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Evolutionary Theories of Aging Article ID: WMC003275 ISSN 2046-1690 The Germ-soma Conflict Theory of Aging and Death: Obituary to the "Evolutionary Theories of Aging" Corresponding Author: Prof. Kurt Heininger, Professor, Department of Neurology, Heinrich Heine University Duesseldorf - Germany Submitting Author: Prof. Kurt Heininger, Professor, Department of Neurology, Heinrich Heine University Duesseldorf - Germany Article ID: WMC003275 Article Type: Original Articles Submitted on:20-Apr-2012, 01:51:59 PM GMT Published on: 20-Apr-2012, 05:38:59 PM GMT Article URL: http://www.webmedcentral.com/article_view/3275 Subject Categories:AGING Keywords:Aging, Reproduction, Evolution, Darwinian demon, Resources How to cite the article:Heininger K. The Germ-soma Conflict Theory of Aging and Death: Obituary to the "Evolutionary Theories of Aging" . WebmedCentral AGING 2012;3(4):WMC003275 Copyright: This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Source(s) of Funding: No funding Competing Interests: No competing interests Additional Files: References WebmedCentral > Original Articles Page 1 of 139 WMC003275 Downloaded from http://www.webmedcentral.com on 30-Apr-2012, 10:35:59 AM The Germ-soma Conflict Theory of Aging and Death: Obituary to the "Evolutionary Theories of Aging" Author(s): Heininger K Abstract “cheater” phenotypes that are defective to carry the cost of death at reproductive events are less fit under conditions of feast and famine cycles and have a high risk to go extinct. Tracing both the genomic and Regarding aging, the scientific community persists in a physiological “fossil record” and the phenotypic pattern state of collective schizophrenia. This state is owed to throughout phylogenesis demonstrates that evolution the so-called “evolutionary theories of aging”. succeeded to enforce this general principle in According to these theories, aging, following the multicellular unitary organisms by creating a peri-/postreproductive decline of selection pressure, is dichotomy between soma and germline cells, making posited to be haphazard, not selected for, not adaptive, the former the mortal breeder and the latter the and not programmed. And yet, defying these concepts, virtually immortal genetic vector. Importantly, germline aging is phylogenetically conserved and subject to cells control the longevity of the soma from ‘within’ by regulation by classical signaling pathways and a variety of signals, e.g. sexual hormones. These transcription factors. While some blatantly deny this signals, on the one hand, make the mature organism genetic control, others (particularly geneticists) appear vital and attractive for mates and, on the other hand, to accommodate with the obvious incompatibilities. limit the reproductive potential of the parent organism First it is shown that the “evolutionary theories of aging” and drive a variety of aging pacemakers, particularly are based on circular reasoning and fallacious post the senescene of the immune system. hoc, ergo propter hoc argumentations and that their The transgenerational conflict between germline cells basic assumptions are flawed. Second, by a simple and soma over utilization of limited resources is the change of perspective, replacing a soma-centered (as evolutionary rationale of postreproductive aging/death, in the “evolutionary theories of aging”) by a semelparous organisms being a particularly drastic germline-centered point of view and based on witness of the link between reproduction and death. compelling evidence from more than 400,000 scientific Semelparity and iteroparity are threshold traits and as publications (of which more than 4,000 have been such opposite ends of a continuum of life history referenced in this work) a non-group-selective, variation rather than representing fundamentally evolutionary mechanism is elaborated that explains different life history strategies. Although the cost of the co-selection and programming of reproduction and reproduction, e.g. in terms of impaired aging/death. immunocompetence and survival, still shapes the life A gedankenexperiment reveals: A Darwinian demon history trade-offs of iteroparous organisms, the that exhibits both immortality and infinite reproduction temporal uncoupling of reproduction and death is not viable in a world of limited resources. According concealed their evolutionary co-selection. Death in the to the phylogenetic record and deep genetic natural habitat due to environmental hazards such as homologies, death of the soma is identified as the predation, infection, accident, or starvation often ultimate cost of reproduction. At the evolutionary base predates the germ signaling-dependent demise and of the