Authors: Ian Tattersall
This realization had not come easily. Intuitively, it was difficult for nineteenth-century scientists to accept that the ancient Ice Age inhabitants of southern France and northern Spain had created an artistic traditionâembracing painting, engraving, sculpture, and bas-reliefsâthat, at its best, had equaled or even exceeded in its power anything achieved since. After the first (and among the finest) cave paintings were discovered at Altamira in 1879, immediate admiration rapidly gave way to doubts. How could such refined and accomplished art possibly be the work of hugely ancient people? How could it have been produced by “savages” without fixed abode: mere hunters and gatherers who had roamed the landscape and availed themselves of its bounty, quite the antithesis of civilized nineteenth-century folk who worshiped in magnificent cathedrals, built sturdy houses for shelter, and put the land and what grew on it to work for them? It took repeated discoveries of ancient art, in virgin caves and at untouched archaeological sites, to convince the world that you could indeed have both a sophisticated mind and a “primitive” life-style: to make acceptable the notion that, those many tens of millennia ago, people had existed who did not live in houses and till the fields, but who nonetheless made fabulous art, led mysteriously complex lives, and were just like us in all their cognitive essentials.
Monochrome rendering of a now badly faded polychrome wall painting, probably around 14,000 years old, in the cave of Font de Gaume, France. A female reindeer kneels before a male that is leaning forward and delicately licking her forehead. Drawing by Diana Salles after a rendering by H. Breuil.
course those ancient people, and the larger societies whose beliefs and values those images at Lascaux and Altamira embodied, vanished long ago. So, although we have at our disposal miraculously preserved material evidence of the creative spirit of those long-gone humans, we will never know for sure just what those beliefs and values were. Nonetheless, for all their cultural and temporal remoteness, we
be secure in the knowledge that those ancient people of Altamira and Lascaux and elsewhere were
in all essentials, imbued with the same remarkable human spirit that animates us today.
Significantly, the walls of Lascaux and other caves are not decorated only with animal images, drawn with the deftness, observation, and clever stylization that place their creators among the greatest artists ever. Among and upon those instantly recognizable animal figures, the artists placed geometric motifsâgrids, lines of dots, dartlike signsâthat
had very specific meaning to their creators. Sadly, today we have no way of knowing just what it was the artists had intended to express; but if you consider the clear specificity of the images together with the complex ways in which they are juxtaposed, you rapidly begin to realize that this art was not simply representational. It was
Every image in this cave and others, realistic or geometric, is drenched with meaning that goes far beyond its mere form.
Even though we can't know exactly what the art of Lascaux meant either to its creators or to those for whom it was intended (whether the two were the same, we'll never be certain), what is undeniable is that this art signified something well beyond what we are able to observe directly. And this is, oddly enough, one of the most powerful of the many reasons why so many of us resonate to Ice Age art at the most profound of levels. Because, for all the infinite cultural variety that has marked the long road of human experience, if there is one single thing that above all else unites all human beings today, it is our symbolic capacity: our common ability to organize the world around us into a vocabulary of mental representations that we can recombine in our minds, in an endless variety of new ways. This unique mental facility allows us to create in our heads the alternative worlds that are the very basis of the cultural variety that is so much a hallmark of our species. Other creatures live in the world more or less as Nature presents it to them; and they react to it more or less directly, albeit sometimes with remarkable sophistication. In contrast, we human beings live to a significant degree in the worlds that our brains remakeâthough brute reality too often intrudes.
Human beings are unusual in many ways, physical as well as cognitive. But our unique mode of processing information is without any question the element that, more than any other, marks us off as
from other creatures; and it's certainly what makes us
different. What is more, as I hope this book will convince you, it is entirely without precedent. Not only is the ability for symbolic reasoning lacking among our closest
relatives, the great apes; such reasoning was apparently also absent from our closest extinct relativesâand even from the earliest humans who looked exactly like us. At the same time, we modern humans have a huge amount in common intellectually with all of those relatives, vanished and living; and, even more to the point, no
how much we may vaunt our rationality, we are most certainly not entirely rational beings: a point that should need no belaboring to any observer of our species. One major reason for this is that, through the vagaries of a long and eventful evolutionary history, some of the newest components of our brainsâthose strange, complex organs in our heads that govern our behavior and experienceâcommunicate with each other via some very ancient structures indeed.
Because of the peculiar construction resulting from their complex history, our brains are far from directly comparable to a feat of human engineering. Indeed, they are probably not comparable at all. For engineers always strive, even where they are consciously or unconsciously constrained, for
solutions to the problems they are facing. In contrast, during the long and untidy process that gave rise to the modern human brain, what was already there was always vastly more influential on the historical outcomeâwhat actually
happenâthan any potential for future efficiencies could be. And thank goodness for that. After all, if our brains had been designed like machines, if they had been optimized for any particular task, they would
machines, with all of the predictability and tedious soullessness that this would imply. For all their flaws, it is the very messiness and adventitiousness of our brains that makes themâand usâthe intellectually fertile, creative, emotional, and interesting entities that they and we are.
This perspective conflicts with the view of evolution that most of us were taught in schoolâwhere, if it was mentioned at all, this most fundamental of biological phenomena was usually presented as a matter of slow, inexorable refinement, constantly tending toward achieving the perfect. So, before we embark on the human story, it seems reasonable to take a few moments to look more closely at the remarkable process that operated to produce usâbecause, extraordinary as we may justifiably think ourselves, we are actually the result of a perfectly ordinary biological history.
