Broca's Brain

by Carl Sagan

  When the movement of the comets is considered and we reflect on the laws of gravity, it will be readily perceived that their approach to the Earth might there cause the most woeful events, bring back the universal deluge, or make it perish in a deluge of fire, shatter it into small dust, or at least turn it from its orbit, drive away its Moon, or, still worse, the Earth itself outside the orbit of Saturn, and inflict upon us a winter several centuries long, which neither men nor animals would be able to bear. The tails even of comets would not be unimportant phenomena, if the comets in taking their departure left them in whole or in part in our atmosphere.

  J. H. LAMBERT,

  Cosmologische Briefe über

  die Einrichtung des Weltbaues (1761)

  However dangerous might be the shock of a comet, it might be so slight, that it would only do damage at the part of the Earth where it actually struck; perhaps even we might cry quits if while one kingdom were devastated, the rest of the Earth were to enjoy the rarities which a body which came from so far might bring to it. Perhaps we should be very surprised to find that the debris of these masses that we despised were formed of gold and diamonds; but who would be the most astonished, we, or the comet-dwellers, who would be cast on our Earth? What strange beings each would find the other!

  MAUPERTUIS,

  Lettre sur la comète (1752)

  SCIENTISTS, like other human beings, have their hopes and fears, their passions and despondencies—and their strong emotions may sometimes interrupt the course of clear thinking and sound practice. But science is also self-correcting. The most fundamental axioms and conclusions may be challenged. The prevailing hypotheses must survive confrontation with observation. Appeals to authority are impermissible. The steps in a reasoned argument must be set out for all to see. Experiments must be reproducible.

  The history of science is full of cases where previously accepted theories and hypotheses have been entirely overthrown, to be replaced by new ideas that more adequately explain the data. While there is an understandable psychological inertia—usually lasting about one generation—such revolutions in scientific thought are widely accepted as a necessary and desirable element of scientific progress. Indeed, the reasoned criticism of a prevailing belief is a service to the proponents of that belief; if they are incapable of defending it, they are well advised to abandon it. This self-questioning and error-correcting aspect of the scientific method is its most striking property, and sets it off from many other areas of human endeavor where credulity is the rule.

  The idea of science as a method rather than as a body of knowledge is not widely appreciated outside of science, or indeed in some corridors inside of science. For this reason I and some of my colleagues in the American Association for the Advancement of Science have advocated a regular set of discussions at the annual AAAS meeting of hypotheses that are on the borderlines of science and that have attracted substantial public interest. The idea is not to attempt to settle such issues definitively, but rather to illustrate the process of reasoned disputation, to show how scientists approach a problem that does not lend itself to crisp experimentation, or is unorthodox in its interdisciplinary nature, or otherwise evokes strong emotions.

  Vigorous criticism of new ideas is a commonplace in science. While the style of the critique may vary with the character of the critic, overly polite criticism benefits neither the proponents of new ideas nor the scientific enterprise. Any substantive objection is permissible and encouraged; the only exception being that ad hominem attacks on the personality or motives of the author are excluded. It does not matter what reason the proponent has for advancing his ideas or what prompts his opponents to criticize them: all that matters is whether the ideas are right or wrong, promising or retrogressive.

  For example, here is a summary—of a type that is unusual but not extremely rare—of a paper submitted to the scientific journal Icarus, by a qualified referee: “It is the opinion of this reviewer that this paper is absolutely unacceptable for publication in Icarus. It is based on no sound scientific research, and at best it is incompetent speculation. The author has not stated his assumptions; the conclusions are unclear, ambiguous and without basis; credit is not given to related work; the figures and tables are unclearly labeled; and the author is obviously unfamiliar with the most basic scientific literature …” The referee then goes on to justify his remarks in detail. The paper was rejected for publication. Such rejections are commonly recognized as a boon to science as well as a favor to the author. Most scientists are accustomed to receiving (somewhat milder) referees’ criticisms every time they submit a paper to a scientific journal. Almost always the criticisms are helpful. Often a paper revised to take these critiques into account is subsequently accepted for publication. As another example of forthright criticism in the planetary science literature, the interested reader might wish to consult “Comments on The Jupiter Effect” by J. Meeus (1975)* and the commentary on it in Icarus.

