Dear Mr. Ahiakpor and others, You have me there! I meant of course 60 thousand BC, which is the approximate figure that people who favor the hypothesis conjure with (anywhere from 70 to 40 thousand years ago, as far as an outsider to that scholarly literature can make out). I like Robert Wright's suggestion about non-hard-wiredness. Otherwise we will find trade among bacteria, literally, which doesn't seem a very useful way to talk---unless indeed to emphasize the truth that we are all interdependent. And I like John Walker's point about quantification. That's what Alan Page Fiske (Structures of Socal Life, 1991) emphasizes in naming "market pricing" as one of his four "elementary forms of human relations." The other three---communal sharing [do you belong to Our Crowd, yes or no?], authority ranking [I am the chief, so I get more meat], equality matching [we're all in this together, so let's make the amounts of meat exactly the same for everyone]---do not involve prices, that is, exchange rates between two different things, meat for milk, arrow points for cave paintings. Sincerely, Deirdre McCloskey