CODA
None of what I said at the end of chapter 14 implies that our species has necessarily changed our planet in an intentional way. It’s certainly reasonable to suppose that there was no such intention at the start, in a world where our forebears were hunters and gatherers: people who were largely, if not entirely, integrated into their ecosystems. It is, though, highly probable that from the very beginning, apart from death, the only ironclad rule of human experience has been the Law of Unintended Consequences. Our brains are extraordinary mechanisms, and they have allowed us to accomplish truly amazing things; but we are still only good at anticipating—or at least of paying attention to—highly immediate consequences. We are notably bad at assessing risk, especially long-term risk. We believe crazy things, such as that human sacrifice will propitiate the gods, or that people are kidnapped by space aliens, or that endless economic expansion is possible in a finite world, or that if we just ignore climate change we won’t have to face its consequences. Or at the very least, we act as if we do.
All of this is, of course, in perfect agreement with the untidy accretionary history of the human brain. Inside our skulls are fish, reptile, and shrew brains, as well as the highest centers that allow us to integrate information in our unique way; and some of our newer brain components talk to each other via some very ancient structures indeed. Our brains are makeshift structures, opportunistically assembled by Nature over hundreds of millions of years, and in multiple different ecological contexts. When we realize that our symbolic capacities are an incredibly recent acquisition—and not merely the icing on the cake, but the candy bead surmounting the cherry atop the icing—it becomes evident that our brains as they perform now cannot have been fine-tuned by evolution for anything. We have achieved our mental eminence only because a long series of ancestors, stretching back into the most remote reaches of time, happened simply to have been able to cope with prevailing circumstances better than their competitors could. And then a final, still inscrutable, acquisition just happened to make a huge difference. If anything had occurred otherwise, anywhere along that lengthy trail, you wouldn’t be reading this book today.
There is a school of thought that we humans sometimes act so bizarrely because the evolution of our brains has not been able to keep pace with the rapid transformation of society that has occurred since humans began to adopt settled lifestyles at the end of the last glacial episode. Our minds, according to this view, are still responding, sometimes inappropriately, to the exigencies of a bygone “environment of evolutionary adaptedness.” This view has a wonderful reductionist appeal; but in reality our brains are the ultimate general-purpose organs, not adapted “for” anything at all. Yes, you can indeed find regularities in human behaviors, every one of them doubtless limited by basic commonalities in the structure of our controlling organs. But all such regularities are in reality statistical abstractions, and people are absolutely uniform in none of them. As a result, if any statistical phenomenon could be said to govern the human condition, it would be the “normal distribution,” or the “bell curve.” This describes the frequency with which different expressions of the same feature occur within a population. Tall in the center, where most individuals cluster, this bell-shaped curve tails off more or less symmetrically to each side, reflecting the fact that most observations of any feature fall close to the average, with deviations becoming increasingly rare the farther they lie from the mean.
In any human characteristic you might care to specify, physical or behavioral, you will find a bell curve. Only a few of us are very smart, or very dumb; most of us are somewhere in the middle. Ditto with tall/ short, caring/indifferent, strong/weak, chaste/promiscuous, spiritual/ profane, or any other continuous variable you might care to mention. This is, of course, why the internal human condition is virtually impossible to pin down: you can easily find an individual Homo sapiens to exemplify each extreme of any behavioral spectrum you can dream up. For every saint, there is a sinner; for every philanthropist, a thief; for every genius, an idiot. In this perspective, having bad people around is simply the price we pay for having good ones as well. Put another way, there is no need to look for special explanations for altruism when this feature is matched on the other side of the curve by selfishness. Individuals themselves are typically bundles of paradoxes, each of us mixing admirable with less worthy traits, even expressing the same trait differently at different times. We are ruled by our reason, but only until our hormones take over.
Similarly, nobody subscribes to all of those crazy ideas that are floating around, though most of us are attracted to a few of them. One of those crazy ideas is that the human condition can somehow be described by a long laundry list of “human universals”—uniquely human psychological and behavioral features that everybody has. But it nearly always turns out that these “universals” are either not uniquely human, or not universal among humans. Indeed, apart from that basic ability we all share to re-create the world in the mind, perhaps the only other true “human universal” we all show is cognitive dissonance.
