The minimum spanning tree problem is a well-known problem of combinatorial optimization. It was independently discovered in archaeology by Renfrew and Sterud in their method of close proximity analysis. Unlike traditional methods of seriation, this method permits branching structures that reveal clustering in archaeological data. Identifying close proximity analysis as the minimum spanning tree problem permits a more efficient means of computation, an explicit rule of clustering, and a recognition of problems of indeterminacy in the analysis of network data. These points are illustrated with reference to Irwin's recent study of voyaging and cultural similarity in Polynesia.