Broca's Brain: The Romance of Science

by Carl Sagan

  The hosts sang their traditional songs all through the first night and on through the following rainy day. In return, “to enhance our rapport with them,” as Gajdusek says, “we began to sing songs in exchange-among them such Russian songs as ‘Otchi chornye,’ and ‘Moi kostyor v tumane svetit’…” This was received very well, and the Agakamatasa villagers requested many dozens of repetitions in the smoky South Fore longhouse to the accompaniment of the driving rainstorm.

  Some years later Gajdusek was engaged in the collection of indigenous music in another part of the South Fore region and asked a group of young men to run through their repertoire of traditional songs. To Gajdusek’s amazement and amusement, they produced a somewhat altered but still clearly recognizable version of “Otchi chornye.” Many of the singers apparently thought the song traditional, and later still Gajdusek found the song imported even farther afield, with none of the singers having any idea of its source.

  We can easily imagine some sort of world ethnomusicology survey coming to an exceptionally obscure part of New Guinea and discovering that the natives had a traditional song which sounded in rhythm, music and words remarkably like “Otchi chornye.” If they were to believe that no previous contact of Westerners with these people had occurred, a great mystery could be posited.

  Later that same year Gajdusek was visited by several Australian physicians, eager to understand the remarkable findings about the transmission of kuru from patient to patient by cannibalism. Gajdusek described the theories of the origin of many diseases held by the Fore people, who did not believe that illnesses were caused by the spirits of the dead or that malicious deceased relatives, jealous of the living, inflicted disease on those of their surviving kinsmen who offended them, as the pioneering anthropologist Bronislaw Malinowski had recounted for the coastal peoples of Melanesia. Instead, the Fore attributed most diseases to malicious sorcery, which any offended and avenging male, young or old, could execute without the aid of specially trained sorcerers. There was a special sorcery explanation for kuru, but also for chronic lung disease, leprosy, yaws, and so on. These beliefs had been long-established and firmly held, but as the Fore people witnessed yaws yielding entirely to the penicillin injections of Gajdusek and his group, they quickly agreed that the sorcery explanation of yaws was in error and abandoned it; it has never resurfaced in subsequent years. (I wish Westerners would be as quick to abandon obsolete or erroneous social ideas as the Fore of New Guinea.) Modern treatment of leprosy caused its sorcery explanation to disappear as well, although more slowly, and the Fore people today laugh at these backward early opinions on yaws and leprosy. But the traditional views on the origin of kuru have maintained themselves, since the Westerners have been unable to cure or explain, in a manner satisfactory to them, the origin and nature of this disease. Thus, the Fore people remain intensely skeptical of Western explanations for kuru and retain firmly their view that malicious sorcery is the cause.

  One of the Australian physicians, visiting an adjacent village with one of Gajdusek’s native informants as translator, spent the day examining kuru patients and independently acquiring information. He returned the same evening to inform Gajdusek that he was mistaken about people not believing in the spirits of the dead as the cause of disease, and that he was further in error in holding that they had abandoned the idea of sorcery as the cause of yaws. The people held, he continued, that a dead body could become invisible and that the unseen spirit of the dead person could enter the skin of a patient at night through an imperceptible break, and induce yaws. The Australian’s informant had even sketched with a stick in the sand the appearance of these ghostly beings. They carefully drew a circle and a few squiggly lines within. Outside the circle, they explained, it was black; inside the circle, bright-a sand portrait of malevolent and pathogenic spirits.

  Upon inquiry of the young translator, Gajdusek discovered that the Australian physician had conversed with some of the older men of the village who were well known to Gajdusek and who were often his house and laboratory guests. They had attempted to explain that the shape of the “germ” producing yaws was spiral-the spirochete form they had seen many times through Gajdusek’s dark-field microscope. They had to admit it was invisible-it could be seen only through the microscope-and when pressed by the Australian physician on whether this “represented” the dead person, they had to admit that Gajdusek had stressed that it could be caught from close contact with yaws lesions, as, for example, by sleeping with a person with yaws.

  I can well remember the first time I looked through a microscope. After focusing my eyes up near the ocular only to examine my eyelashes, and then peering further into the pitch-black interior of the barrel, I finally managed to look straight down the microscope tube to be dazzled by an illuminated disc of light. It takes a little while for the eye to train itself to examine what is in the disc. Gajdusek’s demonstration to the Fore people was so powerful-after all, the alternatives entirely lacked so concrete a reality-that many accepted his story, even apart from his ability to cure the disease with penicillin. Perhaps some considered the spirochetes in the microscope an amusing example of white-man myth and minor magic, and when another white man arrived querying the origin of disease, they politely returned to him the idea they believed he would be comfortable with. Had Western contact with the Fore people ceased for fifty years, it seems to me entirely possible that a future visitor would discover to his astonishment that the Fore people somehow had knowledge of medical microbiology, despite their largely pretechnological culture.

  All three of these stories underline the almost inevitable problems encountered in trying to extract from a “primitive” people their ancient legends. Can you be sure that others have not come before you and destroyed the pristine state of the native myth? Can you be sure that the natives are not humoring you or pulling your leg? Bronislaw Malinowski thought he had discovered a people in the Trobriand Islands who had not worked out the connection between sexual intercourse and childbirth. When asked how children were conceived, they supplied him with an elaborate mythic structure prominently featuring celestial intervention. Amazed, Malinowski objected that was not how it was done at all, and supplied them instead with the version so popular in the West today-including a nine-month gestation period. “Impossible,” replied the Melanesians. “Do you not see that woman over there with her six-month-old child? Her husband has been on an extended voyage to another island for two years.” Is it more likely that the Melanesians were ignorant of the begetting of children or that they were gently chiding Malinowski? If some peculiar-looking stranger came into my town and asked me where babies came from, I’d certainly be tempted to tell him about storks and cabbages. Pre-scientific people are people. Individually they are as clever as we are. Field interrogation of informants from a different culture is not always easy.

  I wonder if the Dogon, having heard from a Westerner an extraordinarily inventive myth about the star Sirius-a star already important in their own mythology-did not carefully play it back to the visiting French anthropologist. Is this not more likely than a visit by extraterrestrial spacefarers to ancient Egypt, with one cluster of hard scientific knowledge, in striking contradiction to common sense, preserved by oral tradition, over the millennia, and only in West Africa?

  There are too many loopholes, too many alternative explanations for such a myth to provide reliable evidence of past extraterrestrial contact. If there are extraterrestrials, I think it much more likely that unmanned planetary spacecraft and large radiotelescopes will prove to be the means of their detection.

  CHAPTER 7

  VENUS AND DR. VELIKOVSKY

  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) [5] 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 interpretation 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.