empirical studies of evolvability in tierra preliminary results
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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 - PowerPoint PPT PresentationTRANSCRIPT
Empirical Studies ofEvolvability 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
The first step is to develop quantitative measures of evolvability
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.
Evolution and StasisSize 990629T
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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)
Origin of 27aal
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
Origin of Parasite
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)
Host and Parasite Populations
Indices of Evolvability?Based on Genotypes
NumberTurnover: births + deaths of genotypesDiversity: negative sum of p log pIntegral Sum: all populations over timeIntegral Max: largest pop integral over timeMaximum ProportionAverage Age
Genotype NumberGenoNum 990629T
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Turnover: births + deathsGeTnOvr 990629T
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Diversity: - sum of p log pGenoNum 990629T
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Maximum ProportionGenMaxProp 990629T
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Integral Sum: all populationsGeIntegral 990629T
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Integral Max: largest pop integralGenMaxIntg 990629T
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Integral Max & Max ProportionGenMaxIntg GenMaxProp 990629T
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Integral Sum: all populationsGeIntegral 990629T
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Integral Max: largest pop integralGenMaxIntg 990629T
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Average AgeGenoAge 990629T
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Web Pages
This presentation: http://www.hip.atr.co.jp/~ray/pubs/pubs.html http://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: [email protected] http://www.hip.atr.co.jp/~ray/
The End