Article

Viscous populations evolve altruistic programmed ageing in ability conflict in a changing environment

Evolutionary ecology research (Impact Factor: 0.9). 08/2013; 15(5):527–543.

ABSTRACT

Questions: Is aging evolutionarily adaptive? Can programmed aging widely evolve as altruism in viscous populations (i.e., widely distributed populations with limited offspring dispersal) in changing environment?

Features of Model: The model is individual-based. The probabilities of survival and reproduction are determined by abilities, and abilities increase with both inherited abilities and age-related abilities, so the old can survive and reproduce even if they are genetically less adapted to the environment (termed ‘ability conflict’). Inherited traits are determined by multiple independent loci; so active aging can enhance the local accumulation of adaptive inherited abilities in viscous populations.

Ranges of key variables: Dispersal varied from 0 (no dispersal) to 1 (global). The probability of environment-change during each calculation cycle varied from 0 to 1.

Conclusions: Altruistic aging evolves in structured viscous biological populations with ability conflict in a changing environment to allow the survival of genetically fitter young progenies. To evolve altruistic aging requires no more environmental change than does sex, suggesting that the generality of altruistic aging should be no less than sex in viscous populations. If selfish mutants appear only at low rates, higher-level selection would be stabilized even if the environment changes slowly. More extrinsic death can decrease aging rate (intrinsic death rate) to ensure the same expected lifespan in altruistic aging, providing testable predictions against traditional aging theories. My individual-based model also shows how traditional mathematical population genetics largely underestimated the prevalence of group selection.

Keywords: evolvability; genetic creativity; kin selection; longevity; population viscosity; senescence

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Available from: Jiang-Nan Yang, Sep 24, 2014
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    ABSTRACT: The longstanding debate about whether aging may have evolved for some adaptive reason is generally considered to pit evolutionary theory against empirical observations consistent with aging as a programmed aspect of organismal biology, in particular conserved aging genes. Here I argue that the empirical evidence on aging mechanisms does not support a view of aging as a programmed phenomenon, but rather supports a view of aging as the dysregulation of complex networks that maintain organismal homeostasis. The appearance of programming is due largely to the inadvertent activation of existing pathways during the process of dysregulation. It is argued that aging differs markedly from known programmed biological phenomena such as apoptosis in that it is (a) very heterogeneous in how it proceeds, and (b) much slower than it would need to be. Furthermore, the taxonomic distribution of aging across species does not support any proposed adaptive theories of aging, which would predict that aging rate would vary on a finer taxonomic scale depending on factors such as population density. Thus, while there are problems with the longstanding non-adaptive paradigm, current evidence does not support the notion that aging is programmed or that it may have evolved for adaptive reasons.
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Questions & Answers about this publication

  • Jiang-Nan Yang added an answer in Ecology and Evolution:
    Why the sexually reproductive organisms invest more resources for reproduction while the cost of asexually reproductive organism is low?
    The organism that reproduce sexually invest resources (cost of rearing and supporting throughout life) in both male and female individuals and it seems an extra cost on male counterpart. If they start to reproduce asexually then an extra cost on male counterpart will be exempted and population also increase in twice.
    Jiang-Nan Yang
    You can find a model simulating the change of the probability of sexual vs. asexual development in respond to environmental change in this paper:
    https://www.researchgate.net/publication/255170953_Viscous_populations_evolve_altruistic_programmed_aging_in_ability_conflict_in_a_changing_environment
    • Source
      [Show abstract] [Hide abstract]
      ABSTRACT: Questions: Is aging evolutionarily adaptive? Can programmed aging widely evolve as altruism in viscous populations (i.e., widely distributed populations with limited offspring dispersal) in changing environment? Features of Model: The model is individual-based. The probabilities of survival and reproduction are determined by abilities, and abilities increase with both inherited abilities and age-related abilities, so the old can survive and reproduce even if they are genetically less adapted to the environment (termed ‘ability conflict’). Inherited traits are determined by multiple independent loci; so active aging can enhance the local accumulation of adaptive inherited abilities in viscous populations. Ranges of key variables: Dispersal varied from 0 (no dispersal) to 1 (global). The probability of environment-change during each calculation cycle varied from 0 to 1. Conclusions: Altruistic aging evolves in structured viscous biological populations with ability conflict in a changing environment to allow the survival of genetically fitter young progenies. To evolve altruistic aging requires no more environmental change than does sex, suggesting that the generality of altruistic aging should be no less than sex in viscous populations. If selfish mutants appear only at low rates, higher-level selection would be stabilized even if the environment changes slowly. More extrinsic death can decrease aging rate (intrinsic death rate) to ensure the same expected lifespan in altruistic aging, providing testable predictions against traditional aging theories. My individual-based model also shows how traditional mathematical population genetics largely underestimated the prevalence of group selection. Keywords: evolvability; genetic creativity; kin selection; longevity; population viscosity; senescence
      Full-text · Article · Aug 2013 · Evolutionary ecology research
  • Jiang-Nan Yang added an answer in Evolution:
    What are relevant levels of selection?
    According to the multi-level selection theory, selection may occur between different genes, individual organisms, groups, species and so on.

    Is there good evidence to support each of these potential levels? Are there logical arguments to support or deny any of these levels? Are there even more levels of selection (e.g. ecological communities)?
    Jiang-Nan Yang
    As I have recently shown in a paper, aging is an altruism selected at higher-levels. What are relevant levels of selection? Well, I think there are a lot. Viscous populations contain a continuity of levels from individual to kin to group. All relevant.

    Finally, I do not like mathematical definition of selection very much. Mathematics always runs into danger of over-simplification. Mathematics deals with similarity/identity, but selection works on differences and changes. So, mathematical definition is not necessarily rigorous in evolution. I like individual-based models, which respects more about individual differences.

    https://www.researchgate.net/publication/255170953_Viscous_populations_evolve_altruistic_programmed_aging_in_ability_conflict_in_a_changing_environment
    • Source
      [Show abstract] [Hide abstract]
      ABSTRACT: Questions: Is aging evolutionarily adaptive? Can programmed aging widely evolve as altruism in viscous populations (i.e., widely distributed populations with limited offspring dispersal) in changing environment? Features of Model: The model is individual-based. The probabilities of survival and reproduction are determined by abilities, and abilities increase with both inherited abilities and age-related abilities, so the old can survive and reproduce even if they are genetically less adapted to the environment (termed ‘ability conflict’). Inherited traits are determined by multiple independent loci; so active aging can enhance the local accumulation of adaptive inherited abilities in viscous populations. Ranges of key variables: Dispersal varied from 0 (no dispersal) to 1 (global). The probability of environment-change during each calculation cycle varied from 0 to 1. Conclusions: Altruistic aging evolves in structured viscous biological populations with ability conflict in a changing environment to allow the survival of genetically fitter young progenies. To evolve altruistic aging requires no more environmental change than does sex, suggesting that the generality of altruistic aging should be no less than sex in viscous populations. If selfish mutants appear only at low rates, higher-level selection would be stabilized even if the environment changes slowly. More extrinsic death can decrease aging rate (intrinsic death rate) to ensure the same expected lifespan in altruistic aging, providing testable predictions against traditional aging theories. My individual-based model also shows how traditional mathematical population genetics largely underestimated the prevalence of group selection. Keywords: evolvability; genetic creativity; kin selection; longevity; population viscosity; senescence
      Full-text · Article · Aug 2013 · Evolutionary ecology research

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