THe Third Chimpanzee: the evolution and future of the human animal

Harper Collins, New York, 1991

The Third Chimpanzee: The Evolution and Future of the Human Animal, published in 1991, was the first of my six books written for the general public.  I look back on it today as the least tightly organized, but the most enjoyable, best written, and most wide-ranging, of my books. 

As it turned out, writing The Third Chimpanzee defined a crossroads in my life: a shift from writing technical articles on narrow subjects, destined to be read by just a handful of academic experts, to writing books on big subjects, aimed both at experts and at the general public. 

Like most children, while growing up I was fascinated by a much wider range of things than an adult could pursue professionally as a career.  However, when I graduated college and chose a career of academic research, I discovered that scholars are expected to devote their lives to studying and writing about just one tiny slice, occasionally a few tiny slices, of life’s broad palette.  By 1976, I had published papers only about two slices of the palette: fluid transport by the gallbladder, and New Guinea birds.  A chance opportunity to write a popular magazine article in 1976 did lead to invitations to write for more magazines, about subjects far afield: volcanoes, sex, wheels, tribal peoples, and other topics.  But although these magazine articles gave me an excuse to spend some time re-exploring my childhood range of interests, I was still spending most of my time writing about gallbladders and New Guinea birds for the few experts interested in those subjects.

Then in 1985 came a phone call that changed my life. The director of the Fellows' Program of the MacArthur Foundation phoned to say that I had just been awarded a MacArthur Foundation Fellowship for five years, with no strings attached. The awards were made to me and to two dozen other people in the belief that we had something unusual to contribute to the world, and that five years of freedom might encourage and permit us to contribute more effectively.  Instead of being elated by this unexpected good fortune, I found myself depressed for the only time in my life.  It took me a week to realize why. The award was in effect a statement: Jared, the MacArthur judges think that you could contribute more to the world than an understanding of gallbladders and New Guinea birds; you haven't been living up to your potential; what are you going to do about it?

My answer to myself unfolded gradually, spurred  by another  phone call, this time from a scientist friend who had decided to make a full-time career out of writing for the general public. I realized that I didn't have to give up gallbladders, New Guinea birds, or my university teaching job,

but I could still put a lot more thought into writing for the public. The magazine articles that I had written between 1976 and 1985, and the public's response to them, had convinced me that I enjoyed writing for the public and that the public enjoyed my writing. I could contribute far more to the world by weaving together and explaining information drawn from geography, history, science, languages, and music than I could by making new discoveries about narrow technical subjects.  The birth of my twin sons in 1987 also made me appreciate that making further such discoveries wasn’t the most effective way for me to try to improve the conditions of the world in which my sons would be living out their lives. 

But my background and my ongoing technical research weren't wasted, because they gave me the scientific outlook and much of the technical background for weaving together geography and those other subjects. To succeed, a book about science for the public has to please two audiences. First, it has to be interesting and understandable to the general public; my childhood range of interests, my mother's influence, and my school's training in how to write had equipped me to address that first audience. Second, the book has to pass technical critical appraisal by scientists expert in the book's various subjects. The only way that I could hope to satisfy that second audience was by discussing those subjects at length with those experts, and by asking them to read and correct my drafts. I had already found, in writing magazine articles, that most scientists whom I asked to help me in understanding their work were pleased to do so, pleased to meet someone else sharing their enthusiasm for their specialty, and generous with their time and knowledge.

I began writing The Third Chimpanzee during the years of my MacArthur Fellowship, completed the manuscript's draft just before the end of my fellowship term in 1990, and published it in 1991.  The book deals with what struck me then as the biggest and most fascinating question of science and  history, which drew on the widest range of my interests: how humans evolved from being just another big animal to acquiring language and music, becoming aware of history and geography, and understanding birds and the stars. 