Because of its peculiar cognitive properties, our species and its individual members are entities of entirely different kinds. For, while individual human beings are substantially—though not entirely—the products of their own particular genomes, coming into the world as broadly the kind of persons they will be as adults, this is not true in the same way for the human species as a whole. Indeed, the universal human condition will always remain elusive (and incessantly debated) for the very good reason that it is inherently unspecifiable.
So, what are we to make of ourselves? After a long evolutionary history we have arrived at a point at which our accidental cognitive prowess is allowing us unwittingly to change the very surface of the Earth on which we live. Indeed, it has recently been proposed (with typical human arrogance) that we should rename the current Holocene epoch of geological time the “Anthropocene” (roughly, the “new human age”). Many geologists cringe at this suggestion (the invention of an ecologist and an atmospheric chemist) because the depredations of a single species have never been used as a criterion for defining a phase of geological time. Nonetheless, it is nothing short of alarming how human intervention is affecting a huge array of processes that will clearly be reflected in the record available to future geologists, should there be any. To take just one example of many, over the eons all the natural might of the elements has typically lowered the surfaces of the continents by a few tens of meters per million years. In shocking contrast, a recent analysis has shown that trends in human activity that started only around the beginning of the first millennium have led to a current rate of worldwide erosion that is ten times higher.
If this were simply another statistical abstraction, maybe it wouldn’t matter much to members of such a supremely inward-looking species as our own. But we humans are already reaping enormous practical consequences of all that removal of the continental crust, in terms both of vastly accelerated inland erosion, and of coastal sedimentation. We are literally reshaping the planet on which we live. And behaviors that a resilient environment could simply absorb when Homo sapiens was thin on the ground become hugely damaging to human populations when there are seven billion of us around. What’s more, the effects cut both ways: the more enormous and complex the human enterprise grows, the more fragile it becomes. A flood that would have been a mere inconvenience to scattered groups of hunter-gatherers becomes a human tragedy of major dimensions in the crowded landscapes of Bangladesh or the Mississippi Valley. In many unintentional as well as intended ways we have indeed shown ourselves to be Masters of the Planet; but that is no guarantee that the Planet will not bite back when overstressed.
Clearly, then, we are already threatened by some of the correlates of those very attributes that make us so remarkable. And this makes it natural, of course, to ask whether we are condemned by the evolutionary “design” of our brains to continue in our self-destructive ways. Fortunately, the answer is “no”—at leas
t in principle. For example, while it has been shown that certain tendencies to violence originating in unusual brain activity may well be inherited, it is also known that those tendencies can usually be modified by environment and experience. What is more, societies as wholes are not necessarily subject to the same imperfections as individuals are—though, sadly, this cannot be said of their leaders. Indeed, complex societies, with all their rules and regulations, bizarre procedures, and sometimes draconian means of coercement, exist most usefully to compensate for the manifold deficiencies of individuals, especially those whose behaviors lie toward the negative extremes of some of those many bell curves. It is not least because of the often grating social and legal strictures that govern our existences that most of us behave reasonably responsibly most of the time; and it may not be hopelessly unrealistic to suggest that, once the gravity of our situation becomes clear to a majority, societies may actually be capable of taking the hard decisions that will be necessary if we are to maintain an equilibrium with the planet that supports us.
Still, while we are not perfected beings, we have nonetheless come a long way in the past seven million years. Does this mean that we can passively wait for evolution to complete its job? With a bit of patience, will the workings of natural selection eventually make us cleverer, and better aware of the full range of consequences of our actions? Unfortunately, this time the answer is also no, or at least not if present demographic trends continue. Our ancestors evolved during a time when hominids were thinly scattered over the landscape, in tiny and therefore genetically unstable populations that were subjected to frequent environmental stresses and disruptions. These were ideal conditions in which new populations and species could emerge and incorporate significant genetic and physical innovations. Indeed, more than likely it was just those highly unsettled prevailing circumstances that, in combination with our cultural proclivities, accounted for the unusually fast tempo of hominid evolution during the Pleistocene.
