IMHICIHU   13380
INSTITUTO MULTIDISCIPLINARIO DE HISTORIA Y CIENCIAS HUMANAS
Unidad Ejecutora - UE
capítulos de libros
Título:
Reduction constraints and shape convergence along tool ontogenetic trajectories
Autor/es:
JUDITH CHARLIN; MARCELO CARDILLO
Libro:
Convergent Evolution in Stone-Tool Technology
Editorial:
MIT press
Referencias:
Año: 2018; p. 109 - 129
Resumen:
Tool reduction is essentially a continuos process by which the initial form (size and shape) of artifacts is modified generally in a directional way from the first use to discard. Like ontogeny, reduction is a patterned allometric process that changes in extent and degree. Although architectural (blank size and shape, quality and type of lithic raw material, etc.) and functional (performance to a given task) constraints determine the starting tool form, it is the use and resharpening of tools that accounts for the subsequent changes. This fact is unavoidable because morphometric variation is an inherent factor to use-life of lithic artifacts (Andrefsky 2006, Hiscock 2007, Shott 2005). Resharpening should not only be considered like a confouding factor, but an integral part of the tool itself (Iovita 2010). Even though stone tools change during their use-lives, they change in one direction and the possible changes are limited: neither a stone tool would be larger after reduction nor an edge could sharpen as its use proceeds.Fortunately, through different lines of evidence and kind of analyses many of the allometric changes due to reduction were identified. Here, I attempt to show how these changes lead to shape convergence among tools, although they have been used in different ways. In this case convergence can be seen as a by-product of the ontogenetic trajectory of stone tools along their use-lives. Performance requirements, random errors plus ontogenetic trajectories conform the morphospace of lithic tools. As tool convergence by reduction is in general not controlled, we actually do not know how usual it is within lithic assemblages, but we should be aware that they exist and can bias inter-assemblage comparisons as well as typological classifications, like several works have already shown. To exemplify this, I am presenting the case study of Late Holocene archaeological projectile points from Southern Patagonia (Argentina and Chile) known as Fell, Magallanes or Bird IV and V or simply ?Patagonian? and ?Ona? points, respectively (Bird 1938, 1946, 1988). An ethnographic sample of Ona arrow points from Tierra del Fuego is also included in the analysis to test the existence of parallelism, a particular case of convergence (McGhee 2011). Projectile point shape changes are analysed by applying geometric morphometric landmark-based methods (Bookstein 1991).