Posted on 09/04/2002 11:23:46 AM PDT by betty boop
Stephen Wolfram on Natural Selection
Excerpts from A New Kind of Science, ©2002, Stephen Wolfram, LLC
The basic notion that organisms tend to evolve to achieve a maximum fitness has certainly in the past been very useful in providing a general framework for understanding the historical progression of species, and in yielding specific explanations for various fairly simple properties of particular species.
But in present-day thinking about biology the notion has tended to be taken to an extreme, so that especially among those not in daily contact with detailed data on biological systems it has come to be assumed that essentially every feature of every organism can be explained on the basis of it somehow maximizing the fitness of the organism.
It is certainly recognized that some aspects of current organisms are in effect holdovers from earlier stages in biological evolution. And there is also increasing awareness that the actual process of growth and development within an individual organism can make it easier or more difficult for particular kinds of structures to occur.
But beyond this there is a surprisingly universal conviction that any significant property that one sees in any organism must be there because it in essence serves a purpose in maximizing the fitness of the organism.
Often it is at first quite unclear what this purpose might be, but at least in fairly simple cases, some kind of hypothesis can usually be constructed. And having settled on a supposed purpose it often seems quite marvelous how ingenious biology has been in finding a solution that achieves that purpose….
But it is my strong suspicion that such purposes in fact have very little to do with the real reasons that these particular features exist. For instead…what I believe is that these features actually arise in essence just because they are easy to produce with fairly simple programs. And indeed as one looks at more and more complex features of biological organisms ¯ notably texture and pigmentation patterns ¯ it becomes increasingly difficult to find any credible purpose at all that would be served by the details of what one sees.
In the past, the idea of optimization for some sophisticated purpose seemed to be the only conceivable explanation for the level of complexity that is seen in many biological systems. But with the discovery…that it takes only a simple program to produce behavior of great complexity [for example, Wolfram’s Rule 110 cellular automaton ¯ a very simple program with two-color, nearest neighbor rules], a quite different ¯ and ultimately much more predictive ¯ kind of explanation immediately becomes possible.
In the course of biological evolution random mutations will in effect cause a whole sequence of programs to be tried…. Some programs will presumably lead to organisms that are more successful than others, and natural selection will cause these programs eventually to dominate. But in most cases I strongly suspect that it is comparatively coarse features that tend to determine the success of an organism ¯ not all the details of any complex behavior that may occur….
On the basis of traditional biological thinking one would tend to assume that whatever complexity one saw must in the end be carefully crafted to satisfy some elaborate set of constraints. But what I believe instead is that the vast majority of the complexity we see in biological systems actually has its origin in the purely abstract fact that among randomly chosen programs many give rise to complex behavior….
So how can one tell if this is really the case?
One circumstantial piece of evidence is that one already sees considerable complexity even in very early fossil organisms. Over the course of the past billion or so years, more and more organs and other devices have appeared. But the most obvious outward signs of complexity, manifest for example in textures and other morphological features, seem to have already been present even from very early times.
And indeed there is every indication that the level of complexity of individual parts of organisms has not changed much in at least several hundred million years. So this suggests that somehow the complexity we see must arise from some straightforward and general mechanism ¯ and not, for example, from a mechanism that relies on elaborate refinement through a long process of biological evolution….
…[W]hile natural selection is often touted as a force of almost arbitrary power, I have increasingly come to believe that in fact its power is remarkably limited. And indeed, what I suspect is that in the end natural selection can only operate in a meaningful way on systems or parts of systems whose behavior is in some sense quite simple.
If a particular part of an organism always grows, say, in a simple straight line, then it is fairly easy to imagine that natural selection could succeed in picking out the optimal length for any given environment. But what if an organism can grow in a more complex way…? My strong suspicion is that in such a case natural selection will normally be able to achieve very little.
There are several reasons for this, all somewhat related.
First, with more complex behavior, there are typically a huge number of possible variations, and in a realistic population of organisms it becomes infeasible for any significant fraction of these variations to be explored.
Second, complex behavior inevitably involves many elaborate details, and since different ones of these details may happen to be the deciding factors in the fates of individual organisms, it becomes very difficult for natural selection to act in a consistent and definitive way.
