The Origins of a Market Economy in the Valley of Oaxaca
The founding of Monte Albán in ca. 500 BCE and the eventual extension of its political power over the rest of the valley is credited with initiating wide-spread economic changes, specifically, through fostering systems of specialized production and exchange.
A rapidly expanding urban population and intensified rural agricultural production all likely stimulated demand for artisan products. At the same time, greater regional stability under Monte Albán’s authority presumably allowed both producers and consumers to move safely about the landscape, expanding the scale of exchange and laying the foundations for a regional market economy.
Our research focuses on the evolution of this regional market system from the pre-Monte Albán Rosario phase (ca. 700 – 500 BCE) through the Late Classic Xoo phase (600 – 850 CE). Based on detailed clay surveys and a sample of nearly 5000 ceramic vessels, we have identified the chemical signatures of nearly 30 different source areas within the Valley – a resolution that allows us to track inter-community ceramic exchange and monitor changes in the scale and intensity of exchange through time.
I. Clay Survey in the Valley of Oaxaca
The complex geology of the valley creates a diversity of distinctive clay zones. We sampled natural clays in more than 400 locations to model regional trends in clay geochemistry. This detailed knowledge of the valley enables fine-scale provenance determination of ceramic composition groups.
Influence of Geology on Clay
Precambrian gneiss [pC(Gn)] elevates the concentrations of the rare earth elements (such as La) in clays along the western side of the valley.
Calcareous sedimentary rocks, such as Ki(lu-ar) and Ki(cz), augment calcium content, particularly in the valley’s center.
Tertiary andesites [Tom(A)] and ignimbrites [Tom(Ig)] increase the alkali metal content of clays, as indicated by high Cs in the E arm of the valley.
II. Analysis of Oaxacan Ceramics
Once we had identified the geographic sources of pottery, we were able to trace the movement of individual pottery vessels from producer to consumer and map out how widely these products were traded. By examining a large number of vessels from sites throughout the valley, we are able to shed new light on intercommunity economic interactions from ca. 700 BCE to 850 CE.
For example, for the Rosario phase, we identified at least 20 composition groups representing different geochemical source areas for pottery production. These chemically distinctive ceramics were widely exchanged throughout the valley, reflecting robust network connections that were well-established prior to the founding of Monte Albán.