Is the "Propensity to Truck, Barter, and Exchange" Unique to Human Evolution?

In the history of political philosophy, it is common for political thinkers to make claims about human nature as compared with the nature of other animals.  Noticing this as a young student of political philosophy, I wondered whether modern biological research could confirm or deny such claims, and this led me into a long career of applying Darwinian science to the study of political philosophy.

So, for example, I remember the first time that I read Adam Smith's claim in The Wealth of Nations that the "propensity to truck, barter, and exchange one thing for another" is uniquely human and not found in any other animals.  I wondered whether this was true, and, if true, what it would mean for our understanding of human social life. 

In recent years, Haim Ofek (in his book Second Nature: Economic Origins of Human Evolution) and Matt Ridley (in his book The Rational Optimist) have argued that what we now know about human evolution confirms Smith's insight about the unique importance of exchange for human history.  The whole of human history for the past 200,000 years can be understood as the progressive extension of human cooperation through exchange and the division of labor--from foraging bands to agrarian states to modern commercial societies in global networks of trade.  Both Ofek and Ridley see this as arising from a human propensity to exchange that cannot be seen in any other animal. And yet I am still trying to make up my mind about this.

In the first chapter of The Wealth of Nations, Smith explains the division of labor as the primary cause for the increasing productivity of labor, which includes the famous example of the pin factory.  In the second chapter, he explains how this division of labor arises in human history.

"This division of labour, from which so many advantages are derived, is not originally the effect of any human wisdom, which foresees and intends that general opulence to which it gives occasion.  It is the necessary, though very slow and gradual consequence of a certain propensity in human nature which has in view no such extensive utility; the propensity to truck, barter, and exchange one thing for another.

 "Whether this propensity be one of those original principles in human nature, of which no further account can be given; or whether, as seems more probable, it be the necessary consequence of the faculties of reason and speech, it belongs not to our present subject to enquire.  It is common to all men, and to be found in no other race of animals, which seem to know neither this nor any other species of contracts.  Two greyhounds, in running down the same hare, have sometimes the appearance of acting in some sort of concert.  Each turns her towards his companion, or endeavours to intercept her when his companion turns her towards himself.  This, however, is not the effect of any contract, but of the accidental concurrence of their passions in the same object at that particular time.  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; I am willing to give this for that.  When an animal wants to obtain something either of a man or of another animal, it has no other means of persuasion but to gain the favour of those whose service it requires.  A puppy fawns upon its dam, and a spaniel endeavours by a thousand attractions to engage the attention of its master who is at dinner, when it wants to be fed by him.  Man sometimes uses the same arts with his brethren, and when he has no other means of engaging them to act according to his inclinations, endeavours by every servile and fawning attention to obtain their good will.  He has not time, however, to do this upon every occasion.  In civilized society he stands at all times in need of the cooperation and assistance of great multitudes, while his whole life is scarce sufficient to gain the friendship of a few persons.  In almost every other race of animals each individual, when it is gown up to maturity, is entirely independent, and in its natural state has occasion for the assistance of no other living creature.  But man has almost constant occasion for the help of his brethren, and it is in vain for him to expect it from their benevolence only.  He will be more likely to prevail if he can interest their self-love in his favour, and shew them that it is for their own advantage to do for him what he requires of them.  Whoever offers to another a bargain of any kind, proposes to do this.  Give me that which I want, and you shall have this which you want, is the meaning of every such offer; and it is in this manner that we obtain from one another the far greater part of those good offices which we stand in need of.  It is not from the benevolence of the butcher, the brewer, or the baker, that we expect our dinner, but from their regard to their own interest.  We address ourselves, not to their humanity but to their self-love, and never talk to them of our own necessities but of their advantages.  Nobody but a beggar chuses to depend chiefly upon the benevolence of his fellow-citizens."

Smith then indicates that the emergence of a division of labor through exchange appears originally among savages living as hunter-gatherers, where someone might specialize in making bows and arrows that he can trade for some meat captured by a hunter, so that each fills a particular occupation, and thus their joint labor becomes more productive than would be the case if each were working only for himself.  This is part of Smith's understanding of human social evolution as passing through four stages--from foraging to herding to farming to commerce.

At the beginning of this passage, we see the fundamental idea that is common to Smith's social thought and Darwin's biology--the possibility of design-without-a-designer ("not originally the effect of any human wisdom") through emergent or spontaneous order.  (I have written about this in a previous post.) 

Smith then poses an evolutionary question: Was the propensity to exchange an original principle of human evolution, or was it a late by-product of earlier evolved "faculties of reason and speech"?  Although he chooses not to take up this question here, he considers it more probable that reason and speech came first, and then the propensity to exchange came later as a by-product.  In the Lectures on Jurisprudence, Smith says that the "real foundation" of exchange and the division of labor is "that principle to persuade which so much prevails in human nature."  Like Aristotle, Smith seems to believe that human beings are more political than other political animals because human beings have a capacity for logos--reason or speech--that allows them to persuade one another to cooperate for common ends, which makes exchance and the division of labor possible.  Ofek argues, however, that the evidence of human evolutionary history now suggests that exchange was an early agent of human evolution that favored the evolution of human reason and speech.

