Possibility Space in Evolution
The possible becomes actual over evolutionary time, as everyone knows. But what is the most plausible account about how this takes place? In a worldview, one needs an account not only of the possible becoming actual, but also of the origins of possibilities. In the genesis of biodiversity on Earth, these possibilities becoming actual are somehow there, or come to be there, in the genetics. For an account of their unfolding we need bioscience, but here also, one must increasingly pass from bioscience to metaphysics.
We face questions about the increase of complexity and diversity, about contingency and inevitability in such increase, about novelty and progress. Continuing the inquiry begun in the previous Metanexus essay, we face the question of the origin of information, what Dawkins calls a spectacular “information explosion” (1995, p. 145).
We face the limit questions about the possibilities of genesis, with questions looming about the possibility of divine presence. This is the fertility question in its metaphysical form, the generation of the actual out of the possible, and the generation of those possibilities, and even a Generator of such possibilities. The possibility route to be found is not so much logical, or empirical, or even physical; it is historical. What possibility spaces are needed to get from beginnings to where we have now arrived, in Earth history?
At the other extreme from those emphasizing the contingency, there are eminent biologists–though they tend to be molecular biologists rather than paleontologists–who find this storied natural history to be inevitable, at least in outline, and therefore predictable. Christian de Duve concludes: “Life was bound to arise under the prevailing conditions, and it will arise similarly wherever and whenever the same conditions obtain. There is hardly any room for ‘lucky accidents’ in the gradual, multistep process whereby life originated.” After life arises there is contingency as to its directions and species, but this is “constrained contingency” so that the general trends in the development of life–cellular organisms, multicellular organisms, solar energized organisms, increasingly diverse and complex organisms, and intelligent organisms–are likewise inevitable. “Life and mind emerge not as the results of freakish accidents, but as natural manifestations of matter, written into the fabric of the universe. I view this universe [as] … made in such a way as to generate life and mind, bound to give birth to thinking beings” (1995, p. xv-xvi, p. xviii).
“This universe breeds life inevitably,” concludes George Wald (1974, p. 9). Life is an accident waiting to happen, because it is blueprinted into the chemicals, rather as sodium and chlorine are preset to form salt, only much more startlingly so because of the rich implications for life and because of the openness and information transfer also present in the historical life process. Whatever place dice-throwing plays in its appearance and maturation, life is something arranged for in the nature of things. The dice are loaded.
When the predecessors of DNA and RNA appear, enormously complex molecules appear bearing the possibility of genetic coding and information, they are conserved, writes Melvin Calvin, “not by accident but because of the peculiar chemistries of the various bases and amino acids…. There is a kind of selectivity intrinsic in the structures.” The evolution of life, so far from being random, is “a logical consequence” of natural chemistries (1975, p. 176, p. 169). Manfred Eigen concludes “that the evolution of life… must be considered an inevitable process despite its indeterminate course” (1971, p. 519; 1992). Life is destined to come as part of the narrative story, although the exact routes it will take are open and subject to historical vicissitudes. Stuart Kauffman agrees: “I believe that the origin of life was not an enormously improbable event, but law-like and governed by new principles of self-organization in complex webs of catalysts” (1993, p. xvi; 1995).
Such accounts suggest that the possibilities are always there, latent in the physics and chemistry, although the resulting Earth history is not so “fine-tuned” as astrophysics and nuclear physics have found in their cosmologies. But even in earthen biology, the possibilities must, or almost must, become actual. Alternately put, there are few possibilities beyond those that do actualize. But of course all such possibilities are seen only retrospectively. If, as is impossible, some scientist had under observation the elementary particles forming after the first three minutes, nothing much in them suggests anything specific about the coding for life that would take place, fifteen billion years later, on Earth.
After Earth forms, the lifeless planet is irradiated by solar energy, as are other planets as well. The events in physics and chemistry there are considerably lawlike and predictable, at least statistically, although in geology and meteorology the system is quite complex owing to shifting initial conditions, possibly even at times chaotic. Still, in orogeny and erosion, or the shifting of the tectonic plates, the possibilities always seem there.
At the microscopic levels, quantum physics depicts an open system and nested sets of possibilities; but, at first, all the atoms and molecules take nonliving tracks. Only later, do some atoms and molecules begin to take living tracks, called forth as interaction phenomena when cybernetic organisms appear. If there is some “inside order” to matter that makes it prolife, it is in the whole system and not just in the particles. Despite the anthropic principle, such order is not generally evident in the systemic astronomy, since far the vastest parts of the universe are lifeless. Life is an earthbound probability. Nor, on Earth, are the meteorological or geomorphological systems all that suggestive of inevitable life. They mostly seem kaleidoscopic variations on geophysical and geochemical processes.
