Maybe the Monkey Kingdom needs a Federal Reserve
The researchers first trained chimpanzees in the basic rules of trade: you give to me, I give to you. They used apple slices, which chimps generally like, and grapes, which chimps really like -- think Winnie the Pooh and honey. The chimpanzees picked up the concept quickly, perhaps because they're accustomed to trading grooming services rather than physical commodities. However, the chimps were still deeply reluctant to engage in exchange unless they could get something for nothing, which in chimp terms amounted to grapes for carrots. ... Why not? Because chimps live in a society that can't enforce deals or punish cheating, surmised the researchers. It's a different story when it comes to services, such as picking ticks out of each others' hair -- but that sort of exchange doesn't lend itself to developing the specialized economic productivity that's given humans NAFTA, American Idol and the leisure to swap fruit with primates.
I'm not sure I entirely follow this but it seems like the researchers were looking for the wrong thing. It is not trading something for nothing to give up something you don't want for something you do want. It is simply a matter of preference, and trade always involves the exchange less desirable things for more desirable things, its only that the subjective evaluation is different in the case of the two parties to the exchange. Also barter seems to be used in a strange way here: it doesn't mean exchanging items of the same value; it means only exchange in absence of money, that is, a good we acquire not to consume but to trade again.
Maybe someone can read the full study and gain more insight.