  Vigorous criticism is more constructive in science than in some other areas of human endeavor because in science there are adequate standards of validity that can be agreed upon by competent practitioners the world over. The objective of such criticism is not to suppress but rather to encourage the advance of new ideas: those that survive a firm skeptical scrutiny have a fighting chance of being right, or at least useful.

  EMOTIONS IN THE scientific community have run very high on the issue of Immanuel Velikovsky’s work, especially his first book, Worlds in Collision, published in 1950. I know that some scientists were irked because Velikovsky was compared to Einstein, Newton, Darwin and Freud by New York literati and an editor of Harper’s, but this pique arises from the frailty of human nature rather than the judgment of the scientist. The two together often inhabit the same individual. Others were dismayed at the use of Indian, Chinese, Aztec, Assyrian or Biblical texts to argue for extremely heterodox views in celestial mechanics. Also, I suspect, not many physicists or celestial mechanicians are comfortably fluent in such languages or are familiar with such texts.

  My own view is that no matter how unorthodox the reasoning process or how unpalatable the conclusions, there is no excuse for any attempt to suppress new ideas—least of all by scientists. Therefore I was very pleased that the AAAS held a discussion on Worlds in Collision, in which Velikovsky took part.

  In reading the critical literature in advance, I was surprised at how little of it there is and how rarely it approaches the central points of Velikovsky’s thesis. In fact, neither the critics nor the proponents of Velikovsky seem to have read him carefully, and I even seem to find some cases where Velikovsky has not read Velikovsky carefully. Perhaps the publication of most of the AAAS symposium (Goldsmith, 1977) as well as the present chapter, the principal conclusions of which were presented at the symposium, will help to clarify the issues.

  In this chapter I have done my best to analyze critically the thesis of Worlds in Collision, to approach the problem both on Velikovsky’s terms and on mine—that is, to keep firmly in mind the ancient writings that are the focus of his argument, but at the same time to confront his conclusions with the facts and the logic I have at my command.

  Velikovsky’s principal thesis is that major events in the history of both the Earth and the other planets in the solar system have been dominated by catastrophism rather than by uniformitarianism. These are fancy words used by geologists to summarize a major debate they had during the infancy of their science which apparently culminated, between 1785 and 1830, in the work of James Hutton and Charles Lyell, in favor of the uniformitarians. Both the names and the practices of these two sects evoke familiar theological antecedents. A uniformitarian holds that landforms on Earth have been produced by processes we can observe to be operating today, provided they operate over immense vistas of time. A catastrophist holds that a small number of violent events, occupying much shorter periods of time, are adequate. Catastrophism began largely in the minds of those geologists who accepted a literal interpretati
on of the Book of Genesis, and in particular the account of the Noahic flood. It is clearly no use arguing against the catastrophist viewpoint to say that we have never seen such a catastrophe in our lifetimes. The hypothesis requires only rare events. But if we can show that there is adequate time for processes we can all observe operating today to produce the landform or event in question, then there is at least no necessity for the catastrophist hypothesis. Obviously both uniformitarian and catastrophic processes can have been at work—and almost certainly both were—in the history of our planet.

  Velikovsky holds that in the relatively recent history of the Earth there has been a set of celestial catastrophes, near-collisions with comets, small planets and large planets. There is nothing absurd in the possibility of cosmic collisions. Astronomers in the past have not hesitated to invoke collisions to explain natural phenomena. For example, Spitzer and Baade (1951) proposed that extragalactic radio sources may be produced by the collisions of whole galaxies, containing hundreds of billions of stars. This thesis has now been abandoned, not because cosmic collisions are unthinkable, but because the frequency and properties of such collisions do not match what is now known about such radio sources. A still popular theory of the energy source of quasars is multiple stellar collisions at the centers of galaxies—where, in any case, catastrophic events must be common.

