Shadows of Forgotten Ancestors

by Carl Sagan

  9. The North American Review 90 (April 1860), pp. 487 and 504.

  10. The London Quarterly Review 215 (July 1860), pp. 118–138.

  11. The North British Review 64 (May 1860), pp. 245–263.

  12. The London Quarterly Review 36 (July 1871), pp. 266–309.

  13. George Bernard Shaw, Back to Methusaleh: A Metabiological Pentateuch (New York: Brentano’s, 1929), p. xlvi. The last sentence is in fact the modern evolutionary point of view.

  14. James Watt, U.S. Secretary of the Interior in the first Reagan term, justified despoiling public lands on the grounds that he was unsure how much time we had “until the Lord comes.” Manuel Lujan, U.S. Secretary of the Interior under President Bush, argued against protecting endangered species because “[M]an is at the top of the pecking order. I think that God gave us dominion over these creatures … consider the human being on a higher scale. Maybe that’s because a chicken doesn’t talk … God created Adam and Eve, and from there all of us came. God created us pretty much as we look today.” (Ted Gup, “The Stealth Secretary,” Time, May 25, 1992, pp. 57–59.) Genesis urges us to “subdue” Nature, and predicts that “fear” and “dread” of us is to be upon “every beast.” These religious precepts have practical consequences in the human assault on the environment (cf. John Passmore, Man’s Responsibility for Nature: Ecological Problems and Western Traditions [New York: Scribner’s, 1974]). Leaders of a wide variety of religions have nevertheless taken forthright stands and political action to protect the environment (e.g., Carl Sagan, “To Avert a Common Danger: Science and Religion Forge an Alliance,” Parade, March 1, 1992, pp. 10–15).

  15. Alfred Russel Wallace, the co-discoverer with Darwin of evolution by natural selection—a generous and self-effacing man who described himself as “shy, awkward and unused to good society”—differed with him on one crucial matter. He was willing to accept that every beast and vegetable had so evolved, but not humans. Some divine (and self-reproducing) spark had to be injected at a comparatively recent date in the evolutionary process, he held. Wallace’s evidence?

  Unlike the racists of his time, Wallace was struck that the brain size and anatomy of all humans are sensibly the same: “The more I see of uncivilized people, the better I think of human nature, and the essential differences between civilized and savage men seem to disappear … We find many broad statements as to the low state of morality and of intellect in all prehistoric men which the facts hardly warrant.” (Quoted in Loren Eiseley, Darwin’s Century [New York: Doubleday, 1958], p. 303.) But pretechnological peoples, he thought, had no need of a brain able, say, to invent steam engines. So the human brain must somehow have been contrived early in order to perform complex adaptive functions much later. Such foresight, he well understood, was inconsistent with the fortuitous and short-term nature of natural selection. Thus, “some higher intelligence may have directed the process by which the human race was developed.” (Ibid., p. 312.)

  However, Wallace greatly underestimated the complexity of pre-industrial societies. There has never been a pretechnological human culture. Fashioning stone tools and hunting large animals are by no means easy. Big brains were an advantage to us from the start.

  Wallace was also transfixed by the spate of spiritualist demonstrations so popular in late Victorian England, including spirit rapping, seances, conversations with the dead, materializations of “ectoplasm,” and the like. These seemed to reveal a hidden spirit component of humans, but of no other living things. So far as we know, this heady brew was concocted out of equal parts skillful charlatans and credulous upper-class audiences. The magician Harry Houdini played an important role in later exposing some of these impostures. Wallace was hardly the only eminent Victorian to be taken in.

  When, toward the end of this book, we explore the extraordinary cognitive talents of chimpanzees as revealed in laboratory tests, a similar question occurs to us: How can they be preadapted to solve such complex problems? And the answer, or at least part of it, may be the same as for Wallace’s conundrum: In their everyday lives in the wild, chimps need a broad-gauge, multi-purpose intelligence—not nearly as advanced as what humans have, but much more than we might think.

  16. Nora Barlow, editor, The Autobiography of Charles Darwin (New York: Harcourt Brace, 1958), p. 95.

  17. James H. Jandl, Blood: Textbook of Hematology (Boston: Little Brown, 1987), pp. 319 et seq. See also David G. Nathan and Frank A. Oski, Hematology of Infancy and Childhood, 3rd ed. (Philadelphia: W. B. Saunders, 1987), Chapter 22.

  18. A. C. Allison, “Abnormal Haemoglobin and Erythrocyte Enzyme Deficiency Traits,” in D. F. Roberts, editor, Human Variation and Natural Selection, Symposium of the Society for the Study of Human Biology 13 (1975), pp. 101–122.

