Terrell notes that the current political schism between Republicans and Democrats has a foundation in different views about the whether an individual's primary purpose is to look out for communal or self interests.
...modern evolutionary research, anthropology, cognitive psychology and neuroscience have come down on the side of the philosophers who have argued that the basic unit of human social life is not and never has been the selfish, self-serving individual. Contrary to libertarian and Tea Party rhetoric, evolution has made us a powerfully social species, so much so that the essential precondition of human survival is and always has been the individual plus his or her relationships with others.Luhrman does a piece "Wheat people versus rice people" which references the same work mentioned in MindBlog's May 21st post, and notes several other studies on individualistic versus collective cultures.
Rand et al. offer economic game experiments to illustrate how static network structure stabilizes human cooperation
Finally Crockett et al. do an experiment relevant to social cohesion, showing that harm to others outweighs harm to self in moral decision making - most people sacrifice more money to reduce a stranger’s pain than their own pain (the pain being delivered by electric shocks).