Andrew Cassel discusses the research of Alan Fiske, a professor of anthropology at UCLA, who has studied communities all over the world. Fiske concludes that just as every human language is composed of the same grammatical elements (subjects, verbs, etc.), all relationships are built from exactly four kinds of interactions: communal sharing, equality matching, authority ranking and market pricing. [Hat tip to Brad Feld)

Editor's Note: this article is no longer available for free - I didn't realize that at the time I added it...