying or broadening resource exploitation. Thresholds define the points at which exchange networks become viable strategies. These consist of two distinct categories—resource costs and benefits, and the accessibility of viable networks.
In optimality approaches, the net benefit capture can be limited by several factors that may be grouped into the three categories of time limitations, energy limitations, or hazard limitations. Expanding the benefits gained from any one particular strategy may run into conflicts with time needed for other activities (time-limited), require more energy than the benefit justifies (energy-limited), or may expose the individual(s) to greater hazards from risks (hazard-limited) inherent in the strategy (Charnov 1976; Winterhalder and Smith 2000). In short, the net gain per unit of investment decreases per unit time, thus intensifying the exploitation of resources involves increasing costs and decreasing rates of benefit return. As an example, Figure 2.3 demonstrates the decreasing rates of energy return from expanding diet breadth to include increasingly higher cost and lower benefit small grain resources native to eastern North America (data from Gremillion 2004). Expanding diet breadth to incorporate new wild grain species in the diet will yield additional calories but at an increasing cost in procurement and processing time and energy (e.g., Gremillion 2004). Thus the energy return gained through intensification efforts is discounted by increased energy and time invested in procuring those resources. In other words, resources become more costly.
Figure 2.3. Decreasing return rates associated with wild utilized during the Archaic period in eastern North America (after Gremillion 2004:Table 4)
The accessibility of viable networks is another critical threshold value. In this sense, thresholds are defined by the number of individuals that must already be combined in networks, and the accessibility of these networks to new individuals (Granovetter 1978). In some cases this may be dependent on population density—raising the old issue of population density as a driving force behind increasing interaction and social complexity—but this is not the only way in which network thresholds can be achieved. Conceivably, network thresholds can be approached in at least two non-exclusive ways; internally-generated and externally-generated. Internally-generated thresholds come from increasing interaction within and between communities across small social distances, and represent the expansion and increasing integration of local exchange systems from within. Such expansion and integration can lead to increasing network accessibility to individuals in those communities, and may be associated with decreasing risk of non-reciprocation since ‘w’ is more effectively modeled. Internally-generated thresholds will likely to be linked in some cases to increasing population density. On the other hand, thresholds can be achieved without increasing population density in the case of externally-generated thresholds. Exchange networks may have their origins in areas far distant from some regions they come to characterize. For example, in the Archaic of the North American midcontinent, exchange systems eventually incorporate the region from the Great Lakes to the Gulf Coast, and the Appalachians to the Great Plains. Yet populations need not be high in all those areas. Exchange systems can originate in one or a few areas—say the Ohio Valley or lower Mississippi Valley in this example—and then expand outward through the fitness enhancing behaviors of individuals around the network peripheries. As networks become increasingly interconnected and integrated, they simultaneously become more productive sources of benefits for those located around their peripheries. Thresholds in more distant areas are thus exceeded even without increasing local population densities, as distantly generated exchange networks become more integrated and available to peripheral areas and thus provide more viable benefits to people who are in a position to access those networks. Network theory demonstrates that such networks can be generated without deliberate or purposeful action and may feature the rapid development of structural properties such as the sudden appearance of large network systems known as “giant components” (Achlioptas et al. 2009; Bohman 2009). In a sense, this is the development of a network infrastructure that, through bridges connecting several local spheres of exchange, provides access to distant materials and ideas. Such an infrastructure is the foundation of Renfrew’s (1972) “down the line” model of exchange, in which materials move from hand-to-hand through local systems, ultimately moving large distances over multiple transactions. However, the number of transactions needed to move materials and knowledge over long distances may be limited, as it is the few individuals that form bridges between local spheres of exchange that power such systems (Kochen 1989; Milgram 1992; Travers and Milgram 1969; Watts 1999)
As thresholds are reached, those individuals with access to developing exchange networks reach a point at which exploiting exchange opportunities will yield a greater potential benefit to their fitness than further intensifying resource exploitation. This can be modeled as shown in Figure 2.4. As benefits from existing resource strategies decrease due to increased time or energy costs, and as thresholds of network interconnectedness are exceeded, individuals with access to those networks would realize a net benefit gain by utilizing exchange systems to build and maintain relationships with others who have access to socially meaningful resources. At that point, optimality suggests that those individuals will switch strategies to exploit exchange networks.
