Baudisch Inevitable Aging?

Contributions to Evolutionary-Demographic Theory
1. Auflage 2008
ISBN: 978-3-540-76656-8
Verlag: Springer-Verlag
Format: PDF
Kopierschutz: Adobe DRM (»Systemvoraussetzungen)

E-Book, Englisch, 170 Seiten

Aging is inevitable: this is gerontological dogma. And humans do inevitably grow old, which is probably why it seems so unlikely to us that other forms of life could escape aging. Escaping aging is not escaping death. Death is an inherent part of life, and it can strike any time. But the question is whether death necessarily becomes more likely as life proceeds. And it does not. The theoretical results in this monograph indicate that life provides alternative strategies. While some organisms will deteriorate over adult ages, for others mortality appears to fall or remain constant, at least over an extended period of life after reproductive maturity. This is empirically observed especially for species that keep on growing during adult ages. Perhaps the diversity of aging matches the diversity of life. My thesis, the central insight of this monograph, is: to deeply understand why some species age it is necessary to understand why other species do not.

Autoren/Hrsg.

Baudisch, Annette

Inhaltsverzeichnis

1;Foreword;7
2;Preface;12
3;Contents;14
4;List of Figures;18
5;List of Tables;20
6;1 Introduction;21
6.1;1.1 Synopsis;21
6.2;1.2 Background;23
6.2.1;1.2.1 Senescence – Paradox? – Inevitable?;23
6.2.2;1.2.2 Evolutionary Theories of Senescence;24
6.2.3;1.2.3 Measuring Senescence;25
6.2.4;1.2.4 Measuring Fitness;29
6.2.5;1.2.5 Optimal Life History;30
6.2.6;1.2.6 Interesting Recent Developments;33
6.3;1.3 Orientation;35
7;Part I Hamilton;37
7.1;2 Hamilton’s Indicators of the Force of Selection;38
7.1.1;2.1 Introduction;38
7.1.2;2.2 Hamilton’s Derivations;39
7.1.2.1;2.2.1 The Framework;39
7.1.2.2;2.2.2 Hamilton’s Indicator of Survival;40
7.1.3;2.3 Alternative Indicators;41
7.1.3.1;2.3.1 Different Parametrization;41
7.1.3.2;2.3.2 When Selection Pressure Increases;41
7.1.3.3;2.3.3 Fertility Indicators;42
7.1.3.4;2.3.4 Are Some Indicators Better?;43
7.1.3.5;2.3.5 Optimization vs. Mutational Burden;45
7.1.4;2.4 Mutation–Selection Balance;45
7.1.4.1;2.4.1 Additive vs. Proportional Parametrization;46
7.1.4.2;2.4.2 A Simple Box Model;47
7.1.5;2.5 The Importance of Mutation Accumulation;51
7.1.6;2.6 Conclusion;52
7.2;3 Further Challenges;54
7.2.1;3.1 General Problem with All Indicators;54
7.2.2;3.2 Theoretical Arguments;57
7.2.2.1;3.2.1 Mutation–Selection Balance;57
7.2.2.2;3.2.2 Unraveling;57
7.2.2.3;3.2.3 Variable Environments;59
7.2.2.4;3.2.4 Other Mechanisms;60
7.2.3;3.3 Empirical Evidence;60
7.2.3.1;3.3.1 Testing Preconditions for Mutation Accumulation;60
7.2.3.2;3.3.2 Checking Predictions from Mutation Accumulation;61
7.2.3.3;3.3.3 Empirical Evidence for Non-senescence;63
7.2.4;3.4 Conclusion;64
8;Part II Optimization Models;66
8.1;4 Optimization Models Based on Size;67
8.1.1;4.3 An Optimization Model that Leads to Non-senescence;75
8.1.1.1;4.3.1 The State Ratchet;76
8.1.1.2;4.3.2 The Maximum Principle;77
8.1.1.3;4.3.3 An Alternative Derivation;81
8.1.1.4;4.3.4 The Simplest Model Leads to Sustenance;83
8.1.1.5;4.3.5 Introducing Nonlinearity Can Lead to Enhancement;85
8.1.2;4.4 An Optimization Model that Leads to Senescence;86
8.1.3;4.5 Discussion;89
8.1.4;4.6 Next Steps;91
8.1.5;4.1 Size Matters;67
8.1.6;4.2 A Size-Based Life-History Model;69
8.1.7;4.2.1 The General Optimization Problem;71
8.1.8;4.2.2 The Specific Optimization Problem;72
8.2;5 An Optimization Model Based on Vitality;92
8.2.1;5.1 The Vitality Model;93
8.2.1.1;5.1.1 The Parameters;98
8.2.2;5.2 The Vitality Model as a Control Problem;100
8.2.2.1;5.2.1 Problem Formulation;100
8.2.2.2;5.2.2 Solution;102
8.2.2.3;5.2.3 The Role of the Second State Variable;104
8.2.2.4;5.2.4 Hamilton and Reproductive Value - Revisited;105
8.2.3;5.3 The Constrained Vitality Model;107
8.2.3.1;5.3.1 Expected Solutions;111
8.2.4;5.4 Numerical Results;115
8.2.4.1;5.4.1 The Five Varieties of Life History Strategies;115
8.2.4.2;5.4.2 When Senescence Is Optimal and when It Is Not;125
8.2.5;5.5 Discussion;133
8.2.5.1;5.5.1 Senescence vs. Non-senescence;133
8.2.5.2;5.5.2 The . Parameters in Nature;134
8.2.5.3;5.5.3 The Mortality Paradox;136
8.2.5.4;5.5.4 Plateaus;138
8.2.6;5.6 Summary;138
8.3;6 Directions for Research;140
8.3.1;6.1 Orientation;140
8.3.2;6.2 Direct Extensions of my Models;140
8.3.2.1;6.2.1 Linking Burden & Optimization;140
8.3.2.2;6.2.2 Measurable Quantities and Testable Hypotheses;141
8.3.2.3;6.2.3 The Diversity of Aging;142
8.3.2.4;6.2.4 The Characteristics of Senescent vs. Non-senescent Species;142
8.3.2.5;6.2.5 Alternative Applications;144
8.3.3;6.3 Other Modeling Extensions;144
8.3.3.1;6.3.1 Density E.ects;144
8.3.3.2;6.3.2 Intergenerational Transfers;145
8.3.3.3;6.3.3 Environmental Fluctuations;146
8.3.3.4;6.3.4 Population Dynamics;147
8.3.3.5;6.3.5 Summary;147
8.3.4;6.4 Prospects for Evolutionary Demography;148
8.3.4.1;6.4.1 Moving Beyond the Burden of “Deleterious Fixations”;148
8.3.4.2;6.4.2 The Need for Data, Methods, and Measures;150
8.3.4.3;6.4.3 A New Burning Question;152
8.3.5;6.5 Conclusion;155
9;A Vitality Model - Appendix;157
9.1;A.1 Solving Di.erential Equations;157
9.2;A.2 Proof of Non-Existence of an Optimal Solution for a Special Case;159
9.3;A.3 The Algorithm;160
10;References;164
11;Index;181