in the archaeological and biochemical record, and that gives us our most direct information about how we have changed. Fossilized bones and tools can often be dated, permitting us to deduce just when we changed. We shall examine the basis of the conclusion that we are still ninety-eight per cent chimps in our genes, and try to figure out what in the remaining two per cent was responsible for our great leap forward. The second part (Chapters Three to Seven) deals with changes in the human life-cycle, which were as essential to the development of language and art as were the skeletal changes discussed in Part One. It is restating the obvious to mention that we feed our children after the age of weaning, instead of leaving them to find food on their own; that most adult men and women associate in couples; that most fathers as well as mothers care for their children; that many people live long enough to experience being grandparents; and that women undergo menopause. To us, these traits are the norm, but by the standards of our closest animal relatives they are bizarre. They constitute major changes from our ancestral condition, PROLOGUE though they do not fossilize and so we do not know when they arose. For that reason they receive much briefer treatment in human paleontology texts than do our changes in brain size and pelvis, but they were crucial to our uniquely human cultural development, and merit equal attention. With Parts One and Two having surveyed the biological underpinnings of our cultural flowering, Part Three (Chapters Eight to Twelve) considers the cultural traits that we believe distinguish us from animals. Those that come to mind first are the ones of which we are proudest: language, art, technology, and agriculture, the hallmarks of our rise. Yet our distinguishing cultural traits also include black marks on our record, such as abuse of toxic chemicals. While one can debate whether all these hallmarks rank as uniquely human, they at least constitute huge advances on animal precursors. But animal precursors there must have been, since these traits flowered only recently on an evolutionary time scale. What were those precursors? Was their flowering inevitable in the history of life on Earth, for example, so inevitable that we expect there to be many other planets out in space, inhabited by creatures as advanced as ourselves? Besides chemical abuse, our self-destructive traits include two serious enough that they may lead to our fall. Part Four (Chapters Thirteen to Sixteen) considers the first of these: our propensity for xenophobic killing of other human groups. This trait has direct animal precursors—namely, the contests between competing individuals and groups that, in many species besides our own, may be resolved by murder. We have merely used our technological prowess to improve our killing power. In Part Four we shall consider the xenophobia and extreme isolation that marked the human condition before the rise of political states began to make us more homogenous culturally. We shall see how technology, culture, and geography affected the outcome of two of the most familiar historical sets of contests between human groups. We shall then survey the worldwide recorded history of xenophobic mass murder. This is painful material, but here above all is an example of how our refusal to face up to our history condemns us to repeat past mistakes on a more dangerous scale. The other dark trait that now threatens our survival is our accelerating assault on our environment.
This too has its direct animal precursors. Animal populations that for one reason or another escaped control by predators and parasites have in some cases also escaped their own internal controls on their numbers, multiplied until they damaged their resource base, and occasionally have eaten their way into extinction. Such a risk applies with special force to humans, because predation on us is now negligible, no habitat is beyond our influence, and our power to kill individual animals and destroy habitats is unprecedented. Unfortunately, many people still cling to the Rousseau-esque fantasy that this tendency appeared in us only with the Industrial Revolution, before which we lived in harmony with Nature. If that were true, we would have nothing to learn from the past except how virtuous we once were, and how evil we have now become. Hence Part Five (Seventeen to Nineteen) seeks to dismantle this fantasy by facing up to our long history of environmental mismanagement. In Part Five as in Part Four, the emphasis is on recognizing that our present situation is not novel, except in degree. The experiment has already been run many times, and the outcome is there for us to learn from.
This book concludes with an epilogue that traces our rise from animal status. It also traces the acceleration in our means to bring about our fall. I would not have written this book if I thought that the risk was remote, but I also would not have written it if I considered our situation hopeless. Lest any readers get so discouraged by our track record and present predicament that they overlook this message, I point out the hopeful signs and the ways in which we can learn from the past. For those of you who would like suggestions for further reading, a section at the end will guide you to more books and articles on the material of each chapter. A volume that ranges over such a broad canvas as this one has to be selective. Every reader is bound to find some absolutely crucial favourite subjects omitted and some other subjects pursued in inordinate detail. So that you will not feel you were misled, I shall lay out at the start my own particular interests, and where they come from.
My father is a physician, my mother a musician with a gift for languages. Whenever I was asked as a child about my career plans, my response was that I wanted to be a doctor like my father. By my last year in college, that goal had become gently transformed into the related goal of medical research, and so I trained in physiology, the area in which I now teach and do research at the University of California Medical School in Los Angeles.
However, I had also become interested at the age of seven in bird-watching, and I had been fortunate to go to a school that let me delve into languages and history. After I got my PhD., the prospect of devoting the rest of my life to the single professional interest of physiology began to look increasingly oppressive. At that point a happy constellation of events and people gave me the chance to spend a summer in the highlands of New Guinea. Ostensibly, the purpose of my trip—was to measure nesting success of New Guinea birds, a project that collapsed dismally within a few weeks when I found myself unable to locate even a single bird's nest in the jungle. Yet the real purpose of the trip succeeded completely: to indulge my thirst for adventure and bird-watching in one of the wildest remaining parts of the world. What I saw then of New Guinea's fabulous birds, including its bowerbirds and birds of paradise, led me to develop a parallel second career in bird ecology, evolution, and biogeography. Since then, I have returned to New Guinea and the neighbouring Pacific islands a dozen times to pursue my bird research.
I found it hard to work in New Guinea amid the accelerating destruction of the birds and forests that I loved, without getting involved in conservation biology. So I began to combine my academic research with practical work as a consultant for governments, by applying what I knew about animal distributions to designing national park systems and surveying their proposed national parks. It was also hard to work in New Guinea, where languages replace each other every twenty miles, and where learning bird names in each local language proved to be the key to tapping New Guineans' encyclopedic knowledge of their birds, without returning to my earlier interest in languages. Most of all, it was hard to study the evolution and extinction of bird species without wanting to understand the evolution and possible extinction
Those are the paths by which I came to be interested in the particular aspects of humans that are emphasized in this book. I do not feel as if I am thereby making excuses for inappropriately slanted coverage. Numerous excellent books by anthropologists and archaeologists already discuss human evolution in terms of tools and bones, which this book can therefore summarize more briefly. However, those other volumes devote much less space to my particular interests of the human life-cycle, human geography, human impact on the environment, and humans as animals. Those subjects are as central to human evolution as are the more traditional subjects involving tools and bones.
What may at first seem here to be a plethora of examples drawn from New Guinea is also, I believe, appropriate. Granted, New Guinea is just one island, located in a particular part of the world (the tropical Pacific), and hardly providing a random cross-section of modern humanity. But New Guinea harbours a much bigger slice of humanity than you would at first guess from its area. About a thousand of the world's approximately 5,000 languages are spoken only in New Guinea. Much of the cultural diversity that survives in the modern world is contained within New Guinea. All highland peoples in New Guinea's mountainous interior were stone-age farmers until very recently, while many lowland groups were nomadic hunter-gatherers and fishermen practising somewhat casual agriculture. Local xenophobia was extreme, cultural diversity correspondingly so, and travel outside one's tribal territory would have been suicidal. Many of the New Guineans who have worked with me are deadly and expert hunters who lived out their childhood in the days of stone tools and xenophobia. Thus, New Guinea is as good a model as we have left today of what much of the rest of the human world was like until recently.