Note that a change in the value or return rate of resource methods can dramatically alter the benefits to be gained through exchange networks. Technological changes in processing or procurement methods can increase the return rate for some resources, while the adoption of new strategies such as agriculture can dramatically alter the above model. This does not need to occur everywhere within a growing network, as a disruption in the connectedness of a network in one area can alter the value of that exchange networks to participants in more distant areas.
As thresholds are reached, those individuals with access to developing exchange networks reach a point at which exploiting exchange opportunities will yield a greater potential benefit to their fitness than further intensifying resource exploitation. This can be modeled as shown in Figure 2.4. As benefits from existing resource strategies decrease due to increased time or energy costs, and as thresholds of network interconnectedness are exceeded, individuals with access to those networks would realize a net benefit gain by utilizing exchange systems to build and maintain relationships with others who have access to socially meaningful resources. At that point, optimality suggests that those individuals will switch strategies to exploit exchange networks.
Note that a change in the value or return rate of resource methods can dramatically alter the benefits to be gained through exchange networks. Technological changes in processing or procurement methods can increase the return rate for some resources, while the adoption of new strategies such as agriculture can dramatically alter the above model. This does not need to occur everywhere within a growing network, as a disruption in the connectedness of a network in one area can alter the value of that exchange networks to participants in more distant areas.
Figure 2.4. A proposed optimality curve for exchange network benefits. Two models are presented: in a) the benefits of network participation remain constant while other resource values decline; b) shows the predicted increasing network benefits as a logistical curve that reflects increasing network connectedness and access.
Testing the Adaptive Networks Hypothesis
Several predictions follow from the outlined hypothesis which may be tested using archaeological data. In particular, the hypothesis first predicts that certain individuals will have access to viable exchange strategies before others in their community and second, they pursue exchange networks to promote their own interests and enhance their fitness. Their interest and fitness benefits come in many forms, including increased access to resources, and status from access to the exotic as well as serving as ‘brokers’ in their community. Barth (1966) describes ‘brokers’ as providing important links in exchange networks, links that form bridges from one exchange system to another. Granovetter (1973, 1983) later identified, clarified, and defined this same phenomenon through social network theory, and labeled it the ‘strength of weak ties.’ These bridges, for example the A-B segment in Figure 2.5, provide the connections that connect smaller more completely integrated networks, equivalent to communities or societies in this discussion, into larger systems. To further stretch the bridge metaphor, the individuals at each end of the bridge extract a toll from the materials and information flowing through this link—they become irreplaceable (Tooby and Cosmides 1996) as sources of socially valuable material and gain benefits from this position. In this example, the individuals represented by A and B are those individuals for whom the network benefit threshold has been met and who stand to gain benefits through forming exchange networks. A testable aspect of this model is to examine the association between materials transmitted through exchange and reproductive fitness (e.g., Hayden and Schulting 1997)
Finally, following the uncertain nature of trust and the consequences of non-reciprocation, exchange is risky not only to participants but to the community at large. Consequently, mitigation of risk is likely to have involved rules concerning standardization of exchange materials and practices, and placing the practice of exchange within a ritualized context.
Archaeological data can be used to explore these aspects of the hypothesis by formulating the following questions. First, does the presence and nature of exotic materials suggest that the exchange benefit thresholds have been crossed and exchange is a viable strategy for some members of the community? Second, are the benefits of exchange networks widespread in the community, or, as predicted, limited to a few ‘brokers’? Third, do those brokers demonstrate greater fitness or social position than other community members? Finally, is there a standardized or ritualized context for exchange that may serve to mitigate risk and optimize potential benefits?
