Authors: Carl Sagan
The sea is murky. Sight and smell, which work well for mammals on the land, are not of much use in the depths of the ocean. Those ancestors of the whales who relied on these senses to locate a mate or a baby or a predator did not leave many offspring. So another method was perfected by evolution; it works superbly well and is central to any understanding of the whales: the sense of sound. Some whale sounds are called songs, but we are still ignorant of their true nature and meaning. They range over a broad band of frequencies, down to well below the lowest sound the human ear can detect. A typical whale song lasts for perhaps fifteen minutes; the longest, about an hour. Often it is repeated, identically, beat for beat, measure for measure, note for note. Occasionally a group of whales will leave their winter waters in the midst of a song and six months later return to continue at precisely the right note, as if there had been no interruption. Whales are very good at remembering. More often, on their return, the vocalizations have changed. New songs appear on the cetacean hit parade.
Very often the members of the group will sing the same song together. By some mutual consensus, some collaborative song-writing, the piece changes month by month, slowly and predictably. These vocalizations are complex. If the songs of the humpback whale are enunciated as a tonal language, the total information content, the number of bits of information in such songs, is some 10
6
bits, about the same as the information content of the
Illiad
or the
Odyssey
. We do not know what whales or their cousins the dolphins have to talk or sing about. They have no manipulative organs, they make no engineering constructs, but they are social creatures. They hunt, swim, fish, browse, frolic, mate, play, run from predators. There may be a great deal to talk about.
The primary danger to the whales is a newcomer, an upstart animal, only recently, through technology, become competent in the oceans, a creature that calls itself human. For 99.99 percent of the history of the whales, there were no humans in or on the deep oceans. During this period the whales evolved their extraordinary audio communication system. The finbacks, for example, emit extremely loud sounds at a frequency of twenty Hertz, down near the lowest octave on the piano keyboard. (A Hertz is a unit of sound frequency that represents one sound wave, one crest and one trough, entering your ear every second.) Such low-frequency sounds are scarcely absorbed in the ocean. The American biologist Roger Payne has calculated that using the deep ocean sound channel,
two whales could communicate with each other at twenty Hertz essentially anywhere in the world. One might be off the Ross Ice Shelf in Antarctica and communicate with another in the Aleutians. For most of their history, the whales may have established a global communications network. Perhaps when separated by 15,000 kilometers, their vocalizations are love songs, cast hopefully into the vastness of the deep.
For tens of millions of years these enormous, intelligent, communicative creatures evolved with essentially no natural enemies. Then the development of the steamship in the nineteenth century introduced an ominous source of noise pollution. As commercial and military vessels became more abundant, the noise background in the oceans, especially at a frequency of twenty Hertz, became noticeable. Whales communicating across the oceans must have experienced increasingly greater difficulties. The distance over which they could communicate must have decreased steadily. Two hundred years ago, a typical distance across which finbacks could communicate was perhaps 10,000 kilometers. Today, the corresponding number is perhaps a few hundred kilometers. Do whales know each other’s names? Can they recognize each other as individuals by sounds alone? We have cut the whales off from themselves. Creatures that communicated for tens of millions of years have now effectively been silenced.
*
And we have done worse than that, because there persists to this day a traffic in the dead bodies of whales. There are humans who hunt and slaughter whales and market the products for lipstick or industrial lubricant. Many nations understand that the systematic murder of such intelligent creatures is monstrous, but the traffic continues, promoted chiefly by Japan, Norway and the Soviet Union. We humans, as a species, are interested in communication with extraterrestrial intelligence. Would not a good beginning be improved communication with terrestrial intelligence, with other human beings of different cultures and languages, with the great apes, with the dolphins, but particularly with those intelligent masters of the deep, the great whales?
For a whale to live there are many things it must know how to do. This knowledge is stored in its genes and in its brains. The genetic information includes how to convert plankton into blubber; or how to hold your breath on a dive one kilometer below the surface. The information in the brains, the learned information, includes such things as who your mother is, or the meaning of the song you are hearing just now. The whale, like all the other animals on the Earth, has a gene library and a brain library.
