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.