[1] Because obsidian—a volcanic glass prized in antiquity for the sharp edges it yields when worked—forms only at a limited number of geological sources, each with a distinctive chemical signature, archaeologists can match a tool recovered at a site to the outcrop from which its raw material came. [2] When obsidian from a single source turns up at settlements hundreds of kilometers away, the finding is often taken as direct evidence of long-distance trade between the source region and the distant community. [3] Yet the mere presence of a distant material does not by itself establish that the two regions were ever in contact.
[4] The archaeologist Renfrew, studying the distribution of obsidian across the ancient Near East, observed that its abundance at a site typically declines in a regular way with distance from the source. [5] He argued that this gradient is better explained not by direct expeditions but by “down-the-line” exchange, in which material passes through many hands, each community retaining a portion and passing the remainder to its neighbors. [6] Under such a scheme, obsidian could travel enormous distances without any single person, or any direct relationship between source and destination, spanning the whole route. [7] The pattern that looks like evidence of contact between two remote points may instead record a chain of purely local transactions. [8] The lesson is a general one for the study of material culture: the movement of objects and the movement of people need not coincide, and an artifact's final resting place testifies more reliably to the object's journey than to any meeting between its makers and its last possessors.