  Collisions and catastrophism are part and parcel of modern astronomy, and have been for many centuries (see the epigraphs at the beginning of this chapter). For example, in the early history of the solar system, when there were probably many more objects about than there are now—including objects on very eccentric orbits—collisions may have been frequent. Lecar and Franklin (1973) investigate hundreds of collisions occurring in a period of only a few thousand years in the early history of the asteroid belt, to understand the present configuration of this region of the solar system. In another paper, entitled “Cometary Collisions and Geological Periods,” Harold Urey (1973) investigates a range of consequences, including the production of earthquakes and the heating of the oceans, which might attend the collision with the Earth of a comet of average mass of about 1018 grams. The Tunguska event of 1908, in which a Siberian forest was leveled, is often attributed to the collision with the Earth of a small comet. The cratered surfaces of Mercury, Mars, Phobos, Deimos and the Moon bear eloquent testimony to the fact that there have been abundant collisions during the history of the solar system. There is nothing unorthodox about the idea of cosmic catastrophes, and this is a view that has been common in solar system physics at least back to the late-nineteenth-century studies of the lunar surface by G. K. Gilbert, the first director of the U.S. Geological Survey.

  What, then, is all the furor about? It is about the time scale and the adequacy of the purported evidence. In the 4.6 billion-year history of the solar system, many collisions must have occurred. But have there been major collisions in the last 3,500 years, and can the study of ancient writings demonstrate such collisions? That is the nub of the issue.

  VELIKOVSKY has called attention to a wide range of stories and legends, held by diverse peoples, separated by great distances, which stories show remarkable similarities and concordances. I am not expert in the cultures or languages of any of these peoples, but I find the concatenation of legends Velikovsky has accumulated stunning. It is true that some experts in these cultures are less impressed. I can remember vividly discussing Worlds in Collision with a distinguished professor of Semitics at a leading university. He said something like “The Assyriology, Egyptology, Biblical scholarship and all of that Talmudic and Midrashic pilpul is, of course, nonsense; but I was impressed by the astronomy.” I had rather the opposite view. But let me not be swayed by the opinions of others. My own position is that if even 20 percent of the legendary concordances that Velikovsky produces are real, there is something important to be explained. Furthermore, there is an impressive array of cases in the history of archaeology—from Heinrich Schliemann at Troy to Yigael Yadin at Masada—where the descriptions in ancient writings have subsequently been validated as fact.

  Now, if a variety of widely separated cultures share what is palpably the same legend, how can this be understood? There seem to be four possibilities: common observation, diffusion, brain wiring and coincidence. Let us consider these in turn.

  Common Observation: One explanation is that the cultures in question all witnessed a common event and interpreted it in the same way. There may, of course, be more than one view of what this common event was.

  Diffusion: The legend originated within one culture only, but during the frequent and distant migrations of mankind, gradually spread with some changes among many apparently diverse cultures. A trivial example is the Santa Claus legend in America which evolved from the European Saint Nicholas (Claus is short for Nicholas in German), the patron saint of children, and which ultimately is derived from pre-Christian tradition.

  Brain Wiring: A hypothesis sometimes also known as racial memory or the collective unconscious. It holds that there are certain ideas, archetypes, legendary figures, and stories that are intrinsic to human beings at birth, perhaps in the same way that a newborn baboon knows to fear a snake, and a bird raised in isolation from other birds knows how to build a nest. It is apparent that if a tale derived from observation or from diffusion resonated with the “brain wiring,” it is more likely to be culturally retained.

  Coincidence: Purely by chance two independently derived legends may have similar content. In practice, this hypothesis fades into the brain-wiring hypothesis.

