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Empirical Studies of Evolvability in Tierra Preliminary Results

Empirical Studies of Evolvability in Tierra Preliminary Results. Tom Ray ATR Kyoto Japan Zoology, University of Oklahoma. Objectives. The objective is to understand how the design and configuration of Tierra-like systems affects the properties of their evolution

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Empirical Studies of Evolvability in Tierra Preliminary Results

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  1. Empirical Studies ofEvolvability in TierraPreliminary Results Tom Ray ATR Kyoto Japan Zoology, University of Oklahoma

  2. Objectives • The objective is to understand how the design and configuration of Tierra-like systems affects the properties of their evolution • The first step is to develop quantitative measures of evolvability

  3. Simple Test • Under certain conditions, Tierra tends to evolve towards smaller replicators. • Once a minimal size is reached, evolution stops. • A good index should be able to discriminate the period of evolutionary optimization from the stasis that follows.

  4. Evolution and Stasis

  5. Period of Stasisorigin of dominant genotype • In the run of 99-06-29, genotype 27aal appeared at t=800, and dominated the remainder of the run (until end at t=2500)

  6. Origin of 27aal

  7. Period of Stasisorigin of dominant parasite • At t=1200 a 15 byte parasite entered into an ecologically and evolutionarily stable equilibrium with the 27 byte host

  8. Origin of Parasite

  9. Viable Mutants • The 27 byte replicator includes three loci at which two instructions are acceptable (8 neutral mutants) • In addition there are viable variants including one-byte insertions or deletions • The 15 byte parasite includes one locus at which two instructions are acceptable and one locus at which any (of 32) instructions are acceptable (64 neutral mutants)

  10. Host and Parasite Populations

  11. Indices of Evolvability?Based on Genotypes • Number • Turnover: births + deaths of genotypes • Diversity: negative sum of p log p • Integral Sum: all populations over time • Integral Max: largest pop integral over time • Maximum Proportion • Average Age

  12. Genotype Number

  13. Turnover: births + deaths

  14. Diversity: - sum of p log p

  15. Maximum Proportion

  16. Integral Sum: all populations

  17. Integral Max: largest pop integral

  18. Integral Max & Max Proportion

  19. Integral Sum: all populations

  20. Integral Max: largest pop integral

  21. Average Age

  22. Web Pages • This presentation: http://www.hip.atr.co.jp/~ray/pubs/pubs.htmlhttp://www.hip.atr.co.jp/~ray/pubs/evolvability/ evolvability.html • Tierra Home Page: http://www.hip.atr.co.jp/~ray/tierra/tierra.html • Tom Ray: tray@ou.edu http://www.hip.atr.co.jp/~ray/

  23. The End

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