Nature's Destiny: How the Laws of Biology Reveal Purpose in the Universe. By Michael J. Denton. New York: The Free Press, 1998.
Autor: Marie I. George, St. John's University, New York
Publicado en: The Thomist, 65, 2, April 2001, 323-326.
Fecha de publicación: April 2001
Denton ambitiously presents us with a scientific version of the thesis that "all things in the material universe exist for man." He intends first to show that the "the cosmos is uniquely fit for life as it exists on earth and for organisms of design and biology very similar to our own species" (xiii). He also intends to examine the more problematic thesis that the laws of nature are fine-tuned to enable life's becoming. From the fitness of the universe for life's being and becoming, he argues in favor of the teleological claim that life and mankind are the goals to which the universe is ordered.
In chapter 1 Denton examines evidence from physics which indicate that if a number of factors in the universe's development had been other than they are, carbon-based life could not exist. For example if the speed of expansion of the universe had been on slightly greater or lesser than it was, matter would not have been able to accumulate into galaxies. In chapter 2 he cites the numerous properties that water has which make it ideal as a medium within which life processes can be carried out, and make it part of a hospitable environment for life. He points out, for example, six properties of water that are all means to the end of weathering, a process that is responsible for distributing throughout the hydrosphere the minerals upon which life depends.
Chapter 3 is devoted to showing the fitness of light. Denton points out that the electromagnetic radiation of the sun is restricted to a tiny region of the total electromagnetic spectrum, equivalent to one card in a deck of 1025, and that the very same infinitely minute region is precisely that required for life. In addition both the atmospheric gases and water are opaque to all regions of the spectrum except this same tiny region. Denton concludes: "it is as if a card player had drawn precisely the same card on four occasions from a deck of 1025" (60).
Chapters 4-10 make a case that the table of elements, the earth, carbon, the gases O2 and CO2, HCO3-, DNA, proteins, metals, and constituents of the cell, such as phospholipids, are fit for sustaining life. Summarizing is not helpful here, since the case that Denton is making depends on the numerous details that he describes. What Denton is trying to show is that the very matter out of which living things and the environment upon which they depend have properties that fall within a very narrow range of precisely what living things need in order to live. Human artisans do not make the very matter of their artifacts, but may take matter which is already there and prepare it in ways that are appropriate for the artifact they intend to make. E.g., an artisan takes clay and bakes it into tiles to give the clay the hardness and lack of porousness that is needed in a floor. Denton is examining the very building blocks of living things and their environment and showing how those things have features that make them especially suited for their roles. He is insistent that it is the number and specificity of properties that matter must have to make life possible that makes or breaks the teleological argument: "If the existence of life had been compatible with a greater range of values for the fundamental constants, or, in other words, if the design of the celestial machine could have been different at least to some degree and yet still have sustained life, then the teleological conclusion would be far weaker. It is the necessity that it be exactly as it is--adjusted to what is in effect near infinite precision in a long train and series of things that makes the teleological conclusion so compelling" (15). Denton is arguing that the universe is like a model kit that has precision parts that can only be put together one way to make one thing. Thus he maintains that life in the cosmos will have the same type of biology as that which is found on earth, and that it "cannot be instantiated in any other exotic chemistry or class of material forms" (xiii).
Is Denton too insistent on finding fine-tuning everywhere? After giving evidence "that there is one environment determined by the laws of nature (the hydrosphere of a planet of the same size and distance from its sun as Earth) that is uniquely and ideally fit for carbon-based life," he goes on to say: "If there had been several other types of environment having some fitness for carbon-based life...the design hypothesis would have been effectively disproved" (97). Design is more manifest when there is only one way for parts to fit together and produce the result. And Denton certainly amasses a substantial amount of evidence that this sort of design is in fact the case. However, design is not excluded by the fact that there are alternate ways of getting the same result. Denton himself notes that: "The strategy of using several different means to achieve a particular goal, where each of the individual means is sufficient by itself to achieve the goal, is used in all manner of situations to guarantee that the goal will always be achieved, even if one or more of the means fails" (337). Things that are very precisely designed tend to be more vulnerable to breaking down. Perhaps nature does not put all her eggs in one basket.