The Third Chimpanzee begins with a major puzzle that emerged in the 1980’s from studies of DNA, the genetic material.  We routinely draw a fundamental distinction between humans and animals.  Humans write, read, talk, and build telescopes and bombs; no animal does any of those things.  Although it’s been clear since Darwin that humans evolved from animals, and that our closest animal relatives are the African great apes (the chimpanzees and gorillas), the enormous differences between us and (other) animals would have made it a reasonable guess that we shared even with chimpanzees and gorillas only a small fraction of our DNA: 20%? 40%?? 65%???  Then came the bombshell of DNA studies of the 1980’s: humans and chimpanzees share more than 98% of their DNA!  Somewhere within the remaining 2% must reside the small differences that have huge consequences, and that let us write, read, talk, and build telescopes and bombs, while we confine our speechless and bomb-less close relatives the chimpanzees and gorillas to cages and zoos.  The first two chapters of The Third Chimpanzee suggest what those decisive small differences might be.

Obviously, at least some of those differences involve our brains, which are four times larger than those of chimpanzees.  Also frequently discussed is our upright posture, freeing up our hands for using tools.  Less often discussed is our distinctive sexuality, which occupies the next five chapters of The Third Chimpanzee.  Adult humans are approximately as big as adult chimpanzees, and smaller than adult gorillas and orang-utans.  Why, then, do male humans have a considerably larger penis than any of those apes, and testes larger than those of gorillas and orang-utans but smaller than those of chimpanzees?  Does the extra length of the human penis constitute wasted protoplasm that would have been more useful if it had been invested instead in a larger brain or a sixth finger?  Most of us don’t pick our mates and sex partners by sober evaluation of an explicit checklist of attributes.  Instead, we come into a room, and within a few seconds we sense who attracts us, even though we usually can’t specify what attributes rang a bell in us within those few seconds.  What goes into those quick choices?  Why do men and women differ in their interests in and motives for extramarital sex and other behaviors related to sex and reproduction?  The Third Chimpanzee began my academic exploration of human sexuality, which I expanded six years later in my book Why Is Sex Fun?

The Third Chimpanzee then focuses on several traits that apparently are uniquely human and absent among animals: language, art, agriculture, and drug abuse.  However, the discoveries that we humans are genetically so similar to chimpanzees, and that the human evolutionary line diverged from the chimpanzee line only about 6,000,000 years ago, suggests that our language, art, agriculture, and drug abuse must have animal antecedents: where among animals can we recognize those antecedents?  While no animal on our planet has evolved antecedents of our space probes and radio signals that we send out of our solar system, we know that there are billions of billions of stars other than our sun, that many of the stars recently surveyed have planets orbiting them, and that some of those planets are likely to offer to conditions suitable for the evolution of life.  Why, then, haven’t we already been contacted by the seemingly inevitable space probes, radio signals, and intelligent beings that must have repeatedly arisen elsewhere in the universe?  Astronomers (Earthly human ones) in 1974 tried to establish a dialog with those expected intelligent extraterrestrials, by sending radio signals describing what we Earthlings are like, and where our planet is located.  I argue that those astronomers made what could have been the most horrible, suicidally imprudent mistake ever committed by any Earthlings – if it were not for the reasons why I’m confident that we’ll never make contact with intelligent extraterrestrials.

The next-to-the-last section of The Third Chimpanzee explores a theme that I expanded in my subsequent book Guns, Germs, and Steel: how some human groups have spread at the expense of other human groups.  One of the chapters is about the most debated question of historical linguistics: the question of whence, when, and how speakers of Indo-European languages (the language family that includes English, French, Russian, and Urdu) spread at the expense of other languages.  Included in this section of The Third Chimpanzee is also the grimmest chapter in any of my books, on genocide.  All of us old enough to have seen, in photos or first hand, the liberated Nazi concentration camps in 1945 swore then, “Never again!” Despite that determination, since 1945 there have been at least two genocides that produced body counts exceeding 1,000,000, and four more with counts exceeding 100,000.  Why do people do it, and what can be done to stop it?

The last three chapters of The Third Chimpanzee are on a subject expanded 14 years later in my book Collapse: how we humans often inadvertently destroy the natural resources on which we depend, and thereby threaten our own survival.  Already in 1991, ample information was available to tell the stories of the destruction of the moas and other large birds of New Zealand, of the elephant birds and large mammals of Madagascar, and of the giant ground sloths and most of the other large mammals of North and South America.  Since I first released The Third Chimpanzee in 1991, scientists have accumulated exciting new discoveries in all areas that the book discussed.  A new edition released in 2006 adds a section summarizing some of those exciting discoveries, which enrich without fundamentally overturning our understanding that I originally presented.