The Dragons of Eden

by Carl Sagan

  The computer terminal is a commonplace on the Dartmouth campus. A very high proportion of Dartmouth undergraduates learn not only to use such programs but also to write their own. Interaction with computers is widely viewed as more like fun than like work, and many colleges and universities are in the process of imitating and extending Dartmouth’s practice. Dartmouth’s preeminence in this innovation is related to the fact that its president, John G. Kemeny, is a distinguished computer scientist and the inventor of a very simple computer language called BASIC.

  The Lawrence Hall of Science is a kind of museum connected with the University of California at Berkeley. In its basement is a rather modest room filled with about a dozen inexpensive computer terminals, each hooked up to a time-sharing mini-computer system located elsewhere in the building. Reservations for access to these terminals are sold for a modest fee, and they may be made up to one hour in advance. The clientele is predominantly youngsters, and the youngest are surely less than ten years old. A very simple interactive program available there is the game Hangman. To play Hangman you type on a fairly ordinary typewriter keyboard the computer code “XEQ-$HANG.” The computer then types out:

  HANGMAN

  CARE FOR THE RULES?

  If you type “YES”, the machine replies:

  GUESS A LETTER IN THE WORD I’M THINKING OF.

  IF YOU ARE RIGHT, THEN I WILL TELL YOU. BUT

  IF YOU ARE WRONG (HA, HA) YOU WILL BE CLOSER

  (SNICKER, SNICKER) TO DEATH BY HANGING!

  THE WORD HAS EIGHT LETTERS.

  YOUR GUESS IS …?

  Let us say you type the response: “E”. The computer then types:

  — — — — — — — E

  If you guess wrong, the computer then types out an engaging simulacrum (within the limitations of the characters available to it) of a human head. And in the usual manner of the game there is a race between the gradually emerging word and the gradually emerging form of a human being about to be hanged.

  In two games of Hangman I recently witnessed, the correct answers were “VARIABLE” and “THOUGHT”. If you win the game the program—true to its mustache-twirling villainy—types out a string of non-letter characters from the top row of the typewriter keyboard (used in comic books to indicate curses) and then prints:

  RATS, YOU WIN

  CARE FOR ANOTHER CHANCE TO DIE?

  Other programs are more polite. For example, “XEQ-$KING” yields:

  THIS IS THE ANCIENT KINGDOM OF SUMERIA, AND YOU ARE ITS VENERATED RULER. THE FATE OF SUMERIA’S ECONOMY AND OF YOUR LOYAL SUBJECTS IS ENTIRELY IN YOUR HANDS. YOUR MINISTER, HAMMURABI, WILL REPORT TO YOU EACH YEAR ON POPULATION AND ECONOMY. USING HIS INFORMATION YOU MUST LEARN TO ALLOCATE RESOURCES FOR YOUR KINGDOM WISELY. SOMEONE IS ENTERING YOUR COUNCIL CHAMBER…

  Hammurabi then presents you with relevant statistics on the number of acres owned by the city, how many bushels per acre were harvested last year, how many were destroyed by rats, how many are now in storage, what the present population is, how many people died of starvation last year, and how many migrated to the city. He begs to inform you of the current exchange rate of land for food and queries how many acres you wish to buy. If you ask for too much, the program prints:

  A statue of Gudea, the Neo-Sumerian governor of Lagash, about 2150 B.C. Cuneiform writing, which covers Gudea’s robe, was widespread in this era, the Third Dynasty of Ur, a time of maritime trade, commercial exuberance, and the earliest known legal code—all intimately connected with the proliferation of literacy.

  The Metropolitan Museum of Art, Purchase,

  The Harris Brisbane Dick Fund, 1959. Reproduced by permission.

  HAMMURABI: PLEASE THINK AGAIN. YOU HAVE ONLY TWENTY-EIGHT HUNDRED BUSHELS IN STORE.

  Hammurabi turns out to be an extremely patient and polite Grand Vizier. As the years flicker by, you gain a powerful impression that it may be very difficult, at least in certain market economies, to increase both the population and landholdings of a state while avoiding poverty and starvation.

  Among the many other programs available is one called Grand Prix Racing which permits you to choose from among a range of opponents, running from a Model T Ford to a 1973 Ferrari. If your speed or acceleration are too low at appropriate places on the track, you lose; if too high, you crash. Since distances, velocities and accelerations must be given explicitly, there is no way to play this game without learning some physics. The array of possible courses of computer interactive learning is limited only by the ingenuity of the programmers, and that is a well that runs very deep.

  Since our society is so profoundly influenced by science and technology, which the bulk of our citizens understand poorly or not at all, the widespread availability in both schools and homes of inexpensive interactive computer facilities could just possibly play an important role in the continuance of our civilization.

  The only objection I have ever heard to the widespread use of pocket calculators and small computers is that, if introduced to children too early, they pre-empt the learning of arithmetic, trigonometry and other mathematical tasks that the machine is able to perform faster and more accurately than the student. This debate has occurred before.