But that was then, and this is now. Since our adoption of settled existences at the end of the last Ice Age, the human population has mushroomed, until we are now packed across the globe with precious little elbow room left. These new conditions have changed the rules of the game entirely. Modern human populations have simply become too large and dense to witness the fixation of any significant genetic novelties that might in theory make us smarter and more protective of our own long-term interests. Short of a dramatic change in our demographic circumstances, we are stuck with our murky selves.
Many will find this prospect substantially less than optimal; but luckily it is far from the entire story. This is because, while the prospects for biological improvement seem rather dim in the absence of some (easily imaginable) cataclysm that might re-establish normal evolutionary rules, human innovation in the broader sense has not run into a brick wall. There is no question that our cognitive as well as our anatomical systems are far from perfect in a whole variety of areas. But our rational abilities and our extravagant neophilia nonetheless remain beyond remarkable. From the very first stirrings of the human symbolic spirit, the technological and creative histories of humankind have revolved around an energetic exploration of the innovative potential released by our new way of processing information about the world. And if one thing is clear above all, it is that this exploration of our existing capacity is far from exhausted. Indeed, one might even argue that it has barely begun. So, while the auguries appear indeed to be for no significant biological change in our species, culturally, the future is infinite.
ACKNOWLEDGMENTS
This book is the distillation of a longish career during which I have learned from, and been influenced by, many colleagues. They are too many to cite by name, but all know who they are, and all have my deepest appreciation. Still, while for me personally it is something of a culmination, in a larger sense this volume is merely a progress report. Science is a moving target, and nothing will give me deeper pleasure than to see the ideas I have expressed in these pages overtaken by developments in a fast-moving field. What we were taught when I came into paleoanthropology almost fifty years ago looks engagingly quaint today; and I have no doubt that today’s state of the art will look equally odd a half-century from now.
My appreciation goes to Amir Aczel for introducing me to my editor at Palgrave Macmillan, Luba Ostashevsky. Luba encouraged me to start this book, and steadfastly saw it through. Also at Palgrave Macmillan I’d like to thank Laura Lancaster and Donna Cherry for holding my hand through the production process, and Ryan Masteller for his copyedit. And it was fun working with Christine Catarino and Siobhan Paganelli.
I will always be grateful to Jane Isay and Michelle Press for showing me how rewarding it can be to write for a general audience. Thanks, too, to all those photographers and artists, acknowledged in the captions, who produced the illustrations, with a special nod to Jay Matternes and Jenn Steffey. And my gratitude goes above all to my wife Jeanne, for her support and forbearance during all that writing.
NOTES AND BIBLIOGRAPHY
Immediately below is a short list of recent books that may be of interest to those with a desire to read further about human evolution. The coverage of each work will be evident from its title; especially well illustrated are Johanson and Edgar (2006), Sawyer et al. (2007), and Tattersall and Schwartz (2000). For a comprehensive bibliography covering all the topics mentioned in this book, see Tattersall (2009), which also contains the history of discovery and ideas in paleoanthropology that is largely neglected here. For the widest possible coverage at a semi-technical level of topics relating to hominid paleontology and Paleolithic archaeology, Delson et al. (2000) is highly recommended. Following this general list is a chapter-by-chapter bibliography identifying the main primary sources consulted for this book, and all works from which quotations are made.
Delson, E., I. Tattersall, J. A. Van Couvering, A. S. Brooks. 2000. Encyclopedia of Human Evolution and Prehistory, 2nd. ed. New York: Garland Press.
DeSalle, R., I. Tattersall. 2008. Human Origins: What Bones and Genomes Tell Us About Ourselves. College Station, TX: Texas A&M University Press.
Eldredge, N. 1995. Dominion. New York: Henry Holt.
Gibbons, A. 2006. The First Human: The Race to Discover Our Earliest Ancestors. New York: Doubleday.
Hart, D., R. W. Sussman. 2009. Man the Hunted: Primates, Predators, and Human Evolution. Expanded ed. New York: Westview/Perseus.
