shadow of forgotten ancestors

Most of the philosophers adjudged great in the history of Western thought held that humans are fundamentally different from the other animals. Plato, Aristotle, Marcus Aurelius, Epictetus, Augustine, Aquinas, Descartes, Spinoza, Pascal, Locke, Leibniz, Rousseau, Kant, and Hegel were all proponents ‘of the view that man differs radically in kind from [all] other things’; except for Rousseau, they all held the essential human distinction to be our 'reason, intellect, thought, or understanding.’ Almost all of them believed that our distinction arises from something made neither of matter nor of energy that resides within the bodies of humans, but of no one else on Earth. No scientific evidence for such a 'something’ has ever been produced. Only a few of the great Western philosophers—David Hume, for instance—argued, as Darwin did, that the difference between our species and others were only of degree.
—  Carl Sagan & Ann Druyan, ‘Shadows of Forgotten Ancestors’
We know the insect decides who to eat, who to run away from, who to find sexually attractive. On the inside, within its tiny brain, does it have no perception of making choices, no awareness of its own existence? Not a milligram’s worth of self-consciousness? Not a hint of a hope for the future? Not even a little satisfaction at a day’s work well done? If its brain is one millionth the mass of ours, shall we deny it one millionth of our feelings and our consciousness? And if, after carefully weighing such matters, we insist it is still ‘only’ a robot, how sure are we that this judgment does not apply to us as well?
—  Carl Sagan & Ann Druyan, ‘Shadows of Forgotten Ancestors’
Who are we? Where do we come from? Why are we this way and not some other? What does it mean to be human? Are we capable, if need be, of fundamental change, or do the dead hands of forgotten ancestors impel us in some direction, indiscriminately for good or ill, and beyond our control? Can we alter our character? Can we improve our societies? Can we leave our children a world better than the one that was left to us? Can we free them from the demons that torment and haunt our civilization? In the long run, are we wise enough to know what changes to make? Can we be trusted with our own future?
—  Carl Sagan & Ann Druyan, ‘Shadows of Forgotten Ancestors’
Our written records carry us only a millionth of the way back to the origin of life. Our beginnings, the key events in our early development, are not readily accessible to us. No firsthand accounts have come down to us. They cannot be found in living memory or in the annals of our species. Our time-depth is pathetically, disturbingly shallow… We are cut off from our past, separated from our origins, not through some amnesia or lobotomy, but because of the brevity of our lives and the immense, unfathomed vistas of time that separate us from our coming to be.
—  Carl Sagan & Ann Druyan, ‘Shadows of Forgotten Ancestors’