  In Plato’s Phaedrus—the same Socratic dialogue I referred to earlier for its metaphor of chariot, charioteer and two horses—there is a lovely myth about the god Thoth, the Egyptian equivalent of Prometheus. In the tongue of ancient Egypt, the phrase that designates written language means literally “The Speech of the Gods.” Thoth is discussing his invention* of writing with Thamus (also called Ammon), a god-king who rebukes him in these words:

  This discovery of yours will create forgetfulness in the learners’ souls, because they will not use their memories; they will trust to the external written characters and not remember of themselves. The specific which you have discovered is an aid not to memory, but to reminiscence, and you give your disciples not truth, but only the semblance of truth; they will be hearers of many things and will have learned nothing; they will appear to be omniscient and will generally know nothing; they will be tiresome company, having the show of wisdom without its reality.

  Example of early Egyptian hieroglyphics from a tablet of Sesostris I at Karnak.

  HIRMER FOTOARCHIV MÜNCHEN

  I am sure there is some truth to Thamus’ complaint. In our modern world, illiterates have a different sense of direction, a different sense of self-reliance, and a different sense of reality. But before the invention of writing, human knowledge was restricted to what one person or a small group could remember. Occasionally, as with the Vedas and the two great epic poems of Homer, a substantial body of information could be preserved. But there were, so far as we know, few Homers. After the invention of writing, it was possible to collect, integrate and utilize the accumulated wisdom of all times and peoples; humans were no longer restricted to what they and their immediate acquaintances could remember. Literacy gives us access to the greatest and most influential minds in history: Socrates, say, or Newton have had audiences vastly larger than the total number of people either met in his whole lifetime. The repeated rendering of an oral tradition over many generations inevitably leads to errors in transmission and the gradual loss of the original content, a degradation of information that occurs far more slowly with the successive reprinting of written accounts.

  Books are readily stored. We can read them at our own pace without disturbing others. We can go back to the hard parts, or delight once again in the particularly enjoyable parts. They are mass-produced at relatively low cost. And reading itself is an amazing activity: You glance at a thin, flat object made from a tree, as you are doing at this moment, and the voice of the author begins to speak inside your head. (Hello!) The improvement in human knowledge and survival potential following the invention of writing was immense. (There was also an improvement in self-reliance: It is possible to learn at least the rudiments of an art or a science from a book and not be dependent on the lucky accident that there is a
nearby-master craftsman to whom we may apprentice ourselves.)

  A microprocessing unit of a microcomputer, about half a centimeter on a side. It is an integrated circuit deposited on a single crystal silicon chip and containing about 5,400 transistors.

  When all is said and done, the invention of writing must be reckoned not only as a brilliant innovation but as a surpassing good for humanity. And assuming that we survive long enough to use their inventions wisely, I believe the same will be said of the modern Thoths and Prometheuses who are today devising computers and programs at the edge of machine intelligence. The next major structural development in human intelligence is likely to be a partnership between intelligent humans and intelligent machines.

  * In defense of the Pygmies, perhaps I should note that a friend of mine who has spent time with them says that for such activities as the patient stalking and hunting of mammals and fish they prepare themselves through marijuana intoxication, which helps to make the long waits, boring to anyone further evolved than a Komodo dragon, at least moderately tolerable. Ganja is, he says, their only cultivated crop. It would be wryly interesting if in human history the cultivation of marijuana led generally to the invention of agriculture, and thereby to civilization. (The marijuana-intoxicated Pygmy, poised patiently for an hour with his fishing spear aloft, is earnestly burlesqued by the beer-sodden riflemen, protectively camouflaged in red plaid, who, stumbling through the nearby woods, terrorize American suburbs each Thanksgiving.)

  * According to the Roman historian Tacitus, the Egyptians claimed to have taught the alphabet to the Phoenicians, “who, controlling the seas, introduced it to Greece and were credited with inventing what they had really borrowed.” According to legend, the alphabet arrived in Greece with Cadmus, Prince of Tyre, seeking his sister, Europa, who had been stolen away to the island of Crete by Zeus, king of the gods, temporarily disguised as a bull. To protect Europa from those who would steal her back to Phoenicia, Zeus ordered a bronze robot made which, with clanking steps, patrolled Crete and turned back or sank all approaching foreign vessels. Cadmus, however, was elsewhere—-unsuccessfully seeking his sister in Greece when a dragon devoured all his men; whereupon he slew the dragon and, in response to instructions from the goddess Athena, sowed the dragon’s teeth in the furrows of a plowed field. Each tooth became a warrior; and Cadmus and his men together founded Thebes, the first civilized Greek city, bearing the same name as one of the two capital cities of ancient Egypt. It is curious to find in the same legendary account the invention of writing, the founding of Greek civilization, the first known reference to artificial intelligence, and the continuing warfare between humans and dragons.

  9

  KNOWLEDGE

  IS OUR DESTINY:

  TERRESTRIAL AND

  EXTRATERRESTRIAL

  INTELLIGENCE

  The silent hours steal on…

  WM. SHAKESPEARE

  King Richard III

  The question of all questions for humanity, the problem which lies behind all others and is more interesting than any of them is that of the determination of man’s place in Nature and his relation to the Cosmos. Whence our race came, what sorts of limits are set to our power over Nature and to Nature’s power over us, to what goal we are striving, are the problems which present themselves afresh, with undiminished interest, to every human being born on earth.

