TIERRA UPDATE:
(Source release, abstract, publications, lectures, new results)
This message contains:
1) Announcement of release of Tierra source code
2) Abstract describing Tierra
3) List of related publications and upcoming lectures
4) Some interesting new and unpublished results
1) Announcement of release of Tierra source code
We are releasing the source now, although it is under rapid development
and major improvements are only days away. If you use the software, be sure
to pick up new versions soon from the ftp site. The source in the ftp site
will be replace on a roughly weekly basis.
The complete source code for the Tierra simulator is
available by anonymous ftp at:
tierra.slhs.udel.edu [128.175.41.34] and
life.slhs.udel.edu [128.175.41.33]
in the directory /tierra.
to get it, ftp to tierra or life, log in as user "anonymous" and give your
real name (eg. tom at udel.edu) as a password.
then give the command `cd tierra', to get a list of files type `dir'.
you will see the following files:
README.T1 A detailed description of tierra and how to use it.
README.T2 in two parts
Part01 the source code in shar format
... in seven parts
Part07
announce this announcement
tierra1.tex Parts 1 & 2 of a manuscript describing Tierra,
tierra2.tex in LaTeX format.
The shar files contain the README files, so if you want the source code,
you don't need to copy README separately. To unpack the shar files, use
`unshar', or `sh'.
The version released includes significant contributions from
Tom Uffner, Dan Pirone and Marc Cygnus. The software remains copyrighted
("all rights reserved"), and is not being placed in the public domain.
However, it will be made available free of charge and may be freely
distributed. The intent is that it not be used for profit making activities
unless some royalty arrangement is entered into with the authors.
A DOS version of the Tierra software with a decent frontend will be ready
for sale ($70) by November.
2) Abstract describing Tierra
**** BEGIN ABSTRACT ****
Synthetic organisms have been created based on a computer metaphor of
organic life in which CPU time is the ``energy'' resource and memory is
the ``material'' resource. Memory is organized into informational
patterns that exploit CPU time for self-replication. Mutation generates
new forms, and evolution proceeds by natural selection as different
genotypes compete for CPU time and memory space.
Observation of nature shows that evolution by natural selection is
capable of both optimization and creativity. Artificial models of evolution
have demonstrated the optimizing ability of evolution, as exemplified by
the field of genetic algorithms. The creative aspects of evolution have been
more elusive to model. The difficulty derives in part from a tendency of
models to specify the meaning of the ``genome'' of the evolving entities,
precluding new meanings from emerging. I will present a natural model of
evolution demonstrating both optimization and creativity, in which the
genome consists of sequences of executable machine code.
>From a single rudimentary ancestral ``creature'',
very quickly there evolve parasites, which are not able to replicate in
isolation because they lack a large portion of the genome. However, these
parasites search for the missing information, and if they locate it in a
nearby creature, parasitize the information from the neighboring genome,
thereby effecting their own replication.
In some runs, hosts evolve immunity to attack by parasites.
When immune hosts appear, they often increase in frequency, devastating the
parasite populations. In some runs where the community comes to be
dominated by immune hosts, parasites evolve that are resistant to immunity.
Hosts sometimes evolve a response to parasites that goes beyond immunity,
to actual (facultative) hyper-parasitism. The hyper-parasite deceives the
parasite causing the parasite to devote its energetic resources to replication
of the hyper-parastie genome. This drives the parasites to extinction.
Evolving in the absence of parasites, hyper-parasites completely dominate
the community, resulting in a relatively uniform community characterize by
a high degree of relationship between individuals. Under these circumstances,
sociality evolves, in the form of creatures which can only replicate in
aggregations.
The cooperative behavior of the social hyper-parasites makes them vulnerable
to a new class of parasites. These cheaters, hyper-hyper-parasites, insert
themselves between cooperating social individuals, deceiving the social
creatures, causing them to replicate the genomes of the cheaters.
