Bruce Sterling. Artificial life
bruces@well.sf.ca.us Literary Freeware: Not For Commercial Use
From THE MAGAZINE OF FANTASY AND SCIENCE FICTION, Dec 1992.
F&SF, Box 56 Cornwall CT 06753 $26/yr; outside US $31/yr F&SF Science column #4 ARTIFICIAL LIFE The new scientific field of study called "Artificial Life" can be defined as "the attempt to abstract the logical form of life from its material manifestation." So far, so good. But what is life?
The basic thesis of "Artificial Life" is that "life" is best understood as a complex systematic process. "Life" consists of relationships and rules and interactions. "Life" as a property is potentially separate from actual living creatures.
Living creatures (as we know them today, that is) are basically made of wet organic substances: blood and bone, sap and cellulose, chitin and ichor. A living creature — a kitten, for instance — is a physical object that is made of molecules and occupies space and has mass.
A kitten is indisputably "alive" — but not because it has the "breath of life" or the "vital impulse" somehow lodged inside its body. We may think and talk and act as if the kitten "lives" because it has a mysterious "cat spirit" animating its physical cat flesh. If we were superstitious, we might even imagine that a healthy young cat had *nine* lives. People have talked and acted just this way for millennia.
But from the point-of-view of Artificial Life studies, this is a very halting and primitive way of conceptualizing what's actually going on with a living cat. A kitten's "life" is a *process, * with properties like reproduction, genetic variation, heredity, behavior, learning, the possession of a genetic program, the expression of that program through a physical body. "Life" is a thing that *does,* not a thing that *is* — life extracts energy from the environment, grows, repairs damage, reproduces.
And this network of processes called "Life" can be picked apart, and studied, and mathematically modelled, and simulated with computers, and experimented upon — outside of any creature's living body.
"Artificial Life" is a very young field of study. The use of this term dates back only to 1987, when it was used to describe a conference in Los Alamos New Mexico on "the synthesis and simulation of living systems." Artificial Life as a discipline is saturated by computer-modelling, computer-science, and cybernetics. It's conceptually similar to the earlier field of study called "Artificial Intelligence." Artificial Intelligence hoped to extract the basic logical structure of intelligence, to make computers "think." Artificial Life, by contrast, hopes to make computers only about as "smart" as an ant — but as "alive" as a swarming anthill.
Artificial Life as a discipline uses the computer as its primary scientific instrument. Like telescopes and microscopes before them, computers are making previously invisible aspects of the world apparent to the human eye. Computers today are shedding light on the activity of complex systems, on new physical principles such as "emergent behavior," "chaos," and "self-organization." For millennia, "Life" has been one of the greatest of metaphysical and scientific mysteries, but now a few novel and tentative computerized probes have been stuck into the fog. The results have already proved highly intriguing.
Can a computer or a robot be alive? Can an entity which only exists as a digital simulation be "alive"? If it looks like a duck, quacks like a duck, waddles like a duck, but it in fact takes the form of pixels on a supercomputer screen — is it a duck? And if it's not a duck, then what on earth is it? What exactly does a thing have to do and be before we say it's "alive"?
It's surprisingly difficult to decide when something is "alive." There's never been a definition of "life," whether scientific, metaphysical, or theological, that has ever really worked. Life is not a clean either/or proposition. Life comes on a kind of scale, apparently, a kind of continuum — maybe even, potentially, *several different kinds of continuum.* One might take a pragmatic, laundry-list approach to defining life. To be "living," a thing must grow. Move. Reproduce. React to its environment. Take in energy, excrete waste. Nourish itself, die, and decay. Have a genetic code, perhaps, or be the result of a process of evolution. But there are grave problems with all of these concepts. All these things can be done today by machines or programs. And the concepts themselves are weak and subject to contradiction and paradox.
Are viruses "alive"? Viruses can thrive and reproduce, but not by themselves — they have to use a victim cell in order to manufacture copies of themselves. Some dormant viruses can crystallize into a kind of organic slag that's dead for all practical purposes, and can stay that way indefinitely — until the virus gets another chance at infection, and then the virus comes seething back.
