Archaeology Of Trade And Exchange Research Paper

1. The Development Of Trade And Exchange In Archaeology

Since the 1980s there has been an upsurge in studies on the archaeology of trade and exchange. The reasons for this are twofold. First, advances in science and technology have allowed and made easily available the sourcing and characterization of many materials. This provides evidence for the physical identification of their movement. Second, archaeologists began to see the usefulness in using trade and exchange in modeling the distribution of materials over space, and in explaining changes in societies over time.

1.1 Technological Developments

Developments in technology since the 1960s have led to an upsurge in chemical ‘sourcing’ or characterization studies. Yet the identification of traded archaeological material is not a recent phenomenon. Perhaps the most famous early study was by Anna Shepard, who in the 1930s and 1940s postulated the exchange of pottery over wide areas of the Southwest USA by analyzing mineral inclusions in thin sections to pinpoint the origins of the minerals (Shepard 1965). Chemical techniques to identify the elemental composition of archaeological materials as a means of characterization are also not new. Neutron activation analysis was applied on coins from the Louvre in 1952, while in 1957 oriental ceramics were analyzed using nondestructive methods of x-ray fluorescence spectrometry (XRF) and x-ray diffraction (XRD) analysis (Young and Whitmore 1957). However, access to these techniques was restricted and costly.

A major advance in the chemical analysis of archaeological material came from the initiative of Dr. R. Oppenheimer. On March 8, 1956 he assembled a group of archaeologists and chemists at the Institute of Advanced Studies, Princeton, to discuss the possibility of applying methods of nuclear research to the study of archaeology (Sayre and Dodson 1957). As a result of this meeting, work was undertaken at two laboratories—the Brookhaven National Laboratory in the USA and the Research Laboratory for Archaeology and the History of Art at Oxford, UK. Techniques used included neutron activation analysis (NAA) and spectrographic methods. These early studies were reasonably successful, being able to separate pottery wares from Asia Minor, Greece, and Italy, and different factories of Samian ware. These studies laid the foundations for chemical analyses for the next three decades, in which thousands of analyses using varying techniques were carried out on many types of object including pottery, stone (obsidian, marble, chert, volcanic rocks), amber, and metals including coins. Apart from NAA, XRF, XRD, and spectrographic methods, techniques currently in use include proton induced x-ray emission and proton induced gamma ray emission (PIXE-PIGME), inductively coupled plasma emission spectrometry (ICP), lead isotope analysis, and electron microscopy, to mention a few. Major changes in the instrumentation of these techniques since the 1970s have meant that more elements can be analyzed with a higher precision. The choice of technique depends on availability to the archaeologist and cost. See Harbottle (1982) for a list of materials that can be characterized.

1.2 Theoretical Developments

The importance of trade and exchange in archaeology is the result of a reorientation in the ways archaeologists have perceived trade exchange operating in the past. The realization that migrationist invasion models could not adequately explain the distribution of material across the landscape, nor change in societies over time, led archaeologists to look at other mechanisms. Inspired by the works of economic anthropologists such as Polanyi (1957), who defined three types of trade and exchange (reciprocity, redistribution, and market exchange), and anthropologists such as Malinowski (1922), who studied trade and exchange in a Melanesian society, archaeologists realized that trade and exchange were embedded within the social and economic structures of society. By studying trade and exchange, the intention was to reconstruct the economies and organizations of past societies and their changes over time. The access to and control over prestige goods through trade and exchange were seen as prime movers for change leading to ranked societies.

A major proponent for the study of ancient trade and exchange was Colin Renfrew. In a classic paper on trade and culture process in European prehistory, Renfrew (1969) argued that trade was a causal factor for cultural change leading to the beginning of urbanization in the Aegean. An increase in trade with new wealth, craft specialization, and communication, led to change from a ‘village subsistence economy into an urban society.’ This was a marked shift away from inferring invasions or diffusion from a ‘higher culture’ to account for the Aegean Early Bronze Age. See Rathje (1971) for a similar case study involving the Maya.