The only genetic change imposed on the simulator is
random bit flips in the machine code of the creatures. However, it turns
out that parasites are very sloppy replicators. They cause significant
recombination and rearrangement of the genomes. This spontaneous sexuality
is a powerful force for evolutionary change in the system.
One of the most interesting aspects of this instance of life is
that the bulk of the evolution is based on adaptation to the biotic
environment rather than the physical environment. It is co-evolution
that drives the system.
**** END ABSTRACT ****
3) List of related publications and upcoming lectures
The recent publicity about my work (Technology Review, April 1991;
Science News, August 10, 1991; New York Times, August 27, 1991; Computerworld
September 30, 1991) has generated a lot of interest. I wanted to list the
relevant publications, and also the upcoming seminars.
Ray, T. S. 1991. ``Is it alive, or is it GA?''
Proceedings of the 1991 International Conference on Genetic Algorithms,
Eds. Belew, R. K., and L. B. Booker, San Mateo, CA: Morgan Kaufmann, 527--534.
Ray, T. S. 1991. ``An approach to the synthesis of life.''
Artificial Life II, Santa Fe Institute Studies in the Sciences of
Complexity, vol. XI, Eds. C. Langton, C. Taylor, J. D. Farmer, & S. Rasmussen,
Redwood City, CA: Addison-Wesley, 371--408.
Ray, T. S. 1991. ``Population dynamics of digital organisms.''
Artificial Life II Video Proceedings, Ed. C. G. Langton,
Redwood City, CA: Addison Wesley.
Ray, T. S. 1991. ``Evolution and optimization of digital organisms.''
Scientific Excellence in Supercomputing: The IBM 1990 Contest Prize Papers,
Eds. Keith R. Billingsley, Ed Derohanes, Hilton Brown, III.
Athens, GA, 30602, The Baldwin Press, The University of Georgia.
Publication date: December 1991.
I will be at the Santa Fe Institute Feb. 1 thru Aug. 31, 1992.
This work will also be presented in the following upcoming seminars:
University of Maryland, Zoology, October 29, 1991
University of Kentucky, Lexington, Biology, October 31, 1991
University of Delaware, Entomology, November 5, 1991
Stony Brook, Department of Ecology and Evolution, November 6, 1991
Drexel University, Electrical Engineering, November 8, 1991
The University of the Arts, Philadelphia, Design in Cyberspace lectures,
November 12, 1991
IBM, T. J. Watson Research Center, Yorktown Heights, NY, November 13, 1991
Thinking Machines Corp., Cambridge, November 14, 1991
Digital Equipment Corp., Hudson, MA, November 15, 1991
American Society of Information Science, New Jersey, November 19, 1991
Texas Instruments, Dallas, November 21, 1991
Harvard University, Biology (Lewontin's lab), December 2, 1991
Boston University, Computational Sciences Center, December 3, 1991
MIT Nanotechnology Study Group, December 3, 1991
University of Massachusetts Boston, Biology, December 5, 1991
Yale University, Biology, December 6, 1991
University of Arizona, Ecology & Evolutionary Biology, March 10, 1992
Cornell University, Mathematical Sciences Institute, CA Workshop, May 1992
Gordon Conference on Theoretical Biology, New Hampshire, June 8--12, 1992
4) Some interesting new and unpublished results
Below is a report of an interesting result that is not described in
any of the publications listed above:
A COMPLEX ADAPTATION
The adaptation described below is a classic example of intricate design in
evolution. One wonders how it could have arisen through random bit flips,
as every component of the code must be in place in order for the algorithm
to function. Yet the code includes a classic mix of apparent intelligent
design, and the chaotic hand of evolution. The optimization technique is a
very clever one invented by humans, yet it is implemented in a mixed up but
functional style that no human would use (unless perhaps very intoxicated).
The arms race described in the manuscripts took place over a period of
a billion instructions executed by the system. An