How about a frozen human embryo? It can be just as dormant as a dormant virus, and certainly can't survive without a host, but it can become a living human being. Some people who were once frozen embryos may be reading this magazine right now! Is a frozen embryo "alive" — or is it just the *potential* for life, a genetic life- program halted in mid-execution?
Bacteria are simple, as living things go. Most people however would agree that germs are "alive." But there are many other entities in our world today that act in lifelike fashion and are easily as complex as germs, and yet we don't call them "alive" — except "metaphorically" (whatever *that* means).
How about a national government, for instance? A government can grow and adapt and evolve. It's certainly a very powerful entity that consumes resources and affects its environment and uses enormous amounts of information. When people say "Long Live France," what do they mean by that? Is the Soviet Union now "dead"?
Amoebas aren't "mortal" and don't age — they just go right on splitting in half indefinitely. Does that mean that all amoebas are actually pieces of one super-amoeba that's three billion years old?
And where's the "life" in an ant-swarm? Most ants in a swarm never reproduce; they're sterile workers — tools, peripherals, hardware. All the individual ants in a nest, even the queen, can die off one by one, but as long as new ants and new queens take their place, the swarm itself can go on "living" for years without a hitch or a stutter.
Questioning "life" in this way may seem so much nit-picking and verbal sophistry. After all, one may think, people can easily tell the difference between something living and dead just by having a good long look at it. And in point of fact, this seems to be the single strongest suit of "Artificial Life." It is very hard to look at a good Artificial Life program in action without perceiving it as, somehow, "alive." Only living creatures perform the behavior known as "flocking." A gigantic wheeling flock of cranes or flamingos is one of the most impressive sights that the living world has to offer.
But the "logical form" of flocking can be abstracted from its "material manifestation" in a flocking group of actual living birds. "Flocking" can be turned into rules implemented on a computer. The rules look like this: 1. Stay with the flock — try to move toward where it seems thickest.
2. Try to move at the same speed as the other local birds.
3. Don't bump into things, especially the ground or other birds.
In 1987, Craig Reynolds, who works for a computer-graphics company called Symbolics, implemented these rules for abstract graphic entities called "bird-oids" or "boids." After a bit of fine- tuning, the result was, and is, uncannily realistic. The darn things *flock!* They meander around in an unmistakeably lifelike, lively, organic fashion. There's nothing "mechanical" or "programmed- looking" about their actions. They bumble and swarm. The boids in the middle shimmy along contentedly, and the ones on the fringes tag along anxiously jockeying for position, and the whole squadron hangs together, and wheels and swoops and maneuvers, with amazing grace. (Actually they're neither "anxious" nor "contented," but when you see the boids behaving in this lifelike fashion, you can scarcely help but project lifelike motives and intentions onto them.) You might say that the boids simulate flocking perfectly — but according to the hard-dogma position of A-Life enthusiasts, it's not "simulation" at all. This is real "flocking" pure and simple — this is exactly what birds actually do. Flocking is flocking — it doesn't matter if it's done by a whooping crane or a little computer-sprite.
Clearly the birdoids themselves aren't "alive" — but it can be argued, and is argued, that they're actually doing something that is a genuine piece of the life process. In the words of scientist Christopher Langton, perhaps the premier guru of A-Life: "The most important thing to remember about A-Life is that the part that is artificial is not the life, but the materials. Real things happen. We observe real phenomena. It is real life in an artificial medium." The great thing about studying flocking with boids, as opposed to say whooping cranes, is that the Artificial Life version can be experimented upon, in controlled and repeatable conditions. Instead of just *observing* flocking, a life-scientist can now *do* flocking. And not just flocks — with a change in the parameters, you can study "schooling" and "herding" as well.
The great hope of Artificial Life studies is that Artificial Life will reveal previously unknown principles that directly govern life itself — the principles that give life its mysterious complexity and power, its seeming ability to defy probability and entropy. Some of these principles, while still tentative, are hotly discussed in the field.
