About Thumbs, Toes & Tears

And other traits that make us the strange and remarkable creatures we are

From the prologue of Thumbs, Toes and Tears

We are - all of us - freaks of nature. We don't generally see ourselves this way, of course. After all, being human, what could be more ordinary than a human being? But it turns out that our personal (and biased) impressions that we are unremarkable simply don't stand up against the plain, objective facts. The way we walk, for example, teetering on long, paired stilts of articulated bone, is unique among mammals, and as preposterous in its way as elephant trunks and platypus feet. We also communicate by tossing oddly intricate noises at one another, which somehow carry complex packages of feeling, thought and information. We share and understand these sounds, as if they were scents drifting on the wind, and our minds special noses that sniff the fragrance of their meaning. Using them we have been known to change one another's minds, even bring one another to tears. We also seem determined to invent, to the point of being dangerous, incessantly bending the things, living and otherwise, around us to our own ends. Because of this habit, we have, for better or worse, created national economies, erected the pyramids Chichen Itza, fashioned exquisite art, sculpture and music, invented the steam engine, moon rockets, the digital computer, stealth bombers and "weaponized" diseases. Nothing on the planet seems to escape our urge to remake it. These days we are even tailoring genes to remake ourselves.

This book is about how we became the strange creatures we are, and why we do the peculiarly human things we do. It wonders what makes us cry, why we fall in love, invent, deceive, laugh uproariously with close friends and kiss the ones we care about. It asks what evolutionary twists and turns set in motion events that made the symphonies of Mozart, the insights and art of Leonardo, the drama, humor and knee-wobbling poetry of Shakespeare possible, not to mention bad soap operas, Hollywood movies and London musicals. It speculates on why chimpanzees, despite sharing so much of our DNA, do not reflect upon the meaning of life, or if they do why they haven't so far shared their insights. In the end it wonders how you became you and how our species became, of all of the species it could have become, the thoroughly unprecedented one it is.

I know you are interested in these questions because one of the hallmarks of human beings is that we are insatiably curious, especially when it comes to the subject of ourselves. This is not a new insight. Philosophers, poets, theologians and scientists from Plato to Darwin, St. Augustine to Freud have already penned volumes about our humanness that bow endless rows of the sturdiest library shelves. You might ask if these thinkers have fallen gasping to the mat trying to wrestle these questions into submission, why this book should have any better luck. The simple answer is we have far more solid information to work with.

During the past decade enormous strides have been made in two broad scientific fields: genetics and neurobiology. Advances in genetics are helping us gain insights into the way all living things evolve and develop. Each of us has come to exist in the unique form we do because of the combinations of genes that our parents passed along. You are, to a large degree, the person you are because of the messages these genes sent, and continue to send, to the ten thousand trillion cells that have assembled just so to form you. Hardly a day goes by without some news about a remarkable discovery that further illuminates the molecular machinery of the DNA that makes life possible.

The other area is brain research. Being a human being (as opposed to a wasp or a fruit fly), all of your behaviors and actions are not dictated by your genes alone. Your brain holds many of the secrets that make humans human. Genes may be outrageously complicated, but the human brain makes our genetic code look like the crayon drawings of a four year old. Though it weighs a mere three and a half pounds, it consists of 100 billion neurons, each of which is connected in a thousand different ways to the other neurons around it. This means that each waking moment your brain is linked along 100 trillion separate paths, trafficking in thought and insight, processing great streams of sensory input, running the complex plumbing of your body, generating (but not always resolving) all of your colliding and conflicting emotions, conscious and unconscious. These connections, by one estimate, make your possible states of mind during the course of your life greater than all of the electrons and protons in the universe. Given the immensity of this number you are never likely to think all of the thoughts you are actually capable of thinking, nor feel every possible feeling. Nevertheless, each shining day we give it a try.

Over the past decade scientists have been developing ways to scan and reveal in increasingly refined detail of how our brains are constructed and operate. They are far from resolving its mysteries, but we know much more today about its behavior than we did even a short time ago. Positron Emission Tomography (PET) scanning and fMRI (Functional Magnetic Resonance Imaging) are revealing movies of our thoughts, or more precisely the flow of chemicals in the brain as we think and feel. Today we have a far better understanding of how language, laughter and thought play themselves out in the brain than we did as recently as the turn of the century. Right now the resolution of these movies is cellular, but they will soon reveal the brain at a molecular level, making the reading of minds much more than a parlor trick.

