Shadows of Forgotten Ancestors: A Search for Who We Are

Shadows of Forgotten Ancestors: A Search for Who We Are

by Carl Sagan, Ann Druyan


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"Dazzling...A feast. Absorbing and elegantly written, it tells of theorigins of life on earth, describes its variety and charaacter, and culminates in a discussion of human nature and teh complex traces ofhumankind's evolutionary past...It is an amazing story masterfully told."
World renowned scientist Carl Sagan and acclaimed author Ann Druyan have written a ROOTS for the human species, a lucid and riveting account of how humans got to be the way we are. It shows with humor and drama that many of our key traits--self-awareness, technology, family ties, submission to authority, hatred for those a little different from ourselves, reason, and ethics--are rooted in the deep past, and illuminated by our kinship with other animals. Astonishing in its scope, brilliant in its insights, and an absolutely compelling read, SHADOWS OF FORGOTTEN ANCESTORS is a triumph of popular science.

Product Details

ISBN-13: 9780345384720
Publisher: Random House Publishing Group
Publication date: 09/28/1993
Edition description: Reprint
Pages: 528
Sales rank: 284,374
Product dimensions: 6.20(w) x 10.64(h) x 0.92(d)

About the Author

Carl Sagan served as the David Duncan Professor of Astronomy and Space Sciences and Director of the Laboratory for Planetary Studies at Cornell University. He played a leading role in the Mariner, Viking, Voyager, and Galileo spacecraft expeditions, for which he received the NASA Medals for Exceptional Scientific Achievement and (twice) for Distinguished Public Service.
His Emmy- and Peabody–winning television series, Cosmos, became the most widely watched series in the history of American public television. The accompanying book, also called Cosmos, is one of the bestselling science books ever published in the English language. Dr. Sagan received the Pulitzer Prize, the Oersted Medal, and many other awards—including twenty honorary degrees from American colleges and universities—for his contributions to science, literature, education, and the preservation of the environment. In their posthumous award to Dr. Sagan of their highest honor, the National Science Foundation declared that his “research transformed planetary science . . . his gifts to mankind were infinite." Dr. Sagan died on December 20, 1996.