Third, whenever the overall behavior of a system is more complex than its underlying program, almost any mutation in the program will lead to a whole collection of detailed changes in the behavior, so that natural selection has no opportunity to pick out changes which are beneficial from those which are not.
Fourth, if random mutations can only, say, increase or decrease a length, then even if one mutation goes in the wrong direction, it is easy for another mutation to recover by going in the opposite direction. But if there are in effect many possible directions, it becomes much more difficult to recover from missteps, and to exhibit any form of systematic convergence.
And finally…for anything beyond the very simplest forms of behavior, iterative random searches rapidly tend to get stuck, and make at best excruciatingly slow progress towards any kind of global optimum….
It has often been claimed that natural selection is what makes systems in biology able to exhibit so much more complexity than systems that we explicitly construct in engineering. But my strong suspicion is that in fact the main effect of natural selection is almost exactly the opposite: it tends to make biological systems avoid complexity, and to be more like systems in engineering.
When one does engineering, one normally operates under the constraint that the systems one builds must behave in a way that is readily predictable and understandable. And in order to achieve this one typically limits oneself to constructing systems out of fairly small numbers of components whose behavior and interactions are somehow simple.
But systems in nature need not in general operate under the constraint that their behavior should be predictable and understandable. And what this means is that in a sense they can use any number of components of any kind ¯ with the result…that the behavior they produce can often be highly complex.
However, if natural selection is to be successful at systematically molding the properties of a system then once again there are limitations on the kinds of components that the system can have. And indeed, it seems that what is needed are components that behave in simple and somewhat independent ways ¯ much as in traditional engineering.
At some level it is not surprising that there should be an analogy between engineering and natural selection. For both cases can be viewed as trying to create systems that will achieve or optimize some goal….
…[I]n the end, therefore, what I conclude is that many of the most obvious features of complexity in biological organisms arise in a sense not because of natural selection, but rather in spite of it.
Interesting, BB. The mathematicians I know have always maintained that the physical world is made up of discrete units and that continuums are simply useful mathematically. Mathematicians, in general, look at the world this way. Physicists, in general, don't.
You are correct about free will, computers do not have that. However, the DNA code is remarkably like a computer program and that is why evolutionists are desperately trying to find some ways to give 'intelligence' to materialistic processes. I personally do not think that man is a machine, just that the body is an incredibly complex machine which required an intelligent designer to create. Consciousness, art, logic and many other abilities of humans are certainly not materialistic.
BTW - the quote on Friedkin was more to interest readers on the article which I think is good and because I thought it a bit funny that some philosopher would have the same theory as Douglas Adams's stories. I also am a bit tired of the Gore name and have been thinking of changing it, Al is not even a joke nowadays.
On the evidence of Wolfram’s statements in the book itself, these criticisms appeared unfounded to me. For example, Kurzweil starts “with Wolfram’s apparent hubris, evidenced in the title itself.” Where Kurzweil sees hubris and immodesty, I saw great humility in certain of Wolfram’s remarks, some of which I’ve quoted above. Moreover, it seems clear to me that Wolfram has had a great deal of help in preparing this book for publication, especially WRT the end notes. His preface, wherein he gives credit where credit is due to literally hundreds of people, doesn’t strike me as confirming the hubris hypothesis. Further, Kurzweil’s suggestion that by virtue of the fact that Wolfram is a highly successful business entrepreneur in addition to being an eminent scientist somehow renders him insufficiently objective in his work seemed gratuitous to me. Analyze the work, I say, not Wolfram.
Still and all, what we’re dealing with here may very well be, in fact, a new kind of science. It certainly appears in several respects to be quite different from what Kurzweil is doing – although after the first few pages of this 10+-page review, Kurzweil seems mostly to agree with many of the things that Wolfram is saying in his book.
It appears the crucial points of disagreement seem to be in regard to evolutionary theory as presently understood, as well as basic methodological approaches to science in general. I think Kurzweil was incorrect in concluding that Wolfram had positively stated that a Class 4 cellular automaton was a model for a human being. I don’t recall Wolfram ever saying such a thing in this book. What he has said is that his speculations in the areas of biological and other living systems “must involve a significant component of hypothesis. For I no longer control the basic rules of the systems I am studying, and instead I must just try to deduce these rules from observation – with the potential that despite my best efforts my deductions could simply be incorrect.”
