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| Nonzero: The Logic of Human Destiny, Part II
Last week, in my first posting, I made three assertions:
(1) that both biological evolution and cultural evolution have direction, in the sense that they are very likely to generate more complex structures over time.
(2) that this directionality can be described in terms of game theory: the growth of biological complexity consists of more and more genes playing more and more elaborate non-zero-sum games with one another; and the growth of social complexity consists of more and more people playing more and more elaborate non-zero-sum games with each other.
(3) finally, I asserted that this sort of directionality provides at least some evidence that the evolutionary process is subordinate to a larger purpose--a "higher" purpose, you might even say.
Obviously, that's a lot of asserting! Also obviously, I'm not going to be able to back up all of these assertions in the course of my several Metanexus postings. So I'm going to ask you to accept the first two assertions for the sake of argument. (Skeptics--and for that matter non-skeptics--are encouraged to look at my book, Nonzero, where I spend 300pages arguing that the observed growth of both biological complexity and human social complexity was so probable as to border on the inevitable.) I'm going to spend my remaining Metanexus postings on assertion number three--the question of "purpose". Assuming you will indeed indulge me by stipulating that both biological and cultural evolution have direction, how do we decide whether that direction is indicative of purpose? And, more problematic still, what are the hallmarks of a "higher"--even "divine"--purpose?
I think the first step toward seeing evidence of purpose in the evolutionary process is to see what exactly was wrong with William Paley's famous 19th-century teleological analysis. In case you've forgotten the details, Paley used the evident functionality of plants and animals to argue for the existence of God. If you come across a rock, he noted, you have no reason to conclude that it was made for a purpose. But if you come across a pocket watch, you know that it was made by a watchmaker, for the purpose of keeping time. And plainly, living things are more like watches and other artifacts than like rocks; animals are evidently designed to eat, to breathe, to do other things. As Paley put it, "There is precisely the same proof that the eye was made for vision, as there is that the telescope was made for assisting it."
Since Darwin published the theory of natural selection, Paley's logic has often been depicted as one giant heap of muddle. But it's not. Paley wasn't wrong to say that plants and animals are evidently functional. And he wasn't wrong to say that this functionality strongly suggested a designer. He was just wrong to assume that the designer was a being rather than a process (natural selection, it turned out). The eye, loosely speaking, *was* made for vision--it just wasn't handcrafted by God. (Or, to speak of the eye's *ultimate* function--and the ultimate "purpose" for which natural selection "designs" things--the eye was made to aid the transmission of genes into future generations.)
My point is just that there are indeed certain things that, we all more or less agree, have the hallmarks of purpose--of having been designed to pursue a particular end. And once we're clear on what those hallmarks are, we can look at a system such as biological evolution by natural selection and ask: Does it, too, have the hallmarks of purpose?
In my book I explore the hallmarks of purpose by imaging two extraterrestrial observers who happen upon planet Earth and try to figure out whether various of its living systems are purposeful.
The first extraterrestrial lands in a greenhouse. He notices that the green objects surrounding him tend to get taller. Does this alone--simple directionality--imply purpose in the common sense of the word? No. Water flows from high to low, but we don't think of water as being imbued with purpose.
But these plants do more than move directionally. The extraterrestrial documents this fact by using his awesome powers to relocate the sun. He notices that within days the plants have reoriented themselves so that their leaves once again face it. What's more, if he cuts off the end of a branch, a new twig sprouts. All told, the plants seem strongly inclined to grow upward even when you throw a roadblock in the way--by cutting them back, say, or by moving their source of energy.
Based only on these observations, we could say that these plants meet what the philosopher Richard Braithwaite proposed half a century ago as a rough-and-ready criterion of teleological behavior: "persistence towards the [hypothesized] goal under varying conditions."
Personally, though, I don't find Braithwaite’s criterion for purpose quite satisfactory. After all, by his criterion, rivers might still qualify as teleological; erect a hill in their path, and they meander around it, thus persisting in their direction even under "varying conditions". But I do think that by adding one element to his criterion we can come up with something that succeeds in separating plants and animals and other purposeful systems, on the one hand, from rivers on the other. Namely: plants and animals, in their "persistince towards the goal under varying conditions," make the necessary adjustments *by* *processing *information*. The plant that the extraterrestrial is watching absorbs data reflecting the state of its environment--where the sunlight is coming from, for example--and this information guides the plant's growth accordingly.