Read an Excerpt

Chapter 1
Nothing lives forever, in Heaven as it is on Earth. Even the stars grow old, decay, and die. They die, and they are born. There was once a time before the Sun and Earth existed, a time before there was day or night, long, long before there was anyone to record the Beginning for those who might come after.
Nevertheless, imagine you were a witness to that time:
An immense mass of gas and dust is swiftly collapsing under its own weight, spinning ever faster, transforming itself from a turbulent, chaotic cloud into what seems to be a distinct, orderly, thin disk. Its exact center smolders a dull, cherry red. Watch from on high, above the disk, for a hundred million years and you will see the central mass grow whiter and more brilliant, until, after a couple of abortive and incomplete attempts, it bursts into radiance, a sustained thermonuclear fire. The Sun is born. Faithfully, it will shine over the next five billion years—when the matter in the disk will have evolved into beings able to reconstruct the circumstances of its origin, and theirs.
Only the innermost provinces of the disk are illuminated. Farther out, the sunlight fails to penetrate. You plunge into the recesses of the cloud to see what wonders are unfolding. You discover a million small worlds milling about the great central fire. A few thousand sizable ones here and there, most circling near the Sun but some at great distances away, are destined to find each other, merge, and become the Earth.
This spinning disk out of which worlds are forming has fallen together from the sparse matter that punctuates a vast region of interstellar vacuum within the Milky Way galaxy. The atoms and grains that make it up are the flotsam and jetsam of galactic evolution—here, an oxygen atom generated from helium in the interior inferno of some long-dead red giant star; there, a carbon atom expelled from the atmosphere of a carbon-rich star in some quite different galactic sector; and now an iron atom freed for world-making by a mighty supernova explosion in the still more ancient past. Five billion years after the events we are describing, these very atoms may be coursing through your bloodstream.
Our story begins here in the dark, pullulating, dimly illuminated disk: the story as it actually turned out, and an enormous number of other stories that would have come to be had things gone just a little differently; the story of our world and species, but also the story of many other worlds and lifeforms destined never to be. The disk is rippling with possible futures.
For most of their lives, stars shine by transmuting hydrogen into helium. It happens at enormous pressures and temperatures deep inside them. Stars have been aborning in the Milky Way galaxy for ten billion years or more—within great clouds of gas and dust. Almost all the placenta of gas and dust that once surrounded and nourished a star is quickly lost, either devoured by its tenant or spewed back into interstellar space. When they are a little older—but we are still talking about the childhood of the stars—a massive disk of gas and dust can be discerned, the inner lanes circling the star swiftly, the outer ones moving more stately and slowly. Similar disks are detectable around stars barely out of their adolescence, but now only as thin remnants of their former selves—mostly dust with almost no gas, every grain of dust a miniature planet orbiting the central star. In some of them, dark lanes, free of dust, can be made out. Perhaps half the young stars in the sky that are about as massive as the Sun have such disks. Still older stars have nothing of the sort, or at least nothing that we are yet able to detect. Our own Solar System to this day retains a very diffuse band of dust orbiting the Sun, called the zodiacal cloud, a wispy remake of the great disk from which the planets were born.
The story these observations are telling us is this: Stars formed in batches from huge clouds of gas and dust. A dense clump of material attracts adjacent gas and dust, grows larger and more massive, more efficiently draws matter to it, and is off on its way to stardom. When the temperatures and pressures in its interior become high enough, hydrogen atoms—the most abundant material in the Universe by far—rare jammed together and thermonuclear reactions are initiated. When it happens on a large enough scale, the star turns on and the nearby darkness is dispelled. Matter is turned into light.
The collapsing cloud spins up, squashes down into a disk, and lumps of matter aggregate together—successively the size of smoke particles, sand grains, rocks, boulders, mountains, and worldlets. Then the cloud tidies itself up through the simple expedient of the largest objects gravitationally consuming the debris. The dust-free lanes are the feeding zones of young planets. As the central star begins to shine, it also sends forth great gales of hydrogen that blow grains back into the void. Perhaps some other system of worlds, fated to arise billions of years later in some distant province of the Milky Way, will put these rejected building blocks to good use.
In the disks of gas and dust that surround many nearby stars, we think we see the nurseries in which worlds, far-off and exotic, are accumulating and coalescing. All over our galaxy, vast, irregular, lumpy, pitch-black, interstellar clouds are collapsing under their own gravity, and spawning stars and planets. It happens about once a month. In the observable Universe—containing as many as a hundred billion galaxies—perhaps a hundred solar systems are forming every second. In that multitude of worlds, many will be barren and desolate. Others may be lush and fertile, on which beings exquisitely adapted to their several circumstances are growing up, coming of age, and attempting to piece together their beginnings. The Universe is lavish beyond imagining.
As the dust settles and the disk thins, you can now make out what is happening down there. Hurtling about the Sun is a vast array of worldlets, all in slightly different orbits. Patiently you watch. Ages pass. With so many bodies moving so quickly, it is only a matter of time before worlds collide. As you look more closely, you can see collisions occurring almost everywhere. The Solar System begins amid almost unimaginable violence. Sometimes the collision is fast and head-on, and a devastating, although silent, explosion leaves nothing but shards and fragments. At other times—when two worldlets are in nearly identical orbits with nearly identical speeds—the collisions are nudging, gentle; the bodies stick together, and a bigger, double worldlet emerges.
In another age or two, you notice that several much larger bodies are growing—worlds that, by luck, escaped a disintegrating collision in their early, more vulnerable days. Such bodies—each established in its own feeding zone—plow through the smaller worldlets and gobble them up. They have grown so large that their gravity has crushed out the irregularities; these bigger worlds are nearly perfect spheres. When a worldlet approaches a more massive body, although not close enough to collide, it swerves; its orbit is changed. On its new trajectory, it may impact some other body, perhaps smashing it to smithereens; or meet a fiery death as it falls into the young Sun, which is consuming the matter in its vicinity; or be gravitationally ejected into the frigid interstellar dark. Only a few are in fortunate orbits, neither eaten, nor pulverized, nor fried, nor exiled. They continue to grow.
Beyond a certain mass, the bigger worlds are attracting not just dust, but great streams of interplanetary gas as well. You watch them develop, eventually each with a vast atmosphere of hydrogen and helium gas surrounding a core of rock and metal. They become the four giant planets, Jupiter, Saturn, Uranus, and Neptune. You can see the characteristic banded cloud patterns emerge. Collisions of comets with their moons splay out elegant, patterned, iridescent, ephemeral rings. Pieces of an exploded world fall back together, generating a jumbled, odd-lot, motley new moon. As you watch, an Earth-sized body plows into Uranus, knocking the planet over on its side, so once each orbit its poles point straight at the distant Sun.
Closer in, where the disk gas has by now been cleaned away, some of the worlds are becoming Earth-like planets, another class of survivors in this game of world-annihilating gravitational roulette. The final accumulation of the terrestrial planets takes no more than 100 million years, about as long compared to the lifespan of the Solar System as the first nine months is relative to the lifetime of an average human being. A doughnut-shaped zone of millions of rocky, metallic, and organic worldlets, the asteroid belt, survives. Trillions of icy worldlets, the comets, slowly orbit the Sun in the darkness beyond the outermost planet.
The principal bodies of the Solar System have now formed. Sunlight pours through a transparent, nearly dust-free interplanetary space, warming and illuminating the worlds. They continue to course and careen about the Sun. But look more closely still and you can make out that further change is being worked.
None of these worlds, you remind yourself, has volition; none intends to be in a particular orbit. But those that are on well-behaved, circular orbits tend to grow and prosper, while those on giddy, wild, eccentric, or recklessly tilted orbits tend to be removed. As time goes on, the confusion and chaos of the early Solar System slowly settle down into a steadily more orderly, simple, regularly spaced, and, to your eyes, increasingly beautiful set of trajectories. Some bodies are selected to survive, others to be annihilated or exiled. This selection of worlds occurs through the operation of a few extremely simple laws of motion and gravity. Despite the good neighbor policy of the well-mannered worlds, you can occasionally make out a flagrant rogue worldlet on collision trajectory. Even a body with the most circumspect circular orbit has no warrantee against utter annihilation. To continue to survive, an Earth-like world must also continue to be lucky.
The role of something close to random chance in all this is striking. Which worldlet will be shattered or ejected, and which will safely grow to planethood, is not obvious. There are so many objects in so complicated a set of mutual interactions that it is very hard to tell—just by looking at the initial configuration of gas and dust, or even after the planets have mainly formed—what the final distribution of worlds will be. Perhaps some other, sufficiently advanced observer could figure it out and predict its future—or even set it all in motion so that, billions of years later, through some intricate and subtle sequence of processes, a desired outcome will slowly emerge. But that is not yet for humans.
You started with a chaotic, irregular cloud of gas and dust, tumbling and contracting in the interstellar night. You ended with an elegant, jewel-like solar system, brightly illuminated, the individual planets neatly spaced out one from another, everything running like clockwork. The planets are nicely separated, you realize, because those that aren’t are gone.

