The Dragons of Eden: Speculations on the Evolution of Human Intelligence by Carl Sagan (PDF)

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“A history of the human brain from the big bang, fifteen billion years ago, to the day before yesterday . . . It’s a delight.”—The New York TimesDr. Carl Sagan takes us on a great reading adventure, offering his vivid and startling insight into the brain of man and beast, the origin of human intelligence, the function of our most haunting legends—and their amazing links to recent discoveries. “How can I persuade every intelligent person to read this important and elegant book? . . . He talks about all kinds of things: the why of the pain of human childbirth . . . the reason for sleeping and dreaming . . . chimpanzees taught to communicate in deaf and dumb language . . . the definition of death . . . cloning . . . computers . . . intelligent life on other planets. . . . Fascinating . . . delightful.”—The Boston Globe“In some lost Eden where dragons ruled, the foundations of our intelligence were laid. . . . Carl Sagan takes us on a guided tour of that lost land. . . . Fascinating . . . entertaining . . . masterful.”—St. Louis Post-Dispatch

User’s Reviews

Reviews from Amazon users which were colected at the time this book was published on the website:

⭐Carl Sagan (1934-1996) was an American astronomer, astrophysicist, author, cosmologist, and highly successful popularizer of astronomy, astrophysics and other natural sciences. His 1980 TV series ‘Cosmos: A Personal Journey’ made him a household name.He wrote in the Introduction to this 1977 book, “I was pleased and honored to deliver the first Jacob Bronowski Memorial Lecture in Natural Philosophy in November 1975… In writing this book, I have expanded substantially the scope of that lecture, and have been in return provided with an exhilarating opportunity to learn something about subjects in which I am not expert. I found irresistible the temptation to synthesize some of what I learned into a coherent picture, and to tender some hypotheses on the nature and evolution of human intelligence that may be novel, or that at least have not been widely discussed. The subject is a difficult one. While I have formal training in biology, and have worked for many years on the origin and early evolution of life, I have little formal education in, for example, the anatomy and physiology of the brain. Accordingly, I offer the following ideas with a substantial degree of trepidation; I know very well that many of them are speculative and can be proved or disproved only on the anvil of experiment. At the very least, this inquiry has provided me with an opportunity to look into an entrancing subject; perhaps my remarks will stimulate others to look more deeply.” (Pg. 5)In the first chapter, he presents his famous ‘Cosmic Calendar’: “The most instructive way I know to express the cosmic chronology is to imagine the fifteen-billion-year lifetime of the universe … compressed into the span of a single year. Then every billion years of Earth history would correspond to about twenty-four days of our cosmic year, and one second of that year to 475 real revolutions of the Earth about the Sun… On this scale, the events of our history books… are so compressed that it is necessary to give a second-by-second recounting of the last seconds of the cosmic year… In the history of life, an equally rich tapestry must have been woven in other periods… But we have detailed records only for the very end of the cosmic year… The construction of such tables and calendars is inevitably humbling. It is disconcerting to find that in such a cosmic year the Earth does not condense out of interstellar matter until early September; dinosaurs emerge on Christmas Eve; flowers arise on December 28th; and men and women originate at 10:30 P.M. on New Year’s Eve. All of recorded history occupies the last ten seconds of December 31; and the time from the waning of the Middle Ages to the present occupies little more than one second… it is clear that what happens on and near earth at the beginning of the second cosmic year will depend very much on the scientific wisdom and the distinctly human sensitivity of mankind.” (Pg. 13-17)He points out, “There is a popular contention that half of more of the brain is unused. From an evolutionary point of view this would be quite extraordinary: why should it have evolved if it had no function? But actually the statement is made on very little evidence… it is deduced from the finding that many lesions of the brain … have no apparent effect on behavior. This view does not take into account (1) the possibility of redundant function; and (2) the fact that some human behavior is subtle. For example, lesions in the right hemisphere of the cerebral cortex may lead to impairments in thought and action, but in the nonverbal realm, which is, by definition, difficult for the patient or the physician to describe.” (Pg. 31)He explains, “It is because of this immense number of functionally different configurations of the human brain that no two humans, even identical twins raised together, can ever be really very much alike… Indeed, in the face of these numbers, the wonder is that there are any regularities at all in human behavior. The answer must be that all possible brain states are by no means occupied; there must be an enormous number of mental configurations that have never been entered or even glimpsed by any human being in the history of mankind. From this perspective, each human being is truly rare and different and the sanctity of individual human lives is a plausible ethical consequence.” (Pg. 43-44)He acknowledges, “the brain is … ten thousand times more densely packed with information than is a computer, although the computer is much larger… a modern computer able to process the information in the human brain would have to be about ten thousand times larger in volume than the human brain… The brain must be extraordinarily cleverly packaged and ‘wired,’ with such a small total information content and so low a processing rate, to be able to do so many significant tasks so much better than the best computer.” (Pg. 47-48)He notes, “the most nearly unique human characteristic is the ability to associate abstractly and to reason. Curiosity and the urge to solve problems are the emotional hallmarks of our species; and the most characteristically human activities are mathematics, science, technology, music and the arts—a somewhat broader range of subjects than is usually included under the ‘humanities.’ Indeed, in its common usage the very word seems to reflect a peculiar narrowness of vision about what is human. Mathematics is as much a ‘humanity’ as poetry.” (Pg. 81-82)He suggests, “Perhaps the Garden of Eden is not so different from Earth as it appeared to our ancestors of some three of four million years ago, during a legendary golden age when the genus ‘Homo’ was perfectly interwoven with the other beasts and vegetables. After the exile from Eden we find, in the biblical account, mankind condemned to death; hard work… the domination of men over women; the domestication of plants (Cain); the domestication of animals (Abel); and murder (Cain plus Abel). These all correspond reasonably well to the historical and archaeological evidence. In the Eden metaphor, there is no evidence of murder before the Fall. But those fractured skulls of bipeds on the evolutionary line to man may be evidence that our ancestors killed, even in Eden, some manlike animals.” (Pg. 98)He observes, “As a consequence of the enormous social and technological changes of the last few centuries, the world is not working well. We do not live in traditional and static societies. But our governments, in resisting change, act is if we did. Unless we destroy ourselves utterly, the future belongs to those societies that, while not ignoring the reptilian and mammalian parts of our being, enable the characteristically human components of our nature to flourish; to those societies that encourage diversity rather than conformity; to those societies willing to invest resources in a variety of social, political, economic and cultural experiments, and prepared to sacrifice short-term advantage for long-term benefit; to those societies that treat new ideas as delicate, fragile and immensely valuable pathways to the future.” (Pg. 203-204)He argues, “the phrase ‘right to life’ is an excellent example of a ‘buzz word,’ designed to inflame rather than to illuminate. There is no right to life in any society on Earth today, nor has there been at any former time… the argument about the ‘potential’ to be human seems to me particularly weak. Any human egg or sperm under appropriate circumstances has the potential to become a human being…. In addition, it is possible that … we may be able to clone a whole human being from a single cell taken from essentially anywhere in the donor’s body. If so, any cell in my body has the potential to before a human being… Am I committing mass murder if I prick my finger and lost a drop of blood?… The key practical question is to determine when a fetus becomes human… This essential human quality, I believe, can only be our intelligence. If so, the particular sanctity of human life can be identified with the development and functioning of neocortex… Perhaps the transition would fall toward the end of the first trimester or nest the beginning of the second trimester of pregnancy.” (Pg. 206-209)He states, “Machines are just passing over an important threshold at which, to some extent at least, they give an unbiased human being the impression of intelligence… many humans are reluctant to admit this possibility. But I think it is inevitable. To me it is not in the least demeaning that consciousness and intelligence are the result of ‘mere’ matter sufficiently complexly arranged; on the contrary, it is an exalting tribute to the subtlety of matter and the laws of Nature.” (Pg. 221) Later, he adds, “The next major structural development in human intelligence is likely to be a partnership between intelligent humans and intelligent machines.” (Pg. 236)He speculates, “the idea of electromagnetic radiation for interstellar communication should be a cosmic commonplace—a convergent idea evolving independently on countless worlds throughout the galaxy … If we are fortunate enough to make contact with some of those other beings, I think we will find that much of their biology, psychology, sociology and politics will seem to us stunningly exotic and deeply mysterious. But I suspect we will have little difficulty in understanding each other on the simpler aspects of astronomy, physics, chemistry and perhaps mathematics.” (Pg. 243)He concludes, “There is today in the West … a resurgent interest in vague, anecdotal and often demonstrably erroneous doctrines that, if true, would betoken at least a more interesting universe, but that, if false, imply an intellectual carelessness… and a diversion of energies not very promising for our survival… It may be that there are kernels of truth in a few of these doctrines, but their widespread acceptance betokens a lack of intellectual rigor, and absence of skepticism, a need to replace experiments by desires… In contrast, the aperture to a bright future lies almost certainly through … reason alloyed with intuition… a courageous working through of the world as it really is.” (Pg. 247-248)This book (though more than forty year old) will be of great interest to those studying current issues in science.

