ALSO BY SPENCER WELLS
The Journey of Man
Deep Ancestry
To Pam, for peace, love, and understanding
The gods presented her with a box into which each had put something harmful, and forbade her ever to open it. Then they sent her to Epimetheus, who took her gladly although Prometheus had warned him never to accept anything from Zeus. He took her, and afterward when that dangerous thing, a woman, was his, he understood how good his brother’s advice had been. For Pandora, like all women, was possessed of a lively curiosity. She had to know what was in the box. One day she lifted the lid and out flew plagues innumerable, sorrow and mischief for mankind. In terror Pandora clapped the lid down, but too late. One good thing, however, was there—Hope. It was the only good the casket had held among the many evils, and it remains to this day mankind’s sole comfort in misfortune.
(AS RETOLD BY EDITH HAMILTON)
Contents
Foreword
One: Mystery in the Map
Two: Growing a New Culture
Three: Diseased
Four: Demented
Five: Fast-Forward
Six: Heated Argument
Seven: Toward a New Mythos
Acknowledgments
Sources and Further Reading
Foreword
True, western societies are much better off materially than they were 40 years ago, but why is there so much crime, vandalism and graffiti? Why are divorce rates so high? Why are we seeing declines in civic engagement and trust? Why have obesity and depression reached epidemic proportions, even amongst children? Why do people call this the age of anxiety? Why do studies in most developed countries show that people are becoming unhappier?
—RICHARD TOMKINS,
Financial Times, October 17, 2003
As I write this, I am 36,000 feet above the Arabian Sea, sipping a glass of wine and typing on my laptop. I’m returning from Mumbai, India, where I gave a lecture at a science and technology festival organized by the Indian Institute of Technology. I spent twice as long getting there and back as I did on the ground, and with the ten-and-a-half-hour time change I was more than a little disoriented while I was there. Still, India is one of my favorite countries and it was worth the jet-lag whiplash, bouncing halfway around the world and back over a long weekend.
The students at the institute who invited me wanted to hear about my work on genetics and human migration, a subject I have studied for the better part of the past two decades. The work my colleagues and I have carried out has shown unequivocally that all humans have a recent common origin in Africa, within the past 200,000 years, and that we only started to leave Africa to populate the rest of the world in the past 60,000. I spent an hour describing some of the new data from the field, discussing recent unpublished findings, and generally painting a picture of the genetic history of our species. At the end, as I normally do after such lectures, I took questions. These ranged from technical queries about the laboratory methods we use for analyzing human DNA to more general ones. The final question was something that I’ve been asked many times before, and will certainly be asked in the future: What is the broader relevance of your work?
It does seem somewhat esoteric to study the arcane details of distant human history, I suppose, but it has always fascinated me. With the right samples and a smattering of statistics, it is possible to discern the details of how our species populated the globe. “But why is this important?” the student asked. I began my answer as a scientist, describing the importance of basic research in which there is no particular practical application. Governments fund such work in many subjects, I explained, because it is possible that some new finding may end up being very important in fields that are more pragmatic—medicine, for instance. Moreover, what defines us as a species is our complex culture, and scientific inquiry for its own sake is an important part of understanding our role in the world. Imagine encountering intelligent life from another planet, I said; would such an auspicious meeting include explaining mundane details like how the latest video-game console operates or would it focus on who we are as two highly evolved species and what brought us to our present state of being? We need to learn our history to understand who we are, and to speculate on where we might be going. “L’histoire est un grand présent, et pas seulement un passé,” as the French philosopher Alain wrote. History is a grand view of the present, and not simply something in the past.
But there was another reason this information was important, I explained. We live today in a highly globalized world, one where people come into contact with others they may never have encountered only a century before. Africans mix with Europeans, Asians, and Native Americans to create a social mélange that is unprecedented in human history. Couple this exposure with linguistic and cultural differences, and you have a potentially volatile recipe. We are keenly attuned to such differences, and they help define how we see ourselves. Part of what our genetic work shows, though, is how trivial these differences really are—underneath the surface, at the level of our DNA, we are nearly identical. The broader relevance of our work, I explained, is that we should really start to see past the superficial features that divide us, and start to recognize that we are all part of an extended human family. To the extent that we can see ourselves as connected at the genetic level, we might be able to overcome some of our prejudices.
This notion seemed to have special relevance to the members of this audience, many of whom had recently witnessed the brutal terrorist attack in which Islamic militants from Pakistan had bombed and gunned down people in several locations in south Mumbai and taken control of two landmark hotels, the Taj and the Oberoi. Over the course of four days the terrorists killed 164 innocent people. (Nine of the militants died as well.) For India, the social impact was like 9/11 in the United States, though thankfully with fewer deaths. It would have been natural to feel enraged, to want vengeance, to use this attack as an excuse for further violence. However, the Indian reaction, according to my host at the conference, was not to dwell on negative emotions. “It has brought us all together—all India,” he told me as we were weaving through traffic the night I arrived.