unicellular/multicellular transition, microbial may hinder the individuals to exploit their full longevity organisms have a “feast and famine” lifestyle. potential. A protected environment, however, like in Following the exhaustion of a resource, they build human societies, laboratories and captivity unmasks multicellular structures that generate spores that can the process of aging. resist the nutrient-depleted environment. The In contrast to unitary organisms, modular organisms metamorphosis to spores is fuelled by energy and (e.g. plants, benthic aquatic invertebrates) that have building blocks provided by the – not altruistic, but no segregated germline and in which the adult body rather spore-induced cytocidal – death of clonal itself is a reproductive unit, may evade senescence. siblings. Their phenotypes identify these processes as However, they are subject to territorial, ancient reproductive events creating distinct density-dependent mortality patterns, due to e.g. generations: germs (that can germinate later under self-thinning or chemical warfare, and density-limited more favorable conditions) and fruiting bodies (that seed recruitment driven by interindividual competition nurse and disseminate the spores and die). In contrast, for resources. Thus, the different lifestyle of sessile WebmedCentral > Original Articles Page 2 of 139 WMC003275 Downloaded from http://www.webmedcentral.com on 30-Apr-2012, 10:35:59 AM organisms (being unable to move away from local apoptosis, reproduction, and post-reproductive death resource competition) and mobile organisms (that, 7. Semelparous and iteroparous life-history strategies even when dispersing take their internal “competitor” 7.1 Aging is a corollary of iteroparous reproduction with them) determined their transgenerational 7.2 Plasticity of semelparous and iteroparous resource management systems. The germ-soma life-history strategies conflict shaped the different bauplans of unitary and 8. The costs of reproduction modular organisms, is the motor driving animal 8.1 Germ cells exact at least part of the costs of coevolutionary “Red Queen” dynamics and possibly reproduction fuelled the Cambrian explosion of animals. 9. Reproduction and aging/death: modulated by This update of the evidence-based germ-soma conflict resource availability and utilization theory (Heininger, 2002a) integrates the wealth of data 9.1 Diapause and hibernation: metabolic dormancy as in a holistic eco-evo-devo approach. The germ-soma response to environmental dearth conflict theory takes into account and explains the 9.2 Dietary restriction, aging and reproduction known facts related to aging and postreproductive 9.3 Nutrient and energy-sensing pathways, death: the near-universality, the genetic programming, reproduction and aging and the reproduction-, resource-utilization-, and 9.4 Phosphate and aging stress-resistance-dependent modulation (including 10. Stress and aging such phenomena as late-life mortality plateaus and 10.1 Stress resistance, hormesis and aging/death gender dimorphic life expectancies). This change of 10.2 The general and oxidative stress of aging paradigm resolves the inconsistencies of the 10.3 The metabolic stress of aging pseudoevolutionary and unjustifiably so-called 10.3.1 Klotho, key pleiotropic node of the resource “evolutionary theories of aging” and roots the utilization-stress-aging network phylogenetically conserved programming of aging and 10.4 The organism, its stress response and aging death solidly in the evolutionary theories of Darwin, 11. Germline cells engender somatic aging and death Wallace and Weismann 11.1 Reproductive maturity and lifespan: a temporal Table of Contents relationship 1. Introduction 11.2 Germline signals drive somatic aging 2. The “Structure of Scientific Revolutions” 11.2.1 Prokaryotes 2.1 The Structure of Scientific Revolutions 11.2.2 Basal eukaryotes 2.2 Interconnected thinking 11.2.3 Plants 2.3 The “Law of Causality” 11.2.4 Metazoa 3. Aging is due to the declining force of natural 11.3 Immunocompetence, a key target of germ cell selection: a fata morgana signaling 4. Gedankenexperiment: Darwinian demon 11.3.1 Immunosuppressive action of reproductive 5. The limited resources paradigm and the “tragedy of activity the commons” 11.3.2 Immunosenescence 5.1 Reproduction outgrows resources 11.4 Germline-derived signals limit the soma’s 5.2 Resource limitation is a pervasive ecological reproductive potential phenomenon 12. The germ-soma conflict 5.3 Competion for food and space in plants and 12.1 The physiognomy of conflict: yin and yang sessile animals 12.2 Multicellularity and conflict 5.4 The Tragedy of the Commons 12.3 Mediation of germ-soma conflict by antagonistic 5.5
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