1Department of Anthropology, Emory University, 2Neuroscience Institute, Georgia State University, 3Coulter Department of Biomedical Engineering, Emory and Georgia Institute of Technology, 4Institute of Affective and Social Neuroscience, Shenzhen University
April 15, 2016 9:15, Imperial Ballroom B
Over 100 years of theorizing has linked Paleolithic tool-making to human brain evolution, but empirical evidence has been scarce. To address this, we have adopted an experimental neuroscience approach, training modern subjects to make stone tools and collecting behavioral and neuroimaging data. Functional imaging identified a bilateral frontoparietal network supporting stone tool-making. Some elements, including especially the right Inferior Frontal Gyrus (rIFG), respond more strongly to more complex (Late Acheulean>Oldowan) tool-making, indicating increasing cognitive demands over Lower Paleolithic technological change. Structural imaging of subjects learning to make stone tools showed that training elicits plastic remodeling of the same network, again including rIFG. We thus argued that Paleolithic tool-making not only indexes cognitive and brain changes but was also sufficiently demanding to induce adaptation through a behaviorally driven process of phenotypic accommodation (aka "The Baldwin Effect"). This hypothesis predicted that experimentally induced plastic changes should parallel derived human brain features, which was confirmed by a "virtual dissection" of human and chimpanzee superior longitudinal fasciculus showing expanded human connectivity to rIFG. Here we present new evidence that individual variation in white matter integrity (fractional anisotropy) under rIFG over the course of training predicts actual tool-making success (Oldowan productivity, Acheulean refinement). Right IFG supports cognitive control functions (conditional response inhibition, task switching) important to complex sequential behaviors including tool-making and language. We propose that rIFG underwent adaptations for Paleolithic technology that were exapted to support the rich, proto-linguistic communication that provided the selective context for subsequent language-specific adaptations in the left hemisphere.
This work funded by Leverhulme Trust Grant F/00 144/BP, National Science Foundation Award SMA-1328567, and John Templeton Foundation Grant 47994.