This added criterion for purpose, by the way, was popular among cyberneticists at mid-century. Arturo Rosenblueth, Norbert Wiener, and Julian Bigelow wrote in their 1943 paper "Behavior, Purpose and Teleology," in the journal Philosophy of Science[10:18-24], that "all purposeful behavior may be considered to require negative feedback." This criterion is also consistent with an assertion commonly made by philosophers: that a good definition of a purposeful system should include such things as robots and anti-aircraft guns that automatically track a moving target via feedback from radar.
If you accept this criterion for purpose--persistence toward the hypothesized goal under varying conditions via the processing of information--the question becomes: does evolution by natural selection fulfill it? I think the answer is yes.
To see why, let's imagine a second extraterrestrial visitor. She is very long-lived--to her, a billion years is a week. She arrives on Earth in 1 billion, BC, and her mission is to see whether organic evolution seems to be a purposeful, goal-seeking process.
She soon comes up with a good candidate for the goal--the creation of organic complexity, in several senses: broadening the diversity of species; raising the average complexity of species; expanding the outer limit of complexity (in other words, in the long run, the complexity of the most complex species on the planet tends to grow); and expanding the outer limit of behavioral flexibility--that is, of intelligence.
What's more, she notices the same sort of stubbornness that the other etraterrestrial had noticed about plants: when she "prunes" the tree of life, evolution regenerates branches. The branches may not look exactly like the ones pruned, but they're certainly reminiscent. If she wipes out all life on an island, the island get repopulated, and previously filled niches get filled, even if not by the exact species that filled them before. If she wipes out all life that can fly, flight gets reinvented, again and again, until the air is once again full of flying objects. (We know that flight--like other nifty properties, such as eyesight--has been invented numerous times, independently, by natural selection.) If she wipes out the most complex life, or the smartest life, replacements are eventually forthcoming. Indeed, even if she doesn't personally do the wiping out--even if a meteor shows up and causes a mass extinction--the biosphere's resilience soon becomes manifest.
And, rather as a plant reorients itself when the source of light moves, evolution channels life toward the most benign environments. If lush lands dry up, while dry lands become wet, the balance of the biomass shifts accordingly. Of course, some life stays behind in the newly dry lands, and adapts to it. Indeed, in general what is striking is the varying conditions under which evolution creates complex life.
All told, I submit, evolution by natural selection fulfills that first, rough-and-ready criterion of goal-directed behavior, the one championed by Richard Braithwaite: "persistence toward the goal under varying conditions." But what about the further condition, the one that separates living things from rivers? Does natural selection do its adjusting to varying conditions by processing information?
Yes, I think so. Natural selection sends packets of information--genes--into the world. If they proliferate, this positive feedback signifies an environment with which they are adaptively compatible. (In fact, their proliferation *constitutes adaptation to this environment; through this positive feedback life "senses" and reacts adaptively to environmental change.) Of course, sometimes new genes don't proliferate. This negative feedback signifies a lack of adaptive compatibility with the environment. Trial and error is a system of information processing--even if, as here, the trials are randomly generated. The noted geneticist Theodosius Dobzhansky once wrote, "natural selection is a process conveying `information' about the state of the environment to the genotypes of its inhabitants."
I don't claim that this argument *proves* that biological evolution has a designed-in purpose, like plants and animals. But I do claim that biological evolution has a set of properties that is found in such designed, purposive things as animals and robots and is not found in such evidently purposeless things as rocks and rivers. This isn't proof of teleology, but it's evidence of it.
Or, to put the point another way: It may indeed be that evolution is not teleological. But if that's the case, then evolution is the only thing I can think of that exhibits flexible directionality via information processing and isn't teleological.
Or, to put the point yet another way: If you were the second extraterrestrial, and could watch the whole history of life on earth in time-lapse, you would be hard pressed to draw a clear analytical distinction between the blossoming of the biosphere and the blossoming of a flower.
Okay-that's about enough for this week. In my next posting I'll make other arguments for attributing purpose to the direction that, I contend, is characteristic of evolution. But next time I'll focus on cultural evolution, not biological evolution. And next time I'll address not just the issue of whether evolution may serve a "larger" purpose, but whether it may serve a truly "higher" purpose--whether it may tend to move toward something we might call good.
Thanks for tuning in.
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Published 2000.02.06
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