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 controversiaclass="underline" *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?"