THE VAGARIES OF EVOLUTION
Let's start right at the beginning, with the overarching pattern in which Nature is organized, because this is the clearest tip-off we have to the
lying behind our appearance on the planet. There is a clear order in the living world. The way in which the diversity of animals and plants around us is structured is not haphazard in the least. Instead, it shows an across-the-board pattern of groups within groups. Among the mammals, for example, human beings are most similar to apes; the apes and humans together are most similar to the monkeys of the Old and New Worlds; and apes, humans, and monkeys all resemble lemurs more closely in their anatomies than they do anything else. Jointly, these primates form a distinctive cluster within Mammalia, the order that groups together all the warm-blooded, furry animals that suckle their young. All mammals in turn belong to a bigger group known as Vertebrata (the backboned animalsâfish, amphibians, reptiles, and birds, as well as mammals), and so on.
other organism is similarly nested into the living world; and graphically, this pattern of resemblance is best expressed in the form of a repeatedly branching tree. Ultimately, every one of all the many millions of living organisms can be embraced within one single gigantic Tree of Life. In this greatest of all trees, biologists group the tiniest branch tips (species, e.g.,
) into genera (e.g., the genus
), which are in turn grouped into families (Hominidae), which are grouped into orders (Primates), and so on. As you move up the tree, each successive level departs farther in its configuration from the common ancestral form at the bottom, and from equivalent neighboring branches. And although it is possible to study this self-evident Tree of Life in purely structural terms, the most interesting thing is to know what caused it.
The only testable (and thoroughly tested) scientific explanation of this pattern of resemblance is common ancestry. The similarities that clue us in to the shape of the tree are inherited from a series of shared ancestral forms, whose descendants have diverged from them in various respects. Similar forms share a recent common ancestor, while more disparate ones shared an ancestor much more remotely in timeâallowing differences to accumulate over a longer period. No matter how dissimilar they may now appear to the eye, all life forms are ultimately linked at the genomic level to a single common ancestor that lived more than 3.5 billion years ago.
nineteenth-century naturalists Charles Darwin and Alfred Russel Wallace were the first to come up with a convincing mechanism by which divergence from a common ancestor could occur. Darwin called this instrument of change “natural selection.” Once pointed out, this natural process seemed so self-evident that Darwin's famous contemporary Thomas Henry Huxley publicly berated himself for his own failure to think of it. In a nutshell, natural selection is simply the preferential survival and reproduction of individuals that are better “adapted” to their environments than their fellows, in features inherited from their parents. And it is pretty much a mathematical consequence of the fact that, in all species, each generation produces more offspring than survive to reproduce. The idea here is that, over enough time, those with more advantageous inherited characteristics will have greater reproductive success, and therefore will nudge the population in the direction of better adaptation. In this way, members of the lineage will change in average appearance and ultimately evolve into a new species.
That was the theory, anyway, though it has subsequently been noticed that natural selection may well act mostly to trim off both extremes of the available variation, keeping the population more or less stable. Another complication is that, when we think of adaptation, we usually have in mind one single anatomical feature, or behavioral property, of the animal in question: the structure of its foot or pelvis, say, or its “intelligence.” Thinking of just one feature in isolation, it is easy to envision how that structure might have been improved over time by natural selection. Yet we now know that all organisms are astonishingly complex genetic entities, in which a remarkably small number of structural genes (exactly how many we humans have isn't known for sure, though most current bets are in the 23,000 range) govern the development of an enormous number of bodily tissues and processes. In the end, natural selection can only vote up or down on the entire individual, which is a real mash-up of genes and of the characteristics they promote. It cannot single out specific features to favor or disfavor.
This, though, blurs the “fitness” picture. It is, for example, of little value to be the smartest member of your species if, in an environment crawling with predators, you are also the slowestâor even just the most unfortunate. What's more, in an indifferent world your reproductive
may not in the end have much to do with how magnificently you are adapted to any one thing. Whether or not that predator gets you, or whether or not you get the girl, may simply be a function of blind luck and circumstance. The upshot of complications such as these is that evolutionary histories, certainly as we see them reflected in the fossil record, are not produced by the reproductive fates of individuals alone. Indeed, in a world of constantly changing environments, and of ceaseless competition among different kinds of organisms for ecological space, it is more often the fates of entire populations and species that determine the larger evolutionary patterns we observe when we look back at the fossil record.
And there are yet other reasons for not expecting that evolution should produce tidy perfection. As I've already suggested, change can only build on what is there already, because there is no way that evolution can conjure up
solutions to whatever environmental or social problems may present themselves. As a result, we are all built on modified versions of a template ultimately furnished us by an ancient ancestor. History severely limits what you can potentially become not simply because you must necessarily be a version of what went before, but because genomes, dedicated as they are to the propagation of mind-bogglingly complex systems, turn out to be hugely resistant to change. In fact, they provide the ultimate example of “if it ain't broke, don't fix it.” After all, fiddling around with anything as intricate as a genome is asking for trouble: most random changes to a functioning system this complicated simply won't succeed. The fact that changes in the genetic code carry huge risks explains the inherent conservatism of genomes. It also explains why some organisms that look hugely different to the eye have amazingly similar genes: I've heard it said that we share over 40 percent of our genes with a banana, while a gene that is highly active in determining human skin color is also responsible for regulating the dark stripes on the side of a zebrafish.