For instance: the principle of *bottom-up* initiative rather than *top-down* orders. Flocking demonstrates this principle well. Flamingos do not have blueprints. There is no squadron-leader flamingo barking orders to all the other flamingos. Each flamingo makes up its own mind. The extremely complex motion of a flock of flamingos arises naturally from the interactions of hundreds of independent birds. "Flocking" consists of many thousands of simple actions and simple decisions, all repeated again and again, each action and decision affecting the next in sequence, in an endless systematic feedback.
This involves a second A-Life principle: *local* control rather than *global* control. Each flamingo has only a vague notion of the behavior of the flock as a whole. A flamingo simply isn't smart enough to keep track of the entire "big picture," and in fact this isn't even necessary. It's only necessary to avoid bumping the guys right at your wingtips; you can safely ignore the rest.
Another principle: *simple* rules rather than *complex* ones. The complexity of flocking, while real, takes place entirely outside of the flamingo's brain. The individual flamingo has no mental conception of the vast impressive aerial ballet in which it happens to be taking part. The flamingo makes only simple decisions; it is never required to make complex decisions requiring a lot of memory or planning. *Simple* rules allow creatures as downright stupid as fish to get on with the job at hand — not only successfully, but swiftly and gracefully.
And then there is the most important A-Life principle, also perhaps the foggiest and most scientifically controversial: *emergent* rather than *prespecified* behavior. Flamingos fly from their roosts to their feeding grounds, day after day, year in year out. But they will never fly there exactly the same way twice. They'll get there all right, predictable as gravity; but the actual shape and structure of the flock will be whipped up from scratch every time. Their flying order is not memorized, they don't have numbered places in line, or appointed posts, or maneuver orders. Their orderly behavior simply *emerges,* different each time, in a ceaselessly varying shuffle.
Ants don't have blueprints either. Ants have become the totem animals of Artificial Life. Ants are so 'smart' that they have vastly complex societies with actual *institutions* like slavery and and agriculture and aphid husbandry. But an individual ant is a profoundly stupid creature. Entomologists estimate that individual ants have only fifteen to forty things that they can actually "do." But if they do these things at the right time, to the right stimulus, and change from doing one thing to another when the proper trigger comes along, then ants as a group can work wonders.
There are anthills all over the world. They all work, but they're all different; no two anthills are identical. That's because they're built bottom-up and emergently. Anthills are built without any spark of planning or intelligence. An ant may feel the vague instinctive need to wall out the sunlight. It begins picking up bits of dirt and laying them down at random. Other ants see the first ant at work and join in; this is the A-Life principle known as "allelomimesis," imitating the others (or rather not so much "imitating" them as falling mechanically into the same instinctive pattern of behavior).
Sooner or later, a few bits of dirt happen to pile up together. Now there's a wall. The ant wall-building sub-program kicks into action. When the wall gets high enough, it's roofed over with dirt and spit. Now there's a tunnel. Do it again and again and again, and the structure can grow seven feet high, and be of such fantastic complexity that to draw it on an architect's table would take years. This emergent structure, "order out of chaos," "something out of nothing" — appears to be one of the basic "secrets of life." These principles crop up again and again in the practice of life- simulation. Predator-prey interactions. The effects of parasites and viruses. Dynamics of population and evolution. These principles even seem to apply to internal living processes, like plant growth and the way a bug learns to walk. The list of applications for these principles has gone on and on.
It's not hard to understand that many simple creatures, doing simple actions that affect one another, can easily create a really big mess. The thing that's *hard* to understand is that those same, bottom-up, unplanned, "chaotic" actions can and do create living, working, functional order and system and pattern. The process really must be seen to be believed. And computers are the instruments that have made us see it.
Most any computer will do. Oxford zoologist Richard Dawkins has created a simple, popular Artificial Life program for personal computers. It's called "The Blind Watchmaker," and demonstrates the inherent power of Darwinian evolution to create elaborate pattern and structure. The program accompanies Dr. Dawkins' 1986 book of the same title (quite an interesting book, by the way), but it's also available independently.
