The Wealth of Hominids - Matt Ridley's "The Rational Optimist"

This is the first of several essays inspired by Matt Ridley's new book, The Rational Optimist.

Every so often a book comes along that punctuates the relative equilibrium of my understanding of the theory of evolution, dramatically altering my appreciation of the processes by which life on this planet has changed over time.

In 1976 Richard Dawkins' The Selfish Gene, with its startling premise that the gene, and not the individual organism, was the fundamental unit of natural selection, made me aware that Darwin's then more than century-old theory was not gathering dust, but was being actively refined, and its details even debated.

About the same time E. O. Wilson's Sociobiology appeared, assuring me that knowledge of biology can indeed inform our understanding of the behavior of animals, including ourselves, all in the face of a bitter opposition, which, to this day, mistakenly conflates Wilson's scientific description of biological tendencies with political prescription for biological determinism.

In 1981 with Lucy, Donald Johanson introduced me to the nuts and bolts of the practice of paleoanthropology and helped me realize that the study of human origins involves not only the reconstruction of the skeletons of our ancient ancestors and cousins, but also the reconstruction of their lives.

And of course there are the books by Stephen Jay Gould, too numerous to mention, many collections of his essays for Natural History magazine, in which he disabused me of the received wisdom concerning the pace and direction of evolution and replaced it with stories of accident and contingency, calling my attention to the modest evolutionary spandrels nestled between the showy arches that, together, constitute the cathedral of this wonderful life.

More recently, Daniel Dennett in Darwin's Dangerous Idea opened my eyes to the fact that the central thesis of Darwin's On the Origin of Species - that is that remarkably complex systems could evolve from simple beginnings, without direction, according only to the dictates of selective forces - operates beyond the domain of biology and that, because of its universal applicability, occupies a singular position in our intellectual firmament.

I now count Matt Ridley's The Rational Optimist in this list of important influences.

The War Room, a documentary
of the 1992 Clinton campaign

Optimist opens with a bold proposal, an assault on a persistent question about our beginnings, that is, what exactly was it, a little more than 100,000 years ago, give or take, that stirred us - even by then long fully-formed humans beings - from eons of technological lassitude and launched us onto a trajectory of ever-increasing material prosperity?

Ridley's answer, always acknowledging a debt to his hero Adam Smith, could well be expressed as a variation on that watchword of the 1992 Clinton presidential campaign, "it's the economics, stupid."

A startling, and unexpected, implication of his thesis is that our humanity, contrary to conventional thinking, is not a legacy bequeathed to us, something that we possess unconditionally, but a dynamic process, one for which we are specifically suited, a glorious dance, but one which lasts only so long as the music plays, and that music, according to Ridley, is the activity of barter and exchange.

Creatures that we would recognize as modern humans have been around for some time, the better part of 200,000 years.  Not only do we share the same basic body plan and, from all indications, cognitive capabilities with these predecessors, but so did they with their own hominid contemporaries, the unfairly maligned Neanderthals, who, if cranial capacity is any indication, may have been a tad smarter.

Obsidian handaxe from the
Ethiopian Acheulean period
(courtesy of Melka Kunture
Museum)

Speech is unlikely to have distinguished these first cousins from one another; genetic analysis indicates that both species possessed a variant of the FOXP2 gene, which is an established marker for that facility.  Indeed, their common ancestor, homo heidelbergensis, dating back half a million years or more was likely to have been a talker, too.  And speech is not all that they had in common with heidelbergensis.  The archeological record demonstrates that both predecessor and successor species, separated by tens of thousands of generations, employed, with minor modifications, the same set of tools.  In particular, the centerpiece of their technology, the Acheulean handaxe, itself, had remained largely unchanged for hundreds of thousands of years.

Why then, after a near eternity of tiresome technological sameness, does a new, expanded and far more capable toolkit appear and begin to become established 100,000 years ago?

Was it some dramatic change in climate that triggered this great leap forward?  According to Ridley, likely not;  such climatic swings occurred in preceding geological epochs and, yet, there is no indication that they prompted advances in human intelligence or, for that matter, that they should have.  Perhaps a propitious genetic mutation was responsible?  As the author points out, though, the evidence for new tools appears erratically, distributed both in space and in time, a pattern hardly consistent with the diffusion of a favorable trait from a single point of origin. And, once these innovations take hold, they point toward a process of escalating technological progress whose rate, nonetheless, varies from place to place, a phenomenon not indicative of an "intrinsic" new human capability.

