The Accidental Species: Misunderstandings of Human Evolution (20 page)

In the end, one can only feel a kind of pity for creationists. Many believe in the literal truth of Genesis, despite the fact that the Bible was written at various times by different hands, and despite the fact that the text has been translated into English from classical Hebrew, a language so tricky that people of formidable learning, such as St. Jerome, Thomas Aquinas, Rashi, and Maimonides, spent their lives trying to understand its nuances in order to extract meaning from the same scriptures to which many people of perhaps lesser intellects cleave without question. Those living in medieval times had perhaps no good reason to doubt the literal truth of the Bible. People living today do not have this excuse.

Evolution itself, however, is
not
in question.

Evolution happened, and there is, out there, a true skein of ancestry and descent between some primordial blob and every creature living or extinct, but we can never trace it with absolute certainty, or if we stumble across part of it, we can never know that we have done so.

What is in question, however, are the ways we interpret the evidence given to us by fossils. It’s not that fossils don’t provide us with primary evidence for evolution as a fact, because they plainly do so. What is at stake is a common misreading of evolution that flatters our prejudices: that we are the pinnacle of creation, and the various stages toward this manifest destiny can and should be discernible in the fossil record. The picture of a simple, linear evolution, with each species of human being succeeded by a more sophisticated form, “culminating in Man,” can only be extremely inaccurate, and also misleading.

Although it’s fun to take potshots at creationist misbehavior, it is perhaps worth asking why creationists remain indefatigable despite the evidence, devoting such time and effort and skill to monitoring the writings of “evolutionists” and extracting such morsels that suit them. When you take a step back, you can see that we have seen this mindset elsewhere, among those scientists who look into the unknown and see a set of circumstances that dashes the more comforting scenarios on which they have perhaps based their reputations. I think that what motivates creationists and such scientists is a very human fear of the unknown, and the uncertainty that accompanies it.

The fundamental difference between religion and science is that the former is all about the celebration of certainty, whereas the latter is all about the quantification of doubt. Creationists understand this instinctively. What they cannot afford to see happen is that people start wondering about their place in the universe, and asking whether the certainties in which they have been raised might not be so certain after all. They are so desperate to avoid this that they have tried to subvert science by invoking a bogus replacement called “creation science,” perhaps the most shocking oxymoron ever invented, given that creationism and science concern such fundamentally different things.

Scientists have been less ready to appreciate this distinction, to their cost. When confronted by creationists, they are inclined to close ranks and present a united front of “fact” against “mythology.” Such a strategy only plays into the creationists’ hands, leaving them free to mine the works of evolutionary biologists for quotes—the subtext being that scientists are always squabbling behind the scenes, and the united front they want you good honest folks to believe is a cover-up.

In my view the best way that scientists can confront creationism is to be as honest as possible. Science is not all about truth given to us by authority, but doubts that arise from the ground up. You, the citizen, should never be afraid to ask a silly question—and you, the scientist, should never be afraid to admit that you don’t know the answers.

So much for the fossils. What of humans living today? What actually defines a human being, so that you can tell one apart from, say, a postbox, or the back end of a cow? What is Man, if no longer the microcosm that measures the macrocosm? To quote scripture again, “What is man, that thou art mindful of him?” (Psalms 8:4).

My task in the rest of this book is to show that this question is meaningless. Were one to accept the argument I put forward in
chapters 2–5
of this book, the very idea of a distinctive nature of humanity is already questionable. Once one acknowledges that the ladder of creation with
Homo sapiens
at the top is the result of a fundamental misreading of evolution, you can see that when viewed objectively, we humans are no more or less deserving of special consideration than any other species. There is certainly nothing so special about humanness—as opposed to hamsterness or geraniumness—that demands the elevation of humans to a higher order of being.

