Dragons of Eden

by Carl Sagan

  Calculus, Newtonian physics and geometrical optics were all derived by fundamentally geometrical arguments and are today taught and demonstrated largely by analytical arguments: creating the mathematics and physics is more of a right-hemisphere function than teaching it. This is common today as well. Major scientific insights are characteristically intuitive, and equally characteristically described in scientific papers by linear analytical arguments. There is no anomaly in this: it is, rather, just as it should be. The creative act has major right-hemisphere components. But arguments on the validity of the result are largely left-hemisphere functions.

  It was an astonishing insight by Albert Einstein, central to the theory of general relativity, that gravitation could be understood by setting the contracted Riemann-Christoffel tensor equal to zero. But this contention was accepted only because one could work out the detailed mathematical consequences of the equation, see where it made predictions different from those of Newtonian gravitation, and then turn to experiment to see which way Nature votes. In three remarkable experiments—the deflection of starlight when passing near the sun; the motion of the orbit of Mercury, the planet nearest to the sun; and the red shift of spectral lines in a strong stellar gravitational field—Nature voted for Einstein. But without these experimental tests, very few physicists would have accepted general relativity. There are many hypotheses in physics of almost comparable brilliance and elegance that have been rejected because they did not survive such a confrontation with experiment. In my view, the human condition would be greatly improved if such confrontations and willingness to reject hypotheses were a regular part of our social, political, economic, religious and cultural lives.

  I know of no significant advance in science that did not require major inputs from both cerebral hemispheres. This is not true for art, where apparently there are no experiments by which capable, dedicated and unbiased observers can determine to their mutual satisfaction which works are great. As one of hundreds of examples, I might note that the principal French art critics, journals and museums of the late nineteenth and early twentieth centuries rejected French Impressionism in toto; today the same artists are widely held by the same institutions to have produced masterpieces. Perhaps a century hence the pendulum will reverse direction again.

  This book itself is an exercise in pattern recognition, an attempt to understand something of the nature and evolution of human intelligence, using clues from a wide variety of sciences and myths. It is in significant part a right-hemisphere activity; and in the course of writing it I was repeatedly awakened in the middle of the night or in the early hours of the morning by the mild exhilaration of a new insight. But whether the insights are genuine—and I expect many of them will require substantial revision—depends on how well my left hemisphere has functioned (and also on whether I have retained certain views because I am unaware of the evidence that contradicts them). In writing this book I have been repeatedly struck by its existence as a meta-example: in conception and execution it illustrates its own content.

  In the seventeenth century there were two quite distinct ways of describing the connection between mathematical quantities: you could write an algebraic equation or you could draw a curve. René Descartes showed the formal identity of these two views of the mathematical world when he invented analytical geometry, through which algebraic equations can be graphed. (Descartes, incidentally, was also an anatomist concerned about the localization of function in the brain.) Analytical geometry is now a tenth-grade commonplace, but it was a brilliant discovery for the seventeenth century. However, an algebraic equation is an archetypical left-hemisphere construction, while a regular geometrical curve, the pattern in an array of related points, is a characteristic right-hemisphere production. In a certain sense, analytical geometry is the corpus callosum of mathematics. Today a range of doctrines find themselves either in conflict or without mutual interaction. In some important instances, they are left-hemisphere versus right-hemisphere views. The Cartesian connection of apparently unrelated or antithetical doctrines is sorely needed once again.

  I think the most significant creative activities of our or any other human culture—legal and ethical systems, art and music, science and technology—were made possible only through the collaborative work of the left and right cerebral hemispheres. These creative acts, even if engaged in rarely or only by a few, have changed us and the world. We might say that human culture is the function of the corpus callosum.

  * Marijuana is often described as improving our appreciation of and abilities in music, dance, art, pattern and sign recognition and our sensitivity to nonverbal communication. To the best of my knowledge, it is never reported as improving our ability to read and comprehend Ludwig Wittgenstein or Immanuel Kant; to calculate the stresses on bridges; or to compute Laplace transformations. Often the subject has difficulty even in writing down his thoughts coherently. I wonder if, rather than enhancing anything, the cannabinols (the active ingredients in marijuana) simply suppress the left hemisphere and permit the stars to come out. This may also be the objective of the meditative states of many Oriental religions.

  * I wonder if there is any significance to the fact that Latin, Germanic and Slavic languages, for example, are written left to right, and Semitic languages, right to left. The ancient Greeks wrote in boustrophedon (“as the ox plows”); left to right on one line, right to left on the next.

  * A quite different set of circumstances is revealed by another pair of verbal polar opposites: black and white. Despite English phrases of the sort “as different as black and white,” the two words appear to have the same origin. Black comes from the Anglo-Saxon “blaece,” and white from the Anglo-Saxon “bloc,” which is still active in its cognates “blanch,” “blank,” “bleak,” and the French “blanc.” Both black and white have as their distinguishing properties the absence of color, and employing the same word for both strikes me as very perceptive of King Arthur’s lexicographer.

