In chaos theory, the butterfly effect is the sensitive dependence on initial conditions, where a small change at one place in a
deterministic nonlinear system can result in large differences to a later state. The name of the effect, coined by Edward Lorenz, is derived from the theoretical example of a hurricane's formation being contingent on whether or not a distant butterfly had flapped its wings several weeks before.
http://en.wikipedia.org/wiki/Butterfly_effect
My interest though, (beside having spent some student time in Paris,) is sort of with the ironies of language and my recollections of the trends. Dr. King spoke of "Negroes" and Malcolm X talked about "black people" and my father, a WW II vet, a liberal, referenced "colored people," thinking, I'm sure, that it was the most respectful form of address at the time. And "Afro-Americans" was big for a while, as long as the hairstyle anyway.
Writer Stanley Crouch, referred to himself as Negro to emphasize his American ancestry, differentiate from Jamaicans, or Haitians, or Brazilians who are also black.
Never having been black myself, I lament the lost opportunities. What were they thinking? What was I thinking? It's a kind of nostalgia.
--imm