Broca's Brain: The Romance of Science

by Carl Sagan

  It is also possible that the content rather than the material of the message would clearly point to a science or technology beyond the abilities of our ancestors: for example, a vector calculus rendition of Maxwell’s equations (with or without magnetic monopoles), or a graphical representation of the Planck black-body distribution for several different temperatures, or a derivation of the Lorentz transformation of special relativity. Even if the ancient civilization could not understand such writings, they might revere them as holy. But no cases of this sort have emerged-despite what is clearly a profitable market for tales of ancient or modern extraterrestrial astronauts. There have been debates on the purity of magnesium samples from purported crashed UFOs, but their purity was within the competence of American technology at the time of the incident. A supposed star map said to be retrieved (from memory) from the interior of a flying saucer does not, as alleged, resemble the relative positions of the nearest stars like the Sun; in fact, a close examination shows it to be not much better than the “star map” which would be produced if you took an old-fashioned quill pen and splattered a few blank pages with ink spots. With one apparent exception, there are no stories sufficiently detailed to dispose of other explanations and sufficiently accurate to portray correctly modern physics or astronomy to a prescientific or pretechnical people. The one exception is the remarkable mythology surrounding the star Sirius that is held by the Dogon people of the Republic of Mali.

  There are at most a few hundred thousand Dogon alive today, and they have been studied intensively by anthropologists only since the 1930s. There are some elements of their mythology that are reminiscent of the legends of the ancient Egyptian civilization, and some anthropologists have assumed a weak Dogon cultural connection with ancient Egypt. The helical risings of Sirius were central to the Egyptian calendar and used to predict the inundations of the Nile. The most striking aspects of Dogon astronomy have been recounted by Marcel Griaule, a French anthropologist working in the 1930s and 1940s. While there is no reason to doubt Griaule’s account, it is important to note that there is no earlier Western record of these remarkable Dogon folk beliefs and that all the information has been funneled through Griaule. The story has recently been popularized by a British writer, R. K. G. Temple.

  In contrast to almost all prescientific societies, the Dogon hold that the planets as well as the Earth rotate about their axes and revolve about the Sun. This is a conclusion that can, of course, be achieved without high technology, as Copernicus demonstrated, but it is a very rare insight among the peoples of the Earth. It was taught, however, in ancient Greece by Pythagoras and by Philolaus, who perhaps held, in Laplace’s words, “that the planets were inhabited and that the stars were suns, disseminated in space, being themselves centers of planetary systems.” Such teachings, among a wide variety of contradictory ideas, might be just an inspired lucky guess.

  The ancient Greeks believed there were only four elements-earth, fire, water and air-from which all else was constructed. Among the pre-Socratic philosophers there were those who made special advocacy for each one of these elements. If it had later turned out that the universe was indeed made more of one of these elements than another, we should not attribute remarkable prescience to the pre-Socratic philosopher who made the proposal. One of them was bound to be right on statistical grounds alone. In the same way, if we have several hundred or several thousand cultures, each with its own cosmology, we should not be astounded if, every now and then, purely by chance, one of them proposes an idea that is not only correct but also impossible for them to have deduced.

  But, according to Temple, the Dogon go further. They hold that Jupiter has four satellites and that Saturn is encircled by a ring. It is perhaps possible that individuals of extraordinary eyesight under superb seeing conditions could, in the absence of a telescope, have observed the Galilean satellites of Jupiter and the rings of Saturn. But this is at the bare edge of plausibility. Unlike every astronomer before Kepler, the Dogon are said to depict the planets moving correctly in elliptical, not circular, orbits.

  More striking still is the Dogon belief about Sirius, the brightest star in the sky. They contend that it has a dark and invisible companion star which orbits Sirius (and, Temple says, in an elliptical orbit) once every fifty years. They state that the companion star is very small and very heavy, made of a special metal called “Sagala” which is not found on Earth.

  The remarkable fact is that the visible star, Sirius A, does have an extraordinary dark companion, Sirius B, which orbits it in an elliptical orbit once each 50.04 ±0.09 years. Sirius B is the first example of a white dwarf star discovered by modern astrophysics. Its matter is in a state called “relativistically degenerate,” which does not exist on Earth, and since the electrons are not bound to the nuclei in such degenerate matter, it can properly be described as metallic. Since Sirius A is called the Dog Star, Sirius B has sometimes been dubbed “The Pup.”