⭐One of the late Carl Sagan’s hallmark qualities was to engage in speculation to a degree that was unusual for a rigorous scientist. While this sometimes resulted in largely unnecessary scorn and mockery from his fellow scientists, his honest skepticism combined with his open-mindedness also led to some of the most memorable popular science writing of our times. These qualities are on full display in this fascinating book, written in 1977 . Sagan tackles a topic that is far from his expertise – the evolution of human intelligence – and largely succeeds in presenting highly thought-provoking theses for us to ponder. Much of the book discusses what was then frontier research in neuroscience, but what makes it different are Sagan’s regular speculations.The book tries to make sense of two important facts about the human brain: our strikingly different cognitive abilities relative to other animals and the interplay between emotion and reason. Sagan is quite upbeat about chimp intelligence and he spends a sizable part of the book talking about experiments that reveal chimps’ prowess in using sign language. He also talks about the mysterious communication used by whales and dolphins that still defies comprehension. Clearly apes can come quite close to using the kind of simple vocabulary that humans do, so why are humans the only ones which actually crossed the language barrier, profiting from breakthrough linguistic inventions like recursive embedding and complex sentence construction? Sagan advances a chilling and all too likely hypothesis, that humans killed off apes who they thought came dangerously close to mimicking their linguistic capabilities. Given how closely language is tied to human intelligence, it then ensured that humans would be the dominant species on the planet; chimps, gorillas and orangutans were presumably saved because they lived deep inside the inaccessible jungle. Sagan’s discussion of animal intelligence hems uncomfortably close to ethical discussions about the killing of animals that are still so pertinent; what gives us the right to clearly assign personhood to a one-month-old fetus but not to a two-year-old chimpanzee, to have serious qualms about terminating the life of the former while cheerfully ending the life of the latter? Coming on the heels of this comparison is Sagan’s commonsense (in my opinion) take on abortion: he tries to reach a compromise by arguing that it should be unethical to kill a human fetus after it develops the first rudiments of a cerebral cortex, presumably the one thing that distinguished humanity from other species. Later work would probably cast some doubt on this assertion, since reptiles have also now been found to possess cortical cells.This part provides a good segue into the even more interesting part of the book which deals with some fascinating speculations on the reptilian origins of human intelligence. Sagan’s fulcrum for this discussion is a theory by psychiatrist Paul McLean who divided the brain into three parts (the “triune brain”). At the top is the uniquely human cerebral cortex which controls thought, reason and language. The second layer is the limbic system containing structures like the amygdala which modulate emotions like anxiety. The limbic system also includes the basal ganglia and the R complex, an ancient, inherited assembly responsible for instinctive behavior, including responding to reward and punishment. Finally you have the “neural chassis” which just like a car’s chassis includes structures like the brain stem responsible for basic and primitive functions: breathing, blood flow and balance for instance.Sagan’s focus is the R complex, part of the “reptilian brain”. It is quite clear that parts of this brain structure are found in reptiles. Reptiles and mammals have an ancient relationship; reptiles originated 500 million years before human beings, so we came into a world that was full of hissing, crawling, terrestrial, arboreal and aquatic reptiles. As Sagan describes, it’s no surprise that many of the world’s foremost civilizations and religions used reptiles as key