Scientists also keep nibbling away at the mysterious edges of paleoanthropology, psychology, physiology, sociology and computer science, to mention only a handful, shedding light bit by bit on the special brand of behaviors we call human. In other words, we remain largely unknown to ourselves, but we are making progress.

All living things are unique. The forces that drive evolution make them so, honing each down to the razor edge of itself, providing it with a handful of qualities that make it the only animal of its kind. The elephant has its trunk. Bombardier beetles manufacture and precisely shoot boiling hot toxic chemicals from their tails. Peregrine falcons have wings that propel them unerringly through the air at 70 miles an hour to their catch. These traits define each of these creatures and determine the way they act. So, I wondered, what unique traits define and shape us?

Six uniquely human physical and behavioral traits eventually surfaced: our big toes, our thumbs, our uniquely shaped pharynx and throat; laughter, tears, and kissing. What, you may ask, can something as common as a big toe, as silly as laughter or as obvious as a thumb, possibly have anything to do with our ability to invent writing, express joy, fall in love or bring forth the genius of ancestral China? What could they have to say about rockets and radio, symphonies, computer chips, tragedy or the spellbinding art of the Sistine Chapel? Just this.

Each of these human accomplishments can trace its origin to these traits. Each marks a fork in the evolutionary road where we went one way and the rest of the animal kingdom went the other, and each opens a small passageway on the peculiar geography of the human heart and mind, marking trailheads that lead to the tangled outback of what makes us tick.

Take the knobby big toes we find at the ends of our feet. If they hadn't begun to straighten and strengthen more than five million years ago our ancestors would never have been able to stand upright, and their front feet would never have been freed to become hands. And if our hands had not been freed we would not have evolved the opposed and specialized thumbs we have which made the first tools possible.

Both our toes and thumbs are linked to the third trait - our unusual throats and the uniquely shaped pharynx inside which enables us to make more precise sounds than any animal. Standing up straightened and elongated our throats so that our voice box dropped. In time that made speech possible, but we also needed a brain that could generate the complex mental constructions that language and speech demand. Because toolmaking required a brain that could manipulate objects, it supplied the neural foundations for logic, syntax and grammar so that eventually it could not only take objects and arrange them in an orderly manner, it could conceive ideas for our pharynx to transform into the sound symbols we call words and organize them so that they made sense as well.

A mind capable of language is also a self-aware mind. Consciousness melded our old primal drives with newly evolved intelligence in entirely unexpected ways that even language couldn't successfully articulate. This explains the origins of three other traits unique to our kind: laughter, kissing and crying. Though we can glimpse their origins in the hoots, calls and ancient behaviors of our primate cousins, no other species carries these particular arrows in their the quivers they use to communicate.

Some may argue we cannot possibly be reduced to six of anything. And that may be true. And some may argue that these traits are not unique to us. Kangaroos stand upright, after all. And dogs whimper and whine. And don't chimpanzees pucker and smack their lips? Yes, but kangaroos, hop, they don't stride, dogs do not cry tears of sorrow or joy or pride. In fact, they don't cry any tears at all. No other animal does, not even elephants, contrary to some apocryphal stories. And while chimps can be trained to kiss, they do not naturally climb, during their adolescence, into the back seats of Chevrolets, or anything else for that matter, to neck.
The larger point is the extraordinary abilities and behaviors we have -- for better or worse -- as a species come from somewhere, and if we keep dogging them with the question "why" long enough, we arrive at their roots. The investigation of one illuminates the other and together, in the peculiar arithmetic of evolution, they eventually add up to the strange, astonishing and perplexing creatures that we are. The point, perhaps, isn't so much to pin ourselves beneath the unforgiving glass of a microscope to arrive at definitive and irrefutable answers. No such answers exist and we are far too complex a race to be reduced to the sum of so many split hairs. Maybe the important thing is to ask interesting questions, and follow where that unusual path takes us. With this book, that is what I have tried to do.

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