The Blind Watchmaker program creates patterns from little black-and-white branching sticks, which develop according to very simple rules. The first time you see them, the little branching sticks seem anything but impressive. They look like this: Fig 1. Ancestral A-Life Stick-Creature After a pleasant hour with Blind Watchmaker, I myself produced these very complex forms — what Dawkins calls "Biomorphs." Fig. 2 — Six Dawkins Biomorphs It's very difficult to look at such biomorphs without interpreting them as critters — *something* alive-ish, anyway. It seems that the human eye is *trained by nature* to interpret the output of such a process as "life-like." That doesn't mean it *is* life, but there's definitely something *going on there.* *What* is going on is the subject of much dispute. Is a computer-simulation actually an abstracted part of life? Or is it technological mimicry, or mechanical metaphor, or clever illusion?
We can model thermodynamic equations very well also, but an equation isn't hot, it can't warm us or burn us. A perfect model of heat isn't heat. We know how to model the flow of air on an airplane's wings, but no matter how perfect our simulations are, they don't actually make us fly. A model of motion isn't motion. Maybe "Life" doesn't exist either, without that real-world carbon-and-water incarnation. A-Life people have a term for these carbon-and-water chauvinists. They call them "carbaquists." Artificial Life maven Rodney Brooks designs insect-like robots at MIT. Using A-Life bottom-up principles — "fast, cheap, and out of control" — he is trying to make small multi-legged robots that can behave as deftly as an ant. He and his busy crew of graduate students are having quite a bit of success at it. And Brooks finds the struggle over definitions beside the real point. He envisions a world in which robots as dumb as insects are everywhere; dumb, yes, but agile and successful and pragmatically useful. Brooks says: "If you want to argue if it's living or not, fine. But if it's sitting there existing twenty- four hours a day, three hundred sixty-five days of the year, doing stuff which is tricky to do and doing it well, then I'm going to be happy. And who cares what you call it, right?" Ontological and epistemological arguments are never easily settled. However, "Artificial Life," whether it fully deserves that term or not, is at least easy to see, and rather easy to get your hands on. "Blind Watchmaker" is the A-Life equivalent of using one's computer as a home microscope and examining pondwater. Best of all, the program costs only twelve bucks! It's cheap and easy to become an amateur A-Life naturalist.
Because of the ubiquity of powerful computers, A-Life is "garage-band science." The technology's out there for almost anyone interested — it's hacker-science. Much of A-Life practice basically consists of picking up computers, pointing them at something promising, and twiddling with the focus knobs until you see something really gnarly. *Figuring out what you've seen* is the tough part, the "real science"; this is where actual science, reproducible, falsifiable, formal, and rigorous, parts company from the intoxicating glamor of the intellectually sexy. But in the meantime, you have the contagious joy and wonder of just *gazing at the unknown* the primal thrill of discovery and exploration.
A lot has been written already on the subject of Artificial Life. The best and most complete journalistic summary to date is Steven Levy's brand-new book, ARTIFICIAL LIFE: THE QUEST FOR A NEW CREATION (Pantheon Books 1992).
The easiest way for an interested outsider to keep up with this fast-breaking field is to order books, videos, and software from an invaluable catalog: "Computers In Science and Art," from Media Magic. Here you can find the Proceedings of the first and second Artificial Life Conferences, where the field's most influential papers, discussions, speculations and manifestos have seen print.
But learned papers are only part of the A-Life experience. If you can see Artificial Life actually demonstrated, you should seize the opportunity. Computer simulation of such power and sophistication is a truly remarkable historical advent. No previous generation had the opportunity to see such a thing, much less ponder its significance. Media Magic offers videos about cellular automata, virtual ants, flocking, and other A-Life constructs, as well as personal software "pocket worlds" like CA Lab, Sim Ant, and Sim Earth. This very striking catalog is available free from Media Magic, P.O Box 507, Nicasio CA 94946.