Reduction constraints and shape convergence along tool ontegenetic trajectories: An example from late Holocene projectile points of southern Patagonia

JUDITH CHARLIN Y MARCELO CARDILLO

Convergent Evolution in stone tool technology

MIT press

Año: 2018; p. 110 - 130

With some exceptions (e.g., Lycett 2007, 2009; Lycett et al. 2010), the study of convergence in stone tools is an issue scarcely addressed in archaeology, at least as an explicit line of research. However, there is much evidence to suggest that this phenomenon is more common than expected and that it can take place at different scales, from particular artifact traits to overall tool shapes, as well as in manufacture techniques.With respect to Patagonia, where we work, archaeologists tend to focus on processes of divergence throughout the Holocene (Borrero 2001a; Charlin and Borrero 2012; Perez et al. 2011). These studies have focused on cultural and technological divergence in relation to biogeographical barriers such as the Santa Cruz River?the largest drainage in southern Patagonia (Borrero 1998; Cardillo and Charlin 2016; Franco 2002)?and the Magellan Strait (Borrero 1989-1990; Cardillo et al. 2015; Charlin et al. 2013; Morello et al. 2012) and the creation of Tierra del Fuego ca. 8,000 B.P. (McCulloch et al. 1997, 2005). In general, morphological and technological similarities among tools are usually explained by population contact and shared technical knowledge (e.g., Nami 1992), but these statements rest more on assumptions than proof.The goals of the present work are threefold. First, we discuss the role of reduction as a constraint that channels shape variation and leads to tool convergence. We explore this with a case study of Late Holocene projectile points from southern Patagonia. Second, we examine the existence of parallelism, a particular case of convergence (McGhee 2011), between two populations of projectile points (one ethnographic and the other archaeological). Both populations share a common ancestry but were later isolated by the formation of the Strait of Magellan. Third, we highlight the utility of geometric morphometric methods (Bookstein 1991; Rohlf and Bookstein 1990) as a tool to study artifact form in general and artifact convergence in particular.