  19. Nora Barlow, op. cit., p. 93.

  20. An influential modern assessment from the Darwinian perspective of the behavior of animals in groups is E. O. Wilson’s Sociobiology: The New Synthesis (Cambridge, MA: Harvard University Press, 1975). The book in general excited little controversy, but the closing chapter—in which natural selection was applied to humans—elicited a storm of criticism, including the pouring of a pitcher of water over the author’s head at a scientific meeting. Wilson has taken care to stress that human behavior is the product of both hereditary and environmental influences, and has generally made his claims modestly and cautiously: “I might easily be wrong—in any particular conclusion, in the grander hopes for the role of the natural sciences, and in the trust gambled on scientific materialism … The uncompromising application of evolutionary theory to all aspects of human existence will come to nothing if the scientific spirit itself falters, if ideas are not constructed so as to be submitted to objective testing and hence made mortal.” (E. O. Wilson, On Human Nature [Cambridge, MA: Harvard University Press, 1978], pp. x-xi.)

  We can glimpse something of the fervor of this debate in the following, perhaps intemperate, remarks: “American social scientists fear and despise biology, although few of them have troubled to learn any … Again and again in the writings of social scientists, we find ‘biological’ equated with ‘Invariant’ … This usage betrays an incomprehension of the domain of biology.” (Martin Daly and Margo Wilson, Homicide [New York: Aldine de Gruyter, 1988], p. 154.)

  Excellent recent books on evolution for the general reader include those by Richard Dawkins (e.g., The Selfish Gene [Oxford: Oxford University Press, 1976]; The Extended Phenotype [Oxford: Oxford University Press, 1982]; The Blind Watchmaker [New York: Norton, 1986]) and by Stephen J. Gould (e.g., Ever Since Darwin [New York: Norton, 1977]; The Panda’s Thumb [New York: Norton, 1980]; Wonderful Life [New York: Norton, 1990]). By comparing these books, we can glimpse the healthy and vigorous scientific debate that thrives under the aegis of modern evolutionary biology.

  21. John Bowlby, Charles Darwin: A New Life (New York: W. W. Norton, 1990), p. 381.

  22. Francis Darwin, op. cit., Volume I, pp. 134, 135.

  23. Ibid., Volume III, p. 358.

  24. See, e.g., Leonard Huxley, Thomas Henry Huxley (Freeport, NY: Books for Libraries, 1969); Cyril Bibby, Scientist Extraordinary (Oxford: Pergamon, 1972).

  25. Cyril Bibby, T. H. Huxley: Scientist, Humanist and Educator (London: Watts, 1959), pp. 35, 36.

  26. Thomas H. Huxley, “On the Hypothesis that Animals Are Automata, and its History” (1874), in Collected Essays, Volume I, Method and Results: Essays (London: Macmillan, 1901), p. 243.

  27. Francis Darwin, editor, The Life and Letters of Charles Darwin (London: John Murray, 1888), Volume III, p. 358.

  28. Bibby, 1959, op. cit., p. 259.

  29. All quotations except that attributed to Emma Darwin at the end are taken from eyewitness accounts, although most were written down years and even decades after the event. A memorable essay on the debate, “Knight Takes Bishop?” is in Steven J. Gould’s Bully for Brontosaurus (New York: W. W. Norton, 1991). Our version of Huxley’s response to Wilberforce is from the recollections of G. Johnstone Stoney,
who was present. (Stoney did pioneering work on the escape to space of planetary atmospheres, and was the first to understand why the Moon is airless.) It differs from Huxley’s own later recollection, which went like this: “If then, said I, the question is put to me would I rather have a miserable ape for a grandfather or a man highly endowed by nature and possessed of great means of influence, & yet who employs those faculties & that influence for the mere purpose of introducing ridicule into a grave scientific discussion—I unhesitatingly affirm my preference for the ape.” (Bibby, 1959, op. cit., p. 69.)

  Chapter 5

  LIFE IS JUST A THREE-LETTER WORD

  1. The Bhagavad Gita, translated by Juan Mascaró (London: Penguin, 1962), Introduction, p. 14.

  2. Lucien Stryk and Takashi Ikemoto, translators, Zen Poems of China and Japan: The Crane’s Bill (New York: Grove Press, 1973), p. 87.

