The environmental and cultural context of the south-central Andean highlands framed the circumstances in which emerged the long distance traffic in various products during the prehispanic period. The domestication of camelids sometime in the past 6000 years allowed for more efficient transport of bulky goods. There remain many unknown aspects to the network that articulated dedicated agriculturalists with pastoralists in the prehispanic past, however archaeological and ethnographic evidence allows for inference regarding the following major points:

(1) Network configuration.Products available by ecozone were transported in numerous, segmentary articulations between ecozones while other products, only available in a few locations, were apparently conveyed diffusively and were between transported ecozones and across homogeneous terrain like the altiplano (XFigure 3-4X).

(2) Motivations for change in mode of interaction.The domestication of animals and plants, changes in sedentism, and the development of social inequalities were some of the factors that contributed to development of long distance caravans. It is evident that the original modes of interaction: Direct acquisition and down-the-line exchange, were supplemented by household organized caravan trade, and finally administered caravan trade, but the timing of these changes is difficult to establish with precision.

(3) Means of trade.Features of the Andean barter economy such as enduring trade relationships between households in complementary zones cemented by institutions like over-reciprocation and fictive kinship, are well demonstrated ethnographically in the region. However, seasonal market-like gatherings are also reported in the region and exchange of goods in those contexts may have been more alienable, and transactions may have been more synchronic in nature. Such gatherings may also have had evolutionary significance because they potentially relate to the development of early leadership in regional centers including ceremony, feasting, the use of monumental architecture, and centralized control of trade in certain goods.

The persistent themes in mountain agropastoral settings of non-autarkic economies and risk reduction through mixed subsistence strategies serve as a reminder that variability was probably the rule in exchange relations as well. Absolutes in exchange patterns were probably rare, and a degree of both self-interested trade and elements of embedded, social and symbolic fraternity likely existed between trade partners since early antiquity. While a number of plausible models have been proposed for the later Prehispanic periods where both household-level and elites-administered trade caravans appear to have transported a variety of goods in the region, the initial contexts for caravan trade remain largely unexplained. These initial contexts are particularly important because this mode of organization contributed to the regional context and institutional base in which early leaders in the Titicaca Basin had to operate in order to begin the process of expanding their influence in access to labor, resources, and ideology of their communities.

If enduring regional interaction had persisted since the early days of the pastoral economy during the preceramic, this may be connected to the factors that lead to an increasing consolidation of power in the Titicaca Basin during the Formative Period. These questions are central to understanding the foundations of regional integration that emerged in the Lake Titicaca Basin during the Middle and Late Formative Periods. The above discussion has sought to elaborate upon a possible context for early household-level caravan organization that is principally based on the "circuit mobility" model of Nunez and Dillehay (Dillehay and Nuñez 1988;1995 [1979]) but without following the adaptationalist approach, and with more specific empirical contexts for early caravans. In the ensuing discussion of obsidian procurement and circulation in the south-central Andes existing evidence from obsidian circulation in the region is presented that provides the context for examining obsidian production in more detail.