I did not mean to suggest that social existence is the result of
pure competiton between groups: cooperation is also a means of
maximising benefits, which leads to complex patterns of cooperation
and competition that I should have explicitly mentioned. The point
being that self-interest gives rise to both and is one reasonably
predictable element of human nature.
Also, several private emails have pointed out that I meant the
shakers, not the quakers. (probably a song title in there
somewhere....)