At Home in the Universe: The Search for the Laws of Self-Organization and Complexity, by Stuart Kauffman, New York: Oxford University Press, 321 pages, $25.00
Back in the ninth grade, I was subjected to that bogeyman of all liberal intellectuals, a creationist biology teacher. For the most part, he followed the standard curriculum (which even in the mid-1970s was heavy on ecology and "environmental" science), but when it came time to discuss evolution, his heterodoxy appeared. It was mostly standard stuff–nothing likely to faze a free-thinking 14-year-old. There was one point, however, where my teacher, a gentle man truly concerned about our immortal souls, hit on an argument I found disturbing.
He pointed out that evolutionary theory had no good, or even very plausible, way to explain how life could have arisen from non-living materials to begin with. There are some simple probability calculations one can perform to guess how long it would take randomly interacting molecules of a prebiotic sort, even under favorable conditions, to spontaneously form the very particular building blocks of today's organisms. The results aren't pretty for a non-miraculous account of life's origins–the biosphere looks like an extremely unlikely accident.
It is not only at the origins of life that mainstream biology invokes accident as a central explanatory principle. As Stuart Kauffman, fellow at the Santa Fe Institute and winner of a MacArthur "genius" grant, points out in At Home in the Universe, "Biologists see organisms as tinkered-together contraptions, and evolution as a tinkerer. Organisms are Rube Goldberg machines; the jawbone of an early fish became the inner ear of a mammal. Organisms really are full of the strangest solutions to design problems. Biologists delight in discovering these and noting to one another, and particularly to those of us inclined toward theory in biology, `You'd never have predicted that!' Inevitably the assertion is correct." Kauffman cites a statement by Jacques Monod, a Nobel-winning biologist, that "Evolution is chance caught on the wing."
We and everything living, in this view, are entirely historical accidents. Kauffman's research program–one might almost say his obsession–is to demonstrate the possibility of providing better explanations than "accidents happen" when confronted with the intricate structure and behavior of complex evolving systems.
At Home in the Universe is a popularization of his 1993 tome, The Origins of Order, where Kauffman first set out a comprehensive statement of his vision. That vision takes in not only biology but also economy, culture, and society. It seeks a new synthesis between reductionism and holism, as well as chance and necessity; it tries to lay a mathematical foundation for predicting the occurrence of spontaneous order while considering the role of evolution and selection; it bids fair to bring forth a new technology of universal biochemical synthesis. It is not modest.
Kauffman's basic tactic is to admit that the specific manifestations of complex evolving systems are accidental, but to provide grounds for believing that something like them–something orderly, self-regulating, and complex–is statistically likely, even inevitable, given the right initial conditions. A second thrust explores the limitations of natural selection as a mechanism for generating order and fitness, showing how evolving systems can get sidetracked by mutational drift, internal complexity, and myopic adherence to local rather than global optima.
A third theme is the role of coevolution–interactions between adapting populations that affect the fitness of one another–in creating order and stimulating a better fit with the environment. And running through it all is the conjecture that complex systems have a tendency to evolve "to the edge of chaos," where most of the component parts have stable relationships, but there are also areas of instability which allow the system to respond to contingencies in the environment.
The origin-of-life issue is where Kauffman argues, on statistical grounds, that life is not a cosmically improbable accident but rather the most likely consequence of random chemical processes–that "there are compelling reasons to believe that whenever a collection of chemicals contains enough different kinds of molecules, a metabolism will crystallize from the broth." This is a view of life as a process, a pattern found amid the electron dance of chemicals, much as sound is a pattern of motion imposed on the collisions of gas molecules.
Think of a living entity as a set of chemical reactions (powered by a flow of energy from outside sources) that is "orderly" in the sense that the same kinds of chemicals, in roughly the same proportions, are produced over time from an external supply of basic "food" molecules. Let us suppose further that all the chemical reactions in the set must be catalyzed (facilitated by another molecule, a catalyst) if they are to proceed rapidly enough to keep the network going. The problem is where the catalysts come from, and the only possible solution is for them to be the products of some of the reactions in the network. Thus, for a set of interacting chemicals to look like a living entity, each chemical's generating reaction must have a catalyst within the set. Kauffman calls this property "catalytic closure" and refers to sets that have it as "collectively autocatalytic systems."
When put this way, it sounds pretty implausible. What are the chances that you could find a set of chemicals and reactions that just happened to have catalytic closure? Kauffman's big idea is to show that this intuition is wrong, that a) you have enough random catalyzed reactions in a set of chemicals, you get catalytic closure, b) the ratio of reactions to molecule types increases as the number of molecule types increases, and therefore c) if you gather up enough different chemicals, and each has a very small random chance of catalyzing any given reaction, then you are guaranteed to generate a collectively autocatalytic system.