2. Current Theory And Research

From these earlier studies a number of influential edited volumes on the archaeology of trade and exchange appeared: Sabloff and Lamberg-Karlovsky (1975), Ericson and Earle (1982), Earle and Ericson (1977), Renfrew and Shennan (1982), and Renfrew and Cherry (1986). These proceedings covered an eclectic array of topics from the Old and New Worlds, and provided the benchmark for trade and exchange studies for the next decade. These studies were important not only in identifying the movement of materials in the past, but also in cementing links with the chemists, geologists, or physicists who undertook the physicochemical analyses which demonstrated that trade and exchange took place. These studies are also important in initiating innovative research into the archaeology of trade and exchange, such as correlating the distribution of materials with modes of exchange and types of social organization, or exploring the relationship between trade and exchange with production and consumption patterns. These innovations will be discussed below.

Within this research a distinction has been made between two schools of thought about the way in which trade and exchange should be modeled: formalist and substantivist. The formalist approach works within the paradigm of market economics. Here, all exchange transactions can be viewed by economic rationalism, based on cost efficiency. Falloff models presented in Sect. 2.2 below are based on cost efficiencies. The substantivist school, on the other hand, views exchange as being embedded in social and economic processes. This approach allows an investigation into social groups, and social change. In reality, archaeologists draw from both approaches to model ancient trade and exchange.

Research mostly followed the following steps:

(a) identifying that exchange/trade took place;

(b) modeling the distribution patterns of the exchanged/traded material.

2.1 Identifying What Is Moving And What Is Not

Trade or exchange must be demonstrated rather than assumed. Archaeologists often view stylistic similarities over large distances as a consequence of exchange. Stylistic similarities in pottery, for instance, have been equated with the trade or exchange of pots from one or a restricted number of centers. Yet, in many instances this is not the case. One pottery tradition, Lapita, for instance, is spread from Papua New Guinea to Tonga, a distance of over 4,000 km. It is stylistically homogeneous, having a suite of shared decorated motifs made by a dentate stamping technique. Before the 1970s it was thought that this pottery was made in one or a handful of manufacturing centers and then exchanged to other communities, thus accounting for its spread within Melanesia. Yet, after extensive petrographic and chemical analysis, it was established that with the exception of a couple of assemblages, most Lapita pottery is locally made. It was people and ideas that were exchanged, not the pots. Thus, if local production of an object is demonstrated then models other than the trade/exchange of the object must be developed to account for stylistic similarity.

Identifying the source of an object and studying the context of production is not easy. The use of a ‘resource zone concept of source’ is useful here in defining a geographical region from which the object was produced (Clark et al. 1992). For instance, the exact spot where the firing of a pot took place, or where obsidian was extracted is not crucial here, only whether the pottery is of local origin or not, or whether the obsidian originated from a defined area. Attributing an object to a general regional zone (or procurement zone) is often more important than trying to identify a precise spot for manufacture.

The aim of many physicochemical analyses is to discern the geographical origin of the object under study. Ideally, the sources of material with restricted distribution could be characterized and ‘fingerprinted’ chemically or petrographically. Obsidian, for instance, is chemically homogeneous, and its sources can be chemically fingerprinted. Obsidian found in archaeological contexts can be analyzed and related back to the source. Identifying the potential source areas of a material requires an intensive search within a known region. For instance, in a recent study on obsidian exchange within the western Pacific over a 20,000 year time span, archaeologists have concentrated on the source areas within West New Britain, Papua New Guinea. Over a number of years, obsidian flows were mapped and samples taken for characterization, with the result that a finer discrimination of sources was possible with five source localities chemically defined (Summerhayes et al. 1998). By analyzing obsidian found in archaeological sites (some up to 3,700 km distant), it was possible not only to trace obsidian to its source localities, but also to define changes in the selection of different sources over time. For an overview of archaeological approaches to obsidian studies, see Shackley (1998).

