The Dragons of Eden

ISBN: 0345281535
ISBN 13: 9780345281531
By: Carl Sagan

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About this book

Dr. 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."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 TIMES

Reader's Thoughts

Aaron Crossen

I read this when my family vacationed to Lexington like 8 years ago. I don't remember anything about it, other than it made me want to read Cosmos.

Kevin Orrman-Rossiter

For me, University was a time of intellectual awakening. In the first two years this was not so much from lectures and interminable pracs that I attended. Rather it was from the realisation of how much art and science and technology I had never come across before. In first year university we were required to study a non-science subject; I enrolled in Psychology. In amongst developing our paper plane skills, lectures on Skinner, perception, personality, emotion, were lectures on human consciousness and intelligence - subjects that I continue to find fascinating. Spurred on by these lectures I bought and read a profound, influential, new release by Carl Sagan: The Dragons of Eden.It is hard to convey how influential this book was for me. I still to this day have not read a science book so fascinatingly and simply written on such an easily misconstrued subject as the evolution of human intelligence. It was only when writing this review that I became aware that The Dragons of Eden was awarded the 1978 Pulitzer prize. Forty years on and ‘Evolution’, like ‘climate change’ have become the bête noire subjects of the conservative right of western democratic politics. As for ‘intelligence’, the self-help book-shelves have become replete with trite nonsense on how to define, measure, and improve your and your team’s ‘intelligence’. I recommend a small dose of Sagan-sense to them all.Read the complete review here:

David Kaczynski

This is simply the best book I was lucky enough to receive as a gift. Written thirty years ago, Sagan's principles in science, philosophy, and humanity seem to grow more valid as the years go on. I used to be an existentialist nutcase in high school, but this book straightened me right out. I can't wait to re-read this beauty


The copy of the book I got was published in 1977 and what isn't out of date is wrong. The subtitle is "Speculations on the evolution of human intelligence", but little in the book is about that topic. The book rambles from from one subject to another,from cute drawings by everyone's favorite: M.C. Escher,to the chemical composition of distant stars. Perhaps the most interesting part is the chart that shows Brain mass vs. Body weight. On that chart moles rate quite highly.Probably not the point the author was trying to make. The next time I see a mole I'll watch for signs of intelligence. There are many tidbits of trivia, one is the fact , that the average person has a 10% chance of having a genetic mutation that can be passed on to the next generation. Needless to say, almost all of these are harmful.


One of the most beautiful things I've ever read came from this book:"If the human brain had only one synapse-- corresponding to a monumental stupidity-- we would be capable of only two mental states. If we had two synapses, then 2^2 = 4 states; three synapses, then 2^3 = 8 states, and, in general, for N synapses, 2^N states. But the human brain is characterized by some 10^13 synapses. Thus the number of different states of a human brain is 2 raised to this power-- i.e., multiplied by itself ten trillion times. This is an unimaginably large number, far greater, for example, than the total number of elementary particles (electrons and protons) in the entire universe."


"There is a popular game, sometimes called Pong, which simulates on a television screen a perfectly elastic ball bouncing between two surfaces. Each player is given a dial that permits him to intercept the ball with a movable "racket". Points are scored if the motion of the ball is not intercepted by the racket. The game is very interesting. There is a clear learning experience involved which depends exclusively on Newton's second law for linear motion. As a result of Pong, the player can gain a deep intuitive understanding of the simplest Newtonian physics - a better understanding even than that provided by billiards, where the collisions are far from perfectly elastic and where the spinning of the pool balls interposes more complicated physics.This sort of information gathering is precisely what we call play. And the important function of play is thus revealed: it permits us to gain, without any particular future application in mind, a holistic understanding of the world, which is both a complement of and a preparation for later analytical activities. But computers permit play in environments otherwise totally inaccessible to the average student."

Greg Metcalf

As I was reading this book again, since a first reading close to twenty years ago, a friend mentioned that if he was going to read a popular science book, he'd read a new one, not one from the seventies. That comment kind of got stuck in my head. It would certainly be interesting to read about how far sign language development with chimpanzees, for example, has come, which must have just gotten started when Sagan wrote about it here. But this book is Carl Sagan playing with possibilities. In a chapter on right and left hemisphere brain functioning, he suggests the possibility that the effect of marijuana might be to inhibit left brain reasoning giving the more intuitive right brain more influence over our thinking, which he compares to there always being stars above us but we need the dominant sun to set before they become visible. What a fascinating notion and how poetically stated. If anything Sagan writes about here has been disproven, he would be the first to say, Isn't this new evidence fascinating? We all wish Carl Sagan were alive and writing books about the cutting edge discoveries of today, but his creative thinking remains an inspiration. At one point, he was writing about how the written word manages to put the voice of someone else in your mind and wrote "(Hello!)" That alone made this well worth a second read.

