same fella ...

there may be as many causalities suggested here as there are interested observers, and there may be no foolproof way to distinguish 'correct' from 'erroneous' suggestions.

since the publication of jerison's evolution of the brain and intelligence (1973). the two main hypotheses advanced to answer the question of why encephalization (refers to the tendency for a species toward larger brains through evolutionary time) has occurred focus on foraging strategies and social intelligence. the two are not necessarily exclusive, but both claim dominion over the arrow of causality. the ecological and the social arguments in a hypothesis about the evolution of group size proposed a notion that brain evolution has proceeded along multiple, parallel paths, but the interaction between various socio-ecological factors has yet to be determined.

encephalization are comparative studies, lack of standardization in brain size measurement can undermine the validity of the field. hypothesis clearly implies that the more energy an animal can invest in her offspring, the larger brains they will have. primates devote more of their energy resources to their brains than do most other mammals, brain size correlated with home range size in the cercopithecines (old world primates like macaques, mandrill) and that of monogamous species have significantly smaller brains than polygynous ones.

brain size has increased over evolutionary time, and behavior has become more complex. the two are undeniably linked, more stimuli become important, as a species niche broadens. there will be selection for enhanced ability to cope with an increased amount of information.

certainly only an extreme adherent of either an ecological or social hypothesis would claim that an animal's foraging strategy depends solely upon the nature of the food resource or upon its maneuvering within a social context. which came first ? can we know ? what is the evolutionary relationship between the mechanisms responsible for interpreting and instigating social behavior ?