"As the ratio of reactions to chemicals increases, the number of reactions that are catalyzed by the molecules in the system increases. When the number of catalyzed reactions is about equal to the number of chemical [types], a giant catalyzed reaction web forms, and a collectively autocatalytic system snaps into existence. A living metabolism crystallizes. Life emerges as a phase transition."
This is a great story. Is it true? The mathematics are fine, but whether the model is a good representation of chemical reality is outside my competence. A couple of things trouble me. First, if random collections of diverse chemical species, suitably confined and energized, have a propensity for coming to life, how come we haven't seen any in nature? As far as I know, all known self-sustaining chemical reaction networks are conventional living cells, complete with RNA, biological amino acids, and so on. No radically different chemical forms of life seem to exist, although Kauffman's theory seems to say that they could be forming regularly in various cracks and clays and crannies. Perhaps they cannot survive competition with "standard" life and so are destroyed soon after snapping into existence; perhaps we simply haven't been looking for them and so have missed them.
Second, if collective autocatalytic systems are so prone to being born, then why haven't the other planets of the solar system become infested with various forms of life (whose chemistry would differ from ours)? Kauffman argues that life of some kind, not necessarily the particular chemical patterns we see in our biosphere, is sufficiently likely to form that we should consider ourselves not "We the accidental" but rather "We the expected."
Just how expected are we? Perhaps it is unfair to consider it hedging when he says, "I shall not be overly surprised if in the coming decades, some experimental group creates such life anew, snapping into existence in some real chemostat, creating protocells that coevolve with one another…I would not be overly surprised. But I would be thrilled." And the Sunday newspaper supplements would be full of chin-pulling pundits worrying over the "troubling implications" under illustrations with Frankenstein themes. But I'm afraid that until the attempt is made and either succeeds or fails conclusively, the catalytic closure theory will generate plenty of goose bumps, but few thrills.
Once we get past the question of how complex systems get started in the first place, and ask how their future evolution occurs, we again face a tension between the historical and natural-law modes of explanation. Historical explanations understand the state of a system primarily by where it has been before, so that accidents of initial conditions or chance events largely determine how things turn out. Natural law explanations seek out underlying forces, present at all times, that shape outcomes. Both modes are usually essential for well-rounded understanding, but the balance between them changes from field to field and sometimes over time in the same field.
Kauffman, with a biology background, sees natural selection as a historical mode of explanation, with random mutations reproduced or not based on their possessors' relative ability to cope with a varying environment. This is not surprising; especially in its modern form, exemplified by Stephen Jay Gould's Wonderful Life, evolutionary theory is relentlessly agnostic about the specific outcomes that are to be expected from natural selection.
The idea of evolution as having tendencies toward "higher" or more complex organisms, for example, is considered, at best a dubious proposition, and at worst a piece of anthropomorphic conceit redolent of religious mysticism and apologetics for social inequality. Even the notion that organisms are "organized" by inherent rather than accidental forces is rejected. As Kauffman notes, "This image fully dominates our current view of life. Chief among the consequences is our conviction that selection is the sole source of order in biology. Without selection, we reason, there could be no order, only chaos."
With this backdrop, At Home in the Universe launches its challenge to the standard dogma, asserting that selection is only part of the story, that "Self-organization may be the precondition of evolvability itself. Only those systems that are able to organize themselves spontaneously may be able to evolve further. How far we have come from a simple picture of selection sifting for fitter variants. Evolution is more subtle and wonderful."
This claim is advanced by a kind of indirect proof: Selection can't possibly do all the marvelous things it would have to to generate the order we see in the world, so what's left must be the result of spontaneous order.
Kauffman argues persuasively based on probabilistic considerations, that as a system's performance depends more and more on the interconnections among its parts, any small change in one of the parts is likely to lead to a catastrophic loss of fitness (the "complexity catastrophe"). As a result, classic, incremental natural selection cannot possibly generate very fit, complex forms with a high number of interconnections compared to the number of parts. He also shows that if there aren't enough interconnections relative to the number of parts and to the rate of mutation, then even if a good solution is found, random mutations will tend to carry the system away from the optimum faster than selection can drag it back (the "error catastrophe").
From a theoretical point of view, then, natural selection can only generate high levels of fitness under a relatively narrow range of circumstances–not too much or too little mutation, too many or too few interconnections. Kauffman suggests that it is spontaneous order that forms the basic "just right" structures from which natural selection is launched; the initial conditions of evolution are not accidental but lawful.
Those ideas may be important in the study of human artifacts and institutions as well as in biology. Kauffman's models show, for example, that the rate of performance improvement for evolving systems slows down as higher performance is achieved. He relates this to the well-known "learning curve" in economics, where the unit cost of production in a plant, firm, or industry declines rapidly at first as production experience is accumulated, but gradually flattens out.
