Quotes by Carl Sagan

When all is said and done, the invention of writing must be reckoned not only as a brilliant innovation but as a surpassing good for humanity. And assuming that we survive long enough to use their inventions wisely, I believe the same will be said of the modern Thoths and Prometheuses who are today devisingcomputers and programs at the edge of machine intelligence.

The entire evolutionary record on our planet, particularly the record contained in fossil endocasts, illustrates a progressive tendency toward intelligence. There is nothing mysterious about this:smart organisms by and large survive better and leave more offspring than stupid ones.

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

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.

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.

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 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.

Perhaps the locale of the subjunctive mood willone day be found. Will Latins turn out to be extravagantly endowed and English-speaking peoples significantly short-changed in this minor piece of brain anatomy?

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?

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.

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.

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.

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.

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.

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.

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.

Both [P. T.] Barnum and H. L. Mencken are said to have made the depressing observation that no one ever lost money by underestimating the intelligence of the American public. The remark has worldwide application. But the lack is not in intelligence, which is in plentiful supply; rather, the scarce commodity is systematic training in critical thinking.

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

One of the saddest lessons of history is this: If we’ve been bamboozled long enough, we tend to reject any evidence of the bamboozle. We’re no longer interested in finding out the truth. The bamboozle has captured us. It’s simply too painful to acknowledge, even to ourselves, that we’ve been taken. Once you give a charlatan power over you, you almost never get it back.

You have to know the past to understand the present.