2.Setting the stage for human religion

1.Increased brain size

In this set of theories, the religious mind is one consequence of a brain that is large enough to formulate religious and philosophical ideas. During human evolution, the hominid brain tripled in size, peaking 500,000 years ago. Much of the brain's expansion took place in the neocortex. This part of the brain is involved in processing higher order cognitive functions that are connected with human religiosity. The neocortex is associated with self consciousness, language and emotion. According to Dunbar's theory, the relative neocortex size of any species correlates with the level of social complexity of the particular species. The neocortex size correlates with a number of social variables that include social group size and complexity of mating behaviors. In chimpanzees the neocortex occupies 50% of the brain, whereas in modern humans it occupies 80% of the brain.

Robin Dunbar argues that the critical event in the evolution of the neocortex took place at the speciation of archaic homo sapiens about 500,000 years ago. His study indicates that only after the speciation event is the neocortex large enough to process complex social phenomena such as language and religion. The study is based on a regression analysis of neocortex size plotted against a number of social behaviors of living and extinct hominids.

Stephen Jay Gould suggests that religion may have grown out of evolutionary changes which favored larger brains as a means of cementing group coherence among savannah hunters, after that larger brain enabled reflection on the inevitability of personal mortality.