I vaguely remembering reading in Rudolf Bahro's _Die Alternative_ that Marx was wrong about the notion of trade starting as inter-community trade. It was in passing. Bahro's focus was on drawing a parallel between the emergence of Asian centralized states at the outset of civilization and the emergence of actually-existing socialism.
Marx didn't have late-20th-century historical info, but Bahro wasn't Marx -- and, more importantly, Bahro didn't provide references (Marx did!) but only presumed it was a fact admitted by modern historians. In the absence of references to follow up on, I remember asking myself -- Whom should I *believe*? Marx or Bahro? Still, I thought the first part of Bahro's book was in the best traditions of Marxist thought.
