Lack of water and endurance running could have caused the exponential growth in human brain: Point of no return model

Abstract

Growth in brain volume is one of the most spectacular changes in the hominid lineage. The anthropological community agrees on that point. No consensus, however, has been reached on selection pressures contributing to that growth. In that respect Martin (1984) can be invoked. In his review of size relationships among primates he stated that despite the relationship between brain size, body size and feeding behavior no single interpretation could be provided that revealed the causality of such relationship. This paper deals with one specific aspect of hominid brain growth; the fact that for most of the hominid period, growth in brain volume was exponential in character. To the best of our knowledge, no attempt has been made to identify a selection mechanism that can facilitate just the exponential features of that growth (as distinct from any of its other characteristics). It is broadly accepted that the dynamics of this growth were peculiar. Growth was very fast, or even rapid in the evolutionary scale of time. The most profound evidence of that opinion was expressed by Haldane that this dramatic increase in brain size was the most rapid evolutionary change known to him.