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PREDICTION, OPTIMIZATION, CHAOS:
THE ROLE OF FITNESS
ISHPSSB 2015 • Montréal • July 6, 2015
Charles H. Pence
Department of...
Smith et. al., 10.1038/ncomms2391
A FOUNDATIONAL
PERSPECTIVE?
F = exp
(
lim
t→∞
1
t ∫ω∈Ω
Pr(ω) ⋅ ln(ϕ(ω, t)) dω
)
DEMOGRAPHIC WEAK
ERGODICITY
Fine details of the initial state of the individual organism at
issue must disappear in the li...
CHAOTIC
DYNAMICS
Doebeli and Ispolatov, fig. 5
[T]he current phenotypic state of a
population can never be understood as the
result of an equilibrium or optimisation
pro...
A CHEAP
HACK?
APPARENT CONTRADICTION:
The P&R model is definable over the
long term
The D&I results indicate ubiquitous
long-term chaos
Fitness and prediction of future
evolutionary outcomes?
Fitness as the quantity that
evolution optimizes in the long run?
PREDICTION
WHAT IS FITNESS FOR?
predictive vs. causal
• individual fitness: N = 1
• trait fitness, traits relativized to include
genotype and environment for pleiotropic/GxE
effe...
FITNESS:
Not very predictive.
OPTIMIZATION
Fitness isn’t what
evolution is optimizing.
generation 1 100% heterozygote (Aa)
generation 2 50% Aa, 25% AA, 25% aa
[T]he current phenotypic state of a
population can never be understood as the
result of an equilibrium or optimisation
pro...
• adaptation as equilibrium or optimal
fitness distribution (e.g., Hartl and
Taubes, 1998)
• adaptation as historical selec...
[The] general new implication of chaos for
unpredictability is that for predicting any
event at any level of precision ϵ >...
• adaptation as equilibrium or optimal
fitness distribution (e.g., Hartl and
Taubes, 1998)
• adaptation as historical selec...
Doebeli and Ispolatov, fig. 1
TAKING
STOCK
prediction: not that interesting – as fitness
was never very predictive anyway
optimization: may make trouble for our
conce...
CONTINGENCY
vs.
CONVERGENCE
Fitness seems to be screened off from
long-term evolutionary outcomes
A rift between the short-term,
adaptive structure of evolution by
natural selection and long-term
evolutionary outcomes!
QUESTIONS?
charles@charlespence.net ⋅ http://charlespence.net
Prediction, Optimization, Chaos: The Role of Fitness
Prediction, Optimization, Chaos: The Role of Fitness
Prediction, Optimization, Chaos: The Role of Fitness
Prediction, Optimization, Chaos: The Role of Fitness
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Prediction, Optimization, Chaos: The Role of Fitness

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An exploration of the intersection between the results concerning fitness presented in Pence and Ramsey (2013) and some modeling results from Doebeli and Ispolatov (2014) that indicate the extensive presence of chaotic population dynamics. Primarily exploring implications of these results for the difference between short-term and long-term evolutionary structure.

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Prediction, Optimization, Chaos: The Role of Fitness

  1. 1. PREDICTION, OPTIMIZATION, CHAOS: THE ROLE OF FITNESS ISHPSSB 2015 • Montréal • July 6, 2015 Charles H. Pence Department of Philosophy and Religious Studies
  2. 2. Smith et. al., 10.1038/ncomms2391
  3. 3. A FOUNDATIONAL PERSPECTIVE?
  4. 4. F = exp ( lim t→∞ 1 t ∫ω∈Ω Pr(ω) ⋅ ln(ϕ(ω, t)) dω )
  5. 5. DEMOGRAPHIC WEAK ERGODICITY Fine details of the initial state of the individual organism at issue must disappear in the limit of large times (Tuljapurkar and Orzack, 1980) or Two organisms experiencing the same selective history must have a constant ratio of fitness values for large times (Seneta, 1981)
  6. 6. CHAOTIC DYNAMICS
  7. 7. Doebeli and Ispolatov, fig. 5
  8. 8. [T]he current phenotypic state of a population can never be understood as the result of an equilibrium or optimisation process, even though the process determining the phenotypic state is entirely adaptive and deterministic. (D&I, 1368–9)
  9. 9. A CHEAP HACK?
  10. 10. APPARENT CONTRADICTION: The P&R model is definable over the long term The D&I results indicate ubiquitous long-term chaos
  11. 11. Fitness and prediction of future evolutionary outcomes? Fitness as the quantity that evolution optimizes in the long run?
  12. 12. PREDICTION
  13. 13. WHAT IS FITNESS FOR? predictive vs. causal
  14. 14. • individual fitness: N = 1 • trait fitness, traits relativized to include genotype and environment for pleiotropic/GxE effects: N = 1 • trait fitness, in natural populations: N small, likely unrepresentative • type fitness, in natural populations: N medium-sized, still likely unrepresentative • type fitness, experimental evolution: large N
  15. 15. FITNESS: Not very predictive.
  16. 16. OPTIMIZATION
  17. 17. Fitness isn’t what evolution is optimizing. generation 1 100% heterozygote (Aa) generation 2 50% Aa, 25% AA, 25% aa
  18. 18. [T]he current phenotypic state of a population can never be understood as the result of an equilibrium or optimisation process, even though the process determining the phenotypic state is entirely adaptive and deterministic. (D&I, 1368–9)
  19. 19. • adaptation as equilibrium or optimal fitness distribution (e.g., Hartl and Taubes, 1998) • adaptation as historical selection-for (e.g., Sober, 1984) • adaptation as current contribution to fitness (e.g., Reeve and Sherman, 1993)
  20. 20. [The] general new implication of chaos for unpredictability is that for predicting any event at any level of precision ϵ > 0, all sufficiently past events are approximately probabilistically irrelevant. (Werndl, 2009, 215)
  21. 21. • adaptation as equilibrium or optimal fitness distribution (e.g., Hartl and Taubes, 1998) • adaptation as historical selection-for (e.g., Sober, 1984) • adaptation as current contribution to fitness (e.g., Reeve and Sherman, 1993)
  22. 22. Doebeli and Ispolatov, fig. 1
  23. 23. TAKING STOCK
  24. 24. prediction: not that interesting – as fitness was never very predictive anyway optimization: may make trouble for our concepts of adaptation
  25. 25. CONTINGENCY vs. CONVERGENCE Fitness seems to be screened off from long-term evolutionary outcomes
  26. 26. A rift between the short-term, adaptive structure of evolution by natural selection and long-term evolutionary outcomes!
  27. 27. QUESTIONS? charles@charlespence.net ⋅ http://charlespence.net

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