Instead, Ridley proposes that, having been equipped with a knack for specialization, itself an artifact of our inculcated roles as hunters and gatherers - a division of labor that, it appears, Neanderthals did not practice - and having reached sufficient population densities so that contact with neighboring groups became commonplace, these early modern humans began to exploit such encounters as opportunities to offer things that they were relatively adept at creating or acquiring in exchange for things, which if they had produced themselves, would have distracted them from making the best use of their skills and available resources.  This kind of varied, asymmetric give-and-take, quite different from the acts of reciprocity that had likely been a characteristic of primate behavior for tens of millions of years, was something new to the world.

David Ricardo
(1772 - 1823)

But the magic here, if it can be called that, is not simply the appearance of barter on the human scene, but the fact that such trade itself encouraged further specialization, and that, in turn, encouraged more trade.  The invisible hand at work is not so much Adam Smith's market, as it is David Ricardo's law of comparative advantage, the seemingly counter-intuitive notion that, in many circumstances, we are better off paying more for goods that we could have made ourselves, if by doing so we gain time and resources otherwise spent to do what we do best, that is, make those things that we make most efficiently.  I say "seemingly counter-intuitive" because, although this abstract law of economics was not explicitly formulated until 1817, it appears to have been implicitly grasped by our forbears as early as the late Pleistocene.

So, with trade promoting more specialization and specialization, by making more goods available at lower cost, promoting more trade, a self-catalyzing cycle leading to open-ended material progress was underway, and the rest, as they say, is history, our history, a history that Ridley details in much of the remainder of his book.

Speculative theories about human origins are, of course, a dime a dozen.  The requirement that they conform to the available evidence certainly reduces the number of contenders.  But how, then, do we go about further winnowing?  Ordinarily, in order to reconcile competing conventional scientific claims, we turn to laboratory experiments, an approach that is not typically available to historical sciences such as evolutionary biology.  Interestingly enough, what sets Ridley's approach apart is that he succeeds in proposing two experimental tests for his theory, one that, it turns out, nature conducted on our behalf 10,000 years ago and another that is within our investigative reach today.

If barter is central to human progress, as Ridley suggests, then a human population once isolated should, at best, stagnate technologically.  Indeed, if forces are at work that deplete its reserves of expertise, such a population, cut off from exchange, might well be expected to regress.

Landsat photo of the
island of Tasmania

The stage was set for Ridley's historical experiment some 35,000 years ago, when human beings first arrived on the island "laboratory" of Tasmania, then still joined to the mainland of Australia by a land bridge.  With them they brought knowledge of how to fashion a variety of things, everything from fish hooks to canoes, samples of the inventory in use in the regions from which they came.  Around 25,000 years later, as the glaciers of that ice age receded and the oceans filled once again, these aboriginal pioneers were cut off from interaction with the outside world.  By the time Europeans reestablished contact in the 17th century, the 5,000 or so hunter-gatherers of Tasmania had reverted to a much more limited set of tools and a much simpler way of life.  Apparently, left to their own devices, so to speak, and deprived of not only the progressive, but also the rejuvenating influences of trade, the Tasmanians entered a decline which ultimately erased much of tens of thousands of years of prior technological advance, just as the author's theory predicts.

Space-filling model
of oxytocin

As a contemporary test of his thesis, Ridley proposes our taking a closer look at the genetics of the oxytocin system in humans.  This neurotransmitter, sometimes called the "cuddle hormone", present in all mammals, is implicated in the regulation of a variety of behaviors, in particular those having to do with female reproduction and infant care.  Recent studies in human subjects, which Ridley cites, indicate that, in addition, oxytocin facilitates a tendency to take social risks, most significantly for his purposes, the extension of trust to strangers.

For exchange to gain a foothold there had to be, at a minimum, a suspension of the hostilities that erupted as a matter of course when bands of unrelated primates, including early humans, encountered one another.  Ridley speculates that, in some sense, there was just the right kind of oxytocin, trust juice, as he calls it, flowing in the veins of our ancestors - and activating appropriately tuned receptors in their brains - to make a critical amount of social risk taking possible.

Once even a marginal inclination to barter with strangers was in place, though, it would have offered such advantages, that selective pressures favoring an even more robust "trust response" would have come into play, modifying the physiological mechanisms in humans by which oxytocin is produced and processed.  If Ridley is right, we carry the biochemical markers for these behaviors with us today, and a targeted analysis of our genome should reveal a timeline for their appearance, a chronology that should be consistent with significant modifications beginning around 100,000 years ago.

It should be noted that by proposing this experiment, Ridley not only offers a test that could substantiate his hypothesis, but also one that could potentially undermine it.  In a world replete with just-so stories masquerading as evolutionary biology, it is refreshing to have a theory to consider that flirts with falsifiability, a criterion that serves to differentiate serious science from plausible conjecture.