What Wolfram is aware of – and clearly also Kurzweil, based on his own statements in this review – is that human beings are composites of a great multiplicity of sub-systems, each of which may be composed of further sub-systems. The simple evolutionary rules of Class 4 cellular automata can be imagined to apply to such sub-systems, which will generate complexity on their own respective levels. The almost unimaginable complexity of the human being as a global system conceivably (hypothetically) derives from the interactions of the sub-systems that compose the whole.
Wolfram does not deny that evolution – natural selection – has a role to play in this process. And as Kurzweil himself concludes, “The lack of predictability of Class 4 cellular automata underlies at least some of the apparent complexity of biological systems, and does represent one of the important biological paradigms that we can seek to emulate in our human-created technology. It does not explain all of biology.” But then, Wolfram never said it did.
Basically, the problem that Kurzweil has with Wolfram’s hypothesis is that Class 4 cellular automata do not generate sufficient complexity all by themselves. But how much complexity is “sufficient?” Clearly Wolfram imagines that we need less complexity to explain biological systems than Kurzweil does. Kurzweil specifically argues that we need something more than what the Class 4 cellular automaton model provides.
Specifically, Kurzweil says, “If we add another simple concept to that of Wolfram’s simple cellular automata, i.e., an evolutionary algorithm, we start to get far more interesting, and more intelligent results.” What we need is “an evolutionary process involving conflict and competition.”
But what’s interesting to me is the proposition that an algorithm is what is necessary to elucidate real processes in nature – for an algorithm is a thing that has been specifically designed to accomplish a specific purpose. The question that is left begging is how much correspondence is there between human purposes, and the purposes of nature. The way these two men seemingly have answered that question may constitute the “big methodological divide” that separates the perspectives of two world-class scientists.
To have an algorithm implies that one has a purpose that one is trying to achieve. One can imagine that if a given algorithm doesn’t achieve it, one can always just keep adding algorithms until one does. One’s purpose, not the actual behavior of a system that is under study, ends up being the important thing under test. Details of systems that are not conducive to the achievement of the purpose (i.e., that don’t get “loaded” into the algorithm) may be deemed irrelevant and get “filtered out.” Which suggests to me an essentially subjective way of looking at nature, even though it looks perfectly “scientific” and “objective.” But this is a very fine point that I imagine relatively few people see. I’m pretty sure Wolfram sees it, though.
That’s why I believe that Wolfram is entirely correct to say that what he’s doing is, in fact, a new kind of science. The evolution of a cellular automaton is not the least bit concerned with achieving a purpose, with satisfying the criteria of human expectation. It is all about exhibiting the more or less untrammeled behavior of a system evolving from simple rules. Understand the system thoroughly first, without “censoring reality”; then you can start formalizing methods to apply the insights.
Wolfram has an extraordinarily visual imagination, it seems. And seemingly the same can be said of Kurzweil. To both of them, pattern recognition is a vastly important component of human intelligence. But Wolfram seems to be much more radical in the conclusions he draws from this. For he says,
“Considering the reputation of physics as an empirical science, it is remarkable how many significant theories were in fact first constructed on largely aesthetic grounds. Notable examples include Maxwell’s equations for electromagnetism (1880s), general relativity (1915), the Dirac equation for relativistic electrons (1928), and QCD (early 1970s). This history makes it seem more plausible that one might be able to come up with an ultimate model of physics on largely aesthetic grounds, rather than mainly by working from detailed experimental observations.” Which, in the end, may be why Wolfram is so interested in encouraging mathematicians and scientists to “retrain their intuitions.”
At the very end of review, Kurzweil says, “It remains at least possible, however, that [Wolfram’s] methods can explain all of physics.” A pretty astounding statement, IMHO. Still, he will not concede this possibility to biology. Which suggests to me that he imagines that the universe in toto is less complex than the human being struggling to survive under chaotic conditions of necessity and scarcity.