Mukesh Kumar

Pure bliss. In the inimitable manner of Carl Sagan, engrossing, enlightening and amusing in equal measure.


This book is dated, but good. I love reading about research on the human brain. Sagan makes lots of corny jokes and asides that are not really appropriate but sort of endearing. The evolution of the brain is the focus and Sagan talks a lot about the "reptilian" brain, the part that we had before we became human. Also the discussion of what really makes us human is so interesting. On the radio some modern researcher said that the brain is a record, a story of what has happened to that particular body. Anyways, this book is archaic compared to what they know now, so I am looking for a modern (post-modern?) read on the amazing human brain!


Difficult to rate, because the science described has moved on so rapidly since 1977, the publication date. I read it in order to feel re-acquainted with Sagan's friendly tone in his effort to popularize science ( live a few blocks from the old KCET studios from the "Cosmos" era). In that regard, it is very ingenious and concise. And frankly, the underlying scientific concepts still need popularizing. Appreciation of genetic science, paleontology, and even psychiatry is now extremely low - "pop culture" has eclipsed science and introspection for too many of the decades since the '70s - so Sagan's hopeful tone evokes nostalgia now. He aspired to be a polymath as well as a popularizer, so at the time of publication, I remember that he was knocked down for straying away from astronomy. But he asked good questions here, and not all of his answers are outdated. He responds to Julian Jaynes, in a fashion. He warns against pseudo-science, which has only proliferated and put national policy at risk, since. Glad to have picked it up!

Erik Graff

Carl Sagan, like Stephen Jay Gould, is one of those scientists gifted as a teacher to non-specialists. This book is about intelligence, a topic both men dealt with, Gould most notably in his Mismeasure of Man. Sagan, however, deals with all intelligence, ending his book with a discussion of nonhuman intelligences, most particularly certain Cetaceans and primates. Noting that chimpanzees and gorillas appear to be intellectually comparable to human five-year-olds, he ends with a plea to extend some of the rights we afford our own children to members of other intelligent species.I read this book outside at the Ennui Cafe on Sheridan and Lunt in East Rogers Park, Chicago. The weather was beautiful, the lake perfect.