  * The only left-handed American presidents have apparently been Harry Truman and Gerald Ford. I am not sure whether this is consistent or inconsistent with the proposed (weak) correlation between handedness and hemisphere function. Leonardo da Vinci may be the most illuminating example of the creative genius of left-handers.

  * Or down, as in elevator direction lights. Our arboreal ancestors had to be very careful about down.

  8

  THE

  FUTURE EVOLUTION

  OF THE BRAIN

  It is the business of the future to be dangerous.… The major advances in civilization are processes that all but wreck the societies in which they occur.

  ALFRED NORTH WHITEHEAD

  Adventures in Ideas

  The voice of the intellect is a soft one, but it does not rest until it has gained a hearing. Ultimately, after endless rebuffs, it succeeds. This is one of the few points in which one may be optimistic about the future of mankind.

  SIGMUND FREUD

  The Future of an Illusion

  The mind of man is capable of anything—because everything is in it, all the past as well as all the future.

  JOSEPH CONRAD

  Heart of Darkness

  HE HUMAN BRAIN seems to be in a state of uneasy truce, with occasional skirmishes and rare battles. The existence of brain components with predispositions to certain behavior is not an invitation to fatalism or despair: we have substantial control over the relative importance of each component. Anatomy is not destiny, but it is not irrelevant either. At least some mental illness can be understood in terms of a conflict among the contending neural parties. The mutual repression among the components goes in many directions. We have discussed limbic and neocortical repression of the R-complex, but through society, there may also be R-complex repression of the neocortex, and repression of one cerebral hemisphere by the other.

  In general, human societies are not innovative. They are hierarchical and ritualistic. Suggestions for change are greeted with suspicion: they imply a
n unpleasant future variation in ritual and hierarchy: an exchange of one set of rituals for another, or perhaps for a less structured society with fewer rituals. And yet there are times when societies must change. “The dogmas of the quiet past are inadequate for the stormy present” was Abraham Lincoln’s description of this truth. Much of the difficulty in attempting to restructure American and other societies arises from this resistance by groups with vested interests in the status quo. Significant change might require those who are now high in the hierarchy to move downward many steps. This seems to them undesirable and is resisted.

  Man ponders himself. By Vesalius, the founder of modern anatomy.

  Courtesy—Library, The New York Academy of Medicine

  But some change, in fact some significant change, is apparent in Western society—certainly not enough, but more than in almost any other society. Older and more static cultures are much more resistant to change. In Colin Turnbull’s book The Forest People, there is a poignant description of a crippled Pygmy girl who was provided by visiting anthropologists with a stunning technological innovation, the crutch. Despite the fact that it greatly eased the suffering of the little girl, the adults, including her parents, showed no particular interest in this invention.* There are many other cases of intolerance to novelty in traditional societies; and diverse pertinent examples could be drawn from the lives of such men as Leonardo, Galileo, Desiderius Erasmus, Charles Darwin, or Sigmund Freud.

  The traditionalism of societies in a static state is generally adaptive: the cultural forms have been evolved painfully over many generations and are known to serve well. Like mutations, any random change is apt to serve less well. But also like mutations, changes are necessary if adaptation to new environmental circumstances is to be achieved. The tension between these two tendencies marks much of the political conflict of our age. At a time characterized by a rapidly varying external physical and social environment—such as our time—accommodation to and acceptance of change is adaptive; in societies that inhabit static environments, it is not. The hunter/gatherer lifestyles have served mankind well for most of our history, and I think there is unmistakable evidence that we are in a way designed by evolution for such a culture; when we abandon the hunter/gatherer life we abandon the childhood of our species. Hunter/gatherer and high technology cultures are both products of the neocortex. We are now irreversibly set upon the latter path. But it will take some getting used to.

  Britain has produced a range of remarkably gifted multidisciplinary scientists and scholars who are sometimes described as polymaths. The group included, in recent times, Bertrand Russell, A. N. Whitehead, J. B. S. Haldane, J. D. Bernal, and Jacob Bronowski. Russell commented that the development of such gifted individuals required a childhood period in which there was little or no pressure for conformity, a time in which the child could develop and pursue his or her own interests no matter how unusual or bizarre. Because of the strong pressures for social conformity both by the government and by peer groups in the United States—and even more so in the Soviet Union, Japan and the People’s Republic of China—I think that such countries are producing proportionately fewer polymaths. I also think there is evidence that Britain is in a steep current decline in this respect.

  Particularly today, when so many difficult and complex problems face the human species, the development of broad and powerful thinking is desperately needed. There should be a way, consistent with the democratic ideals espoused by all of these countries, to encourage, in a humane and caring context, the intellectual development of especially promising youngsters. Instead we find, in the instructional and examination systems of most of these countries, an almost reptilian ritualization of the educational process. I sometimes wonder whether the appeal of sex and aggression in contemporary American television and film offerings reflects the fact that the R-complex is well developed in all of us, while many neocortical functions are, partly because of the repressive nature of schools and societies, more rarely expressed, less familiar and insufficiently treasured.

