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March 29, 2008
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Free Essay, Research Papers, Term Papers |
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rtificial life (commonly called a-life) is the term applied
collectively to attempts 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.
Background
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 tracing 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.
Evolutionary Modeling
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 parasites that learned to
deal with one another anew in each succeeding generation.
Bibliography
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).
Word Count: 617
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