The evolution of the nervous system is described, with speculation on when consciousness first appears and when belief first appears. The developments of nonverbal communication and flexibility of response are traced. With humans the ability for mental simulation and inquiry by thought experiments appears, greatly extending the old method of trial by error. Humans still do most of the old things in the old ways, nonverbal communication, emotional feeling and expression, trial and error, family and kinship, in-group behaviour, aggression, conditioned behaviour, and instinct. System 2 reasoning has evolved, while old system 1 reasoning, of which belief is a part, retains its importance. The unique ability to adapt the environment to suit human needs has evolved.