Several predictions follow from the outlined hypothesis which may be tested using archaeological data. In particular, the hypothesis first predicts that certain individuals will have access to viable exchange strategies before others in their community and second, they pursue exchange networks to promote their own interests and enhance their fitness. Their interest and fitness benefits come in many forms, including increased access to resources, and status from access to the exotic as well as serving as ‘brokers’ in their community. Barth (1966) describes ‘brokers’ as providing important links in exchange networks, links that form bridges from one exchange system to another. Granovetter (1973, 1983) later identified, clarified, and defined this same phenomenon through social network theory, and labeled it the ‘strength of weak ties.’ These bridges, for example the A-B segment in Figure 2.5, provide the connections that connect smaller more completely integrated networks, equivalent to communities or societies in this discussion, into larger systems. To further stretch the bridge metaphor, the individuals at each end of the bridge extract a toll from the materials and information flowing through this link—they become irreplaceable (Tooby and Cosmides 1996) as sources of socially valuable material and gain benefits from this position. In this example, the individuals represented by A and B are those individuals for whom the network benefit threshold has been met and who stand to gain benefits through forming exchange networks. A testable aspect of this model is to examine the association between materials transmitted through exchange and reproductive fitness (e.g., Hayden and Schulting 1997)
Finally, following the uncertain nature of trust and the consequences of non-reciprocation, exchange is risky not only to participants but to the community at large. Consequently, mitigation of risk is likely to have involved rules concerning standardization of exchange materials and practices, and placing the practice of exchange within a ritualized context.
Archaeological data can be used to explore these aspects of the hypothesis by formulating the following questions. First, does the presence and nature of exotic materials suggest that the exchange benefit thresholds have been crossed and exchange is a viable strategy for some members of the community? Second, are the benefits of exchange networks widespread in the community, or, as predicted, limited to a few ‘brokers’? Third, do those brokers demonstrate greater fitness or social position than other community members? Finally, is there a standardized or ritualized context for exchange that may serve to mitigate risk and optimize potential benefits?
Figure 2.5. Graph theory representation of the bridging effect, or the "strength of weak ties", connecting two local networks. The A-B segment represents the exchange link between two local networks or communities, and the individuals represented at A and B are the brokers through which materials and ideas flow from one local network to the next.
Testable Implications
Due to its foundation in evolved human behavioral traits, the adaptive network hypothesis provides a useful tool for examining the development of exchange networks. By viewing the development of exchange networks from the perspective of individual fitness benefits, the hypothesis’ utility lies in its ability to form testable predictions of individual behavior and the emergent phenomena the result from collective fitness enhancing behavior.
The model predicts that at certain threshold points, some individuals will find exchange networks to be a beneficial strategy. Those individuals will engage in exchange in order to enhance their fitness, and may gain benefits in the form of access to material and ideological resources, enhanced social status, social roles as brokers of information and goods to their community, reduction of risk, access to potential mates, and the formation of alliances that can provide further benefits. These benefits come with the risk of non-reciprocation and potential agonistic responses. These risks will be mitigated through social sanctions that prescribe contexts and materials of exchange, and may be further mitigated by anticipating the benefits of alternate strategies such as warfare.
These observations allow for the development of explicitly testable predictions, and provide an important tool for examining the development and functioning of emergent phenomenon, such as regional exchange networks, using archaeological data. Five testable implications emerge from this model.
First, some individuals and some communities are predicted to have greater access to exchange networks and their benefits. The entire community may be too isolated, either geographically or socially, from exchange networks with the result that it is too costly to engage in exchange from that community. In these communities, we expect to see few exotic goods, and exotic goods that are present should appear to result from informal down-the-line exchange rather than intensive and directed interaction with other communities. In other cases, some individuals within a community will have greater access to the benefits of exchange. In this situation, mortuary contexts should reveal the presence of haves and have-nots in the form of differential interment with exotic goods.
Exchange is risky and risk is shared by the entire community. Earlier, this observation was used to suggest that social rules would likely develop which prescribed the type of exchange goods and which exchange is embedded in ritual or formal contexts that serve to reduce risk. In particular, materials exchanged may be standardized in terms of raw material or production criteria to provide clear, understandable, and verifiable costly signals (Bird and Smith 2005) of trustworthiness and veracity across large social distances. This can be identified through analysis of the metric attributes, raw material selection, and production methods of goods that appear to prominently function in exchange over large social distances.
When exchange validates trust, increasing interaction should occur as benefits increase and potential costs of conflict decrease. Also, as benefits increase, networks may become more robust and facilitate the movement of materials over longer distances. These potential results will be visible in the form of increasing frequency of exotic goods through time as well as by an increase in the distance from which exchange materials are obtained.