The nature of this whole encounter, along with the quote from Richard Tomkins that begins this foreword, highlights the theme of this book. During my career as a geneticist and anthropologist I’ve been lucky to work with many people around the world, ranging from senior politicians and the heads of major corporations to tribal foragers eking out a precarious existence in remote wilderness locations. What has struck me over and over again is the huge amount of change taking place in the world today, regardless of where one lives. Some of this change is good, such as the overall decrease in poverty during the course of my lifetime and the drop in the birthrate in developing countries. Other things, though, like 9/11 and the terrorism in Mumbai, have not been so welcome. Everywhere there is a feeling that the world is in flux, that we are on the brink of a historic transition, and that the world will be fundamentally changed somehow in the next few generations. The pace of technological innovation is accelerating, and we are all swept up in it. Think of all of the things indispensable to your daily life that you have learned to use only in the past decade or so. Email, Google, instant messaging, and mobile phones spring to mind immediately, but there’s also hybrid car technology, curbside recycling, and social-networking sites like Facebook. All have found widespread application only since the mid-1990s, and yet today we can’t imagine living without most of them. Trying to imagine what the world will be like at the close of the twenty-first century is nearly impossible.
With all of these amazing technological advances, though, has come a great deal of ancillary baggage. The unprecedented rise in chronic disease in Westerniz
ed societies is perhaps the most obvious example. I say “Westernized” rather than “Western” because of the growing incidence of heart disease, diabetes, and plain old obesity in the developing world, particularly in places such as India and China. As these societies become more like our own, they are taking on many of our worst attributes as well. Psychological disorders such as depression and anxiety are also on the rise, and drugs to treat these disorders are now the most widely prescribed in the United States. This seemingly inexorable march toward Western unhealthiness made me wonder why it happened in the first place. Is there some sort of fatal mismatch between Western culture and our biology that is making us ill? And if there is such a mismatch, how did our present culture come to dominate? Surely we are the masters of our own fate and we created the culture that is best suited to us, rather than our culture driving us?
The answer to this question was a long time in coming, much to the chagrin of my patient editors at Random House and Penguin. It took me on a global quest to discover the similarities between what happened thousands of years ago and what is happening now, as we face what promises to be another apparent turning point in our evolution. During the course of researching my first book, The Journey of Man, I was struck by the effects of the agricultural lifestyle on humans living 10,000 years ago in the Middle East. It turns out, as we’ll see in the first chapter, that early farmers were actually less healthy than the surrounding hunter-gatherer populations. So why did the farmers “win” so resoundingly, to the extent that virtually no one on earth today lives as a hunter-gatherer? What follows is an attempt to excavate today’s “archaeological” record to understand the forces that set in motion the agricultural transition and to understand how that decision created the complex world we now live in. If The Journey of Man was about how humans populated the world, this book is about how we have adapted both psychologically and biologically to live in it during a period of enormous change. They form two bookends to a broad view of human history that takes us from the earliest days of our species to where we might be headed as we hurtle deeper into the twenty-first century.
Stewart Brand, paraphrasing Edmund Leach in the opening sentence of the first Whole Earth Catalog in 1968, said it well: We are as gods; it’s time we got good at it. The biggest revolution of the past 50,000 years of human history was not the advent of the Internet, the growth of the industrial age out of the seeds of the Enlightenment, or the development of modern methods of long-distance navigation. Rather, it was when a few people living in several locations around the world decided to stop gathering from the land, abiding by limits set in place by nature, and started growing their food. This decision has had more far-reaching consequences for our species than any other, and it set in motion the events that we will examine in the following chapters. With the power our species has developed as a result of these changes, we must also learn some humility. In today’s world, where small groups of terrorists can inflict lasting damage on the psyche of entire nations, where apparently simple decisions can affect the biological inheritance of generations far in the future, and where more species are likely to go extinct as a result of our actions than at any point in the past 60 million years, it is time to take stock and realize that with great desires come great consequences.
Chapter One
Mystery in the Map
… the most important, most wondrous map ever produced by humankind.
—PRESIDENT BILL CLINTON,
announcing the completion of the draft human genome sequence on June 26, 2000
A map is not the territory it represents.