Those of a certain turn of mind or upbringing will no doubt balk at this, saying that humans are different from other animals (and plants, and bacteria, and fungi, and so on) because they have an immortal soul. It’s hard to argue against convictions founded on belief rather than empirical evidence, except to counter that each and every species has attributes that allow us to recognize it as such. The Madagascar star orchid, for example, is recognizable by the extraordinarily long floral spurs of its flowers, penetrable only by the very long tongues of a particular species of moth. Such features can be identified and quantified, which cannot be done for the soul, begging the question of the existence of such an attribute.

Even if we leave such imponderables as the existence of the soul to theologians and philosophers, we run into another problem: it’s very hard to define what we think is special about humanity because it’s we, the humans, who are composing the definitions. Objectivity is impossible. The validity as such of any we recognize in ourselves is compromised by an unavoidable subjectivity. Were we all Madagascar star orchids, we would no doubt measure our exalted state by the lengths of our floral spurs relative to those of other orchids.

In the rest of this book, I take a brief tour of several attributes that at some time or another have been regarded as unique to humans. These include bipedality, technology, intelligence, language, and finally sentience or self-awareness. It turns out that most if not all have been seen in one or more nonhuman species—or once one has accounted for a human bias in investigating such attributes, they turn out to be no more special than any other feature of any other organism.

The order in which I examine these attributes is not random, but dictated by how easily we can find actual biological evidence for the evolution of these traits.

Bipedality, for example, can be assessed directly, by looking at fossil bones. We can judge by direct inspection whether a given fossil crea
ture habitually walked on its hind legs, or not. So much so that bipedality is seen as a hallmark of the hominins. A fossil ape is marked as belonging to the hominins if it is bipedal, almost without reference to any other feature. From this is would be easy to imbue the acquisition of bipedality as something special, the first step (pun intended) in the inevitable journey to the human state, as if technology, language, intelligence, and so on would surely follow. Bipedality, however, is just one peculiar posture adopted in a group of animals in which the adoption of peculiar postures is commonplace. Human bipedality is a posture seen nowhere else—but one could say the same for knuckle walking in chimps and gorillas, brachiation in gibbons, and the four-handed swing of orangutans. Furthermore, there have been one or two fossil apes, unrelated to hominins, that were more or less bipedal, and their fate was extinction without achieving technology, language, and so on (as far as we know).

Technology, too, leaves traces in the historical record, although—as we have seen—it is not always easy to link a tool with its maker. When the first stone tools were discovered at Olduvai Gorge alongside the remains of fossil hominins such as
Homo habilis
, people tended to associate the fact of toolmaking with increased intelligence, in particular an attribute known as “planning depth.” To make a tool, a creature should have some “idea” of what the result should look like, or be used for, and therefore have some notion of the future and its place within it. Subsequent work has questioned this idea in two ways.

First, other animals are known to make and use tools. Tool use has been seen in apes, various birds, even octopi, in the sense that an animal will use some object to help it achieve some goal that it would not manage unaided. In some cases the object has even been modified for use—an important distinction. This questions the idea that tool use is a distinctively human attribute.

Second, if tools—or technology—can be defined loosely as devices created by the modification of materials to achieve some specific end, then many organisms have produced technology that makes the earliest stone tools look puny indeed. One might include termite mounds, the nests of bowerbirds, bacterial stromatolites, or even the Great Barrier Reef, as examples of technology. One could always object by saying that such structures are not technological because they were not made using “planning depth,” but such objections run into problems of subjectivity. How can one “know” what a New Caledonian crow is “think
ing” while it fashions a piece of leaf into a probe? Is it thinking about how it will use the tool it is making? Is it thinking about something else entirely? Is it thinking at all?

One does not, in fact, have to inquire as to the thoughts of crows, because there are good arguments for saying that the earliest stone tools, beautiful though they are, required as much planning depth to produce as the nest of a bowerbird—in which case one can say that stone tools are no more “special” than any other structure created by living organisms. The alternative is outrageous—that organisms as “lowly” as bacteria, coral polyps, or bacteria have “planning depth.”

