The Human Instinct: How We Evolved to Have Reason, Consciousness, and Free Will

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Contents

Prologue: Our Story

Chapter 1

Grandeur

Chapter 2

Say It Ain’t So

Chapter 3

Chance and Wonder

Chapter 4

Explaining It All

Chapter 5

The Mind of a Primate

Chapter 6

Consciousness

Chapter 7

I, Robot

Chapter 8

Center Stage

Appendix: The Chromosome 2 Fusion Site

Acknowledgments

About the Author

Notes

Bibliography

Index

To my teachers, especially the incomparable Mr. Paul Zong, who first led me to discover the wonders of biology.

Prologue

Our Story

Stories matter. And once, we had one.

We knew our place. We were the first fruits of creation, stewards of the Earth, masters of the living world. Whether we traced our kind to a rebellious first couple or the upward climb of the Dineh, our people, into the Fourth World, we had a story. That story, or more properly those many stories, confirmed the dignity and value of human existence. They set us apart from the animals. They assured us that our actions mattered, our choices were real, and our lives fit into a fabric of significance.

To be sure, those visions were not all sweetness and light. Many were filled with darkness, many reflected the depths of the human spirit, and many served to spark savage excesses of passion, greed, and even murder. Yet, even in the worst of ages, those narratives filled one of the most basic human needs. They fashioned a sense of place, mission, and value that set our species, for better or for worse, at the pinnacle of the living world. Our Earth was not only the center of the universe; it was home to the only species in that universe that truly mattered.

And then we lost it. Our stories seemed to vanish, and with them our souls, our place in the heavens, and in many ways, ourselves.

The story of that loss has been told many times, sometimes in the context of the enlightenment, of the scientific revolution, or of the great age of discovery. In retrospect, it was surely more triumph than tragedy. The perplexing movements of planets through space yielded to a mathematics of elegance and precision. The bewildering chemistry of matter was reduced to a table of elements, and the elements themselves to aggregates of simple particles. Electricity and magnetism were united, and new tools fashioned to probe ever deeper into the heart of existence.

But of all these great advances, one stood apart in the way it spoke directly to the human conception of self. It was, of course, the theory of evolution by natural selection. To many, it seemed that Charles Darwin’s ideas on the origin of species had drained the lifeblood from our comforting self-portraits. The old certainties were truly gone, and something new had to take their places. But what? In a sense, we had become Darwin’s people, but what could that possibly mean?

Not surprisingly, many were not willing to let the old stories go quietly. While some, like Harvard botanist Asa Gray, were quick to accept Darwin’s great idea, others fought back as though civilization itself were at stake. Books were censored, teachers put on trial, and laws passed to prevent students from learning of any theory teaching that man has descended from a lower order of animals. One such law, in the state of Tennessee, led to the infamous Scopes monkey trial in 1925. That law stood until the Supreme Court struck it down in 1968, but even that great court could not strike down popular resistance to so subversive and revolutionary an idea as evolution.

Even today, many fight back by attacking evolution itself, casting themselves as creationists who reject broad areas of consensus in modern science. To them, cosmology, astronomy, physics, and even geology have conspired to spin an evolutionary epic that is, as one American politician recently claimed, a lie from the pit of hell. Others advance an idea known as intelligent design in which the mechanisms of evolution are rejected as inadequate to account for the complexity of living things. Instead, the actions of a designer are invoked, an intelligent agent standing outside of nature while serving as the grand architect of life. In 2005, this was exactly the argument made in Kitzmiller v. Dover, a highly publicized federal trial in Pennsylvania, a trial in which I served as lead witness against intelligent design.

What both these lines of attack have in common is the call for evolutionary theory to be discarded and replaced by something radically different. The motivations in each case, sometimes expressed quite openly, are not so much to correct a scientific error as they are to replace science itself with a view of human origins consistent with certain religious teachings.

As interesting as it might be to take these arguments apart, point by point, that has already been done, not just in the Kitzmiller trial1 but in a host of popular books by scientists and science writers. No point in beating that poor horse again. But I don’t think the concerns of all who resist evolution should be dismissed as naïve, trivial, or uninformed. In fact, the passionate unease with which some of evolution’s critics regard many of its messages proclaimed in the name of science speaks to the humanist within many scientists, including myself. I believe this unease derives not so much from how we came to be, but rather from what we should make of ourselves as creatures of evolution. In other words, such discontent arises from a fear that accepting the theory of evolution suggests that we are mere products of evolution, neither God’s people nor Darwin’s, but just another of a multitude of creatures pointlessly struggling for existence.