Only in biology do there open up entirely unprecedented levels of achievement and power. Such possibilities are not inside the atoms and molecules apart from their systemic location, since atoms and molecules would not even be collected into a “thin hot soup” except for the Earth world in which this is possible, nor can this or that sequence of DNA code for anything unless there is an environment in which to behave this way or that, with a niche to fill. Even if there is some “selectivity intrinsic in the structures,” this does not rule out a universe of myriad options, only some of which are realized.
Physics and chemistry, unaided, do not get us very near to life and mind. There really isn’t much in the physics and chemistry of atoms and molecules, prior to their biological assembling, that suggests that they have any tendencies to order themselves up to life. Even after things have developed as far as the building blocks of life, there is nothing in a “thin hot soup” of disconnected amino acids to predict that they will connect themselves or be selected along upward, negentropic though metastable courses into proteins, nor that they will arrange for DNA molecules in which to record the various discoveries of structures and metabolisms specific to the diverse forms of life.
All these events may come naturally, but they are still quite a surprise. Recent microbiology has been revealing their enormous complexity. We do not know that life, if it occurs on some other planet, being there built too of the same atoms, must select these same biochemistries, although the amino acids found on meteorites and the prebiotic molecules guessed to be present in interstellar dust clouds can suggest that the potential for life is omnipresent in matter. Laws are important in natural systems, whether extraterrestrial or terrestrial. But natural law is not the complete explanatory category for nature, any more than is randomness and chance. In nature, especially on this historical Earth, there is creativity by which more comes out of less.
Science does not handle historical explanations very competently, especially where there are emergent novelties; science prefers lawlike explanations in which there are no surprises. One predicts, and the prediction comes true. If such precision is impossible, science prefers statistical predictions, probabilities. One predicts, and, probably, the prediction comes true. Biology, meanwhile, though prediction is often possible, is also full of unpredictable surprises–like calcium endoskeletons in vertebrates after millennia of diatomaceous silica and chitinous arthropod exoskeletons. A main turning point in the history of life fused once-independent organisms into the cell and its mitochondria, which became the powerhouses for life. Another critical symbiosis brought free-living chloroplasts into the plant cell, again producing the energy vital for all life.
There is no induction (expecting the future to be like the past) by which one can expect, even probably, trilobites later from prokaryotes earlier, or dinosaurs still later by extrapolating along a regression line (a progression line!) drawn from prokaryotes to trilobites. There are no humans invisibly present (as an acorn secretly contain an oak) in the primitive eukaryotes, to unfold in a lawlike or programmatic way. The ancient ancestral forms are not proto-vertebrates, or pre-terrestrials, nor are gymnosperms about-to-be angiosperms, as though the descendant forms were latent among the functions of the predecessors. Originating events often become what they become only retrospectively: “Vertebrates began (possibly) with the notochords of primitive chordates.” “Eyes began with ….” Nevertheless, there is the epic story–eukaryotes, trilobites, dinosaurs, primates–swarms of wild creatures in seas and on land, followed by humans who come late in the story.
Making this survey, can one insist that the probabilities must always have been there, or at least the possibilities? Can one claim that what did actually manage to happen must always have been either probably probable, or, minimally, improbably possible all along the way? Push this to extremes, as one must do, if one claims that all the possibilities are always there, latent in the dust, latent in the quarks. Such a claim becomes pretty much an act of speculative faith, not in present actualities, since one knows that these events took place, but in past probabilities always being omnipresent. Is the claim some kind of induction or deduction, or most-plausible-case conclusion from present actualities? Speculation about such possibilities being always there is easy, provided one does not have to specify any of the details. But this perennial and vast library of possibilities is mostly imaginary.
For in fact, on Earth, there really isn’t anything in rocks that suggests the possibility of Homo sapiens, much less the American Civil War, or the World Wide Web, or the impeachment of a president, and to say that all these possibilities are lurking there, even though nothing we know about rocks, or carbon atoms, or electrons and protons, suggests this, is simply to let possibilities float in from nowhere (against the caution of Alfred North Whitehead , 1978, p. 46). Unbounded possibilities that one posits ad hoc to whatever one finds has in fact taken place– possibilities of any kind and amount desired in one’s metaphysical enthusiasm–can hardly be said to be a scientific hypothesis. This is hardly even a faith claim with sufficient warrant. It is certainly equally credible, and more plausible, and no less scientific to hold that new possibility spaces open up en route.