—ALFRED KORZYBSKI
CHICAGO, ILLINOIS
My cab wove through the midafternoon traffic, tracing an arc along the frozen shore of Lake Michigan. On my right, the buildings of one of the world’s tallest cities stabbed toward the sky, steel and glass growing out of the Illinois prairie like modern incarnations of the grass and trees that once lined the lake. A thriving metropolis of nearly three million people, Chicago boasts an airport that was once the world’s busiest (it’s now second), with over 190,000 passengers a day passing through its terminals—including, on this particular day, me. This sprawling city prides itself on its dynamic, forward-looking culture—the “tool maker” and “stacker of wheat,” as Carl Sandburg called it. Not the most obvious place to come looking for the past.
The lake took me back in time, though—way back, before it was even there. Lake Michigan is actually a remnant of one of the largest glaciers the earth has ever seen. During the last ice age, the Laurentide ice sheet stretched from northern Canada down along the Missouri River, as far south as Indianapolis, with its eastern flank covering present-day New York and spilling into the Atlantic Ocean. When it melted, around 10,000 years ago, the water coalesced into the Great Lakes, including Michigan. Looking out the window of my cab, at the strong winds ripping across the expanse of ice reaching out from the Chicago shoreline, I felt like history might be rewinding itself. The ice age could have looked a bit like this, I thought.
This wasn’t just idle musing; I’ve spent my life studying the past, effectively trying to rewind history. I became obsessed with it as a child, and devoured anything and everything on ancient Egypt, Greece, and Rome, the great empires of the Middle East, and the European Middle Ages. In high school biology classes I started to think about much more ancient history, its actors playing their parts on a geological stage. I added the history of life to my passion for written history, and when I got to college I decided to study the record written in our own history book—our DNA. The field I became interested in is known as population genetics, which is the study of the genetic composition of populations of living organisms, using their DNA to decipher a record of how they had changed over time. The field originated as an attempt to piece together clues about how our ancestors had moved around, how ancient populations had mixed and split off from each other, and how they had diversified over the eons. In short, really ancient history.
And my quest had brought me here, for the second time. My last visit to the University of Chicago—where I was headed from O’Hare—had been eighteen years earlier, in February 1989, when I was considering going there for graduate school. The lake was frozen then as well, and my early-morning walks to meetings at the university in single-digit temperatures played a small role in my decision to head to school in the somewhat warmer city of Cambridge, Massachusetts. Despite my decision, the University of Chicago was, and is, an outstanding university. Its faculty boasts brilliant researchers and thinkers in many fields, from economics to literature to physics. I had come back to visit one of them.
Jonathan Pritchard had been a graduate student at Stanford when I was a postdoctoral researcher there, and I still clearly remember his early presentations to our group. His mathematician’s mind, coupled with his deep understanding of the processes of genetic change, made him a real asset to the group. We overlapped again briefly when I was at Oxford, but we lost touch over the years, although I followed his work from the papers he published in scientific journals. It was one such publication that led me to get in touch with him to discuss his findings.
This paper, published in the journal PLoS Biology (PLoS stands for Public Library of Science, a prestigious family of scientific journals available on the Web), described a new method his team had developed to look at selection in the human genome. Selection is the Darwinian force that has created exquisite adaptations like the eye and the ear, as well as most of the other really useful traits we humans have. As Darwin taught us, small changes that are advantageous in some way give an organism a greater chance of surviving and reproducing in the perpetual rat race that is life. Since all of these selected characteristics ultimately have their origin in the way our DNA is put together, it is logical to look to our genes to find out about what made us the way we are.
The search for selection at the genetic level has a long history, dating back to way before Watson and Crick deciphered the structure of DN
A in the early 1950s. Pioneering scientists such as Theodosius Dobzhansky, a Russian immigrant to America who helped create the modern science of population genetics back in the early twentieth century, were obsessed with looking for genetic changes that could be explained only by invoking Darwin’s seemingly magical force. In the days before DNA sequences could be studied directly, though, researchers observed large-scale changes in the structure of fruit fly chromosomes. (Fruit flies being the geneticist’s favorite model organism, mostly because their huge salivary gland chromosomes made their patterns of genetic variation easy to study in the days before DNA sequencing.) But while they found some evidence for the past action of selection in fruit flies, the ultimate cause of the patterns they observed remained elusive.
Once it was known that DNA was the ultimate source of genetic variation, and its structure had been discovered and methods developed to determine the actual sequence of the chemical building blocks that make up the double helix (I’m glossing over about fifty years of pioneering research here), population geneticists began to look at DNA sequences directly. In the early days (only around twenty-five years ago), because of technical limitations, they could examine just a few small regions in the genome (the sum total of the genetic building blocks in an individual), and the search for evidence of natural selection usually proved fruitless. It was only with the completion of the Human Genome Project in the late 1990s, and the massive technological breakthroughs that it spawned, that scientists could finally start to reassess the issue that had obsessed Dobzhansky and his colleagues nearly a century before: Is it possible to find evidence of selection at the DNA level and, perhaps more interestingly, can we figure out why it has taken place?
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