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Dr. Thomas S. Ray

Welcome to the researcher page for Tom Ray, Professor of Zoology and Computer Science at the University of Oklahoma. He created and developed the Tierra Project, a computer simulation of artificial life. His background in Ecology has led to a focus in the study of evolution and genomes, and what happens when you replicate those systems in digital computation. His most recent work focuses on the chemical architecture of the human brain and how that gives rise to personality, intelligence, and the evolution of the mind.


1975-1990: Rainforest Biology

  • Skototropism (Growth towards darkness) a tropical vine Monstera gigantea does not engage in random search, but rather finds a suitable tree host by growing towards the darkest sector of the horizon.
  • Antbutterflies: Butterflies that follow army ants to feed on antbird droppings.
  • Diversity
  • Morphology
  • Heterophylly (morphology induced by environmental conditions)

In grad school around 1978, became interested in the concept of reproducing biological evolution in the computer by a “Mysterious teacher over a game of Go” but knew nothing of computers.

Familiarized himself with computers after purchasing his first laptop and debugger in 1988. Reached out to Chris Langton in 1989 and was invited to visit the Artificial Life group at the Los Alamos National Laboratories and the Santa Fe Institute where he met Chris Langton, Steen Rasmussen, and Stephanie Forrest among others. All but Rasmussen were skeptical of Ray's plan.

The objective: create an instantiation of evolution by natural selection in the computational medium. The problem: computer languages are too fragile or “brittle”. Mutate the code, and the whole thing dies.

Determined to succeed, Ray left behind 15 years of biology research to model biological evolution in a digital world.

1990: Tierra is born

  • The instruction set of the CPU, the memory, and the operating system together define the complete “physics and chemistry” of the universe inhabited by the digital organism.
  • The machine language defined by the CPU constitutes the genetic language of the digital organism.

But how do we handle the “brittleness” of machine code?

  • Graceful error-handling
    • CPU should ignore/skip meaningless code

Tierra is a “virtual computer”; a simulation of a computer designed to run the “Tierran” machine language. Ray conducted the first test of this virtual computer with a simple test program. “All hell broke loose”.

Parasite/Host creatures emerged. Parasites replicated from the critical data produced by the host creatures which gave rise to a Lotka-Volterra cycle in which the populations oscillate back and forth. (Sharks and fish)

This led to an evolutionary arms race.

Eventually the host organisms learned to trick the parasites into making copies of the host instead of themselves. This led to the total extinction of the parasite creatures.

The hosts became the only creature in the “world” and slowly started evolving cooperative mechanisms. A social structure emerged. Until finally trusted programs began to “cheat” using the same deceptive tricks the host originally used to overcome the parasites.

At this point, Ray turned off mutation, however the digital organisms continued to evolve. Ray eventually discovered that the organisms had discovered “sexual reproduction” and were reproducing with each other, creating offspring that were mutated combinations of the parents. Ray was no longer in control of the process.

“I stood back and watched like a god satisfied with his creation”

Exploring A New World

Over 30 papers, articles, and journals were published in the span of 5 years. The next 20 years of research is spent pushing the field of artificial life and digital evolution. Highlights include:

1991: Transition to Computational Evolution and Documenting Tierra

  • Genetic Algorithms
  • Evolution and optimization of digital organisms
  • Population dynamics of digital organisms
  • An approach to the synthesis of life


  • Evolution, ecology and optimization of digital organisms


  • How I created life in a virtual universe


  • An Evolutionary Approach to Synthetic Biology: Zen in the Art of Creating Life.


  • A proposal to create a network-wide biodiversity reserve for digital organisms.
  • The first Tierra workshop - derivative works (Charles Ofria, Avida)


  • The last Terria workshop?


  • Evolving Parallel Computation
  • Evolution as Artist (applying evolution to the world of art and the creative process)


  • Documentation of the Tierra program released


  • Aesthetically Evolved Virtual Pets
  • Evolution of Complexity: Tissue Differentiation in Network Tierra


  • Critique of Ray Kurzweil's Age of Spiritual Machines


  • Evolution, Robustness and Adaptation of Sidewinding Locomotion of Simulated Snake-like Robot

2009 (Last* Artificial Life publication): Artificial Life Programs and Evolution. In: Michael Ruse and Joseph Travis editors, Companion to Evolution. Cambridge, Mass.: Harvard University Press. Pp. 429-433. Published Feb 12, 2009, Darwin's 200th birthday

Current Research

“My current research: The diverse set of psychoactive drugs collectively represents a rich set of tools for probing the chemical architecture of the human mind.”

First Mind research publication: Ray, T. S. 2010. Psychedelics and the Human Receptorome. PLoS ONE., February 2, 2010. “It should be possible to use this diverse set of drugs as probes into the roles played by the various receptor systems in the human mind.”


  • Mental Organs and the Origins of Mind

Mind Research:

  • The human mind is populated by mental organs
  • These organs are populations of neurons
  • These neurons bear specific neurotransmitter receptors on their surface

These mental organs:

  • Provide consciousness and provide that consciousness with meaning, content, and salience.
  • Support the facilities of language, logic and reason
  • Evolve by duplication and divergence

and thus provide the mechanisms by which evolution sculpts the mind.


  • Future minds, mental organs and ways of knowing.
    • Technoetic Arts: A Journal of Speculative Research
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coursework/2014f/ray_tom.txt · Last modified: 2014/10/06 20:35 by csymonds