Karl Popper concludes that science discovers “a world of propensities,” open to historical innovation, the possibility space ever enlarging. “In our real changing world, the situation and, with it, the possibilities, and thus the propensities, change all the time… This view of propensities allows us to see in a new light the processes that constitute our world: the world process. The world is no longer a causal machine–it can now be seen as a world of propensities, as an unfolding process of realizing possibilities and of unfolding new possibilities. … New possibilities are created, possibilities that previously simply did not exist. … Especially in the evolution of biochemistry, it is widely appreciated that every new compound creates new possibilities for further new compounds to synthesize: possibilities which previously did not exist. The possibility space… is growing… Our world of propensities is inherently creative” (1990, pp. 17-20). The result is the evolutionary drama. “The variety of those [organisms] that have realized themselves is staggering.” “In the end, we ourselves become possible” (1990, p. 26, p. 19).
But–the reply comes–since all those things did come in subsequent evolutionary and cultural history, their possibilities must have been there all along. Matter is self-organizing, autopoietic. That posits enormous possibilities, there from the start; and nothing in the historical drama ought to take by all that much surprise one who believes in self-organizing nature. Thomas R. Cech, a molecular biologist, reviews the origin of life: “If intrinsic to these small organic molecules is their propensity to self-assemble, leading to a series of events that cause life forms to originate, that is perhaps the highest form of creation that one could imagine. … At least from the perspective of a biologist, I have given an account of how possibilities did, in times past, become actual. When this happened, life originated with impressive creativity, and it does not seem to me that possibilities floated in from nowhere; they were already present, intrinsic to the chemical materials” (1995, p. 33).
True, matter–energized as it is on Earth–is now self- organizing. But that leaves open the question whether, on the adaptive landscapes in which organisms struggle to increase their fitness for survival, landscapes which themselves shift as the organisms make their discoveries, there are changing possibility spaces coming in through evolutionary history. In creating themselves, the creatures need possibility space, opportunity space, transformational space. New possibilities do arrive.
If a ground squirrel is faced with a predator that digs it out of its holes, it can learn to dig faster, or to locate its burrows under rocks. Perhaps it can evolve an unpleasant taste. But it cannot grow wings and fly off to another continent, or build rifles and bullets to shoot its predator. That is not in its possibility space.
Evolving into Homo sapiens is, we can suppose, in the possibility space of Homo habilis (or whatever the hypothetical ancestor). But it takes considerable imagination to find Homo in the possibility space of trilobites (or whatever the remote ancestor in that epoch). The creatures do have, over time, the possibility of speciating and respeciating. But it is not so clear that the creatures, in their self-actualizing do have, or generate all by themselves, all these other kinds of selves int which they are transformed. There is enormously more out of less, and enormous space for the introduction of novelties that do not seem “up to” the faculties of the organism. One can say, if one likes, that a dinosaur is lurking in the possibility space of a microbe, or that microbes self-transform themselves into dinosaurs, which self-transform into primates. But that really is not a claim based on anything we know about the biology or ontology of microbes.
The self-creating is more a holistic, systemic affair; it is what happens to microbes when they are challenged in their habitats and after a very long time. This requires the creation of new possibility spaces. From a God’s eye view, perhaps the possibilities are always there. “My frame was not hidden from thee, when I was being made in secret, intricately wrought in the depths of the earth. Thy eyes beheld my unformed substance” (Psalm 139.15-16). But we humans have no such viewpoint. We do view results and know that the possibilities both got there and got actualized, but it is quite as much an act of faith to see dinosaurs in the possibility spaces of quarks as to see dinosaurs in the possibility space of God.
Looking at a pool of amino acids and seeing dinosaurs or Homo sapiens in them is something like looking at a pile of alphabetical letters and seeing Hamlet. In fact Hamlet is not lurking around a pile of A-Z’s; such a play is not within their possibility space– not until Shakespeare comes around, and in Shakespeare plus a pile of letters, Hamlet does lurk. By shaking a tray of printer’s type, one can get a few short words, which are destroyed as soon as they are composed. If sentences begin to appear (an analogue of the long, symbolically coded DNA molecules and the polypeptide chains), and form into a poem or a short story (an analogue of the organism), one can be quite sure there are some formative, even irreversible, constraints on the sorting and shaking that are catching the upthrusts and directionally organizing them.
