Q4.1: What about Alife systems, like Tierra and VENUS?

     None of these are Evolutionary Algorithms, but all of  them  use  the
     evolutionary metaphor as their "playing field".

     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

     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 characterized 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.

     --- "Tierra announcement" by Tom Ray (1991)

  How to get Tierra?
     The  complete  source code and documentation (but not executables) is
     available   by   anonymous   FTP   at:   tierra.slhs.udel.edu:/   and
     life.slhs.udel.edu:/  in the directories: almond/, beagle/, doc/, and

     If you do not have FTP access you may obtain everything on DOS disks.
     For  details, write to: Virtual Life, 25631 Jorgensen Rd., Newman, CA


     Ray, T. S. (1991)  "Is it alive, or is it GA?" in [ICGA91], 527--534.

     Ray,  T.  S.  (1991)   "An  approach  to  the  synthesis of life." in
     [ALIFEII], 371--408.

     Ray, T. S.  (1991)  "Population dynamics of  digital  organisms."  in

     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

     Ray,  T.  S.  (1992)  "Evolution, ecology and OPTIMIZATION of digital
     organisms."  Santa Fe Institute working paper 92-08-042.

     Ray, T. S.  "Evolution, complexity, entropy, and artificial reality."
     submitted Physica D. Avail. as tierra.slhs.udel.edu:/doc/PhysicaD.tex

     Ray, T. S.  (1993) "An evolutionary approach  to  synthetic  biology,
     Zen  and  the  art of creating life.  Artificial Life 1(1). Avail. as

     Steen Rasmussen's (et al.) VENUS I+II "coreworlds"  as  described  in
     [ALIFEII]  and  [LEVY92],  are  inspired by A.K. Dewdney's well-known
     article (Dewdney 1984). Dewdney proposed a game called  "Core  Wars",
     in  which hackers create computer programs that battle for control of
     a computer's "core" memory (Strack 93).  Since computer programs  are
     just  patterns  of  information, a successful program in core wars is
     one that replicates its pattern within the memory, so that eventually
     most  of  the  memory  contains  its  pattern rather than that of the
     competing program.

     VENUS is a modification of Core Wars in which the  Computer  programs
     can  mutate, thus the pseudo assembler code creatures of VENUS evolve
     steadily.  Furthermore  each  memory   location   is   endowed   with
     "resources"  which,  like  sunshine  are  added at a steady state.  A
     program must have sufficient resources in the regions  of  memory  it
     occupies  in  order  to  execute.   The input of resources determines
     whether the VENUS ecosystem is a "jungle" or a "desert."   In  jungle
     ENVIRONMENTs,  Rasmussen  et al. observe the spontaneous emergence of
     primitive "copy/split" organisms starting  from  (structured)  random
     initial conditions.

     --- [ALIFEII], p.821

     Dewdney,  A.K.  (1984) "Computer Recreations: In the Game called Core
     War Hostile Programs Engage in a Battle of Bits", Sci. Amer.  250(5),

     Farmer  &  Belin  (1992)  "Artificial  Life:  The  Coming Evolution",
     [ALIFEII], 815-840.

     Rasmussen, et al. (1990) "The Coreworld: Emergence and  EVOLUTION  of
     Cooperative  Structures  in  a Computational Chemistry", [FORREST90],

     Rasmussen,  et  al.  (1992)  "Dynamics   of   Programmable   Matter",
     [ALIFEII], 211-254.

     Strack (1993) "Core War Frequently Asked Questions (rec.games.corewar
     FAQ)"        Avail.        by         anon.          FTP         from

     Larry  Yaeger's  PolyWorld as described in [ALIFEIII] and [LEVY92] is
     available via anonymous FTP from ftp.apple.com:/pub/polyworld/

     "The subdirectories in this "polyworld" area contain the source  code
     for the PolyWorld ecological simulator, designed and written by Larry
     Yaeger, and Copyright 1990, 1991, 1992 by Apple Computer.

     PostScript versions of my ARTIFICIAL LIFE III  technical  paper  have
     now  been added to the directory.  These should be directly printable
     from most machines.  Because some unix systems' "lpr" commands cannot
     handle  very large files (ours at least), I have split the paper into
     Yaeger.ALife3.1.ps and Yaeger.ALife3.2.ps.  These files can be ftp-ed
     in  "ascii"  mode.   For  unix  users I have also included compressed
     versions of both these files (indicated by the .Z suffix),  but  have
     left the uncompressed versions around for people connecting from non-
     unix systems.  I  have  not  generated  PostScript  versions  of  the
     images,  because  they are color and the resulting files are much too
     large to store, retrieve,  or  print.   Accordingly,  though  I  have
     removed  a  Word-formatted  version  of the textual body of the paper
     that used to be here, I have left a  Word-formatted  version  of  the
     color  images.   If  you wish to acquire it, you will need to use the
     binary transfer mode to move it to first your unix host and then to a
     Macintosh  (unless  Word on a PC can read it - I don't know), and you
     may need to do something nasty like use ResEdit to set the file  type
     and  creator to match those of a standard Word document (Type = WDBN,
     Creator = MSWD).  [..]"

     --- from the README by Larry Yaeger <larryy@apple.com>

 General Alife repositories?
     Also, all of the following FTP sites carry ALIFE related info:

     ftp.cognet.ucla.edu:/pub/alife/                                     ,
     life.anu.edu.au:/pub/complex_systems/alife/                         ,
     ftp.cogs.susx.ac.uk:/pub/reports/csrp/  ,  xyz.lanl.gov:/nlin-sys/  ,
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