In the course of a pleasant dinner, conversation turned to dictatorship and the organization of markets. At this point, Roger Myerson, remarked upon the absence of inter-species trade. He was not, of course, referring to trade with alien beings from another planet (who would have discovered correlated equilibrium before Nash equilibrium). Rather, the absence of trade with, say, monkeys. Adam Smith, went further and denied the possibility of trade between animals.

Nobody ever saw a dog make a fair and deliberate exchange of one bone for another with another dog. Nobody ever saw one animal by its gestures and natural cries signify to another, this is mine, that yours………

There is a long history of interactions between men and monkeys of various kinds. Monkeys have been marauders of crops, domestic companions, religious symbols and commodities (meat). The interactions between the species seems to fall into one of three categories: pure conflict (keeping out marauders), long run relationships (pets) or exploitation (used in labs and as entertainment). However, no examples of what one might call trade in the sense of voluntary arms length transactions involving barter. For example, why don’t villagers `pay’ bands of roving monkeys to not pillage?

There is evidence to indicating they would be capable of understanding such transactions. Gomes and Boesch, for example, suggest that monkeys trade meat for sex. Then, there is Keith Chen’s monkey study which suggests that one could teach (some) monkeys about money. From the Jesuit traveller Jose de Acosta in the 1500’s we have the following charming account:

I sawe one [monkey] in Carthagene [Cartagena] in the Governour’s house, so taught, as the things he did seemed incredible: they sent him to the Taverne for wine, putting the pot in one hand, and the money in the other; and they could not possibly gette the money out of his hand, before he had his pot full of wine.