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Non-senescence in Neoclassical Growth Theory

Non-senescence in Neoclassical Growth Theory. Personal Background. Energy economics & climate change Legal theory (Law of Evidence) Evolutionary Biology Research objective: Provide academic practitioners with practical tools that meet exacting theoretical standards Motivation: Curiosity.

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Non-senescence in Neoclassical Growth Theory

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  1. Non-senescence in Neoclassical Growth Theory

  2. Personal Background Energy economics & climate change Legal theory (Law of Evidence) Evolutionary Biology Research objective: Provide academic practitioners with practical tools that meet exacting theoretical standards Motivation: Curiosity Livelihood Research • Decision consulting

  3. AGENDA • The Model • Reznick Results • Non-senescence

  4. The model: • Assumes populations consist of distinct genotypes with different traits that affect intrinsic lifespan. • Assumes heritability of these traits is imperfect. • Adheres to the formalities of Dynamic Systems Theory. • Operates in two dynamic modes: • Mode 1: mutation accumulation (purely deleterious mutations) • Mode 2: genotypes select different fecundity/lifespan tradeoffs under a metabolic budget constraint

  5. The dynamic modes: Genotype choice of “Maintenance Investment Program”

  6. The model delivers results consistent with standard theory. • Population fecundity and mortality trends with age • Williams’ Hypothesis • The evolution of semelparity and iteroparity • A natural extension of the Euler-Lotka equation • Differential survival of individuals removed from extrinsic death hazards

  7. AGENDA • The Model • Reznick Results • Non-senescence

  8. The model also helps explain the Reznick results. • Guppies from high predation environments show longer lifespan than low predation guppies (in apparent violation of Williams’ Hypothesis:

  9. The model also helps explain the Reznick results (continued). • Guppies from high predation environments also exhibit higher fecundity than low predation guppies:

  10. The model can explain the increased lifespan. • The “predator pruning hypothesis” of Abrams-Williams-Day: • Different genotypes have different intrinsic lifespan • Predators select individuals nearing the end of their intrinsic lifespan • These individuals show deteriorating escape performance • Genotypes with longer intrinsic lifespan therefore have a selective advantage • Under predation, the intrinsic lifespan of the population increases • But this is not essentially inconsistent with Williams’ Hypothesis

  11. However, it may not explain the increased fecundity rate. • The model takes the different fecundity rates for the High-predation vs. Low-predation populations as a given input. • Current analysis is attempting to see if the model can be predictive of fecundity rates. • Reznick claims that the High-predation populations are “better at everything”—higher fecundity, longer intrinsic lifespan, and better predator avoidance. It is as if they have an inherently greater metabolic budget to work with. • This is a great puzzle.

  12. AGENDA • The Model • Reznick Results • Non-senescence

  13. Under certain conditions, standard theory predicts non-senescent genotypes will dominate senescent ones.

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