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The main purpose of this article is to propse an alternative theory concerning aging and death.
yes. It would be a great lecture at a university.
This is a very well constructed and thoroughly written article concerning aging and death. This article examines various theories such as "The Law of Causality". It states that aging and death can only be understood from a joint ecological and evolutionary perspective. It also states that the germ-soma theory of aging/death has implications for concepts of evolutionary theory.
clinical associate professor.
It is a very big work - almost a book! - about a subject that is on the top of discussion in many academic institutes.
I am a former president and actual director of the Brazilian Association on Aging Studies -SOBRAE
This is a titanic paper (4126 references!) that deserves respect, in particular for the openness in opposing ideas wrongly considered as consolidated and unquestionable only because commonly accepted.
The main (correct) thesis is that the scientific community shows about aging a form of schizophrenia and that the only possible remedy is a Kuhnian paradigm shift (s. also Milewski 2010).
For the sake of brevity, I will not go to appreciate the many points of merit of the work.
I think it is more useful to highlight some weaknesses, and this not to diminish its importance but in order that the A. may further improve his work.
Therefore, the following observations should be taken as constructive contributions.
(1) The A. rightly points out that aging is a phenomenon phylogenetically conserved and so having a function. I would add that such a phenomenon must also have a plausible phylogeny: about this I would suggest the evaluation of a recent work (Libertini, Phylogeny of Age-Related Fitness Decline in the Wild and Related Phenomena, WebMedCentral, 2011, Aging 2(11):WMC002530), which is an attempt to define the phylogeny of aging and related phenomena.
(2) The A. knows well the term phenoptosis proposed by Skulachev. I think that he could highlight the great importance of defining as a unitary category a vast mass of different phenomena having in common the sacrifice of the individual (or of a close relative) as a result of supra-individual selective pressures. Aging in mammals, defined by Skulachev "slow phenoptosis", is only one class of phenomena in the context of a much broader category. However, while other phenoptotic phenomena are in general easily and universally explained as adaptive, on the contrary for “slow phenoptosis” there is the widespread wrong prejudice that it is non-adaptive.
(3) The A. rightly criticizes what he calls Evolutionary Theories of Aging (ETA), namely Mutation Accumulation Th., Disposable Soma Th. and Antagonistic Pleiotropy Th.
However, he should clearly distinguish between non-adaptive-ETA, such as those mentioned above, and adaptive-ETA. This is not a verbal quibble but a clear distinction between two groups of theories that are totally different.
- a) The so-called species with negligible senescence are NOT predicted and are considered as exceptions without a general explanation;
- b) In the comparison between different species, it is predicted a DIRECT correlation between extrinsic mortality and intrinsic mortality (mortality caused or favored by aging);
- c) In the case of scarce resources, it is predicted that aging must be accelerated.
- d) Mechanisms determined and modulated by genes causing specifically a progressive age-related decline of functions (i.e. aging), without other useful functions, are NOT expected and are considered impossible.
On the contrary, for adaptive-ETA:
- a) The so-called species with negligible senescence are predicted as the default condition in the absence of selective pressures that favor aging.
- b) In the comparison between different species, it is predicted an INVERSE correlation between extrinsic and intrinsic mortality.
- c) In the case of scarce resources, it is NOT predicted that aging must be accelerated.
- d) Mechanisms determined and modulated by genes causing specifically a progressive age-related decline of functions (i.e. aging), without other useful functions, are expected and are considered essential for aging.
Empirical data show (s. in particular: Libertini, 2006):
- a) Species with negligible senescence exist:
- b) Ricklefs (1998) has documented an INVERSE relation between extrinsic and intrinsic mortality;
- c) Caloric restriction increases longevity (s. Mitteldorf 2001);
- d) Telomere-telomerase system gradually reduces cell turnover, causing a gradual decline of functions, i.e. aging (s. in particolare Fossel, 2004, Cells, Aging, and Human Disease, and Libertini, 2009, The Role of Telomere-Telomerase System Decline in Age-Related Fitness, available from my personal page: www.r-site.org/ageing.)
These facts thus openly disavow the non-adaptive-ETA and appear to confirm the adaptive-ETA.
(4) It is true that many theories have been proposed to explain aging. However, if the right criterion in science is that consistency between the predictions of a theory and empirical evidence is indispensable, the A. should point out that theories falsified by evidence must be considered as false and no longer acceptable and should indicate which theories are clearly contradicted by empirical facts.
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