DID THE ICE AGE CONTRIBUTE TO THE EVOLUTION OF HUMAN INTELLIGENCE?

We have previously proposed that ecologies that permit line of sight over a distance contribute to the evolution of intelligence. We postulated that the development of steppes and savannas provided wide vistas for predator-prey interactions. Because visual contact can occur over distances that would take tens of minutes to traverse, it became necessary for predators or prey to imagine scenarios involving the potential behavior of other species, and to extrapolate the results of activities facilitating prey capture or escape. It is this ability to imagine future consequences that lies at the root of advanced intellect. The upright posture of humans gives them a line of vision comparable to a much larger quadruped. The severity of global cooling during ice advances resulted in periods of aridity that challenged forest ecologies and produced savannahs and steppes. These environments favored the striding walk of humans and as the interval of visual detection increased, so did the need for a highly encephalized brain. We think that this model includes the evolution of some aspects of human intelligence within a more general model of brain enlargement that resulted from the overall global cooling trend characterizing most of the Cenozoic.