Learning curves and Kauffman's simulations of evolution both display a mathematical form called a power law, where every doubling of cumulative output reduces unit costs by the same percentage. He posits that the similarity in mathematical form is due to a similarity in underlying mechanisms–the gradual exhaustion of opportunities to improve as one reaches higher and higher peaks on a metaphorical "fitness landscape." Kauffman notes that his models of evolution and technological history both show initial progress coming as big changes are made in structure (gasoline versus steam engines in automobiles, for example) while later progress comes from small refinements (power versus manual steering).
Those analogies are suggestive and not implausible, but hardly conclusive; there are lots of processes that might lead to power-law curves, just as lots of different sets of data fit a normal bell curve. For example, the late Allan Newell's Unified Theories of Cognition describes how human skill at simple tasks, such as pushing buttons when certain lights go on (a psychologist's idea of a fun date), follows a power law; Newell then lays out a cognitive theory of learning (called "chunking," to describe the welding together of memories into single units) that generates it. Maybe factory performance follows a power law as practice is accumulated because of the buildup of useful chunks in organizational memory, and not because of diminishing returns to evolutionary search of the problem space. Nevertheless, Kauffman's approach is intriguing because it makes multiple predictions within and across problem domains while its assumptions are quite general.
From the point of view of traditional social science, or indeed of anyone concerned about the role of spontaneous order, competition, and cooperation in regulating human life, At Home in the Universe is most interesting when it attacks the problem of coevolution. Here, Kauffman extends his probability models to multiple populations, each of which constitutes part of the environment of the others, mutating and searching for peaks of fitness. The interesting twist is that when one system mutates, it affects the fitness landscape of all the other systems. Thus, if flies improve their vision and can spot threats at a greater distance, frogs with longer tongues might have an advantage over their less well-endowed cohorts. If one business develops a method of speeding up the delivery of orders to customers, another business may find that it should deliver more slowly (thereby cutting its costs), charge lower prices and attract less time-sensitive customers.
The actual models Kauffman uses are abstract and general, with not a frog tongue or delivery guarantee in sight. He focuses on the question of whether the coevolving populations (or firms, or technologies) will eventually settle down to some kind of steady state, where each population is at an optimum as long as the other ones stay put, or whether they will just keep bouncing around in an endless, chaotic display of one-upsmanship. The results: When the amount of interconnection between the evolving populations is "just right" relative to the internal interconnections among the parts of each system, average fitness for all the populations is highest. Furthermore, in this "just right" zone, the overall system is poised between order and chaos–most of its components most of the time are in a steady state, but every now and then some of them start to evolve in new directions.
Finally, if each population is allowed to evolve its own degree of internal interconnection, holding constant its interconnection to others in the coevolutionary system, each will, as if by an invisible hand, be moved by selection pressure toward the "just right" edge-of-chaos regime. Once again, while the specific details of evolution cannot be predicted, important general features appear to spring up in a lawful manner.
In this case, the models seem to be saying, at least metaphorically, that a freely evolving economy or ecology self-tunes so as to maximize the fitness and survivability of each of its members. I'm not sure just what it would mean in real-world terms for a firm to change the number of internal interconnections it possesses, because I'm not sure exactly what the "parts" of Kauffman's abstract entities should correspond to in an economic context. But if a reasonable interpretation is possible, then the result is of great importance.
Kauffman goes further, investigating how varying degrees of decentralization in a system might affect that system's performance at accomplishing some overall goal. He became interested in this issue after being prodded by management-oriented people in the orbit of the Santa Fe Institute, who wanted theoretical principles to guide the delayering and flattening of organizational hierarchies and the outsourcing and reengineering of work processes.
His model looks at whether systems evolve better solutions when they are broken into interacting but independently searching "patches," or when they are combined into one big evolving organism. The latter configuration, which Kauffman charmingly refers to as "Stalinist," turns out to work well for problems of low complexity, with few conflicting constraints. When problems start to get complicated, where the solution to one aspect can easily foul up another, it turns out to be better to break the system into separate patches.
How many patches are best? Once again, the answer appears to be a "just right" number where the evolutionary process is orderly, but on the edge of chaos, so that the system can persist with good solutions but not get permanently stuck on them without looking for better ones. So neither Gosplan nor a population of yeoman farmers is likely to be a good model for a corporation tackling complex problems; the in-between compromises we see all around us probably make more sense than oft-peddled fantasies of giant cross-functional teams or purely "market-based" management, although we might have guessed that without Kauffman's models.
For anyone–including earnest 14-year-olds–interested in big questions about science, history, and our place in the cosmos, At Home in the Universe offers an unparalleled combination of graceful writing, clear exposition, respect for the reader's intelligence, and the thrill of seeing the world anew. I do not know which, if any, of its ideas will become the seeds of tomorrow's science, but I cannot escape the feeling that Stuart Kauffman has changed the terms in which thoughtful people will discuss the nature of evolution and natural law.
Steven Postrel (Spostrel@aol.com) teaches management strategy at the Kellogg Graduate School of Management at Northwestern University.