  At first glance the Sirius legend of the Dogon seems to be the best candidate evidence available today for past contact with an advanced extraterrestrial civilization. As we begin a closer look at this story, however, let us remember that the Dogon astronomical tradition is purely oral, that it dates with certainty only from the 1930s and that the diagrams are written with sticks in sand. (Incidentally, there is some evidence that the Dogon like to frame pictures with an ellipse, and that Temple may be mistaken about the claim that the planets and Sirius B move in elliptical orbits in Dogon mythology.)

  When we examine the full body of Dogon mythology we find a very rich and detailed structure of legend-much richer, as many anthropologists have remarked, than those of their near geographical neighbors. Where there is a rich array of legends there is, of course, a greater chance of an accidental correspondence of one of the myths with a finding of modern science. A very spare mythology is much less likely to make such an accidental concordance. But when we examine the rest of Dogon mythology, do we find other cases hauntingly reminiscent of some unexpected findings in modern science?

  The Dogon cosmogony describes how the Creator examined a plaited basket, round at the mouth and square at the bottom. Such baskets are still in use in Mali today. The Creator up-ended the basket and used it as a model for the creation of the world-the square base represents the sky and the round mouth the Sun. I must say that this account does not strike me as a remarkable anticipation of modern cosmological thinking. In the Dogon representation of the creation of the Earth, the Creator implants in an egg two pairs of twins, each pair comprised of a male and a female. The twins are intended to mature within the egg and fuse to become a single and “perfect” androgynous being. The Earth originates when one of the twins breaks from the egg before maturation, whereupon the Creator sacrifices the other twin in order to maintain a certain cosmic harmony. This is a variegated and interesting mythology, but it does not seem to be qualitatively different from many of the other mythologies and religions of humanity.

  The hypothesis of a companion star to Sirius might have followed naturally from the Dogon mythology, in which twins play a central role, but there does not seem to be any explanation this simple about the period and density of the companion of Sirius. The Dogon Sirius myth is too close to modern astronomical thinking and too precise quantitatively to be attributed to chance. Yet there it sits, immersed in a body of more or less standard prescientific legend. What can the explanation be? Is there any chance that the Dogon or their cultural ancestors might actually have been able to see Sirius B and observe its period around Sirius A?

  White dwarfs such as Sirius B evolve from stars called red giants, which are very luminous and, it will be no surprise to hear, red. Ancient writers of the first few centuries A.D. actually described Sirius as red-certainly not its color today. In a conversation piece by Horace called “Hoc Quoque Tiresia” (How to Get Rich Quickly) there is a quotation from an unspecified earlier work that says: “The red dog star’s heat split the speechless statues.” As a result of these
less than compelling ancient sources there has been a slight temptation among astrophysicists to consider the possibility that the white dwarf Sirius B was a red giant in historical times and visible with the naked eye, completely swamping the light of Sirius A. In that case perhaps there was a slightly later time in the evolution of Sirius B when its brightness was comparable to that of Sirius A, and the relative motion of the two stars about each other could be discerned with the unaided eye. But the best recent information from the theory of stellar evolution suggests that there simply is not enough time for Sirius B to have reached its present white dwarf state if it had been a red giant a few centuries before Horace. What is more, it would seem extraordinary that no one except the Dogon noticed these two stars circling each other every fifty years, each alone being one of the brightest stars in the sky. There was an extremely competent school of observational astronomers in Mesopotamia and in Alexandria in the preceding centuries-to say nothing of the Chinese and Korean astronomical schools-and it would be astonishing if they had noticed nothing. [4] Is our only alternative, then, to believe that representatives of an extraterrestrial civilization have visited the Dogon or their ancestors?