Johanson, D. C., B. Edgar. 2006. From Lucy to Language, 2nd ed. New York: Simon and Schuster.
Klein, R. 2009. The Human Career: Human Biological and Cultural Origins, 3rd ed. Chicago: University of Chicago Press.
Klein, R., B. Edgar. 2002. The Dawn of Human Culture. New York: Wiley.
Sawyer, J. G., V. Deak, and E. Sarmiento. 2007. The Last Human: A Guide to Twenty-Two Species of Extinct Humans. New Haven, CT: Yale University Press.
Stringer, C. B., P. Andrews. 2005. The Complete World of Human Evolution. London and New York: Thames and Hudson.
Tattersall, I. 2009. The Fossil Trail: How We Know What We Think We Know about Human Evolution, 2nd ed. New York: Oxford University Press.
Tattersall, I. 2010. Paleontology: A Brief History of Life. Consohocken, PA: Templeton Foundation Press.
Tattersall, I., J. H. Schwartz. 2000. Extinct Humans. New York: Westview/Perseus.
Wade, N. 2006. Before the Dawn: Recovering the Lost History of Our Ancestors. New York: Penguin Press.
Wells, S. 2007. Deep Ancestry: Inside the Genographic Project. Washington, DC: National Geographic.
Zimmer, C. 2005. Smithsonian Intimate Guide to Human Origins. New York: HarperCollins.
CHAPTER 1: ANCIENT ORIGINS
For an accessible recent account of Rift Valley formation and the early East African hominoids, see Walker and Shipman (2005). Pickford (1990) discusses eastern African uplift in relation to hominoid evolution, and Harrison (2010) provides an excellent overview of the variety and relationships of fossil hominoids and putati
ve hominid precursors. For more about Oreopithecus see Köhler and Moyà-Solà (1997), Moyà-Solà et al. (1999), and Rook et al. (1999). Pierolapithecus was described by Moyà-Solà et al. (2004). For a history of the recognition of hominids and key criteria see Tattersall (2009). Sahelanthropus was described by Brunet et al. (2002, 2005), and virtually reconstructed by Zollikofer et al. (2005). Orrorin and its environment were described by Senut et al. (2001) and Pickford et al. (2001, 2002). Ardipithecus ramidus was named (initially as Australopithecus ramidus) by White et al. (1994), and its skeleton comprehensively analyzed in a special issue of Science (White et al., 2009). Ardipithecus kadabba was described by Haile-Selassie (2001) and Haile-Selassie et al. (2004). For more on bipedality see Harcourt-Smith (2007). Australopithecus anamensis was first described by Leakey et al. (1995, 1998), and the Kenya material was comprehensively presented by Ward et al. (2001). Claimed Ethiopian material of this species was presented by White et al. (2006), and gradual transformation of A. anamensis into A. afarensis was advocated by Kimbel et al. (2006).
Brunet, M., F. Guy, D. Pilbeam, H. T. Mackaye, A. Likius, D. Ahounta, A. Beauvilain, C. Blondel, H. Bocherens, J.-R. Boisserie, L. De Bonis, Y. Coppens, J. Dejax, C. Denys, P. Duringer, V. Eisenmann, G. Fanone, P. Fronty, D. Geraads, T. Lehmann, F. Lihoreau, A. Louchart, A. Mahamat, G. Merceron, G. Mouchelin, O. Otero, P. P. Campomanes, M. Ponce de León, J.-C. Rage, M. Sapanet, M. Schuster, J. Sudre, P. Tassy, X. Valentin, P. Vignaud, L. Viriot, A. Zazzo, C. Zollikofer. 2002. A new hominid from the Upper Miocene of Chad, Central Africa. Nature: 145–151.
Brunet, M., F. Guy, D. Pilbeam, D. E. Lieberman, A. Likius, H. T. Mackaye, M. S. Ponce de León, C. P. E. Zollikofer, P. Vignaud. 2005. New material of the earliest hominid from the Upper Miocene of Chad. Nature 434: 752–754.
Haile-Selassie, Y. 2001. Late Miocene hominids from the Middle Awash, Ethiopia. Nature 412: 178–181.
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