In chapter 12 Denton draws our attention to evidence that seems to indicate that the laws of nature seem to be fit for only one unique type of thinking being. In so short a space I cannot evaluate his arguments for this unconventional conclusion. I will simply note a point he makes regarding fire. Without fire and the ability to manipulate fire we would not have science, since we would be unable to make scientific instruments. The ability to start a fire requires that very specific parameters of the earth obtain, so that it can have the percentage of oxygen in its atmosphere capable of sustaining fire. The ability to make use of fire depends on having a body of a certain size with hands, vision, and a specific muscular capacity.
In part 2, Denton turns to what he regards as a thesis more difficult to defend, namely, that the laws of the universe are fine-tuned not only to sustain life, but also to produce it and give direction to its evolution. He holds "that the origin of carbon-based life is built into the laws of nature and that carbon-based life is therefore inevitable on any planetary surface where conditions permit it" (265).
As for the evolution of life, Denton maintains that it has to be a directed process: "While fully appreciating modern selection theory we nevertheless arrive at an essentially different view of evolution. It appears to be not a series of accidents, the course of which is determined only by the change of environments during earth history and the resulting struggle for existence, which leads to selections within a chaotic material of mutations...but is governed by definite laws...." (272) He reasons that while isolated random mutations are capable of causing substantial changes in phenotypes, they cannot be a major source of evolutionary novelty because living systems are so intensely integrated their components cannot be changed independently. Change in one component requires simultaneous compensatory changes in other components as well. Some ordering principle must coordinated the requisite suite of changes.
Denton has certainly shown that a number of natural materials are uncannily suited for the production and sustenance of life. I wonder, however, whether he is not overly committed to a determinism, and does not underestimate the role of contingency in life's evolutionary history. He says that life is "a natural phenomena programmed into nature from the beginning, and fated inevitably to arise and evolve on any suitable planetary environment" (xv). Denton rejects S. J. Gould's view that the apparition of Homo sapiens was dependent on a series of contingent events, and that if one replayed life's tape, one would not get the same species the second time around, Homo sapiens included. In some places Denton seems favorable to the view that the development of the tree of life is like that of an individual tree, both being directed by natural law and influenced by chance events. Just as no two trees, even cloned trees, are exactly alike due to chance events, so too the tree of life growing on another planet would not be exactly the same. However, just as the genetic program generally dominates chance in the development of the tree, and so too Denton thinks that determinate laws give direction to evolution, chance simply adding variations to a theme.
At the very end Denton seems to reconciled himself to the possibility that we are the only intelligent life form in the universe. While he thinks that there are a lot of planets hospitable to life, he recognizes that we do not know how easily life establishes itself, and how readily it complexifies (on earth it took quite a while). One wonders how Denton is able to escape Gould's conclusion that human life is just a cosmic accident. I think that what Denton would respond is that thepathways to life are pre-determined in the original constitution of matter. "There is in the end nothing contingent about the choice of oxidation as the major source of energy for life on earth. Without the energy inherent in the chemistry of oxidation, life would have remained frozen forever at the primitive unicellular stage...." (130) He is insistent that if one set out to create complex life from scratch that we would always choose the same materials and "be led via the same chain of mutual adaptations to the same unique solutions" (139). However, I think that Denton would acknowledge thatthat these pathways actually be taken may be due to contingent as well as to determinate events. These pathways, however, are bound to be taken somewhere eventually .
Denton vacillates as to whether imperfections indicate absence of design. In one place he maintains that: "If life is the result of design, then every component must be perfectly fit for the end it serves. There can be no exceptions. If the genetic code is indeed less that optimum, then the entire teleological worldview collapses" (166). Yet in another place, he admits that the biological design of Homo sapiens is not ideal or perfect: "Our design is constrained due to our evolutionary origin. We suffer spinal problems because the spinal column was not designed originally for an upright stance" (260). Denton acknowledges that all material objects are imperfect to some degree. Still, he shows a similar ambivalence in regard to things that are useless. The existence of elements useless to life in the cosmos does not trouble him as he sees them as necessary by-products of a very simple system which allowed for the existence of many elements ideally fit for life (80). But then he takes the extreme position that: "if it were true that the genomes of higher organisms contained vast quantities of junk, then the whole argument of this book would collapse" (290). Perhaps the "junk" DNA does have a function. But if it were some harmless by-product of the evolutionary process, why would the entire teleological account of evolution collapse?
Nature's Destiny, to my mind, is the best of the books that rely upon scientific evidence to argue in favor of the universe's being designed in order to produce life, including intelligent life. The evidence Denton amasses is impressive, and he is aware of the philosophical niceties of the argument, only some of which I have touched on here. I recommend the book highly to all who are interested in anthropic argumentation.