Smith goes on to suggest that while other animals can seem to act in concert when they are in passionate pursuit of the same object--like greyhounds chasing the same hare--this is the consequence not of any contract or deliberate choice but of "the accidental concurrence of their passions" in pursuing the same object at the same time.  Non-human animals are unable to communicate with one another well enough to say: "this is mine, that yours; I am willing to give this for that."

Notice that Smith thinks that non-human animals can engage in persuasion by begging for attention within their families or their groups or even to elicit benevolent care from human beings.  But the range of benevolence for all animals--including human beings--is limited.  In human civilization, individuals need "the cooperation and assistance of great multitudes," and for this they must appeal not to benevolence but to self-love, by persuading other individuals to engage with them in mutually beneficial exchanges.  Indeed, Smith points out that among human beings, even beggars cannot rely totally on charitable benevolence to secure their needs, because they beg for money that they use to buy what they need.

We might wonder whether Darwin would agree with Smith about barter or exchange being unique to human beings in giving rise to the division of labor as a spontaneous order.  Remarkably, Darwin says almost nothing about exchange in human evolution.  But there are at least two passages in Darwin's writings that both Ofek and Ridley cite as supporting their arguments about the human evolution of exchange.

In the Voyage of the Beagle, Darwin describes the savage people that he saw at Tierra del Fuego.  He reports: "Some of the Fuegians plainly showed that they had a fair notion of barter.  I gave one man a large nail (a most valuable present) without making any signs for a return; but he immediately picked out two fish, and handed them up on the point of his spear.  If any present was designed for one canoe, and it fell near another, it was invariably given to the right owner."  Darwin seems, then, to agree with Smith that even those living in the most primitive foraging societies show "the propensity to truck, barter, and exchange one thing for another."

In The Descent of Man, Darwin describes how man became "the most dominant animal" through technological inventions such as tools.

"To chip a flint into the rudest tool, or to form a barbed spear or hook from a bone, demands the use of a perfect hand; for, as a most capable judge, Mr. Schoolcraft, remarks, the shaping fragments of stones into knives, lances, or arrow-heads, shews 'extraordinary ability and long practice.'  This is to a great extent proved by the fact that primeval men practised a division of labour; each man did not manufacture his own flint tools or rude pottery, but certain individuals appear to have devoted themselves to such work, no doubt receiving in exchange the produce of the chase."  (Penguin edition, 2004, 69)

Although he doesn't make it explicit, Darwin implies that the complexity of artifacts in the archaeological record could be interpreted as evidence for a division of labor that promotes the dexterity and inventiveness that comes from specialization.  Ofek and Ridley have adopted this line of reasoning in arguing that the explosion of technological complexity in the Upper Paleolithic record of human evolution is a consequence of exchange and specialization, which is confirmed by evidence that some of the material in the human artifacts was transported over long distances, apparently by trade.

Darwin does not indicate, however, that this propensity for exchange and a division of labor is uniquely human, as Smith does.  Ridley argues that recent research on the evolution of cooperation confirms Smith's view.  Other animals cooperate with one another based on kinship, relatedness, and reciprocity (direct and indirect), and human cooperation show these same evolved mechanisms at work.  But cooperation based on exchange or barter is uniquely human, and it cannot be explained as a form of reciprocity.  Reciprocity means giving each other the same thing.  I'll scratch your back if you scratch mine (direct reciprocity).  Or I'll scratch your back because you have a reputation for scratching the backs of others (indirect reciprocity).  But exchange means giving each other different things.  As Smith puts it, "Give me that which I want, and you shall have this which you want."  Other animals can't do this.

To support this conclusion, Ridley cites some experiments with chimpanzees:

"The primatologist Sarah Brosnan tried to teach two different groups of chimpanzees about barter and found it very problematic.  Her chimps preferred grapes to apples to cucumbers to carrots (which they liked least of all).  They were prepared sometimes to give up carrots for grapes, but they almost never bartered apples for grapes (or vice versa), however advantageous the bargain.  They could not see the point of  giving up food they liked for food they liked even more.  Chimpanzees and monkeys can be taught to exchange tokens for food, but this is a long way from spontaneously exchanging one thing for another: the tokens have no value to the chimpanzees, so they are happy to give them up.  True barter requires that you give up something you value in exchange for something else you value slightly more." (59)

It seems to me though that Ridley is obscuring some of the complexity in these experiments (see Sarah Brosnan, et al., "Chimpanzee Autarky," PloS ONE,  January, 2008, e1518, 1-5.).  Brosnan and her colleagues apparently showed that chimps do barter, at least in a situation where they can trade very low valued items (carrots) for very high valued items (grapes).  But they do not barter where the gains from barter are small--as in trading valuable apples for slightly more valuable grapes.  One possible explanation that they suggest is that the chimps are less inclined to take the risk from giving up a valued food item if the possible gains are too small.

Nevertheless, it does seem that these experiments provide some support for the Smith/Ridley position.  Even if these chimps can learn to barter under some special conditions in the laboratory, they don't seem to spontaneously barter in the wild.  This is in contrast to the human situation where bartering seems to come easily as a spontaneous behavior, even in the most primitive human conditions, as with Darwin's Fuegians.  

It's still not clear to me, however, that Ridley has successfully distinguished exchange from reciprocity.  In fact, sometimes Ridley explains exchange as based on trustworthy reputation, and thus indirect reciprocity (see Ridley, 93-104).