Se caracterizó mediante análisis de fluorescencia de rayos X portable (pXRF) un conjunto de obsidianas (n = 142) del sitio San Gregorio Atlapulco, en Xochimilco, Ciudad de México, procedentes de los niveles precerámicos, a través del análisis de 10 elementos químicos (Mn, Fe, Zn, Ga, Th, Rb, Sr, Y, Zr, Nb); esto nos permitió conocer la composición elemental de cada uno de los artefactos para posteriormente efectuar comparaciones con obsidianas de yacimientos sistemáticamente muestreados. Los resultados indican una amplia dominancia de la subfuente de Soltepec en Otumba (94%), además de otras dos fuentes menores que incluyen a Pachuca. Lo anterior tiene implicaciones importantes sobre los procesos de interacción de los grupos precerámicos del Holoceno medio en la Cuenca de México, y permite vislumbrar la importancia de la obsidiana de Otumba para el período denominado Arcaico, y la formación de redes de intercambio tempranas que continuarían durante el período Formativo.

To describe the structure of production and the organization of exchange of obsidian chipped stone during the Middle Postclassic period (AD 1200–1350) in south-central Veracruz, Mexico, I analyzed 65 residential inventories from the center of Sauce and its hinterland. Previous research on obsidian production found a spatial association with Sauce, which could support the political administration of exchange, or alternatively, identify market exchange nearby. I argue that reliance on spatially based models alone for identifying exchange mechanisms is not advisable because of potential equifinality, in which different forms of exchange appear alike. Local obsidian artifacts have additional interpretive complications: they come from a single geological source, there was universal access to them, and they were employed in potentially specialized activities. I used the articulation of production combined with spatial distribution and residential contextual information to distinguish between redistribution and market exchange. Results indicate that market exchange is the main mechanism. The largest concentrations of primary production indicators and the highest quantities of blade segments were found near the Sauce center, which suggest that political elites at Sauce encouraged market exchange, although they did not direct it to the extent that they were controlling significant amounts of obsidian.

In premodern economic systems where the social embedding of exchange provided actors with the ability to control or monopolize trade, including the goods that enter and leave a marketplace, “restricted markets” formed. These markets produced external revenues that could be used to achieve political goals. Conversely, commercialized systems required investment in public goods that incentivize the development of market cooperation and “open markets,” where buyers and sellers from across social sectors and diverse communities could engage in exchange as economic equals within marketplaces. In this article, we compare market development at the Late Postclassic sites of Chetumal, Belize, and Tlaxcallan, Mexico. We identified a restricted market at Chetumal, using the distribution of exotic goods, particularly militarily and ritually charged obsidian projectile points; in contrast, an open market was built at Tlaxcallan. Collective action theory provides a useful framework to understand these differences in market development. We argue that Tlaxcaltecan political architects adopted more collective strategies, in which open markets figured, to encourage cooperation among an ethnically diverse population.

Recent research has established that south Scandinavia during the Nordic Bronze Age was entirely dependent on imported metal. It was obviously in contact with other parts of Europe and must have participated in a system of long-distance exchange. It is not clear how it would have operated, but it helps to explain the importance of watercraft and drawings of distinctive artefacts in the rock art on the Baltic and Atlantic coasts. A different group of images can be associated with inland areas where the art has a more restricted lexicon. Can the borderland between these traditions shed any light on the relationship between the seashore and the interior, and might this help to identify places where artefacts changed hands? This paper presents the results of fieldwork between Lakes Vänern and Vättern in Västra Götaland county, southern Sweden. It considers the character of inland rock art and whether some locations with more complex panels were used as ‘aggregation sites’.