  The Dogon have knowledge impossible to acquire without the telescope. The straightforward conclusion is that they had contact with an advanced technical civilization. The only question is, which civilization-extraterrestrial or European? Far more credible than an ancient extraterrestrial educational foray among the Dogon might be a comparatively recent contact with scientifically literate Europeans who conveyed to the Dogon the remarkable European myth of Sirius and its white dwarf companion, a myth that has all the superficial earmarks of a splendidly inventive tall story. Perhaps the Western contact came from a European visitor to Africa, or from the local French schools, or perhaps from contacts in Europe by West Africans inducted to fight for the French in World War I.

  The likelihood that these stories arise from contact with Europeans rather than extraterrestrials has been increased by a recent astronomical finding: a Cornell University research team led by James Elliot, employing a high-altitude airborne observatory over the Indian Ocean, discovered in 1977 that the planet Uranus is surrounded by rings-a finding never hinted at by ground-based observations. Advanced extraterrestrial beings viewing our solar system upon approach to Earth would have little difficulty discovering the rings of Uranus. But European astronomers in the nineteenth and early twentieth centuries would have had nothing to say in this regard. The fact that the Dogon do not talk of another planet beyond Saturn with rings suggests to me that their informants were European, not extraterrestrial.

  In 1844 the German astronomer F. W. Bessel discovered that the long-term motion of Sirius itself (Sirius A) was not straight but, rather, wavy against the background of more distant stars. Bessel proposed that there was a dark companion to Sirius whose gravitational influence was producing the observed sinusoidal motion. Since the period of the wiggle was fifty years, Bessel deduced that the dark companion had a fifty-year period in the joint motion of Sirius A and B about their common center of mass.

  Eighteen years later Alvan G. Clark, during the testing of a new 18½-inch refracting telescope, accidentally discovered the companion, Sirius B, by direct visual observation. From the relative motions, Newtonian gravitational theory permits us to estimate the masses of Sirius A and B. The companion turns out to have a mass just about the same as the Sun’s. But Sirius B is almost ten thousand times fainter than Sirius A, even though their masses are about the same and they are just the same distance from the Earth. These facts can be reconciled only if Sirius B has a much smaller radius or a much lower temperature. But in the late nineteenth century it was believed by astronomers that stars of the same mass had approximately the same temperature, and by the turn of the century it was widely held that the temperature of Sirius B was not remarkably low. Spectroscopic observations by Walter S. Adams in 1915 confirmed this contention. Hence, Sirius B must be very small. We know today that it is only as big as the Earth. Because of its size and color it is called a white dwarf. But if Sirius B is much smaller than Sirius A, its density must be very much greater. Accordingly, the concept of Sirius B as an extremely dense star was widely held in the first few decades of this century.

  The peculiar nature of the companion of Sirius was extensively reported in books and in the press. For example, in Sir Arthur Stanley Eddington’s book The Nature of the Physical World, we read: “Astronomical evidence seems to leave practically no doubt that in the so-called white dwarf stars the density of matter far transcends anything of which we have terrestrial experience; in the Companion of Sirius, for example, the density is about a ton to the cubic inch. This condition is explained by the fact that the high temperature and correspondingly intense agitation of the material breaks up (ionises) the outer electron system of the atoms, so that the fragments can be packed much more closely together.” Within a year of its 1928 publication, this book saw ten reprintings in English. It was translated into many languages, including French. The idea that white dwarfs were made of electron degenerate matter had been proposed by R. H. Fowler in 1925 and quickly accepted. On the other hand, the proposal that white dwarfs were made of “relativistically degenerate” matter was first made in the period 1934 to 1937, in Great Britain, by the Indian astrophysicist S. Chandrasekhar; the idea was greeted with substantial skepticism by astronomers who had not grown up with quantum mechanics. One of the most vigorous skeptics was Eddington. The debate was covered in the scientific press and was accessible to the intelligent layman. All this was occurring just before Griaule encountered the Dogon Sirius legend.

  In my mind’s eye I picture a Gallic visitor to the Dogon people, in what was then French West Africa, in the early part of this century. He may have been a diplomat, an explorer, an adventurer or an early anthropologist Such people-for example, Richard Francis Burton-were in West Africa many decades earlier. The conversation turns to astronomical lore. Sirius is the brightest star in the sky. The Dogon regale the visitor with their Sirius mythology. Then, smiling politely, expectantly, they inquire of their visitor what his Sirius myths might be. Perhaps he refers before answering to a well-worn book in his baggage. The white dwarf companion of Sirius being a current astronomical sensation, the traveler exchanges a spectacular myth for a routine one. After he leaves, his account is remembered, retold, and eventually incorporated into the corpus of Dogon mythology-or at least into a collateral branch (perhaps filed under “Sirius myths, bleached peoples’ account”). When Marcel Griaule makes mythological inquiries in the 1930s and 1940s, he has his own European Sirius myth played back to him.

