From: "Luke Weiger"
Cave man 1: Is there a tiger near our cave? Cave man 2 (having a little fun at the expense of his dim friend): There both is and is not a tiger near our cave. Cave man 1: OK.
Cave man 1 didn't live long enough to reproduce.
(((((((
CB: And Cave man 2's chances of living long enough to reproduce are considerably reduced too. It's much easier to beat off tigers in groups (_social_ labor) than by yourself.
We are the descendants of Caveperson A and B who looked after each other unlike Caveman 2. Caveman 2's line died out in isolated, vulnerable, individualistic "groups".
Sociality ( kinship, altruism, _social_ defense against predators, _social_ labor or hunting and gathering) is _the_ adaptive advantage that the human species had and has over other species. Human superior survival fitness, in the Darwinian sense, is fundamentally based on morality, people caring about other people. Altruism was the "caveperson's" greatest assurance of producing viable, fertile offspring.
Bourgeois pursuit of self-interest in indifference to the self-interest of others contradicts humanity's most fundamental principle of Darwinian fitness.
See former University of Michigan professor Marshall Sahlins' _Uses and Abuses of Biology_ on this issue , for example.
Communism seeks to reaffirm the original principle - communalism - that differentiated humans from other species.