But how do we know which view is objectively correct? The observer and the observed seemingly have a way of affecting each other; and the future is unknowable at any rate -- and essentially unpredictable for reasons that both Wolfram and Kurzweil seem to agree about.
I just hope these two guys keep on arguing with each other. Listening to their dispute has been a gloriously wonderful experience.
Dirac is famous for deliberately doing exactly that. He would even dismiss lack of experimental evidence in support of a beautiful theory as of no decisive importance.
-Article for Physics World by Helge Kragh for Dirac's 100th birthday.
Yegads RightWhale! What is a mere generalist like me supposed to do with this information? Or might it be the case that science and philosophy could profit from "comparing notes" every now and then?
Not that either one of them should try to emulate the other. Each has a distinct and, it seems to me, valid way of seeing -- which, in a certain way, seem to be quite "incompatible." At least at the level of surface appearance.
I don't know whether you've had a chance to read Kurzweil's review of Wolfram's book. If not, please take a look at it, if you have the time and interest. I'd love to hear your thoughts.
Dirac didn't think so. He thought that philosophy comes along after the horses, picking up and organizing.
Very interesting, Nebullus. Thank you for this information. (Consider me a "total beginner" in this field, so grateful for the help I get.)
This is not news. We were taught that in 1965. I am not on Kurtzweil's wavelength, much that he says grates on my analytical nerves. We can take Kurtzweil's critique as typical of early reports, experts are hurrying to jump on the "Sink the Wolfram" bandwagon. It won't happen, Wolfram is onto something.
For whatever it's worth, RightWhale, I think so too. Somehow I think we live in momentous times.
Dirac said that he thought of God as a great mathematician who designed the universe using higher math advanced far beyond our own meager math.
I believe that Dirac thought that if we could develop our math enough, we could see the design. Our short lifetimes would probably make development of that kind of math impossible. Even lifetimes that had no end at all might not be enough to develop that level of math. It could be one of that class of problems that can't be solved even with infinite resources.
Extraordinarily interesting, RightWhale. Somehow or other, however, I imagine that if mankind had infinite resources, this problem would be fairly easily soluable by man. The point seems to be (to my way of thinking, at least) that infinite resources are precisely what man does not have in himself.
This seems to be a good time to mention that I am some kind of theist, just in the interest of "full and fair disclosure" here. The present question is, I gather, easier for a philosopher than it is for a scientist, these days.
The above makes me wonder - is Wolfram saying that his algorithms are just the beginning of explaining complex systems and that for example other algorithms would be necessary for the more complex steps?
If he is saying that, then it would quell some of Kurtzwell's objections and part of the problem I have with the theory which is basically this - any algorithm, even one which tries to achieve a certain amount of randomness does place constraints on the results. Life seems to be far too complex and varied to have had even a modest amount of such directionality.
It's interesting to me that such an essentially reductionist system seems so readily embraced by those who have a visceral dislike of reductionist science. Perhaps it's because undecidability of emergent properties makes CA's seem anti-reductionist. But it's exactly the type of reductionism that many scientists, especially chemists, have ascribed to biology. That it is simple rules of interactions between atoms which determine the intelligence that is ours and the undecidability and unprovability is that free will we are so fond of.
This isn't reductionism. That's something political scientists do. Wolfram might go the way of Dirac and his whole-number theory, but he doesn't deny the usefulness of experiment.
If I remember correctly, beckett, you stated some dislike of Dennett once. Dennett has used the CA approach to biology and evolution. Have you read any of it?
Here's the paradox, Nebullis. Of all the people presently alive on this planet right now, I probably stand in the forefront of people who simply, viscerally detest all forms of "reductionist," one-size-fits-all systematic rules.
On the other hand, as someone steeped in philosophy by inclination and training, not to mention the Christian perspective, I can appreciate the significance of simple rules in the evolution of the universe. In fact, the simpler the better.
There is a longstanding tradition among us humans that simplicity, beauty, and elegance are manifestly signs of an ultimate order of things that humans beings at all times are free to name and describe according to their own best lights.
There seems to be an inherent mystery, a paradox in the basic operation of the things of this world, from the human perspective at least.
BTW, Wolfram has some very interesting things to say about AI. Please give me a ring when you get to that part? I'd love to hear your thoughts.
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