symbols; from the snake in Eden to the worship of snakes in ancient Egypt to snake symbolism in modern day India, reptiles and human have shared an indelible bond. Reptiles have also often featured as omens in dreams dictating the fates of empires and societies. Some of our reptilian connections raise mundane but fascinating questions; for instance, Sagan wonders whether the shushing sound we make for communicating silence or disapproval is a leftover of the hissing sound of reptiles.But how does this relationship contribute to our behavior? It is here that the book takes off from firm ground and starts gently gliding on speculation.Sagan’s main springboard for investigating the R complex is Roger Sperry’s seminal work in delineating the separate roles of the left and right hemispheres of the brain. As Sperry demonstrated in amazing split-brain studies, the left brain is more logical and analytical while the right is more synthetic imaginative. Sagan’s contention is that the right brain is really the essence of our reptilian origins, helping us fantasize and imagine, and it’s also a key part of what makes us creative human beings. This is most prominent when we are dreaming. Notice that dreams almost never include details of problem solving, instead they feature highly imaginative scenarios, part familiar and part alien that seem to be largely driven by our fears and hopes: are we partly seeing the world through our ancient reptilian neuroanatomy when we are dreaming, then? Are dreams holdovers from a prehistoric world where, because of inadequate shelter and protection, we had to stay alert and awake during the night to engage with snakes and crocodiles on their own terms? And in the ensuing history of civilization, did reptilian anatomy contribute to our achievements in art and music? Sagan believes that we should encourage the operation of our reptilian brain, constantly tempering its excesses with the logical constraints of the left hemisphere. This distinction between right and left brain behavior also raises very interesting questions regarding whether we can suppress one or another temporarily using drugs and surgery. In fact, it’s likely that that is partly what hallucinogens like LSD do. Here we see Sagan the Renaissance Man, trying to bridge hard scientific thinking with artistic intuition.With its bold style and engaging language, “The Dragons of Eden” won a Pulitzer Prize. While I was aware of it, I always thought it would be too dated. I now realize that I was wrong and am glad I read it; it has given me plenty of fodder to think about and has prompted me to seek out new research on the topic. The book asks fascinating questions about our kinship with other creatures and about the evolution of our brain, topics that will be of perpetual and consummate interest as long as our species is around.

⭐Arrived timely and was exactly as described. Would buy again from this seller.

⭐It’s the original text and so on but don’t expect a regular ‘shop bought’ paperback as the print quality is a bit rubbish along with the paper and the layout on the inside. Still readable though. Images in the book are all showing the screen dots from where they’ve been scanned and reprinted in low res.

⭐This book, while dated in some cases; is a brillaint book about the evolution of humanity. It explains what set us apart from the rest of the animal kingdom.A very nice book to read, though this exact book I recieved had aged poorly, and didn’t exactly smell great!5/5 Read3/5 Physical condition.

⭐Quality of the print was passable but looking beyond this the concept of the biological development of the brain explains a lot about the delusional aspects of our species that are so destructive and have caused endless pain and distress throughout centuries.

⭐I always recommend this book to everyone. I bought it this time for my daughter as a gift. Really good to understand how different areas in our brain works but in the Carl Sagan language. Wonderful!

⭐A classic and highly recommended read. Accessible but not patronising.

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