  A hunter/gatherer simultaneously stalking prey and educating the young. This life style, which has been characteristic of our species for millions of years, is now almost extinct.

  Photo by Nat Farbman, Life.

  Courtesy of Time-Life Picture Agency, © Time Inc.

  As a consequence of the enormous social and technological changes of the last few centuries, the world is not working well. We do not live in traditional and static societies. But our governments, in resisting change, act as if we did. Unless we destroy ourselves utterly, the future belongs to those societies that, while not ignoring the reptilian and mammalian parts of our being, enable the characteristically human components of our nature to flourish; to those societies that encourage diversity rather than conformity; to those societies willing to invest resources in a variety of social, political, economic and cultural experiments, and prepared to sacrifice short-term advantage for long-term benefit; to those societies that treat new ideas as delicate, fragile and immensely valuable pathways to the future.

  A better understanding of the brain may also one day bear on such vexing social issues as the definition of death and the acceptability of abortions. The current ethos in the West seems to be that it is permissible in a good cause to kill nonhuman primates and certainly other mammals; but it is impermissible (for individuals) to kill human beings under similar circumstances. The logical implication is that it is the characteristically human qualities of the human brain that make the difference. In the same way, if substantial parts of the neocortex are functioning, the comatose patient can certainly be said to be alive in a human sense, even if there is major impairment of other physical and neurological functions. On the other hand, a patient otherwise alive but exhibiting no sign of neocortical activity (including the neocortical activities in sleep) might, in a human sense, be described as dead. In many such cases the neocortex has failed irreversibly but the limbic system, R-complex, and lower brainstem are still operative, and such fundamental functions as respiration and blood circulation are unimpaired. I think more work is required on human brain physiology before a well-supported legal definition of death can be generally accepted, but the road to such a definition will very likely take us through considerations of the neocortex as opposed to the other components of the brain.

  Similar ideas could help to resolve the great abortion debate flourishing in America in the late 1970s—a controversy marked on both sides by extreme vehemence and a denial of any merit to opposing points of view. At one extreme is the position that a woman has an innate right of “control of her own body,” which encompasses, it is said, arranging for the death of a fetus on a variety of grounds including psychological disinclination and economic inability to raise a child. At the other extreme is the existence of a “right to life,” the assertion that the killing of even a zygote, a fertilized egg before the first embryonic division, is murder because the zygote has the “potential” to become a human being. I realize that in an issue so emotionally charged any proposed solution is unlikely to receive plaudits from the partisans of either extreme, and sometimes our hearts and our heads lead us to different conclusions. However, based on some of the ideas in previous chapters of this book, I would like to offer at least an attempt at a reasonable compromise.

  There is no question that legalized abortions avoid the tragedy and butchery of illegal and incompetent “back-alley” abortions, and that in a civilization whose very continuance is threatened by the specter of uncontrolled population growth, widely available medical abortions can serve an important social need. But infanticide would solve both problems and has been employed widely by many human communities, including segments of the classical Greek civilization, which is so generally considered the cultural antecedent of our own. And it is widely practiced today: there are many parts of the world where one out of every four newborn babies does not survive the first year of life. Yet by our laws and mores, infanticide is murder beyond any qu
estion. Since a baby born prematurely in the seventh month of pregnancy is in no significant respect different from a fetus in utero in the seventh month, it must, it seems to me, follow that abortion, at least in the last trimester, is very close to murder. Objections that the fetus in the third trimester is still not breathing seem specious: Is it permissible to commit infanticide after birth if the umbilicus has not yet been severed, or if the baby has not yet taken its first breath? Likewise, if I am psychologically unprepared to live with a stranger—in army boot camp or college dormitory, for example—I do not thereby have a right to kill him, and my annoyance at some of the uses of my tax money does not extend to exterminating the recipients of those taxes. The civil liberties point of view is often muddled in such debates. Why, it is sometimes asked, should the beliefs of others on this issue have to extend to me? But those who do not personally support the conventional prohibition against murder are nevertheless required by our society to abide by the criminal code.

  On the opposite side of the discussion, the phrase “right to life” is an excellent example of a “buzz word,” designed to inflame rather than illuminate. There is no right to life in any society on Earth today, nor has there been at any former time (with a few rare exceptions, such as among the Jains of India). We raise farm animals for slaughter; destroy forests; pollute rivers and lakes until no fish can live there; hunt deer and elk for sport, leopards for their pelts, and whales for dog food; entwine dolphins, gasping and writhing, in great tuna nets; and club seal pups to death for “population management.” All these beasts and vegetables are as alive as we. What is protected in many human societies is not life, but human life. And even with this protection, we wage “modern” wars on civilian populations with a toll so terrible we are, most of us, afraid to consider it very deeply. Often such mass murders are justified by racial or nationalistic redefinitions of our opponents as less than human.