However, the failure of exchange networks may lead to increased conflict as trust is not reciprocated. This may be visible in several forms. First, an examination of mortuary populations may show increasing trauma or changes in demographics that suggest interpersonal violence. Conflict may also be visible in the form of sites of battle or massacre, or in increasing reliance on defensive structures or site locations.
Finally, changes in social structure may result from increasing interaction with other communities through exchange. As trust is established through iterated cycles of exchange, relationships may be strengthened through the formation of new inclusive social structures, such as corporate groups, and eventually through intermarriage with other communities. William’s (1969) exogamy rules may even develop in certain situations as individuals and communities experience important benefits through inter-community cooperation. These changes may be observed through analysis of mortuary populations and, in particular, changes in the social roles and positions of adult females and children that may signal the development of corporate groups or rules of exogamy.
Due to its foundation in evolved human behavioral traits, the adaptive network hypothesis provides a useful tool for examining the development of exchange networks. By viewing the development of exchange networks from the perspective of individual fitness benefits, the hypothesis’ utility lies in its ability to form testable predictions of individual behavior and the emergent phenomena the result from collective fitness enhancing behavior.
The model predicts that at certain threshold points, some individuals will find exchange networks to be a beneficial strategy. Those individuals will engage in exchange in order to enhance their fitness, and may gain benefits in the form of access to material and ideological resources, enhanced social status, social roles as brokers of information and goods to their community, reduction of risk, access to potential mates, and the formation of alliances that can provide further benefits. These benefits come with the risk of non-reciprocation and potential agonistic responses. These risks will be mitigated through social sanctions that prescribe contexts and materials of exchange, and may be further mitigated by anticipating the benefits of alternate strategies such as warfare.
These observations allow for the development of explicitly testable predictions, and provide an important tool for examining the development and functioning of emergent phenomenon, such as regional exchange networks, using archaeological data. Five testable implications emerge from this model.
First, some individuals and some communities are predicted to have greater access to exchange networks and their benefits. The entire community may be too isolated, either geographically or socially, from exchange networks with the result that it is too costly to engage in exchange from that community. In these communities, we expect to see few exotic goods, and exotic goods that are present should appear to result from informal down-the-line exchange rather than intensive and directed interaction with other communities. In other cases, some individuals within a community will have greater access to the benefits of exchange. In this situation, mortuary contexts should reveal the presence of haves and have-nots in the form of differential interment with exotic goods.
Exchange is risky and risk is shared by the entire community. Earlier, this observation was used to suggest that social rules would likely develop which prescribed the type of exchange goods and which exchange is embedded in ritual or formal contexts that serve to reduce risk. In particular, materials exchanged may be standardized in terms of raw material or production criteria to provide clear, understandable, and verifiable costly signals (Bird and Smith 2005) of trustworthiness and veracity across large social distances. This can be identified through analysis of the metric attributes, raw material selection, and production methods of goods that appear to prominently function in exchange over large social distances.
When exchange validates trust, increasing interaction should occur as benefits increase and potential costs of conflict decrease. Also, as benefits increase, networks may become more robust and facilitate the movement of materials over longer distances. These potential results will be visible in the form of increasing frequency of exotic goods through time as well as by an increase in the distance from which exchange materials are obtained.
However, the failure of exchange networks may lead to increased conflict as trust is not reciprocated. This may be visible in several forms. First, an examination of mortuary populations may show increasing trauma or changes in demographics that suggest interpersonal violence. Conflict may also be visible in the form of sites of battle or massacre, or in increasing reliance on defensive structures or site locations.
Finally, changes in social structure may result from increasing interaction with other communities through exchange. As trust is established through iterated cycles of exchange, relationships may be strengthened through the formation of new inclusive social structures, such as corporate groups, and eventually through intermarriage with other communities. William’s (1969) exogamy rules may even develop in certain situations as individuals and communities experience important benefits through inter-community cooperation. These changes may be observed through analysis of mortuary populations and, in particular, changes in the social roles and positions of adult females and children that may signal the development of corporate groups or rules of exogamy.
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