Artificial Life

Artificial life (commonly called a-life) is the term
applied collectively to attempts that are being made to
develop mathematical models and computer simulations of the
ways in which living organisms develop, grow, and evolve.
Researchers in this burgeoning field hope to gain deeper
insights into the nature of organic life as well as into
the further possibilities of Computer science and robotics
(see ROBOT). A-life techniques are also being used to
explore the origins and chemical processes of metabolism.
Some investigators have even proposed that some digital
"life" in computers might already be considered a real life
form.
 
The term artificial life was coined in the 1980s by
Christopher Langdon, a computer scientist at Los Alamos
National Laboratory and the Santa Fe Institute. Langdon
organized the first experimental workshop on the subject at
Santa Fe in 1987. Since then, other a-life conferences have
taken place, drawing increasingly wider attention and a
growing number of participants.
 
Theoretical studies of a-life, however, had been in
progress long before the 1980s. Most notably, the
Hungarian-born U.S. mathematician John Von Neumann, one of
the pioneers of computer science, had begun to explore the
nature of very basic a-life formats called cellular
automata (see AUTOMATA, THEORY OF) in the 1950s. Cellular
automata are imaginary mathematical "cells"-analogous to
checkerboard squares-that can be made to simulate physical
processes by subjecting them to certain simple rules called
algorithms (see ALGORITHM). Before his death, von Neumann
had developed a set of algorithms by which a cellular
automaton-a box shape with a very long tail-could
"reproduce" itself.
 
Another important predecessor of a-life research was Dutch
biologist Aristid Lindenmeyer. Interested in the
mathematics of plant growth, Lindenmeyer found in the 1960s
that through the use of a few basic algorithms-now called
Lindenmeyer systems, or L-systems-he could model
biochemical processes as well as trace the development of
complex biological forms such as flowers. Computer-graphics
programs now make use of L-systems to yield realistic
three-dimensional images of plants.
 
The significance of Lindenmeyer's contribution is evident
in the fact that so-called "genetic algorithms" are now
basic to research into a-life as well as many other areas
of interest. Genetic algorithms, first described by
computer scientist John Holland of the University of
Michigan in the 1970s, are comparable to L-systems. A
computer worker trying to answer some question about a-life
sets up a system-an algorithm-by which the computer itself
rapidly grades the multiple possible answers that it has
produced to the question. The most successful of the
solutions are then used to develop new software that yields
further solutions, and the cycle is repeated through
several "generations" of answers.
 
Langdon himself picked up on the work of von Neumann by
attempting to design an "a-life" form on a computer screen.
In 1979 he finally succeeded in developing loop-shaped
objects that actually reproduced themselves, over and over
again. As new generations spread outward from the initial
"organisms" they left "dead" generations inside the
expanding parameter. Langdon noted that the "behavior" of
these a-life forms genuinely mimicked real-life processes
of mutation and evolution. He eventually proposed that
a-life studies could provide keys to understanding the
logical form of any living systems, known or unknown.
 
One of the most striking a-life simulations of evolutionary
processes has been the work of Thomas Ray of the University
of Delaware, who in 1990 set in motion a "world" of
computer programs that he called Tierra. The world started
out with a single ancestor, a program containing 80
instructions. A-life evolution proceeded as mutations
rapidly appeared. The new forms included "parasites" that
interacted
 with the original host forms, producing further mutations
of hosts and parasite that "learned" to deal with one
another anew in each succeeding generation. 
 
Bibliography:
 
Braitenberg, Valentino. Vehicles: Experiments in Synthetic
Psychology (1984)
 
Langdon, Christopher, ed. Artificial Life (1988)
 
Levy, Steven. Artificial Life (1992)
 
Pagels, H. R. The Dreams of Reason (1988)
 
Prata, Stephen. Artificial Life (1993)