Morphometric Analysis of Allometry and Modularity in Early Holocene Thebes and St. Charles Points of Midcontinental North America

Abstract The Central Ohio Archaeological Digitization Survey (COADS) documented large samples of precontact artifacts, notably points, held by private collectors in south-central Ohio, in the United States. COADS captured two-dimensional images of several thousand points and several hundred three-dimensional images. Subjects were processed for landmark-based geometric morphometric (LGM) analysis as entire points and as stems only. Among other things, analysis can test for resharpening allometry—the possibility that preferential resharpening of blades caused change in shape with change in size of points—and related LGM concepts of modularity and integration. This study reports analysis for allometry in early Holocene COADS Thebes and St. Charles points. A clear allometric signal with fairly high modularity resides in the data; blade shape much more than stem shape varies with size, corroborated by independent reduction measures. Separate analysis of stems alone indicated no allometry, as expected since stems vary little with resharpening. Allometry must be considered before attributing variation in midcontinental whole-point shape to adaptation, drift, or other mechanisms.