Shadows of Forgotten Ancestors

Philosophers of marauding high-technology civilizations have often argued that humans deserve a category distinct from and above all the other animals.* It is not enough that humans have a different assortment of the qualities evident in the other animals—more of some traits, fewer of others. A radical difference in kind, not some fuzzy-edged difference in degree, is needed, longed for, sought.

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.”³ 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 differences between our species and others were only of degree.

Many famous scientists, while fully accepting evolution, have parted company with Darwin on this question. For example, Theodosius Dobzhansky: “Homo sapiens is not only the sole tool-making and the sole political animal, he is also the sole ethical animal.”⁴ Or George Gaylord Simpson: “[M]an is an entirely new kind of animal … [T]he essence of his unique nature lies precisely in those characteristics that are not shared with any other animal,”⁵

especially self-awareness, culture, speech, and morality. The difference between humans and non-human animals according to a number of contemporary philosophers⁶ goes like this:Precisely because they are incapable of conceptual thought, animals … are not only (1) incapable of sentence-making that includes statements about the past and future, (2) unable to fabricate tools for remote future use, (3) devoid of a cumulative cultural inheritance that constitutes a long historical tradition, but they are also (4) incapable of any behavior that is not rooted in the perceptually apprehended present situation.

Apart from quibbles about how long is long in (3), every one of these confident assertions now appears false, on the basis of the sort of evidence we have presented or are about to present in this book. Even if we ourselves are not personally scandalized by the notion of other animals as close relatives, even if our age has accommodated to the idea, the passionate resistance of so many of us, in so many epochs and cultures, and by so many distinguished scholars, must say something important about us. What can we learn about ourselves from an apparent error so widespread, propagated by so many leading philosophers and scientists, both ancient and modern, and with such assurance and self-satisfaction?

One of several possible answers: A sharp distinction between humans and “animals” is essential if we are to bend them to our will, make them work for us, wear them, eat them—without any disquieting tinges of guilt or regret. With untroubled consciences, we can render whole species extinct—for our perceived short-term benefit, or even through simple carelessness. Their loss is of little import: Those beings, we tell ourselves, are not like us. An unbridgeable gap has thus a practical role to play beyond the mere stroking of human egos.⁷ Darwin’s formulation of this answer was: “Animals whom we have made our slaves, we do not like to consider our equals.”⁸

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We now proceed, in Darwin’s footsteps,⁹ to examine some of the multitude of proffered definitions of ourselves, explanations of who we are. We will try to see whether they make sense, especially in the light of what we know about the other beings that share the Earth with us.

One of the earliest attempts at an unambiguous characterization of humanity was Plato’s: Man is a featherless biped. When news of this advance in the art of definition reached the philosopher Diogenes, so the story goes, he introduced a plucked chicken into the weighty deliberations of Plato’s celebrated Academy, asking the assembled scholars to salute “Plato’s man.” This is of course unfair, because chickens are ordinarily born with feathers, just as they are ordinarily born with two feet. How we mutilate them afterwards does not change their fundamental nature. But the academicians took Diogenes’ challenge seriously and added another qualification: Humans were redefined as featherless bipeds with broad flat nails.