It is a critical limitation of archaeology, particularly when not given powerful assistance from historical sources, that it remains tied to the spatial distribution of imperishable objects or non-artifactual materials whose temporal sequence is seldom more than very roughly defined. Questions normally asked by archaeologists about trade and diffusion have been those which they can (or think they might be able to) answer directly and incontrovertibly from their data. But we must ask whether such questions are the important ones for an understanding of human society (Adams 1974: 139-140).