  3. Even in our language there remains the idea that motion requires a soul. But if there is a dusty soul that decides for every mote how and when it is to move, what animates that soul? Does it have a still smaller soul—a soul’s soul—and so on, in an infinite regress of microscopic immaterial motivators? No one believes this. And if the soul of the dust mote doesn’t need its own smaller soul to tell it what to do, why does the dust mote itself need a soul? Might it move on its own, without spiritual direction?

  4. The discovery of discrete units of heredity, the genes, dates back to experiments first published in 1866 by the plant breeder Gregor Mendel. His work was essentially unread until his laws of genetics were independently rediscovered at the beginning of the twentieth century. Charles Darwin knew nothing about Mendel’s work; it would have made his task much easier if he had. While nucleic acids were discovered in cells in 1868, their central importance for heredity was first suspected only in the 1940s. The remarkable structure of DNA—with long chains of nucleotides like the letters in a book, and two intertwined strands suggesting a ready means of replication—was first understood in 1953 by James Watson and Francis Crick. Classical genetics had been wholly innocent of the chemistry of the gene.

  5. How reading the genetic instructions of different organisms might unlock the evolutionary record was first stated by Emile Zuckerkandl and Linus Pauling, “Molecules as Documents of Evolutionary History,” Journal of Theoretical Biology 9 (1965), pp. 357–366.

  6. Loren Eiseley, The Immense Journey (New York: Vintage, 1957).

  7. Wen-Hsiung Li and Dan Graur, Fundamentals of Molecular Evolution (Sunderland, MA: Sinauer Associates, 1991), Figure 21, p. 135. The sequences shown are from the DNA encoding the 5S ribosomal-RNA [r-RNA] sequences.

  8. Ibid., pp. 6, 10.

  9. Cf. Edward N. Trifonov and Volker Brendel, Gnomic: A Dictionary of Genetic Codes (New York: Balaban Publishers, 1986), p. 8.

  10. Natalie Angier, “Repair Kit for DNA Saves Cells from Chaos,” New York Times, June 4, 1991, pp. C1, C11.

  11. Daniel E. Dykhuizen, “Experimental Studies of Natural Selection in Bacteria,” Annual Review of Ecology and Systematics 21 (1990), pp. 373–398.

  12. Quoted in Monroe W. Strickberger, Evolution (Boston: Jones and Bartlett, 1990), p. 34.

  13. A semi-popular early exposition by Lord Kelvin of his argument (he was then merely “W. Thomson” of the University of Glasgow) appeared as “On the Age of the Sun’s Heat” in the March 1862 number of Macmillan’s Magazine.

  14. Thomas Henry Huxley, “On a Piece of Chalk,” in Collected Essays, Volume VIII, Discourses: Biological and Geological (London and New York: Macmillan, 1902), p. 31.

  15. Niles Eldredge, Time Frames: The Rethinking of Darwinian Evolution and the Theory of Punctuated Equilibria (New York: Simon and Schuster, 1985). There are several different kinds of “punctuation” possible. Those stressed (and for good reason) by Eldredge and Gould are consistent with the prevailing views of evolutionary biologists since World War II (e.g., George Gaylord Simpson, Tempo and Mode in Evolution [New York: Columbia University Press, 1944]), or, indeed, with the views of Darwin himself (e.g., Richard Dawkins, The Blind Watchmaker [New York: Norton, 1986], Chapter 9). Contrary to the claims of creationists, the debate about punctuated equilibrium poses no challenge to evolution or natural selection. Gould has been especially effective in defending the teaching of Darwinian evolution in the schools.

  16. More exactly, each strand manufactures a complementary strand, in which As are substituted for Ts, Gs for Cs, and vice versa. When, in due time, the complement reproduces, the original strand is duplicated, and so on. But the same genetic information is copied every generation.

  17. RNA is the messenger by which DNA conveys what proteins are to be made by the cell. It is also the catalyst that presides over the linking up of amino acids into the proteins specified by the DNA. (M. Mitchell Waldrop, “Finding RNA Makes Proteins Gives ‘RNA World’ a Big Boost,” Science 256 [1992], pp. 1396–1397, and other articles in the June 5, 1992 issue of Science.) To an increasing number of molecular biologists, these facts suggest an early form of life in which RNA did the information storage, replication, and catalysis all by itself, with DNA and proteins taking over later.

  18. Jong-In Jong, Qing Feng, Vincent Rotello, and Julius Rebek, Jr., “Competition, Cooperation, and Mutation: Improvement of a Synthetic Replicator by Light Irradiation,” Science 255 (1992), pp. 848–850; J. Rebek, Jr., private communication, 1992. A survey of the present state of knowledge is Leslie Orgel, “Molecular Replication,” Nature 358 (1992), pp. 203–209.