To many, there is a sense that accepting evolution also means accepting a worldview that denies the significance of the human species, explains away our social institutions as artifacts of natural selection, and depicts individual thought and behavior as robotic responses to inputs from the environment. As Sam Harris puts it in his book on free will, the idea that we, as conscious beings, are deeply responsible for the character in our mental lives and subsequent behavior is simply impossible to map onto reality.2 However we may regard ourselves, we are driven, according to Harris, by forces over which we have no real control. In Harris’s interpretation of the evolutionary narrative, we seem to be nothing more than casual throw-offs, byproducts of a universe far greater than our imagination, a universe in which we are no more than thoughtless works of nature.

Evolution, this line of thinking goes, is driven entirely by natural forces, by principles that apply to living and nonliving matter alike. If, as Steven Pinker writes, science has exposed the absence of purpose in laws governing the universe,3 then clearly it means that there is an absence of purpose in the evolutionary process itself. In our modern, sophisticated, rational world, those who hold this view of evolution regard the human presence as nothing special. They see us as cosmic accidents of no significance, depict human art and creativity as the pointless byproducts of natural selection, and regard purpose, self, and even consciousness as chemical illusions that signify nothing, whatever their sound and fury. They, in short, grimly accept the view that we humans matter very little in the grand scheme of things. The story of human evolution, according to those who spin this narrative, is one of pointless accident, dark struggle, and ultimate meaninglessness. No wonder so few want to hear the bad news.

But there is something both illogical and unsound with any narrative that depicts a species able to unravel the story of evolution as insignificant carbon-based fuzz on the surface of a small blue planet. In fact, I emphatically believe there is something special about Homo sapiens, something that truly sets us apart. So it is imperative to ask if we need a fundamental revision of evolutionary theory to account for the specialness of human nature. As we will see, I don’t think so. What we really need is to understand and appreciate the beauty and subtlety of evolution in greater depth than ever.

We are living creatures, to be sure, one species among countless millions that have come and gone in our planet’s lifetime. But we are also uniquely the creatures of music and art, of poetry and laughter, of science, reason, and mathematics. We are the children of evolution in every sense, but we are children of the universe as well, and from that realization comes a new and exhilarating way to see our place among other living things and our home among the stars. It is exactly that place I propose to explore in the pages that follow.

Chapter 1

Grandeur

I think Charles Darwin might have seen his critics coming. Unlike most nineteenth-century works of science, On the Origin of Species is still read today. Much of that attention has been earned by the logical power and simplicity of Darwin’s argument. He begins with a chapter on variation among domestic animals and plants, something that every animal and plant breeder in the England of his time would have been familiar with. Chapter 2 points out that similar variation exists in wild species. Having established that individual members of a species vary in their characteristics, chapter 3 then describes a struggle for existence occurring everywhere in the natural world, producing forces that work remarkably like the hand of a breeder to shape the characteristics of every living species. At that point, the stage is set for the theory of evolution by natural selection, which he introduced by name in chapter 4. The remaining ten chapters enlarge and expand upon the evidence for this theory. The book has been called one long argument, and so it is. A powerful and elegant argument.

But there is another reason The Origin is not only read today, but also widely quoted. While much of the book is mired in scientific minutiae and arcane speculation, as it moves toward a conclusion, The Origin shines with a clarity—even a kind of poetry—rarely seen in a scientific document. In particular, having brought his many arguments to their logical conclusions, Darwin seems compelled to tell us what a wonderful vision of nature he has set before us:

When I view all beings not as special creations, but as the lineal descendants of some few beings which lived long before the first bed of the Silurian system was deposited, they seem to me to become ennobled.1

And why are they ennobled? To Darwin, it is because living species are linked to an almost endless history of struggle and success, often against great odds. So distant is that past, so persistent are the triumphs of those shaped by natural selection, that we may look at them with pride, confident of an equally long and glorious future.

As all the living forms of life are the lineal descendants of those which lived long before the Silurian epoch, we may feel certain that the ordinary succession by generation has never once been broken, and that no cataclysm has desolated the whole world. Hence, we may look with some confidence to a secure future of equally inappreciable length. And as natural selection works solely by and for the good of each being, all corporeal and mental endowments will tend to progress towards perfection.2

Every day, in every way, they’re getting better and better—and so are we. The future is secure, and we’re getting closer to perfection. Fine words, even though most biologists today, myself included, would argue that evolution never produces perfection. In fact, it never even gets close. Success in the struggle for existence is all that matters, so being just good enough to get by is good enough. Always has been, always will be. But Darwin spun things differently.

