Biological Determinism, Information Theory, and the Origin of Life
Excerpt from an essay by Paul C.W. Davies, “Biological Determinism, Information Theory, and the Origin of Life,” which appears in Many Worlds, edited by Steven Dick, Philadelphia: Templeton Foundation Press, 2000.
Philosophical and Theological Implications
The philosophical and theological implications of the competing scenarios for the origin of life are starkly different and bear strongly on the possibility of life on other worlds. As Jacques Monod has pointed out, all physical processes are a combination of chance and necessity.(26) By chance one really means contingency, while necessity refers to what most physicists call deterministic law. If chance was the dominant factor, then it is easy to compute that the probability of a known organism forming from random molecular shuffling is absurdly small.(27) Even if one restricts the analysis to the formation of a single small protein, the odds against one such molecule forming anywhere in the observable universe are negligible. This has led many scientists who favor a chance origin for life (which includes Monod) to declare that we are alone in the universe and that the search for extraterrestrial life is pointless.
At the other end of the spectrum are the biological determinists, such as Christian de Duve, who believe that life will inevitably emerge given enough time and suitable conditions.(28) In other words, the emergence of life is a preordained consequence of the laws of nature. Biological determinists do not deny that chance plays a part, only that, at the end of the day, the “cosmic dice” are overwhelmed by the odds in favor of life forming. Although we do not know how many Earthlike planets there are (and there is disagreement over just how like Earth an Earthlike planet must be in this context), recent astronomical evidence suggests that they may be rather common.(29) If so, and if biological determinism is true, then it is likely that the universe is teeming with life.
It is possible to take a middle position and attribute a large but not stupendous measure of luck to the formation of the appropriate organic molecules, with the difference made up by law, so that life is fairly but not overwhelmingly likely. In this case, there might be a few but not many planets per galaxy with life on them. However, this middle position is rather contrived. Since there is no obvious connection between the processes that bring about the formation of life and the processes that bring about the formation of Earthlike planets, it would be a remarkable coincidence if the two sets of numerics were tuned to each other in this way. If the two processes are independent, then we might expect extraterrestrial life to be either everywhere or nowhere (unless spread by a panspermia mechanism). Expressed differently, on the spectrum that lies between total chance at one end and complete determinism at the other, only an exceedingly tiny window would correspond to sparse life. If the truth lies to the deterministic side of that window, life will be common; and if it lies much to the chance side, it will have happened only once in the observable universe.
By “the observable universe” I mean, roughly, a Hubble volume, this being more or less the limit of our instruments. Some cosmological models provide for a spatially infinite universe with an infinity of stars and planets. In this case extraterrestrial life would be certain; i.e., it occurs with probability one, however small is the probability that life will form, so long as it is nonzero.(30) However, the average distance between inhabited planets generally is immensely greater than a Hubble length, and we would not expect to ever observe an alien biosystem.
I argue that on the spectrum between chance and determinism (or certainty), the closer to determinism the truth lies, the more reason we have to feel “at home in the universe” (to borrow Stuart Kauffman’s evocative phrase(31)) and the more circumstantial evidence there would be for some sort of meaning, purpose, or design in nature. I am certainly not the first person to claim this relationship. The link between contingency and atheism has been articulated most eloquently by Monod in his famous book Chance and Necessity. He writes, “Man at last knows that he is alone in the unfeeling immensity of the universe, out of which he has emerged only by chance.”(32) More recently, Stephen Jay Gould has linked a willingness to believe in the progressive nature of evolution with quasi-religious yearning.(33) Gould’s own atheism urges him to resolutely deny any form of biological determinism, since it smacks of the guiding hand of God smuggled into science under the guise of a law of nature. I think both Monod and Gould are absolutely right to perceive bleak atheism in the scenario that life and intelligence are freak accidents, unique in the cosmos. But the flip side is also true. If it turns out that life does emerge as an automatic and natural part of an ingeniously biofriendly universe, then atheism would seem less compelling and something like design more plausible.