  IF WE ARE TO ASSESS critically such apparent concordances, there are some obvious precautions that must first be taken. Do the stories really say the same thing or have the same essential elements? If they are interpreted as due to common observations, do they date from the same period? Can we exclude the possibility of physical contact between representatives of the cultures in question in or before the epoch under discussion? Velikovsky is clearly opting for the common-observation hypothesis, but he seems to dismiss the diffusion hypothesis far too casually; for example, he says (page 303*): “How could unusual motifs of folklore reach isolated islands, where the aborigines do not have any means of crossing the sea?” I am not sure which islands and which aborigines Velikovsky refers to here, but it is apparent that the inhabitants of an island had to have gotten there somehow. I do not think that Velikovsky believes in a separate creation in the Gilbert and Ellice Islands, say. For Polynesia and Melanesia there is now extensive evidence of abundant sea voyages of lengths of many thousands of kilometers within the last millennium, and probably much earlier (Dodd, 1972).

  Or how, for example, would Velikovsky explain the fact that the Toltec name for “god” seems to have been teo, as in the great pyramid city of Teotihuacán (“City of the Gods”) near present-day Mexico City, where it is called San Juan Teotihuacán? There is no common celestial event that could conceivably explain this concordance. Toltec and Nahuatl are non-Indoeuropean languages, and it seems unlikely that the word for “god” would be wired into all human brains. Yet teo is a clear cognate of the common Indoeuropean root for “god,” preserved, among other places, in the words “deity” and “theology.” The preferred hypotheses in this case are coincidence or diffusion. There is some evidence for pre-Columbian contact between the Old and New Worlds. But coincidence is also not to be taken lightly: if we compare two languages, each with tens of thousands of words, spoken by human beings with identical larynxes, tongues and teeth, it should not be surprising if a few words are coincidentally identical. Likewise, we should not be surprised if a few elements of a few legends are coincidentally identical. But I believe that all of the concordances Velikovsky produces can be explained away in this manner.

  Let us take an example of Velikovsky’s approach to this question. He points to certain concordant stories, directly or vaguely connected with celestial events, that refer to a witch, a mouse, a scorpion or a dragon (pages 77, 264, 305, 306, 310). His explanatio
n: divers comets, upon close approach to the Earth, were tidally or electrically distorted and gave the form of a witch, a mouse, a scorpion or a dragon, clearly interpretable as the same animal to culturally isolated peoples of very different backgrounds. No attempt is made to show that such a clear form—for example, a woman riding a broomstick and topped by a pointed hat—could have been produced in this way, even if we grant the hypothesis of a close approach to the Earth by a comet. Our experience with Rorschach and other psychological projective tests is that different people see the same nonrepresentational image in different ways. Velikovsky even goes so far as to believe that a close approach to the Earth by “a star” he evidently identifies with the planet Mars so distorted it that it took on the clear shape (page 264) of lions, jackals, dogs, pigs and fish; and in his opinion this explains the worship of animals by the Egyptians. This is not very impressive reasoning. We might just as well assume that the whole menagerie was capable of independent flight in the second millennium B.C. and be done with it. A much more likely hypothesis is diffusion. Indeed, I have in a different context spent a fair amount of time studying the dragon legends on the planet Earth, and I am impressed at how different these mythical beasts, all called dragons by Western writers, really are.

  As another example, consider the argument of Chapter 8, Part 2 of Worlds in Collision. Velikovsky claims a world-wide tendency in ancient cultures to believe at various times that the year has 360 days, that the month has thirty-six days, and that the year has ten months. Velikovsky offers no justification in physics for this, but argues that ancient astronomers could hardly have been so poor at their trade as to slip five days each year or six days each lunation. Fairly soon the night would be brilliant with moonlight at the astrologically official new moon, snowstorms would be falling in July, and the astrologers would be hung by their ears. Having had some experience with modern astronomers, I am not as confident as Velikovsky is in the unerring computational precision of ancient astronomers. Velikovsky proposes that these aberrant calendrical conventions reflect real changes in the length of the day, month and/or year—and that they are evidence of close approaches to the Earth-Moon system by comets, planets and other celestial visitors.