Carl Sagan, Dragons of Eden: Speculations on the Evolution of Human Intelligence

"Why are there no nonhuman primates with an existing complex gestural language? One possible answer, it seems to me, is that humans have systematically exterminated those other primates who displayed signs of intelligence."

"I would expect a significant development and elaboration of language in only a few generations if all the chimps unable to communicate were to die or fail to reproduce. Basic English corresponds to about 1,000 words. Chimpanzees are already accomplished in vocabularies exceeding 10 percent of that number."

"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 government, in resisting change, act as 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."

"The price we pay for the anticipation of our future is anxiety about it."

"While ritual, emotion and reasoning are all significant aspects of human nature, 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 this very word seems to reflect a peculiar narrowness of vision about what is human. Mathematics is as much a "humanity" as poetry."

"Once intelligent beings achieve technology and the capacity for self-destruction of their species, the selective advantage of intelligence becomes more uncertain."

"a typical chromosomal DNA molecule in a human being is composed of about five billion pairs of nucleotides… But since there are four different kinds of nucleotides, the number of bits of information in DNA is four times the number of nucleotide pairs. Thus if a single chromosome has five billion (5 X 10^9) nucleotides, it contains twenty billion (2 X 10^10) bits of information… We also see that if more than some tens of billions (several times 10^10) of bits of information are necessary for human survival, extragenetic systems will have to provide them: the rate of development of genetic systems is so slow that no source of such additional biological information can be sought in the DNA."

"Lashley also reported no apparent change in the general behavior of a rat when significant fractions—say 10 percent—of its brain were removed. But no one asked the rat of its opinion."

"Somewhere in the steaming jungles of the Carboniferous Period there emerged an organism that for the first time in the history of the world had more information in its brains than in its genes. It was an early reptile which, were we to come upon it in these sophisticated times, we would probably not describe as exceptionally intelligent… Much of the history of life since the Carboniferous Period can be described as the gradual (and certainly incomplete) dominance of brains over genes."

"Evolution is adventitious and not foresighted. Only through the deaths of an immense number of slightly maladapted organisms are we, brains and all, here today."

"The time scale for evolutionary or genetic change is very long. A characteristic period for the emergence of one advanced species from another is perhaps a hundred thousand years; and very often the difference in behavior between closely relatedspecies-say, lions and tigers-do not seem very great... But today we do not have ten million years to wait for the next advance. We live in a time when our world is changing at an unprecedented rate. While the changes are largely of our own making, they cannot be ignored. We must adjust and adapt andcontrol, or we perish."

"In addition, human beings have, in the most recent few tenths of a percent of our existence, invented not only extra-genetic but also extrasomatic knowledge: information stored outside our bodies, of which writing is the most notable example."

"with rare exceptions (chiefly the social insects), mammals and birds are the only organisms to devote substantial attention to the care of their young; an evolutionary development that, through the long period of plasticity which it permits, takes advantage of the large information-processing capability of the mammalian and primate brains. Love seems to be an invention of the mammals."

"Do dogs feel for humans something akin to religious ecstasy? What other strong or subtle emotions are felt by animals that do not communicate with us?"

"It is precisely our plasticity, our long childhood, that prevents a slavish adherence to genetically preprogrammed behavior in human beings more than in any other species… Some substantial adjustment of the relative role of each component of the triune brain is well within our powers."

"Our difficulties in understanding or effectuatingcommunication with other animals may arise from our reluctance to grasp unfamiliar ways of dealing with the world."

"It is interesting that it is not the getting of any sort of knowledge that God has forbidden, but, specifically, the knowledge of the difference between good and evil-that is, abstract and moral judgments, which, if they reside anywhere, reside in the neocortex."

"And despite the insignificance of the instant we have so far occupied in cosmic time, 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."

"Natural selection has served as a kind of intellectual sieve, producing brains and intelligences increasingly competent to deal with the laws of nature."

"As in all such technological nightmares, the principal task is to foresee what is possible; to educate use and misuse; and to prevent its organizational, bureaucratic and governmental abuse."