1. In an interview in the New York Times (10 February 1999), Microsoft’s Bill Gates is quoted as saying, “It seems quite likely that there’s lots of life in the universe.”
2. Most of what follows in this essay is based on the more extended discussion given in my book The Fifth Miracle: The Search for the Origin of Life (London: Allen Lane, 1998).
3. S. Arrhenius, Worlds in the Making (London: Harper, 1908), 216.
4. Arrhenius, Worlds in the Making.
5. F. Hoyle and N.C. Wickramasinghe, Lifecloud (London: Dent, 1978).
6. C. McKay, “Promethean Ice,” Mercury, 25 (1996), 15.
7. F. Crick, Life Itself: Its Origin and Nature (New York: Simon & Schuster, 1981).
8. P. Weber and M. Greenberg, “Can Spores Survive a Million Years in the Radiation of Outer Space?” Nature, 316 (1985), 403; J. Koike et al., “Survival Rates of Some Terrestrial Microorganisms Under Simulated Space Conditions,” Advanced Space Research, 12 (1992), 4721; G. Horneck et al., “Long-term Survival of Bacterial Spores in Space,” Advanced Space Research, 14 (1994), 1041.
9. H.J. Melosh, “The Rocky Road to Panspermia,” Nature, 332 (1988), 687; “Swapping Rocks: Exchange of Surface Material Among the Planets,” The Planetary Report, 14 (1994), 16; K. Nealson et al., Mars Sample Return: Issues and Recommendations (Washington: National Academy Press, 1997); C. Mileikowsky et al., “Natural Transfer of Viable Microbes in Space,” Icarus, in the press (1999); Davies, The Fifth Miracle, chap. 10.
10. T. Gold, The Deep Hot Biosphere (New York: Copernicus, 1999).
11. S. Fox and K. Dose, Molecular Evolution and the Origin of Life (New York: Marcel Dekker, 1977).
12. See, for example, W. Loewenstein, The Touchstone of Life (New York: Oxford University Press, 1998).
13. B.-Oppers, Molecular Theory of Evolution (New York: Springer-Verlag 1985).
14. H. Yockey, Information Theory and Molecular Biology (Cambridge: Cambridge University Press, 1992).
15. G.J. Chaitin, Algorithmic Information Theory (Cambridge: Cambridge University Press, 1990).
16. Yockey, Information Theory.
17. G.J. Chaitin, “Computational Complexity and Godel’s Incompleteness Theorem,” ACM SIGACT News, No. 9 (April 1971), 11.
18. Davies, The Fifth Miracle, chap. 10.
19. R. Dawkins, Climbing Mount Improbable (London: Viking, 1996).
20. K√ƒ¬1⁄4ppers, Molecular Theory of Evolution.
21. M. Eigen, Steps Towards Life, trans. P. Woolley (Oxford: Oxford University Press, 1992).
22. A.G. Cairns-Smith, Seven Clues to the Origin of Life (Cambridge: Cambridge University Press, 1985).
23. Eigen, Steps Towards Life, 12.
24. L. Susskind, “Black Holes and the Information Paradox,” Scientific American, April 1977, 52.
25. G. Milburn, The Feynman Processor (Sydney: Allen & Unwin, 1998).
26. J. Monod, Chance and Necessity, trans. A. Wainhouse (London: Collins, 1972).
27. Yockey, Information Theory.
28. C. de Duve, Vital Dust (New York: Basic Books, 1995).
29. P. Halpern, The Quest for Alien Planets (London: Simon & Schuster, 1997).
30. Paul Davies, Are We Alone? (London: Penguin, 1995) Appendix 2.
31. S. Kauffman, At Home in the Universe (Oxford: Oxford University Press, 1995).
32. Monod, Chance and Necessity, 167.
33. S.J. Gould, Life’s Grandeur (London: Jonathan Cape, 1996).