As stirring as these words about perfection may have seemed to nineteenth-century readers, the final paragraph of The Origin reaches even higher. Darwin wants us to find beauty in the apparent chaos of nature, using the metaphor of a tangled bank alongside a stream to represent the creativity of the evolutionary process:

It is interesting to contemplate an entangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent on each other in so complex a manner, have all been produced by laws acting around us.3

And finally, just in case his readers might be a bit distressed by the realizations that they are merely the products of laws acting around us, he assures us that there is indeed something special, something glorious about the whole process:

There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.4

It’s a stirring sentence. I have often quoted it in my own writings and lectures, and I’m not alone. But if his ideas were on such firm footing, as they clearly were, why did Darwin find it necessary to describe his vision as one of grandeur? I think it may have been because he recognized full well that many, if not most, of his readers would surely think otherwise. If we find our origin in the natural world by means of natural laws, then how can we possibly consider humankind as something apart from the beasts of the field, or even the slimy critters of the soil? Punch, the humor magazine, picked up on this much later with a satirical cartoon on its cover, stating Man is but a worm.5 Building on Darwin’s own writings, the cartoon depicted an earthworm-like creature first arising out of chaos, then morphing into a series of monkeys, next a cave man, then an English aristocrat, and finally into Darwin himself. Hardly a vision rooted in grandeur.

Darwin clearly realized that a little polishing of the human ego would go a long way toward encouraging acceptance of his ideas, and that is exactly what we see in the concluding paragraphs of The Origin. He understood that most would not find this vision grand and decided to do what he could to convince them otherwise. But I’m not sure this appeal to his readers to recognize the grandeur of evolution ever took hold. And I believe that remains the case today, even among many who fully accept the evolutionary story of our origins.

In Ian McEwan’s novel Saturday, his contemporary protagonist begins the single day of the story’s title by contemplating Darwin’s use of that very word. As Henry Perowne, a London neurosurgeon, rises, the phrase comes to him over and over again: There is grandeur in this view of life. Three times he repeats those words, and then remembers why. Last night, in the bath after a tiring day, he had skimmed a biography of Darwin sent him by his all too literate poet daughter, Daisy. He doesn’t remember much—he’d never actually read Darwin himself—but that phrase stuck with him. Musing to himself, he contemplates the forces that drove the great naturalist to compose the final sentence of his masterwork:

Kindly, driven, infirm Charles in all his humility, bringing on the earthworms and the planetary cycles to assist him with a farewell bow. To soften the message, he also summoned up a Creator in later editions, but his heart was never really in it. Those five hundred pages deserved only one conclusion: endless and beautiful forms of life, such as you see in a common hedgerow, including exalted beings like ourselves, arose from physical laws, from war of nature, famine, and death. This is the grandeur. And a bracing kind of consolation in the brief privilege of consciousness.6

We emerge from war, famine, and death, and all we have to show for it is the brief privilege of consciousness? Having rushed headlong through his medical studies and into practice, Perowne, who describes himself as not having touched a non-medical book for fifteen years, permits himself a brief contemplation of the meaning of Darwin’s work. Although a nonbeliever, it leads him to think of religion. He recalls the words of Philip Larkin, where the poet wrote that if he ever needed to construct a religion, he would make use of water.

Perowne, the rationalist, doesn’t hold much stock in Larkin’s answer. But he thinks to himself that if he were ever called in to construct a religion, instead of water,

. . . he’d make use of evolution. What better creation myth? An unimaginable sweep of time, numberless generations spawning by infinitesimal steps complex living beauty out of inert matter, driven on by the blind furies of random mutation, natural selection and environmental change, with the tragedy of forms continually dying, and lately the wonder of minds emerging and with them morality, love, art, cities—and the unprecedented bonus of this story happening to be demonstrably true.7

Demonstrably true, but nonetheless often uninspiring. As he goes about his business, Perowne watches a massive demonstration against the invasion of Iraq but is strangely detached from it by his willingness to appreciate arguments on both sides of the debate. The same profound rationality leads him to dismiss magical realism in literature, even though his daughter urges him otherwise. As the day wears on, a minor traffic accident followed by an attempt by the other driver at extortion places Henry and ultimately his family in danger.

In what might fairly be called the climax of the novel, Henry’s apartment is invaded and his family is held at knifepoint by Baxter, the extortionist. Perowne’s daughter is forced to strip naked, at which point Baxter notices a book of poems with the name Daisy Perowne inscribed on the cover. Intrigued, he demands she read one of her poems. As she seems to comply, Baxter is so taken by the beauty of the poem that he asks her to read it again—at which point it becomes clear to her father and the reader that Daisy isn’t reading one of her own poems at all. Instead, she’s recited, from memory, Matthew Arnold’s classic Dover Beach. For Baxter, the second reading is mesmerizing. His mind seems to wander, which leads to a distracted confrontation in which Perowne and his son are able to overpower and disable the intruders. Afterward, the family realizes that Daisy’s choice of Arnold’s poem, which she had memorized in her youth, had been their literal salvation.

