Bruce Sterling. Artificial life
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.
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