  19. In Lucien Stryk and Takashi Ikemoto, translators, Zen Poems of China and Japan: The Crane’s Bill (New York: Grove Press, 1973), p. xlii.

  Chapter 6

  US AND THEM

  1. Book XXII, line 262.

  2. Lynn Margulis, Symbiosis in Cell Evolution (San Francisco: W. H. Freeman, 1981).

  3. Andrew H. Knoll, “The Early Evolution of Eukaryotes: A Geological Perspective,” Science 256 (1992), pp. 622–627.

  4. Margulis, op. cit.

  5. L. L. Woodruff, “Eleven Thousand Generations of Paramecium,” Quarterly Review of Biology 1 (1926), pp. 436–438.

  6. Z. Y. Kuo, “The Genesis of the Cat’s Response to the Rat,” Journal of Comparative Psychology 11 (1930), pp. 1–30.

  7. Benjamin L. Hart, “Behavioral Adaptations to Pathogens and Parasites: Five Strategies,” Neuroscience and Biobehavioral Reviews 14 (1990), pp. 273–294.

  8. George C. Williams and Randolph M. Nesse, “The Dawn of Darwinian Medicine,” Quarterly Review of Biology 66 (1991), pp. 1–22.

  9. Harry J. Jerison, “The Evolution of Biological Intelligence,” Chapter 12 of Robert J. Sternberg, editor, Handbook of Human Intelligence (Cambridge: Cambridge University Press, 1982), Figure 12–11, p. 774.

  10. A view championed in recent times by the neurophysiologist Paul D. MacLean and described in Carl Sagan’s The Dragons of Eden: Speculations on the Evolution of Human Intelligence (New York: Random House, 1977). MacLean sets forth a comprehensive summary of his views in The Triune Brain in Evolution: Role in Paleocerebral Functions (New York and London: Plenum Press, 1990).

  11. This approach is made most accessible to the general reader in Richard Dawkins’s book The Selfish Gene, revised edition (Oxford: Oxford University Press, 1989). In a vivid passage (pp. 19–20), he describes the genes as swarming “in huge colonies, safe inside gigantic lumbering robots, sealed off from the outside world, communicating with it by tortuous indirect routes, manipulating it by remote control. They are in you and me; they created us, body and mind; and their preservation is the ultimate rationale for our existence … [W]e are their survival machines.”

  12. A related and even more heated controversy—on whether the mother bird has any notion of what she’s doing or is merely some carbon-based automaton—is addressed later in this book. Reciprocal altruism, an exchange of present for future favors, is also admitted by those who deny group selection per se.

  13. Martin Daly and Margo Wilson, Homicide (New York: Aldine de Gruyter, 1988), pp. 88
, 89.

  14. W. D. Hamilton, “The Genetical Evolution of Social Behavior,” Journal of Theoretical Biology 7 (1964), pp. 1–51; John Maynard Smith, “Kin Selection and Group Selection,” Nature 201 (1964), pp. 1145–1147.

  15. Imagine that the huddled group (of, say, insects) is in the shape of a sphere. The heat generated by the group is proportional to its volume (to the cube of its size), but the heat radiatively lost by the group is proportional to its area (to the square of its size). Thus the bigger the group is, the more heat it retains. In a large group, only a small proportion of members are on the surface of the sphere, where an individual is exposed to the cold; the remainder are satisfyingly surrounded by warm bodies on all sides. The smaller the group is, the greater the proportion of individuals on the chilly periphery.

  16. Up to some limit, when the individuals doing the mobbing get in each other’s way.

  17. Dawkins, op. cit., p. 171, citing the work of Amotz Zahavi.

  18. Ibid., Preface to 1989 edition. For an opposing, now minority, point of view, see V. C. Wynne-Edwards, Evolution Through Group Selection (Oxford: Blackwell, 1986): “The view, widely held, that group selection can be dismissed as an effective evolutionary force is based on assumptions, not on evidence … It is an argument uncritically derived from human experience, of cheaters, criminals and oppressors who live at other people’s expense; and it ignores the fact that all viable kinds of exploiters in the animal world must be able when necessary to limit their own numbers” (p. 313).

  It seems strange that, in the real world as well as in contrived optical illusions, two completely different interpretations can give equivalent results. But this is a commonplace in physics—in quantum mechanics, say, or in the study of elementary particles—where two approaches with different starting assumptions and different mathematical apparatus turn out to give identical quantitative answers, and are therefore understood to be equivalent formulations of the solution to the problem.