As an investigation of non-western exchange, this research relies on categories and approaches developed in economic anthropology. The analysis and interpretation applied in the Upper Colca project is rooted in the substantivist tradition, but the weaker elements of the original substantivist approach will be avoided. These weaker elements include an attempt at an explicit delimiting of culture areas (where values are assumed to be shared), and implicit evolutionary links between volume of exchange and social complexity. Concepts from economic anthropology based on the work of Polanyi (1957) that include the idea of social distance as developed by Sahlins (1972) will be used to explore diachronic change in the circulation of obsidian in the prehispanic Andes. More recent discussions of the importance of "ordinary goods" (Smith 1999), in contrast to the usual focus on prestige items, will be considered in light of the cultural importance of coca, herbs, obsidian, and other non-exclusive but widely valued items in the Andes.

A principal theoretical question addressed in this dissertation concerns the circumstances of a large shift in obsidian production during the Early Formative, around 2000-1300 BCE It is argued here that the links between prestige goods circulation with models of competitive display are evident, but that influence is also accrued by individuals, such as llama caravan drivers, who generate consistent traffic between areas by circulating both information and non-local goods on a seasonal or an annual basis. The underlying assumption is not that the act of exchange inherently "creates value" (Appadurai 1986), but rather that the circulation of material goods was a pragmatic incentive for maintaining a range of important social and ideological relationships across space (Browman 1981;Nuñez and Dillehay 1995 [1979]). The caravan model described here is not adaptationalist, however, as it is not proposed that greater efficiency or social harmony led to the emergence of social complexity in the Andean highlands. Rather, the successful manipulation by aggrandizing individuals of the institutions that developed around these regional relationships was one early basis for the incipient concentration of power and the establishment of inequalities that are most apparent at early regional centers in the Andean highlands (Hayden 1998;Stanish 2003). The social and economic foundations for the emergence of these early centers clearly predate the ascendancy of these centers during the Middle and Late Formative in the Titicaca Basin, and obsidian is one class of artifact that was circulating consistently since the preceramic period that may reflect the changing socio-political role of exchange over the long term.

A study of obsidian production and circulation among Andean peoples across a time span of nearly 10,000 years demands the consideration of a wide variety of cultural contexts, economic systems, and socio-political structures. A major question about obsidian circulation through time concerns the nature of obsidian exchange and perceptions of value with increased distance from the geological source.

Obsidian was a raw material essential to the daily existence of common people. In one sense, the distribution of obsidian may have had more in common with the exchange of agricultural commodities or salt, than it did with either long distance trade in prestige goods such as lapis lazuli, turquoise, or exotic pottery, or with commodities traded long distances for ritual purposes, such as spondylus and strombus shells. Thus, one should expect the patterns of obsidian exchange to differ from exchange patterns of these other trade goods and reflect different kinds of social and economic interactions (Burger and Asaro 1977: 18).

Expanding on Burger and Asaro's (1977: 18) observation, this dissertation examines the possibility that archeologically perceptible strategies of quarrying and production at the source, considered in tandem with consumption patterns, can help to describe what these "different kinds of social and economic interactions" may have been.

How did the contexts of exchange and value change as obsidian was conveyed away from the source area geographically and with greater social distance? The expression "regimes of value" (Appadurai 1986: 5, 14-15) has been used to describe arenas where shared perceptions of value are used in the construction of worth and equivalencies for circulating goods. What was the role of frontiers, either between cultural or environmental zones, in the transmission and value ascribed to these goods? While there is no simple answer to these questions, obsidian appears to have fallen somewhere between the probable regional circulation patterns of salt on one hand, and gold or turquoise on the other. The production and circulation represented by salt and gold serve as types on a continuum in this discussion, and the given changing patterns in obsidian circulation in the south-central Andes, the pattern falls at different points along this continuum in different prehispanic time periods.

A second major theme in this research is the association between a camelid-focused economy and obsidian circulation. High altitude pastoralists had easiest access to obsidian sources as obsidian was found on geologically young volcanoes high in the puna ecological zone; and additionally, pastoralists had burden-bearing animals capable of carrying heavy loads (Burger and Asaro 1977: 41). The sharp edges of obsidian flakes have great utility for pastoralist functions including shearing, butchery, and castration, although it is important to note that these characteristics are not unique to obsidian. Alternative local materials, such as high quality cherts, are found in a number of regions in the south-central Andes where exotic obsidian was used. Obsidian appears to have been circulated largely by pastoralists following the advent of a pastoral economy; however a simple utilitarian explanation for obsidian use among pastoralists is incomplete given the regional data from consumption sites.

There is key countermanding evidence to a simple utilitarian association between obsidian consumption and the functional needs of pastoralists. First, the obsidian flakes observed at pastoralist sites, even in excavated contexts, are overwhelmingly small and apparently of insufficient size for use as shearing or butchery tools. These flakes appear to be debris from advanced stages of reduction, perhaps from projectile point production and resharpening, and utilized flakes as one would expect among pastoralists are rarely reported in the literature. Second, the trends in obsidian procurement, as will be described in this document, suggest that the focus was on acquiring large nodules; a fact that that is discordant with the predominantly small sizes of the formal obsidian points and tools found both in the vicinity of the Chivay source and in the larger region, even when accounting for distance-decay issues. If obsidian was principally utilitarian because it was used for projectile points for subsistence hunting, why did obsidian use in projectile points expand dramatically only after the food producing economy became well-established (from 3300 BCE onwards)? Finally, pastoralist sites are often found without obsidian. During the Late Intermediate Period and Late Horizon the evidence shows that camelid herds expanded markedly, yet obsidian circulation seems to have relatively declined. If obsidian was primarily for utilitarian pastoralist activities, why did it decline as the herds expanded? It appears that the distribution of Chivay obsidian was heavily influenced by the interaction of complex phenomena that included demand in a network of exchange and caravan-based links between the western margins of the altiplano and the Titicaca Basin, the enduring social network that connected communities in these different regions.

This research at the Chivay source supports earlier observations by Burger et al. (2000: 348) where the strongest correlation with widely distributed obsidian types appears to have been the availability of large nodules of homogeneous obsidian. Given the diminutive size of the formal obsidian tools found in the archaeological record, and despite the issue of resharpening, there is an important display aspect to large obsidian nodules that is lost in utilitarian explanations linking obsidian with pastoralism. The link between camelid pastoralism and increased obsidian consumption in the south-central Andes is not causal, as pastoralists also make wide use of other materials, yet the appearance of pastoralism followed by the traffic of regularized long distance caravans appears to have been largely responsible for disseminating the material.

In light of the patterns of obsidian production and circulation, the anthropological relevance of obsidian appears to go beyond the fact that the material was used to produce sharp-edged tools of use to pastoralists. The analysis in this dissertation, therefore, focuses on the large-scale social and economic changes that occurred in the south-central Andes and on the possible role of obsidian as a material used by early leaders to represent contact with sustained regional networks and to signal social differentiation.