McEwan, the author, clearly wanted his readers to contemplate the particular poem Daisy recited to Baxter. As if to emphasize this point, he included the full text of Dover Beach on two pages following the conclusion of the novel. It makes a fitting afterword to a novel that began with ironic references to Darwin’s view of the grandeur of life. The poem’s thirty-seven lines contain a deeply thoughtful and melancholy reflection on the onrush of the modern age in mid-nineteenth-century Britain. As Arnold writes:

The Sea of Faith

Was once, too, at the full, and round earth’s shore

Lay like the fields of a bright girdle furled.

But now I only hear

Its melancholy, long, withdrawing roar,

Retreating, to the breath

Of the night-wind, down the vast edges drear

And naked shingles of the world.

To Arnold, the world has changed, changed utterly. The roar of the ocean at Dover seems only to bring the eternal note of sadness in, and the modern age, with all its wonders and delights, Hath really neither joy, nor love, nor light, nor certitude, nor peace, nor help for pain. The same is surely true of the day that Henry Perowne, the successful neurosurgeon, has just endured. The disruptions of the modern age, as described in Saturday, intrude despite one’s best efforts to find certitude, joy, and peace. And that promise of grandeur seems to fade away as surely as the ebbing waves at Dover Beach.

A SCIENCE OF LIFE

Arnold’s poem mirrors much of the popular reaction to Darwin. Once the sea of faith was full and round the Earth. But today we see only its long, withdrawing roar as evolution displaces the old certainties. Arnold penned Dover Beach before The Origin, but he published it in 1867, well after Darwin’s book had shocked much of Victorian society. Ever since, it has been seen as emblematic of the crisis of faith brought about by the emergence of modern science. And, as McEwan’s novel demonstrates, that crisis has not abated.

Setting aside, at least for a moment, the sentiments of artistic intellectuals such as Arnold and McEwan, it’s only fair to ask whether and how such concerns have affected the larger culture. In the United States, where outright rejection of evolution is common, one might ask how this came to be. Ironically, one could make a strong argument that it was our country’s enlightened drive for universal high school education that brought it on.

Although the United States helped to pioneer free public education, the level of such schooling did not usually extend to the secondary level until the beginning of the twentieth century. Indeed, only one of my four grandparents, all born around the turn of that century, was educated past the eighth grade. But as states began to mandate higher levels of education, schools expanded and with them the demand for teachers and instructional material such as textbooks. As historian Adam R. Shapiro explains in his book, Trying Biology,8 this led New York–based textbook publishers to expand their offerings beyond the basic lessons in botany and zoology that had been part of the curriculum up to that time. Specifically, they offered new books geared to biology itself as a secondary-level discipline. These texts were skillfully marketed by local and regional sales agents, and in line with the social optimism of the times, had a distinct focus on applying scientific knowledge for the betterment of society. The title of one such text, George Hunter’s Civic Biology, reflected this trend and drew broad conclusions as to how evolutionary principles might be applied to improve society. As such, the book discussed personal hygiene, proper social behavior, and even eugenics. This, of course, was the very textbook used by substitute teacher John Scopes in Dayton, Tennessee.

Compulsory high school education appeared first mostly in urban school districts. This led to a concern that many of the instructional materials clashed with the more rural values of states such as Tennessee, where evolution was regarded as just such an urban value. Also, as Shapiro notes, in many states, interactions between local school districts and avaricious publishers persuaded state authorities to wrest control of textbook purchases from individual schools. This led to state oversight of instructional materials and opened the door to legislative battles over the content of textbooks, battles that persist to the present day. It was in this context that the State of Tennessee passed a law, early in 1925, leading directly to the trial of that substitute biology teacher just a few months later.

The Scopes Monkey Trial, held in Dayton, Tennessee, in 1925, is widely regarded as one of the key events in the social history of the United States. To many Americans, the Scopes trial represents a heroic battle in which reason and science were pitted against ignorance and superstition. The trial was loosely dramatized in the 1955 play Inherit the Wind, which has been adapted for television and motion pictures no less than four times. Evolution, of course, serves as the stand-in for enlightenment and reason in that battle. One of the authors of the play, Jerome Lawrence, made this explicit, admitting in an interview that we used the teaching of evolution as a parable, a metaphor for any kind of mind control [ . . . ] It’s not about science versus religion. It’s about the right to think.9 In the context of the 1950s, when the play first appeared, that lesson might have been applied to the McCarthy hearings. In more recent revivals, however, it is often seen as a statement about the political power of the religious right in America.