  THIS FULL-CYCLE RETURN of a myth to its culture of origin through an unwary anthropologist might sound unlikely if there were not so many examples of it in anthropological lore. I here recount a few cases:

  In the first decade of the twentieth century a neophyte anthropologist was collecting accounts of ancient traditions from Native American populations in the Southwest. His concern was to write down the traditions, almost exclusively oral, before they vanished altogether. The young Native Americans had already lost appreciable contact with their heritage, and the anthropologist concentrated on elderly members of the tribe. One day he found himself sitting outside a hogan with an aged but lively and cooperative informant.

  “Tell me about the ceremonies of your ancestors at the birth of a child.”

  “Just one moment.”

  The old Indian slowly shuffled into the darkened depths of the hogan. After a fifteen-minute interval he reappeared with a remarkably useful and detailed description of postpartum ceremonials, including rituals connected with breach presentation, afterbirth, umbilical cord, first breath and first cry. Encouraged and writing feverishly, the anthropologist systematically went through the full list of rites of passage, including puberty, marriage, childbearing and death. In each case the informant disappeared into the hogan only to emerge a quarter of an hour later with a rich set of answ
ers. The anthropologist was astonished. Could, he wondered, there be a yet older informant, perhaps infirm and bedriden, within the hogan? Eventually he could resist no longer and summoned the courage to ask his informant what he did at each retreat into the hogan. The old man smiled, withdrew for the last time, and returned clutching a well-thumbed volume of the Dictionary of American Ethnography, which had been compiled by anthropologists in the previous decade. The poor white man, he must have thought, is eager, well-meaning and ignorant. He does not have a copy of this marvelous book which contains the traditions of my people. I shall tell him what it says.

  My other two stories recount the adventures of an extraordinary physician, Dr. D. Carleton Gajdusek, who for many years has studied kuru, a rare viral disease, among the inhabitants of New Guinea. For this work he was the recipient of the 1976 Nobel Prize for Medicine. I am grateful to Dr. Gajdusek for taking the trouble to check my memory of his stories, which I first heard from him many years ago. New Guinea is an island on which mountainous terrain separates-in a manner similar to but more completely than the mountains of ancient Greece-one valley people from another. As a result there is a great profusion and variety of cultural traditions.

  In the spring of 1957 Gajdusek and Dr. Vincent Zigas, a medical officer with the Public Health Service of what was then called the Territory of Papua and New Guinea, traveled with an Australian administrative patrol officer from the Purosa Valley through the ranges of the South Fore cultural and linguistic-group region to the village of Agakamatasa on an exploratory visit into “uncontrolled territory.” Stone implements were still in use, and there remained a tradition of cannibalism within one’s own living group. Gajdusek and his party found cases of kuru, which is spread by cannibalism (but most often not through the digestive tract), in this most remote of the South Fore villages. They decided to spend a few days, moving into one of the large and traditional wa’e, or men’s houses (the music from one of which, incidentally, was sent to the stars on the Voyager phonograph record). The windowless, low-doored, smoky thatched house was partitioned so that the visitors could neither stand erect nor stretch out. It was divided into many sleeping compartments, each with its own small fire, around which men and boys would huddle in groups to sleep and keep warm during the cold nights at an elevation of more than 6,000 feet, an altitude higher than Denver. To accommodate their visitors, the men and boys gleefully tore out the interior structure of half of the ceremonial men’s house, and during two days and nights of pouring rain Gajdusek and his companions were housebound on a high, windswept, cloud-covered ridge. The young Fore initiates wore bark strands braided into their hair, which was covered with pig grease. They wore huge nose pieces, the penises of pigs as armbands, and the genitalia of opossums and tree-climbing kangaroos as pendants around their necks.