Frescoes of dolphins from
bronze age excavations
on the island of Crete

Although Rational Optimist does not directly address the age-old question of human uniqueness - that is, what feature of our biology or of our behavior sets up apart qualitatively, not only from our hominid ancestors, but also from extant species, most notably dolphins and other great apes - much of what Ridley has to say about the critical importance of social risk taking, as evidenced by the extension of trust to unrelated individuals, in the origin of barter and exchange would seem to have significant bearing on that issue.

Of course, the question of human exceptionalism is, itself, problematic; perhaps it is simply the case that we differ from other animals in a large number of small ways, something that, in fact, could be said about the standing of most any creature on this planet; and, understandably, it is difficult, if not impossible, to see beyond our anthropocentric biases in forming an "objective" determination about whether we occupy a special status in the biological world.

Whac-a-mole arcade game
(courtesy of Sakura)

Nonetheless, attempts to answer this provocative question have proven to be instructive, if not conclusive, with the call-and-response argument coming to resemble a version of the Whac-a-mole arcade game.  In this variation the moles are candidate distinguishing human traits (e.g. bipedalism, pair-bonding, tool use, brain size, culture, language, symbolic thinking or empathy).  In the course of play each contender pops its head out of its hole, hoping to dodge the ever-looming mallet of contemporary or ancestral counterexample.  Suffice it to say, historically, moles have not fared well in this competition, although one would have to concede that some do battle on, battered but unbowed.

Sylvio Tuepke / New York Times

To the extent that there is a "last mole standing" in the aftermath all this whacking, that title might go to the characteristically human activity recognized broadly as "cooperation".  As noted above for barter, complex collaboration, much richer than simple in-kind reciprocity, is well outside the the prosocial repertoire practiced by other primates.  Indeed, the simple act of sharing food with strangers, a behavior that emerges, apparently without training, in human infants, and one wonderfully documented in Michael Tomasello's book, Why We Cooperate, finds no correspondent among our great ape brethren.  It is, at a minimum, intriguing that this cooperative disposition of ours, in some sense an urge to help, which sets us apart us from other living species, also closely resembles the willingness to extend trust to strangers that Ridley proposes was instrumental in enabling the process of exchange that set us apart from our hominid ancestors.

Going out on a limb a bit, I might argue that Ridley's insight points us toward a different sort of resolution to the question of human exceptionalism.  Perhaps it is the case that, on one hand, deprived of the opportunity to engage in exchange with outsiders, human groups - to borrow a phrase used by Darwin in Origin - revert to a state of nature, a condition in which they are much like a proverbial third chimpanzee, an admittedly interesting, but unexceptional, bipedal primate.  Yet, on the other hand, it could be that, when the distribution of human bands makes routine contact possible over an extended period of time, the full potential of our facility for cooperation is realized and, we, as a result, do attain a stature that is unique in the animal kingdom.

Lasius niger - black garden ant
(courtesy of
Jens Buurgaard Nielsen)

From this perspective, our oxytocin-fueled inclination toward taking social risks can be seen as a genetic trait, but, in the sense of Richard Dawkins' extended phenotype, one that only finds meaningful expression when the geographical arrangement of human populations conforms to a critical configuration that allows barter to take hold.  E. O Wilson has observed that individual ants, in some sense, don't exist outside the context of the colony to which they belong.  Perhaps an analogous claim could be made for human beings, not so much that they don't exist outside of systems that support barter and exchange, but that, when they are isolated from such, their humanity is not fully expressed.

I'll close by noting that this line of thinking is not without practical, although not immediate, consequence.  Since the dawn of the atomic age and, with it, the prospect of "assured destruction", followed in short order by our first tentative steps toward becoming a space-faring people, much has been made of the proposition that, in order to insure our survival as a species, we must dispatch some brave souls from among our ranks to self-contained orbiting cities or to settlements on nearby, or even distant, planets.  More recently, the possibility of environmental collapse or asteroid impact has increased the sense of urgency that surrounds these proposed missions, with no less a great thinker than Stephen Hawking - the go-to commentator on all matters existential these days - recommending that it's time for us to start preparing "to go to a another star".

Artist impression of a Mars
colony with a cutaway view

I, for one, hope that the planners of these noble ventures keep Matt Ridley's hypothesis in mind when they go to their drawing boards, in particular, that they think carefully about how to maintain an exchange of ideas, if not goods, between far-flung human communities or devise some sort of technological or sociological fix to make up for its absence.  It is sad to contemplate that we might indeed survive as a species, but not as the species we are, that any extraterrestrial colony, bereft of the progressive and rejuvenating influences of trade, in the broadest sense of that word, might as well be christened "New Tasmania".

I would like to thank my friend Bill Shropshire for many stimulating discussions that went into helping me prepare this essay.

The Wealth of Hominids - Matt Ridley's "The Rational Optimist" by Marc Merlin is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.
Based on a work at thoughtsarise.blogspot.com.