There is a third possibility, however, which is that notions such as “planning depth” are entirely illusory and products of the view of human evolution that is narrative and linear. In the real world, organisms just do what they do because that’s what they need to get by on Darwin’s tangled bank. Bees make beautiful honeycombs, coral polyps make mighty reefs, and humans make shoes, ships, and sealing wax, and one need not inquire as to their internal motivations, if any, to assess the adaptive value of these attributes to the organisms concerned.

Technology is usually seen as a hallmark of intelligence, but once one acknowledges that the link between the two is tenuous at best, one starts to wonder what intelligence is, such that it constitutes a unique attribute of humans. There are perhaps few points of discussion more emotive than the meaning of “intelligence.” Like the mythical city that is forever on the horizon but that can never be reached, the meaning of intelligence has forever remained beyond our grasp. How is it defined? How is it measured? Do any measurements (such as “intelligence quotient” or IQ) mean anything apart from the ability to do IQ tests? Will such tests only ever be able to assess aspects of that thing we call intelligence, rather than intelligence itself? In which case, can intelligence be thought of as a discrete, unified attribute, rather than a set of attributes unified after the fact? Is intelligence—whatever it is—heritable?

Intelligence is something like jazz—you know it when you find it, but it’s almost impossible to define. And if measuring intelligence in humans is difficult, measuring it in other species is probably impossible. You might regard someone who can solve the
Times
crossword in less than twelve minutes as intelligent—but this ability might say as much about a person’s upbringing or cultural milieu as any innate capacity. No crow or dolphin or octopus—all animals commonly regarded as intelligent—has ever been caught even attempting the
Times
crossword.

Scientists have sought to understand the evolution of intelligence by fairly crude measures such as brain size or brain volume relative to body mass, but this idea soon runs into problems.
Homo floresiensis
had a very tiny brain indeed, but appears to have made tools (not that this need say much about intelligence, as I noted above). Other animals regarded as intelligent, such as crows, have higher brain volumes relative to body mass (the “encephalization quotient” or EQ) than other birds seen as less intelligent—but their brains are tiny in absolute terms, are as capable in many respects as those of humans, and are in any case constructed entirely differently. All of which leaves any simple equation of brain size with intelligence gasping in the dirt.

Language leaves no fossil record. But when we listen to the kind of language we use every day, we can’t see much distinction between the messages that language conveys and the messages that animals exchange, even though they appear mute—messages about social and sexual status. Anthropologist Robin Dunbar thinks that language originated as a form of social grooming, perhaps no different, qualitatively, than baboons picking lice off one another’s fur. It is perhaps no coincidence that people conventionally greet one another with inquiries as to their state of health—one might say the same of dogs who, on meeting, sniff one another’s bottoms. Human language is special only in its peculiar mode of delivery, not in its function. It is also probably no coincidence that no human group so far discovered is without language, so it requires neither special skill nor intelligence to master.

Sentience is perhaps the knottiest problem of all, because we have to be self-aware to discuss it—or do we? I shall propose, perhaps surprisingly, that sentience is a phenomenon that we experience relatively rarely, if at all, and can often be regarded as a syndrome of teenagers and young adults whose brains are in the throes of development. On the contrary, twenty-four-hour sentience would be a debilitating handicap rather than an evolutionary advantage. Moreover, recent work shows that at least some nonhuman animals, crows in particular, are capable of behavior that we might regard as sentient, suggesting that self-awareness is not an attribute unique to humans or even mammals.

On the other hand, our perception of sentience might itself rest on a grave error. As Daniel Dennett describes in
Consciousness Explained
, it depends on the ability to imagine ourselves as participants in the drama of our own lives, which depends on a conceit called the “Cartesian theater,” which is itself flawed. If this flawed model of sentience applies to
the way in which we think other sentient animals think, then sentience is a red herring that applies as much to other animals as it does to humans. We see it in animals because that’s what we see in ourselves.