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.