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Shadows of Forgotten Ancestors 4.7 out of 5 based on 0 ratings. 10 reviews.
M_L_Gooch_SPHR More than 1 year ago
This is beyond doubt one of the best written science related books that I have read over the years. There are quite a few excellent science writers but none come close to this husband and wife team. While I don't personally believe in all of the theories contained therein, it is still a dazzling, fantastic ride through ancient history. The writers make you feel as if you could actually be standing beside the characters as they absorb you into their world. I read this tome several years ago and can actually say that I still to this day reflect on several of the comments and analysis made within the pages. In fact, the more time goes by, the more I begin to bend my philosophy to match the book.. They masterfully tell the story of human nature and whther it is through brute hypothesis or the elegant writing, it certainly gives us pause to reflect. The account is both riveting and fast paced. It probably reads at a much faster pace than the authors intended which is to their credit. Rarely do I encounter a book that I simply "can't put down". If you want a slant on the dramatic way we became to be who we are, this is an excellent place to start. You will learn why we hate those that are different from us, racism, family ties and why we have the pecking order we live with. The book is quite brilliant in its insights and conclusions. Again I must say I do not adhere to all of these beliefs but they make wonderful food for thought. If you have never read Sagan or Druyan, to me, that is a shame. Buy, borrow or steal this book. It is a illuminating ride. I hope you find my opinion helpful. Michael L. Gooch, Author of Wingtips with Spurs.
robrod1 on LibraryThing More than 1 year ago
One of his best books. Thoughtful and to the point. A must read.
Anonymous More than 1 year ago
Anonymous More than 1 year ago
I have to say I love Sagen, and I love human evolution. So this book was a no brainer for me to pick up. There were lots of interesting bits in the book, but I felt like I was slogging through the primordial muck to get to them. The informatiom on how the earth formed was great! And the theories of how life may have started were important to the story, but there was way more information on protiens, microbs, cells, etc than I really needed. I felt that there was a lot of repetition through out the book, but I stuck with it. Just when I thought I was finally to the intesting part, i.e. human evolution- IT ENDED! To be continued in another volumn? So if you want to know more about neanderthal, erectus, civilization, language developmemt - you aren't going to get it in this book.
Anonymous More than 1 year ago
In the best posible way this book has made me open my eyes to our existence and our fragility. Everyone that has curiosity and natural childlike wonder will enjoy and prpobably gain from this book.
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Guest More than 1 year ago
OK, maybe that's a slight overreach but the point remains that this book is needed and is appreciated. From the scientific equivalent of 'Let there be light' to the present day, this book retraces our best estimations as to what our journey from nothingness toward humanity must have entailed. Through Sagan's unique talents at weaving the scientific story, I felt throughout this book as though it was I who was represented as the newly invented strand of DNA, as the Arboreal ape in its own society, as the collecting bits of matter soon after the formation of the Universe, as in some sense as Carl would have us know, it was was all of us. A wonderful addition to my library indeed.
Guest More than 1 year ago
Guest More than 1 year ago
its a very interesting book for understanding life in all its forms. Has lot of information to substantiate the philosophy of life