Pottery, on the other hand, is more difficult to characterize or fingerprint. Often archaeologists use what is called a ‘criterion of relative abundance,’ which infers that most pottery from a production center is to be found locally. Yet if pottery was produced for exchange only, then little would be found locally, thus limiting the application of this concept. The ‘criterion of relative abundance’ is useful, however, when used with a physicochemical analysis for provenance studies; that is, relating the pottery under study back to its raw materials: non-plastic inclusions (minerals, sands, etc.) and clay. Mineral inclusions found within pottery can be related to local geology and both river and beach sands. Clays, on the other hand, vary greatly in respect of the underlying geology, and a study of the elemental composition of pottery may give a clue to its origin. The chemical analysis of clay is complex. Bishop et al. (1982) note that clay minerals not only depend on their parent material, but are also affected by weathering or hydrothermal activity, climate, and geomorphology. They state that ‘even if a region is considered to be homogeneous in its gross geologic characteristics, significant mineralogical and chemical differences may be discerned between clay deposits’ (Bishop et al. 1982).

In any provenance study of archaeological objects a few words of caution from Garman Harbottle, a nuclear physicist, should best be heeded:

archaeologists love the term sourcing, with its upbeat, positive thrust—that you analyze or examine an artifact and, by comparison with the material of known origin, ‘source’ it. In point of fact, with very few exceptions, you cannot unequivocally source anything. What you can do is characterize the object, or better, groups of similar objects found in a site or archaeological zone by mineralogical, thermo luminescent, density, hardness, chemical and other tests, and also characterize the equivalent source materials, if they are available, and look for the similarities to generate attributions. A careful job of chemical characterization, plus a little numerical taxonomy and some auxiliary archaeological and/or stylistic information, will often do something as useful: It will produce groupings of artifacts that make archaeological sense. This, rather than absolute proof of origin, will often necessarily be the goal. (Harbottle 1982)

For an overview of archaeological approaches to pottery characterization studies, see Neff (1992).

2.2 Distribution Patterns

Archaeologists analyze the distribution of an object from its source or production area to its consumption site in order model the type of trade/exchange that took place. In some instances the nature of the society participating in the trade/exchange system is inferred, such as egalitarian versus chiefly, or nonhierarchical versus hierarchical.

Popular among archaeologists is the use of fall-off curves and modes of trade/exchange. By plotting the frequency of an item against distance from its source (fall-off curve), Renfrew (1975) observed different distribution patterns which he attempted to relate to modes of exchange or access. Some of these modes included reciprocity, down-the-line, and central-place exchange.

How were fall-off curves and modes of exchange related? Down-the-line exchange and reciprocity led to an exponential fall-off in abundance away from the source or production center. The term ‘law of monotonic decrement’ was coined to account for this fall-off in the frequency of an item away from the source (Renfrew 1977). Attempts were also made to define an object’s value by the slope of the curve. A small slope equates with high-value goods, such as spondylus shells in Europe, Maya jade, and Oaxaca iron-ore mirrors. These modes were equated with an egalitarian society (semisedentary agriculturalists and huntergatherers; nonranked; nonhierarchical).

Central-place exchange, on the other hand, was seen as directional (no exponential linear fall-off ), should lead to multinodal fall-off curves, and is indicative of redistribution. Central place relates to the movement of goods toward one place or center, from which they are then distributed. Redistribution has been related to complex chiefly societies (hierarchical, ranked and/or stratified societies). Examples of such societies given by archaeologists include early states such as the Maya, Egypt, the Near East, or chiefdoms such as Hawaii.

Although problems occur with equifinality—that is, different modes of exchange produce similar distributions—this approach is important as it relates the measurement of archaeological material away from the source to trade and exchange modes and the structures of societies.

3. Future Directions

Approaches to the archaeology of trade and exchange will continue to change on three fronts. First, change will occur in tune with developments in archaeological theory. As archaeologists will be asking different questions about the roles of trade and exchange and society, changes in approaches and methodologies will take place. Second, at the same time, it is reasonable to expect advances in characterizing techniques, making them yet more accessible and cheaper to use. Lastly, archaeologists will consolidate knowledge on the sources and distribution of a variety of goods, giving a more complete perspective on the roles of trade and exchange within a society. As an example, attention is drawn to the Pacific where the production and distribution of a number of materials, such as pottery, obsidian, chert, volcanic adzes, and shell artifacts, are used to show that each class of material has different production and distribution patterns. If any class of artifact were taken by itself, a ‘myopic’ view would be seen of the roles of trade and exchange within societies. Only by comparing the production and distribution patterns of the complete range of material available can a proper picture of trade and exchange be given.

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