But there is an important aspect to the actual Scopes trial that is often overlooked in the rush to draw contemporary lessons from its history. The Butler Act, the Tennessee statute under which John Scopes was prosecuted, did not actually forbid the teaching of evolution, despite a preamble proclaiming its intent to prohibit the teaching of the Evolution Theory. Instead, the act merely made it unlawful to teach any theory that denies the story of the Divine Creation of man as taught in the Bible, and to teach instead that man has descended from a lower order of animals. In other words, it was perfectly okay to teach the evolutionary process as applied to oak trees, spider monkeys, whales, and dinosaurs. But leave Homo sapiens out of it!

Incredibly, under the Butler Act, one could have taught Darwin’s On the Origin of Species cover to cover, since that great work actually said nothing about the origin or descent of man. As Darwin scholars know, his thoughts on those issues would come nearly a decade after The Origin. John Scopes, of course, was convicted of violating the Butler Act, and although his conviction was set aside on a technicality,10 the law remained in force until 1967.

Significantly, the language of the Butler Act was typical of antievolution legislation in many states, including the Arkansas statute invalidated in a landmark 1968 Supreme Court case (Epperson v. Arkansas). That law, passed by popular referendum forty years earlier, also focused on the question of human evolution, making it unlawful for any instructor to teach the doctrine or theory that mankind ascended or descended from a lower order of animal. In retrospect, one might wonder why these statutes were worded in this very precise way, to single out human evolution rather than Darwinian evolution in general. After all, if the history of life on our planet is characterized and explained by evolution, doesn’t that mean our own history is as well?

Organized antievolution groups appreciate exactly this point, and for that reason they strongly oppose just about anything in mainstream science that is consistent with the natural history narrative of evolution. That means disputing the big bang, the age of the Earth, the geologic ages, the abiotic origin of life, and especially the notion that the fossil record contains any evidence of speciation or change over time. They recognize, quite logically, that if science can demonstrate the evolution of anything, then their whole project of depicting humanity as a unique and special creation is doomed.

Most people, however, look at things a bit differently, and the focus of their attention is indeed squarely on the human animal. A recent poll11 in the great state of Texas, well and justly known as a hotbed of antievolution sentiment, demonstrates this. When Texas voters were asked whether life had existed in its present form since the beginning of time, just 22 percent agreed. In contrast, 68 percent asserted that life had evolved over time. That might seem to be a stunning result in such a state, but two elements of this particular question were clearly responsible for the 3:1 margin in favor of evolution. First, the question did not mention human evolution. Second, and just as important, one of the possible answers, which garnered 53 percent support among the respondents, stated life had Evolved over time, entirely through ‘natural selection,’ but with a guiding hand from God.12 By keeping any reference to humans off the table, and by including a response that allowed people to choose evolution without seeming to reject their faith, a large majority of Texans supported evolution by natural selection.

What happened when the same polling group was asked about human evolution? Suddenly the numbers changed. Even when presented with a God guided the process explanation, only 50 percent agreed that humans evolved over time, while fully 38 percent asserted that God created human beings pretty much in their present form about 10,000 years ago. When an even more direct question was asked, support for evolution turned into outright rejection. Did human beings as we know them develop from earlier species of animals? Now just 35 percent agreed, while 51 percent disagreed.

It is true, of course, that nearly all of this resistance is religiously inspired. So, a simplistic analysis of the problem might suggest that in the absence of religion, acceptance of evolution would rise to the high levels we see in secular European cultures today. But that assumes that mere acceptance, however grudging, is a goal to be sought, and that secular cultures have a better understanding of what it means to be human. I’m not sure that is true. Still, among many who embrace Darwin’s legacy, there remains a pessimism, a deep restlessness regarding its ultimate message. To these folks, evolution subverts the once profound distinction between beast and human, it tells us we do not stand at the pinnacle of the living world, and it bequeaths a legacy not from the gods or the stars, but rather one written by the grim dictates of survival, chance, and reproduction. In this view, there may be truth in evolution, but it seems to be a truth that drags us into the muck of struggle and strife rather than lifting us to the imagined heavens of our noblest selves. To the fictional Henry Perowne, this may have been just one more part of the mundane reality of contemporary life, but it is hardly something new. It has, in fact, been part of the heavy baggage of evolutionary thought from its very beginnings, articulated by one of the founders of the theory itself.

DOUBTS OF A FATHER

Nearly all creation stories agree on one thing, which is the uniqueness of the human species and the need for a special story to explain