Modern humans stayed anatomically unchanged at least for the past 80,000 years. On the evolutionary level of organization, anatomically fixed things are expected to stay (nearly) fixed in behavior. Our (anatomically) modern ancestors lived up to this rule for the first half, or slightly more, of their tenure on earth. All hell broke loose in the second. The extraordinary changes in the archeological record starting around 40,000 to 30,000 years ago, and carrying through the height of the last ice age to the onset of the Holocene (some 10,000 years ago), suggest remarkable refinements in behavioral structures unexpected of a morphologically fixed organism. Changes in the record further suggest a remarkable increase in regional and temporal diversity of material structures that up to that point varied little through time and space. The Middle to Upper Paleolithic transition, or the creative explosion as this episode has sometimes been labeled (e.g., Pfeiffer, 1982), is most vividly evident in wall paintings preserved in caves, in portable art, personal ornamentation, and in elaborate burials. More subtle are the sudden refinements in tools, and the rapid expansion into new geographic areas, indeed, into two new continents (Australia and the Americas). Underlying all of this is an authentic economic expansion reminiscent of various mercantile and industrial revolutions in recorded history.

The key question, from an evolutionary viewpoint, is how could such remarkable changes take place in functional behavior without apparent change in morphology. One possible explanation ascribes this turn of events to some neurological change that led to an evolution in behavior without an apparent change in anatomical form (e.g., Klein 1992).

The incredible shrinking gut

Laboratories under sail

Among the sailors who crisscrossed the oceans during the sixteenth century few knew how to swim. It was pointless. A sailboat at sea could not be stopped or turned to rescue a shipmate washed or fallen overboard. The hazards of the occupation could not escape the attention of sailors struggling to lash unruly sails in unpredictable gale-force winds. One slip on the upper yards meant almost certain death. Given the state of the art and the perils of the sea, casualties from accidents and disease were exceedingly high even by the standards of the time. As to comforts and niceties of life – nobody could ask for, nor possibly be granted, accommodations beyond the bare minimum.

With lives aboard more expendable than cargo, one can wonder why skippers and ship stewards paid meticulous attention to supplies of food-stuff. A typical list of ship supplies for a journey across the Atlantic around 1577, the year Sir Francis Drake set out to circumnavigate the world, included such diverse items as hardtack, flour, pickled beef and pork, dried peas and codfish, butter, cheese, oatmeal, rice, honey, and vinegar, as well as about eight tons of beer. The selection seems to compare quite favorably even today with any decent hospital or school cafeteria – not counting the beer. Careful attention to an adequate bulk of food supplies before embarking on unpredictably long trips such as the one undertaken by the Mayflower (66 days across the Atlantic in 1620) is perfectly understandable. But why overburden the already hard-pressed logistics of a ship on high seas with a wide variety of food items?

Darwin and the Scottish economists: The first point of junction

The fundamental economic problem of human evolution

In view of the discussion thus far, the issue is no longer the mere existence of a human predisposition to exchange, but its evolutionary origin. Unsure of this origin, Adam Smith himself acknowledged (and deflected) in passing an intriguing question:

The inception of modern economics was thus accompanied (in 1776) by an evolutionary question preceding by nearly a century the Darwinian notion of evolution itself. Adam Smith probably agonized over this question, though as it seems, had the good sense to abort it in due course. Neither he nor his pre-Darwinian readers could fully comprehend the question, let alone conceive a sensible answer to it. With the advantage of hindsight, however, the question seems to present a challenge of the highest order to the modern study of human evolution: Was exchange an early agent of human evolution, or was it merely a late by-product of previously evolved “faculties of reason and speech”?

With the publication of The Descent of Man a century or so later, Darwin had at his disposal a fairly mature notion of evolution applicable to human affairs.

The first appearance of manufactured stone tools in widespread systematic human use, about 2 million years ago, in combination with other evidence (e.g., food sharing), suggests the possibility that some form of exchange, however primitive, was already practiced by traders with brains half the size of a modern human being. If true, the implication is that exchange could have played an important facilitating role already in the first major economic transition in human (or protohuman) history – the transition from the feed-as-you-go strategy of primate feeding to hunting-gathering. The discussion in this chapter will consider these possibilities in light of the available paleoarcheological data, starting with a preliminary review of the physical environment.

