Stone Tools and the Evolution of Human Cognition

2: “Grammars of Action” and Stone Flaking Design Space

13 ABSTRACT Human infants and primates use similar strategies to organize utterances and motor actions. These strategies, called “grammars of action,” are initially similar followed by an ontogenetic divergence in children that leads to a separation of complex linguistic and action grammars. Thus, more complex grammars arose after the emergence of the hominin lineage. Stone tools are by-products of action grammars that track the evolutionary history of hominin cognition, and this study develops a model of the essential motor actions of stoneworking interpretable in action grammar terms. The model shows that controlled flaking is achieved through integral sets of geometrical identifications and motor actions collectively referred to as the “flake unit.” The internal structure of the flake unit was elaborated early in technological evolution and later trends involved combining flake units in more complex ways. Application of the model to the archaeological record suggests that the most complex action grammars arose after 270 kya, although significant epistemological issues in stone artifact studies prevent a more nuanced interpretation. T W O Mark W. Moore UNIVERSITY OF NEW ENGLAND “Grammars of Action” and Stone Flaking Design Space 14 M a r k W . M o o r e INTRODUCTION Experiments conducted by psychologist Patricia Greenfield and her colleagues explored the grammatical strategies of various primates, including monkeys, chimpanzees, bonobos, and human infants (Greenfield 1991, 1998; Greenfield and Schneider 1977; Greenfield, Nelson, and Saltzman 1972). The research demonstrated that human children consistently employ three strategies for ordering utterances and motor actions, referred to collectively as “grammars of action.” Primate experiments showed that grammars of action applied by chimpanzees and children are initially similar, followed by an ontogenetic divergence by children . The authors concluded that more complex grammars of action evolved after the divergence from a common ancestor. Greenfield emphasized utterances in her research rather than motor actions “because there is no fossil record of behavior” (Greenfield 1991:545). Greenfield interpreted these changes according to a modular model of brain function, since superseded by a more nuanced paradigm based on distributed neural networks. Nevertheless, many researchers agree with Greenfield’s thesis that the evolution of higher cognitive functions, such as cognitive flexibility and syntactical ability, are linked with the evolution of motor control (Lieberman 2006). Greenfield’s empirical observations remain robust because they focused on spontaneous motor behaviors (Parker 1990; Parker and Jaffe 2008:156). The enduring value of Greenfield’s model for archaeologists is in the way it explicitly links cognitive evolution with motor actions. Since stone tools are physical correlates of motor actions (the ostensibly absent “fossil record of behavior”), Greenfield’s model is uniquely suited for an archaeological study that tracks the part of the evolutionary story missing from Greenfield’s discussion , from the common chimpanzee/hominin ancestor to modern humans. To do this, a model of the essential motor actions of stoneworking is required that can be translated into “grammars of action.” Although the essential actions of stoneworking are well-understood, studies into early stone flaking have traditionally focused on tools and cores as the accumulation of those actions; a practical model suitable for applying Greenfield’s model has not been forthcoming. This study presents a model of the “design space” of knapping—the essential actions of stoneworking—in terms compatible with Greenfield’s model. The goal of the study is twofold: first, to use the design space model to theoretically pinpoint some of the key turning points in technological evolution, and second, to identify those areas where our empirical evidence is vague or our epistemology weak. 15 “Grammars of Action” and Stone Flaking Design Space GRAMMARS OF ACTION Greenfield’s model links developmental changes in brain anatomy with changes in the hierarchical organization of speech and motor skills (Greenfield 1991). Greenfield’s thesis is that changes in speech and motor skills are reflected ontogenetically in young children. This progression of abilities, when tested against living primates, has phylogenetic implications. The term “grammars of action” reflects the basic similarity between speech structure and motor skills. Laboratory studies of human children show that there are three strategies for ordering motor actions (Greenfield 1991:532; Greenfield, Nelson, and Saltzman 1972) (Figure 2.1). 1. Pairing strategy. A single active object acts on a single static one to create the final structure. This involves one chain-like combination. 2. Pot strategy. Multiple active objects act on a single static one to create the final structure. This also involves chain-like...