Ah, thank you. Made that much clearer for me; I had the slightly incorrect impression that a ZD strategy was any strategy that could be described by such a 4-tuple, but I didn't make the connection that the evolution could apply directly to the probabilities instead of the strategy that generated the probabilities.
Less Wrong had a Prisoner's Dilemma contest some time back, whose results I've forgotten. Perhaps it should be rerun with William H. Press & Freeman Dyson's proposed extortionate strategies.
I hope Pinker gives a response at Edge.org, since P.D played a significant role his book "The Better Angels of Our Nature" as a source of morality embedded in the nature of logic/reality.
Hat-tip to Marginal Revolution.