Testing predictions from the hunter-gatherer hypothesis – 1: Sex differences in the motor control of hand and arm

Original article:

Testing predictions from the hunter-gatherer hypothesis – 1: Sex differences in the motor control of hand and arm

Evolutionary Psychology 5(3): 653-665 Geoff Sanders, Department of Psychology, London Metropolitan University, Calcutta House, Old Castle Street, London, E1 7NT UK, g.sanders@londonmet.ac.ukTom Walsh, Department of Psychology, London Metropolitan University

Abstract

Here, in the first of two reports that test predictions from the hunter-gatherer hypothesis, we focus on sex differences in motor control. Published evidence confounds the cognitive demands, the muscles used and the spatial location in which tasks are performed. To address these issues our participants used hand or arm movements to track a moving target within near space. Study 1 identified an optimal level of task difficulty for the differentiation of male and female performance and showed that women tracked better using their hands and men using their arms. Employing the optimal level of task difficulty, Study 2 replicated the findings of Study 1 and, for men, demonstrated a significant correlation between arm tracking and performance on the nonmotor sex-dimorphic Mental Rotations task. This correlation suggests that the same or related events are responsible for the development of sex differences in motor and cognitive systems. The distal (hand) muscles are controlled by the primary motor cortex via two dorsolateral corticospinal tracts whereas the proximal (arm) muscles are controlled via two ventromedial corticospinal tracts. Our findings point to possible sex differences in these two neural pathways and they are compatible with an evolutionary origin as predicted by the hunter-gatherer hypothesis.

Keywords

hunter-gatherer hypothesis; sex differences; motor control; hand and arm; neural bases; near space.

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