"To write a book in a subject so far from one's primary training is at best incautious. But...the temptation was irresistible." That quote, found in the acknowledgements, sums up both the very serious problems with this work, and also it's ironic charm. You must read this early work of Sagan not as definitive science, but as a prime example of his inimitable ability to connect science to other intellectual concerns such as myth, religion and history, thus stimulating thought in the process.At least Sagan is completely honest: the subtitle itself indicates these are "speculations" which presumably have not been verified. In fact, the book represents a kind of popular science (really, science itself) not seen much anymore. It takes confidence and a willingness to take criticism and the harsh judgement of history, to produce such a work. It's value is of the highest order: that of creative thinking. "This book itself is an exercise in pattern recognition, and attempts to understand something of the nature and evolution of human intelligence, using clues from a wide variety of sciences and myths. It is in significant part a right-hemisphere activity; and in the course of writing I was repeatedly awakened in the middle of night or in the early hours of the morning by the mild exhilaration of a new insight. But whether the insights are genuine – and I expect many of them will require substantial revision – depends on how well my left hemisphere has functioned." [italics mine]The writing is the usual poetic Sagan style, highly readable and yet capable of conveying deep thoughts. The difficulties, however, are serious. It's hard to know what is speculation, what was accepted as fact in 1977, what has been proved true, and what's been superseded. Read the book to marvel at Sagan's mind, not to learn current knowledge on how the brain works.I could list many factual things wrong: excessive reliance on the triunal brain (putting too much emphasis on the brains's "reptilian-complex" as a driver of aggressive behavior and everything else anti-intellectual, for example), offering up the wrong theory for the extinction of the dinosaurs (he says it was a supernova explosion: hard to believe that Sagan, himself a planetary scientist, had not even considered in 1977 the now generally accepted asteroid impact theory!), and I could go on at length. But...there really is no reason to point out the errors. Again, the purpose of this book is not to serve as a textbook, but to stimulate thought—to speculate.The core of the book is his ideas on evolutionary memory, those experiences of proto-humans which to assure species survival were recorded in DNA. This is controversial, for sure, but it's curious how he links several creation myths—Greek, Genesis—to "dragons," which he defines as now-extinct larger, more dangerous reptiles which preyed upon mammals, including humans. "We are descended from reptiles and mammals both. In the daytime repression of the R-complex, in the nighttime stirring of the dream dragons, we may each of us be replaying the hundred-million-year-old warfare between the reptiles and the mammals." Maybe he's suggesting these were actually dinosaurs, maybe not, but he is suggesting some sort of evolutionary survival memory preserved to assist success, such as fear of snakes. This following should give you a flavor of the book. He's stretching mightily to merge poetry with science: "The pervasiveness of dragon myths in the folk legends of many cultures is probably no accident. ... Is it possible that dragons posed a problem for our protohuman ancestors of a few million years ago, and that the terror they evoked and the deaths they caused helped bring about the evolution of human intelligence? Or does the metaphor of the serpent refer to the use of the aggressive and ritualistic reptilian component of our brain in the further evolution of the neocortex? With one exception, the Genesis account of the temptation by a reptile in Eden is the only instance in the Bible of humans understanding the language of animals. When we feared the dragons, were we fearing a part of ourselves? One way or another, there were dragons in Eden."Only Sagan could get away with this poetic image and remain scientific: from almost any other it would be pseudo-science; here it is rational speculation, although certainly offered without any proof.Less seriously, it's fun to read Sagan's view on computers—as of 1977. In almost every book he wrote, he couldn't resist gushing about them! It's possible to string these parts together from his thirty-year-long book publishing career and have a respectable history of computers and their affect on culture and scientific research. Dragons of Eden is a humorous gem in this regard, as, for example: "The computer terminal is a commonplace on the Dartmouth campus. A very high proportion of Dartmouth undergraduates learn not only to use such programs but also to write their own."I intend no criticism, but the extended excerpt below is, shall we say, embarrassing in its outright geekiness. You probably won't be able to resist laughing at his amazement with the invention of computer games, now so completely endemic: "Computer graphics are now being extended into the area of play. There is a popular game, sometimes called Pong, which simulates on a television screen a perfectly elastic ball bouncing between two surfaces. Each player is given a dial that permits him to intercept the ball with a movable "racket." Points are scored if the motion of the ball is not intercepted by the racket. The game is very interesting. There is a clear learning experience involved which depends exclusively on Newton's second law for linear motion. As a result of Pong, the player can gain a deep intuitive understanding of the simplest Newtonian physics…"Although his book won the Pulitzer Prize for General Nonfiction in 1978, Dragons of Eden can no longer be recommended to the general reader. It has aged far too much to be reliable. Still, it retains much interest and beauty for the dedicated Carl Sagan fan.

Itzel Morales

Muuuuuy bueno


Interesting read, as long as one takes into account that it's quite old and outdated by now, so it's not exactly cutting edge. (I read it pretty long ago myself).Still, Sagan has a such a pleasant, conversational style, that even reading it for the speculations alone, makes reading the book a not unpleasant way of whiling away your time.I like the angles he chooses to speculate from, especially the bits about instinct and how myths most probably formed in the human collective subconscious.


One of the lesser points Sagan introduces is the analytical check our "left" brain must impose on our "right" brain's more intuitive connections. Ironically I would argue that Sagan's hesitance to check himself was this book's biggest failure. Often he excitedly drew out connections, usually preceded by a phrase such as "I wonder," that do not stand his left-brained test of reason. With that said, I found the book worth the read. Sagan draws up a quick tour of human evolutionary lineage with a focus on our neocortical developments. He also always had a ready comparison to primates in order to morefully showcase what makes us "human". As always, the line is thinner and more vague than many more orthodox religions would like to believe. One major takeaway was the human ability, through the development of the neocortex, to have built-in "intelligence", I.e. analytical thinking, as compared to "instinct". Whereas instinctual information is programmed into tightly packed DNA (and is therefore limited in nature) and survives solely off adaptive selection, intelligence (or extragenetic info) resides in a larger brain capacity.. it is the ability to think on the fly and respond successfully to innumerable changing environments and situations. Sagan introduces many other varying ideas and usually does a good job supporting them scientifically. All in all, if you ignore anything he says about aliens or computers, it's a good read.

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