Exchange Systems

Trade Networks in Anthropology and Archaeology

Pochteca Traders with Their Cargo
Pochteca Traders with Their Cargo. Illustration from the Florentine Codex, Late 16th century.

An exchange system or trade network can be defined as any manner in which consumers connect with producers. Regional exchange studies in archaeology describe the networks that people used to gain, barter for, purchase, or otherwise obtain raw material, goods, services and ideas from the producers or sources, and to move those goods across the landscape. The purpose of exchange systems can be to fulfill both basic and luxury needs.

Archaeologists identify networks of exchange by using a variety of analytical techniques on material culture, and by identifying raw material quarries and manufacturing techniques for specific types of artifacts.

Exchange systems have been a focus of archaeological research since the mid-19th century when chemical analyses were first used to identify the distribution of metal artifacts from central Europe. One pioneer study is that of archaeologist Anna Shepard who during the 1930s and 40s used the presence of mineral inclusions in pottery sherds to provide evidence for a widespread trade and exchange network throughout the southwestern United States.

Economic Anthropology and Exchange Systems

The underpinnings of the exchange systems research were strongly influenced by Karl Polyani in the 1940s and 50s. Polyani, an economic anthropologist, described three types of trading exchange: reciprocity, redistribution, and market exchange.

Reciprocity and redistribution, said Polyani, are methods that are embedded in long-range relationships that imply trust and confidence: markets, on the other hand, are self-regulating and disembedded from trust relationships between producers and consumers.

  • Reciprocity is a behavioral system of trade, which is based on the more or less equal sharing of goods and services. Reciprocity could be defined simply as "you scratch my back, I'll scratch yours": you do something for me, I'll reciprocate by doing something for you. I'll watch your cows, you'll provide my family with milk.
  • Redistribution involves a collection point from which goods are apportioned out. In a typical redistribution system, a village chief collects a percentage of the produce in a village, and provides it to members of the group based on need, gifts, feasting: any one of a number of etiquette rules that have been established in a given society.
  • Market exchange involves an organized institution, in which goods producers congregate at specified locations at specified times. Either barter or money exchange is involved ​in order to allow consumers to obtain required goods and services from purveyors. Polyani himself argued that markets may or may not be integrated within community networks.

Identifying Exchange Networks In Archaeology

Anthropologists can go into a community and determine the existing exchange networks by talking to the local residents and observing the processes: but archaeologists must work from what David Clarke once called "indirect traces in bad samples." Pioneers in the archaeological study of exchange systems include Colin Renfrew, who argued that it was important to study trade because the institution of a trade network is a causal factor for cultural change.

Archaeological evidence for the movement of goods across the landscape has been identified by a series of technological innovations, building from Anna Shepard's research.

In general, sourcing artifacts - identifying where a particular raw material came from – involves a series of laboratory tests on artifacts which are then compared to known similar materials. Chemical analysis techniques used to identify raw material sources include Neutron Activation Analysis (NAA), X-ray fluorescence (XRF) and various spectrographic methods, among a wide and growing number of laboratory techniques.

In addition to identifying the source or quarry where raw materials were obtained, chemical analysis can also identify similarities in pottery types or other sorts of finished goods, thus determining whether the finished goods were created locally or brought in from a distant location. Using a variety of methods, archaeologists can identify whether a pot that looks as if it were made in a different town is truly an import, or rather a locally made copy.

Markets and Distribution Systems

Market locations, both prehistorically and historically, are often located in public plazas or town squares, open spaces shared by a community and common to nearly every society on the planet. Such markets often rotate: market day in a given community may be every Tuesday and in a neighboring community every Wednesday. Archaeological evidence of such use of communal plazas is difficult to ascertain because typically plazas are cleaned and used for a wide variety of purposes.

Itinerant traders such as the pochteca of Mesoamerica have been identified archaeologically through iconography on written documents and monuments such as stele as well as by the types of artifacts left in burials (grave goods). Caravan routes have been identified in numerous places archaeologically, most famously as part of the Silk Road connecting Asia and Europe. Archaeological evidence seems to suggest that trade networks were much of the driving force behind the construction of roads, whether wheeled vehicles were available or not.

The Diffusion of Ideas

Exchange systems are also the way ideas and innovations are communicated across the landscape. But that's a whole other article.

Sources

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Mathien FJ. 2001. The Organization of Turquoise Production and Consumption by the Prehistoric Chacoans. American Antiquity 66(1):103-118.

McCallum M. 2010. The Supply of Stone to the City of Rome: A Case Study of the Transport of Anician Building Stone and Millstone from the Santa Trinità Quarry (Orvieto). In: Dillian CD, and White CL, editors.

Trade and Exchange: Archaeological Studies from History and Prehistory. New York: Springer. p 75-94.

Polyani K. 1944 [1957]. Societies and Economic Systems. Chapter 4 in The Great Transformation: The Political and Economic Origins of Our Time. Beacon Press, Rinehart and Company, Inc. Boston.

Renfrew C. 1977. Alternative models for exchange and spatial distribution. In. In: Earle TK, and Ericson JE, editors. Exchange Systems In Prehistory. New York: Academic Press. p 71-90.

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Summerhayes GR. 2008. Exchange Systems. In: Editor-in-Chief: Pearsall DM. Encyclopedia of Archaeology. New York: Academic Press. p 1339-1344.