The genetic material of the whale, like the genetic material of human beings, is made of nucleic acids, those extraordinary molecules capable of reproducing themselves from the chemical building blocks that surround them, and of turning hereditary information into action. For example, one whale enzyme, identical to one you have in every cell of your body, is called hexokinase, the first of more than two dozen enzyme-mediated steps required to convert a molecule of sugar obtained from the plankton in the whale’s diet into a little energy—perhaps a contribution to a single low-frequency note in the music of the whale.
The information stored in the DNA double helix of a whale or a human or any other beast or vegetable on Earth is written in a language of four letters—the four different kinds of nucleotides, the molecular components that make up DNA. How many bits of information are contained in the hereditary material of various life forms? How many yes/no answers to the various biological questions are written in the language of life? A virus needs about 10,000 bits—roughly equivalent to the amount of information on this page. But the viral information is simple, exceedingly compact, extraordinarily efficient. Reading it requires very close attention. These are the instructions it needs to infect some other organism and to reproduce itself—the only things that viruses are any good at. A bacterium uses roughly a million bits of information—which is about 100 printed pages. Bacteria have a lot more to do than viruses. Unlike the viruses, they are not thoroughgoing parasites. Bacteria have to make a living. And a free-swimming one-celled amoeba is much more sophisticated; with about four hundred million bits in its DNA, it would require some eighty 500-page volumes to make another amoeba.
A whale or a human being needs something like five billion bits. The 5 × 10
9
bits of information in our encyclopaedia of life—in the nucleus of each of our cells—if written out in, say, English, would fill a thousand volumes. Every one of your hundred trillion cells contains a complete library of instructions on how to make every part of you. Every cell in your body arises by successive
cell divisions from a single cell, a fertilized egg generated by your parents. Every time that cell divided, in the many embryological steps that went into making you, the original set of genetic instructions was duplicated with great fidelity. So your liver cells have some unemployed knowledge about how to make your bone cells, and vice versa. The genetic library contains everything your body knows how to do on its own. The ancient information is written in exhaustive, careful redundant detail—how to laugh, how to sneeze, how to walk, how to recognize patterns, how to reproduce, how to digest an apple.
Eating an apple is an immensely complicated process. In fact, if I had to synthesize my own enzymes, if I
consciously
had to remember and direct all the chemical steps required to get energy out of food, I would probably starve. But even bacteria do anaerobic glycolysis, which is why apples rot: lunchtime for the microbes. They and we and all creatures in between possess many similar genetic instructions. Our separate gene libraries have many pages in common, another reminder of our common evolutionary heritage. Our technology can duplicate only a tiny fraction of the intricate biochemistry that our bodies effortlessly perform: we have only just begun to study these processes. Evolution, however, has had billions of years of practice. DNA knows.
But suppose what you had to do was so complicated that even several billion bits was insufficient. Suppose the environment was changing so fast that the precoded genetic encyclopaedia, which served perfectly well before, was no longer entirely adequate. Then even a gene library of 1,000 volumes would not be enough. That is why we have brains.
Like all our organs, the brain has evolved, increasing in complexity and information content, over millions of years. Its structure reflects all the stages through which it has passed. The brain evolved from the inside out. Deep inside is the oldest part, the brainstem, which conducts the basic biological functions, including the rhythms of life—heartbeat and respiration. According to a provocative insight by Paul MacLean, the higher functions of the brain evolved in three successive stages. Capping the brainstem is the R-complex, the seat of aggression, ritual, territoriality and social hierarchy, which evolved hundreds of millions of years ago in our reptilian ancestors. Deep inside the skull of every one of us there is something like the brain of a crocodile. Surrounding the R-complex is the limbic system or mammalian brain, which evolved tens of millions of years ago
in ancestors who were mammals but not yet primates. It is a major source of our moods and emotions, of our concern and care for the young.