The physical environment

The single most important factor that describes the theater of events in evolution, certainly in human evolution, is climate. The global climate in which civilization flourished is the wrong environmental model for understanding human evolution not only throughout the long ice ages (nearly 90% of the time humans walk the earth) but, in all likelihood, also in the course of the short spikes of interglacial periods (the remaining 10%). The climate observed today and enjoyed by (anatomically) modern people over the past 10,000 years is a placidly warmand, arguably, all too brief interval in a long process of falling temperatures starting about 3.2 million years ago (and greatly intensifying roughly 2.4 million years ago and then again about 900,000 years ago).

If market exchange evolved from some preadaptation observable in humans or animals, then a careful examination of analogies with nepotistic exchange (such as courtship feeding in birds) or symbiotic exchange (such as pollination) is a logical course of action to pursue. In following this approach the first part of this chapter demonstrates the existence of some tempting analogies of market exchange drawn from the behavior of certain animals and plants, as well as from the nonmarket sphere of human affairs. It also demonstrates the risk of drawing premature, if not fanciful, explanations from such analogies.

Alternatively, if market exchange evolved de novo, then the major thrust in the inquiry is best directed toward the mechanisms of the market and the deep structures of exchange itself. This approach is undertaken in the second part of this chapter with the hope that intricacies of market exchange as we know them could provide a clue to their origin. At issue is a catalyst in the form of an activity, or perhaps a single commodity, with the power of spurring exchange between exceedingly reluctant traders at some remote point in antiquity.

Bateman's syndrome

There are certain parallels between the choice of mating partners and the choice of trading partners – chief among them is asymmetry. The asymmetry in the case of sexual selection is due to adaptive pressures that for a widely recognized reason – known as Bateman's principle – act differently on the reproductive behavior of males and females. In a pattern that cuts across nearly all the species of higher organisms, as already noted by Darwin (1874), females are more selective.

Without really being aware of it, human beings economically interact under two distinct routines – nepotistic exchange and market exchange – effortlessly switching back and forth between the two regimes. The tendency to turn on and off two separate processes of decision-making (with implications in action and in demeanor) could have been readily diagnosed as some sort of split-personality disorder had it not been so predictable – repeating itself in nearly the same manner in almost any member of the species. The fundamental difference between the market and the nepotistic (or domestic) routines of human activities was examined in the foregoing discussion (especially in Chapter 2) on the grounds of practical considerations and, so far, only with a secondary emphasis on evolutionary ones. The main implication suggests nothing in the way of a behavioral disorder. What it suggests is the coexistence of two distinct adaptations. The main attempts to trace these two adaptations to their separate evolutionary origins are relegated to two chapters in this volume. The present chapter is primarily concerned with the origins of nepotistic exchange. (Chapter 9 will be similarly concerned with the origins of market exchange.)

Primordial exchange at the lowest levels of organization

Certain advantages of division of labor, supported by exchange, occurred at fairly early stages of life on earth. Consider, for instance, the evolution of one of the most comprehensive and amazing systems of exchange and division of labor in nature: a single body of a multicelled organism. Finely tuned exchange among specialized cells, tissues, and organs is inherent in the physiology of such an organism.

The propensity and capacity to exchange one thing for another between two traders – however unrelated to each other – is a profound distinguishing feature of human subsistence. Human beings are endowed with remarkable skills of trade which they deploy spontaneously when confronted with favorable opportunities; skills that lie dormant in the absence of such opportunities. As is true of other innate human abilities – such as the mastery of spoken language – basic skills of trade are taken for granted precisely because they are either inborn or acquired at a young age without conscious effort. Such skills are not as trivial as they may seem to a casual observer or, for that matter, to their very practitioners. Exchange requires certain levels of dexterity in communication, quantification, abstraction, and orientation in time and space – all of which depend (i.e., put selection pressure) on the lingual, mathematical, and even artistic faculties of the human mind. Moreover, exchange relies on mutual trust: predictable codes of conduct agreeable to the human sense of morality. Exchange, therefore, is a pervasive human predisposition with obvious evolutionary implications. The root cause of this predisposition and its evolutionary consequences in history, and prehistory, are the central concerns of this book.

Was exchange an early agent of human evolution, or is it a mere de novo artifact of modern civilization? The evolutionary literature treats the question with great caution. Many authors, starting with Charles Darwin and Alfred Russel Wallace, preferred to avoid the issue altogether. When the issue comes to the fore, the importance of exchange in recent industrialized societies is readily acknowledged.