Spatial cognition, mobility, and reproductive success in northwestern Namibia

Males occupy a larger range than females in many mammal populations including humans, and show an advantage in certain spatial-cognitive laboratory tasks. Evolutionary psychologists have explained these patterns by arguing that an increase in spatial ability facilitated navigation, which allowed range expansion in pursuit of additional mating and hunting opportunities. This study evaluates this hypothesis in a population with navigational demands similar to those that faced many of our ancestors, the Twe and Tjimba of northwestern Namibia. Twe and Tjimba men have larger visiting ranges than women and are more accurate in both spatial (mental rotations) and navigational (accuracy pointing to distant locations) tasks. Men who perform better on the spatial task not only travel farther than other men, but also have children with more women. These findings offer strong support for the relationship between sex differences in spatial ability and ranging behavior, and identify male mating competition as a possible selective pressure shaping this pattern.