And finally, on the outside, living in uneasy truce with the more primitive brains beneath, is the cerebral cortex, which evolved millions of years ago in our primate ancestors. The cerebral cortex, where matter is transformed into consciousness, is the point of embarkation for all our cosmic voyages. Comprising more than two-thirds of the brain mass, it is the realm of both intuition and critical analysis. It is here that we have ideas and inspirations, here that we read and write, here that we do mathematics and compose music. The cortex regulates our conscious lives. It is the distinction of our species, the seat of our humanity. Civilization is a product of the cerebral cortex.
The language of the brain is not the DNA language of the genes. Rather, what we know is encoded in cells called neurons—microscopic electrochemical switching elements, typically a few hundredths of a millimeter across. Each of us has perhaps a hundred billion neurons, comparable to the number of stars in the Milky Way Galaxy. Many neurons have thousands of connections with their neighbors. There are something like a hundred trillion, 10
14
, such connections in the human cerebral cortex.
Charles Sherrington imagined the activities in the cerebral cortex upon awakening:
[The cortex] becomes now a sparkling field of rhythmic flashing points with trains of traveling sparks hurrying hither and thither. The brain is waking and with it the mind is returning. It is as if the Milky Way entered upon some cosmic dance. Swiftly the [cortex] becomes an enchanted loom where millions of flashing shuttles weave a dissolving pattern, always a meaningful pattern though never an abiding one; a shifting harmony of sub-patterns. Now as the waking body rouses, sub-patterns of this great harmony of activity stretch down into the unlit tracks of the [lower brain]. Strings of flashing and traveling sparks engage the links of it. This means that the body is up and rises to meet its waking day.
Even in sleep, the brain is pulsing, throbbing and flashing with the complex business of human life—dreaming, remembering, figuring things out. Our thoughts, visions and fantasies have a physical reality. A thought is made of hundreds of electrochemical impulses. If we were shrunk to the level of the neurons, we might witness elaborate, intricate, evanescent patterns. One might be the spark of a memory of the smell of lilacs on a country road in
childhood. Another might be part of an anxious all-points bulletin: “Where did I leave the keys?”
There are many valleys in the mountains of the mind, convolutions that greatly increase the surface area available in the cerebral cortex for information storage in a skull of limited size. The neurochemistry of the brain is astonishingly busy, the circuitry of a machine more wonderful than any devised by humans. But there is no evidence that its functioning is due to anything more than the 10
14
neural connections that build an elegant architecture of consciousness. The world of thought is divided roughly into two hemispheres. The right hemisphere of the cerebral cortex is mainly responsible for pattern recognition, intuition, sensitivity, creative insights. The left hemisphere presides over rational, analytical and critical thinking. These are the dual strengths, the essential opposites, that characterize human thinking. Together, they provide the means both for generating ideas and for testing their validity. A continuous dialogue is going on between the two hemispheres, channeled through an immense bundle of nerves, the corpus callosum, the bridge between creativity and analysis, both of which are necessary to understand the world.
The information content of the human brain expressed in bits is probably comparable to the total number of connections among the neurons—about a hundred trillion, 10
14
, bits. If written out in English, say, that information would fill some twenty million volumes, as many as in the world’s largest libraries. The equivalent of twenty million books is inside the heads of every one of us. The brain is a very big place in a very small space. Most of the books in the brain are in the cerebral cortex. Down in the basement are the functions our remote ancestors mainly depended on—aggression, child-rearing, fear, sex, the willingness to follow leaders blindly. Of the higher brain functions, some—reading, writing, speaking—seem to be localized in particular places in the cerebral cortex. Memories, on the other hand, are stored redundantly in many locales. If such a thing as telepathy existed, one of its glories would be the opportunity for each of us to read the books in the cerebral cortices of our loved ones. But there is no compelling evidence for telepathy, and the communication of such information remains the task of artists and writers.