It hardly seems coherent to hold that nonbiological materials are randomly the more and more derandomized across long structural sequences and thus ordered up to life. That is quite as miraculous as walking on water. Something is introducing the order; and, further, something seems to be introducing layer by layer new possibilities of order, new information achieved, not just unfolding the latent order already there from the start in the set- up.
Some will reply that all actual events materialize in a global possibility space, and what while the former become over time, the latter does not. The possibility space is always there. There is no such thing as the creation of possibilities that were not there. New doors may open but only into rooms that previously existed, albeit unoccupied and with no furniture. One does not need to get possibilities from nowhere because there are infinite possibilities everlastingly, or at least since the Big Bang. The proof of this lies in what has subsequently happened.
But surely the possibility space of serious alternatives does enlarge and shrink. There are times of opportunity, in which taking one direction opens up new possibilities, and taking another shuts them out. Along the way, new possibility space for genetic engineering is brought into the picture.
John Maynard Smith and Eors Szathmary analyze “the major transitions in evolution” with the resulting complexity, asking “how and why this complexity has increased in the course of evolution.” “Our thesis is that the increase has depended on a small number of major transitions in the way in which genetic information is transmitted between generations.” Critical innovations have included the origin of the genetic code itself, the origin of eukaryotes from prokaryotes, meiotic sex, multicellular life, animal societies, and language, especially human language. But, contrary to de Duve, Eigen, Calvin, Kauffman, or Cech, they find “no reason to regard the unique transitions as the inevitable result of some general law”; to the contrary, these events might not have happened at all (1995, p. 3). So what makes the critical difference in evolutionary history is increase in the information possibility space, which is not something inherent in the precursor materials, nor in the evolutionary system, nor something for which biology has an evident explanation, although these events, when they happen, are retrospectively interpretable in biological categories. The biological explanation is modestly incomplete, recognizing the importance of the genesis of new information channels.
The philosophical, metaphysical, and theological challenge, left over after the current scientific accounts, is the query what is the most adequate account of the origin of these possibility spaces, of the origin of these information channels and the genetic information thereby discovered. In the course of evolutionary history, one would be disturbed to find matter or energy spontaneously created, but here is information floating in from nowhere. For the lack of better explanations, the usual turn here is simply to conclude that nature is self-organizing (autopoiesis), though, since no “self” is present, this is better termed spontaneously organizing. An autopoietic process can be just a name, like “soporific” tendencies, used to label the mysterious genesis of more out of less, a seemingly scientific name that is really a sort of mystic chant over a miraculously fertile universe.
What is inadequately recognized in the “self-organizing” accounts is that, though no new matter or energy is needed for such spontaneous organization, new information is needed in enormous amounts and that one cannot just let this information float in from nowhere. Over evolutionary history, something is going on “over the heads” of any and all of the local, individual organisms. More comes from less, again and again. A more plausible explanation is that, complementing the self-organizing, there is a Ground of Information, or an Ambience of Information, otherwise known as God.
Calvin, Melvin, 1975. “Chemical Evolution.” American Scientist 63:169-177.
Cech, Thomas R., 1995. “The Origin of Life and the Value of Life.” Pages 15-37 in Holmes Rolston, III, ed., Biology, Ethics, and the Origins of Life.
Dawkins, Richard, 1995. River out of Eden: A Darwinian View of Life. New York: Basic Books, HarperCollins.
de Duve, Christian, 1995. Vital Dust: Life as a Cosmic Imperative. New York: Basic Books.
Eigen, Manfred, 1971. “Selforganization of Matter and the Evolution of Biological Macromolecules,” Die Naturwissenschaften 58:465-523.
Kauffman, Stuart A., 1993. The Origins of Order: Self- Organization and Selection in Evolution. New York: Oxford University Press.
Maynard Smith, John, and Eors Szathmary, 1995. The Major Transitions in Evolution. New York: W. H. Freeman.
Popper, Karl R., 1990. A World of Propensities. Bristol, U.K.: Thoemmes.
Wald, George, 1974. “Fitness in the Universe: Choices and Necessities.” Pages 7-27 in J. Orr et al, eds., Cosmochemical Evolution and the Origins of Life. Dordrecht, Netherlands: D. Reidel.
Whitehead, Alfred North,  1978. Process and Reality, corrected ed., Free Press.