  T. H. HUXLEY, 1863

  nd so at last I return to one of the questions with which I started: the search for extraterrestrial intelligence. While the suggestion is sometimes made that the preferred channel of interstellar discourse will be telepathic, this seems to me at best a playful notion. At any rate, there is not the faintest evidence in support of it; and I have yet to see even moderately convincing evidence for telepathic transmission on this planet. We are not yet capable of significant interstellar space flight, although some other more advanced civilization might be. Despite all the talk of unidentified flying objects and ancient astronauts, there is no serious evidence that we have been or are being visited.

  That, then, leaves machines. Communication with extraterrestrial intelligence may employ the electromagnetic spectrum, and most likely the radio part of the spectrum; or it might employ gravity waves, neutrinos, just conceivably tachyons (if they exist), or some new aspect of physics that will not be discovered for another three centuries. But whatever the channel, it will require machines to use, and if our experience in radioastronomy is any guide, computer-actuated machines with abilities approaching what we might call intelligence. To run through many days’ worth of data on 1,008 different frequencies, where the information may vary every few seconds or faster, cannot be done well by visually scanning the records. It requires autocorrelation techniques and large electronic computers. And this situation, which applies to observations that Frank Drake of Cornell and I have recently performed at the Arecibo Observatory, can only become more complex—that is, more dependent on computers—with the listening devices likely to be employed in the near future. We can design receiving and transmitting programs of immense complexity. If we are lucky we will employ stratagems of great cleverness and elegance. But we cannot avoid utilizing the remarkable capabilities of machine intelligence if we wish to search for extraterrestrial intelligence.

  The number of advanced civilizations in the Milky Way Galaxy today depends on many factors, ranging from the number of planets per star to the likelihood of the origin of life. But once life has started in a relatively benign environment and billions of years of evolutionary time are available, the expectation of many of us is that intelligent beings would develop. The evolutionary path would, of course, be different from that taken on Earth. The precise sequence of events that have taken place here—including the extinction of the dinosaurs and the recession of the Pliocene and Pleistocene forests—have probably not occurred in precisely the same way anywhere else in the entire universe. But there should be many functionally equivalent pathways to a similar end result. The entire evolutionary record on our planet, particularly the record contained in fossil endocasts, illustrates a progressive tendency toward intelligence. There is nothing mysterious about this: smart organisms by and large survive better and leave more offspring than stupid ones. The details will certainly depend on circumstances, as, for example, if nonhuman primates with language have been exterminated by humans, while slightly less communicative apes were ignored by our ancestors. But the general trend seems quite clear and should apply to the evolution of intelligent life elsewhere. Once intelligent beings achieve technology and the capacity for self-destruction of their species, the selective advantage of intelligence becomes more uncertain.

  “Stars” by M. C. Escher.

  And what if we receive a message? Is there any reason to think that the transmitting beings—evolved over billions of years of geological time in an environment vastly different from our own—would be sufficiently similar to us for their messages to be understood? I think the answer must be yes. A civilization transmitting radio messages must at least know about radio. The frequency, time constant, and bandpass of the message are common to transmitting and receiving civilizations. The situation may be a little like that of amateur or ham radio operators. Except for occasional emergencies, their conversations seem almost exclusively concerned with the mechanics of their instruments: it is the one aspect of their lives they are certain to have in common.

  But I think the situation is far more hopeful than this. We know that the laws of nature—or at least many of them—are the same everywhere. We can detect by spectroscopy the same chemical elements, the same common molecules on other planets, stars and galaxies; and the fact that the spectra are the same shows that the same mechanisms by which atoms and molecules are induced to absorb and emit radiation exist everywhere. Distant galaxies can be observed moving ponderously about each other in precise accord with the same laws of gravitation that determine the motion of a tiny artificial satellite about our pale blue planet Earth. Gravity,
quantum mechanics, and the great bulk of physics and chemistry are observed to be the same elsewhere as here.

  Intelligent organisms evolving on another world may not be like us biochemically. They will almost certainly have evolved significantly different adaptations—from enzymes to organ systems—to deal with the different circumstances of their several worlds. But they must still come to grips with the same laws of nature.

  The laws of falling bodies seem simple to us. At constant acceleration, as provided by Earth’s gravity, the velocity of a falling object increases proportional to the time; the distance fallen proportional to the square of the time. These are very elementary relations. Since Galileo at least, they have been fairly generally grasped. Yet we can imagine a universe in which the laws of nature are immensely more complex. But we do not live in such a universe. Why not? I think it may be because all those organisms who perceived their universe as very complex are dead. Those of our arboreal ancestors who had difficulty computing their trajectories as they brachiated from tree to tree did not leave many offspring. Natural selection has served as a kind of intellectual sieve, producing brains and intelligences increasingly competent to deal with the laws of nature. This resonance, extracted by natural selection, between our brains and the universe may help explain a quandary set by Einstein: The most incomprehensible property of the universe, he said, is that it is so comprehensible.