Free comments on published texts

  1. Gavrilov, L.A. & Gavrilova, N.S. (2001) : J. Theor. Biol., 213, pp. 527-545

    Here are some comments on a. m. article I wrote to Dr Gavrilov and Dr Gavrilova on January 10th, 2002 on their request. As the authors did not react, these comments still remain question marks to me (put online on July 19th, 2004):

    Dear Dr Gavrilov & Dr Gavrilova,

    Here are some comments on your very interesting article published in the J. Theor. Biol (2001) 213, 527-545. As you know, I am fascinated by the systematic and clear way you approach aging problems. My comments are therefore mainly question marks for me and perhaps they could be useful to you for your further research if the answer is not obvious now :

    1) According to me, reliability theory is certainly highly valuable to handle many problems of aging and longevity. As already commented, the article re-juvenates and develops your reliability theory based model which has been described in chapter 6 of your book of 1991. The way you have developed the model as a model of series-connected blocks with varying degrees of redundancy is of great interest. Indeed, it seems to easily explain several phenomena such as Gompertz law, high age decrease of mortality rate, the "compensation effect", etc…

    However, some questions remain open.

    My unsolved questioning is on the following :

    2) I still cannot help being a little bit uncomfortable with the compensation effect. The results of your fittings (as showed in your book) and the theoretical derivation of it using your model are very convincing, but I cannot fundamentally understand why it is so nor what this means. Why should the mortality rate of all populations of humans be the same at 95 years ? If this is a natural law, how can we relate it (even in embryonic form) to other natural phenomena and to our underlying knowledge of “how nature works” ?. To be frank, when I saw this kind of correlation for the first time (in articles from Strehler), I considered it as an artefact, and you confirmed this view in your book as well as in your article (p.530 middle left column). Similarly, in order to definitely kill any suspicion of a remote artefact, it would be good that “M” in Eq. 13 and 20a would not depend of “a ”. Anyway, your convincing empirical results condemn me to continue to think of it until I understand and accept it (*).

    (*) I still don't in 2006 : open explanation is urgently required and would be mostly appreciated by the community of researchers !

    3) Is your separation between living organisms and technical devices according to their block redundancy and amount of defective blocks not a little bit too schematic ?. What are the blocks in both kind of systems ? If one goes down to the cell level, technicians will consider that all cells - including those dying very soon because of fatal defects - are true technological marvels compared to man-designed devices. Similarly, considering technical devices, of course, computer or electronical components are tested carefully, but if you go down to the dimension corresponding to the cell, what a huge amount of defects you will find even if they do not necessarily hamper the operating. I would also be happy to see reliable statistics showing in a robust manner that Weibull distribution is better for technical systems and Gompertz law for living systems. Aren’t both equations giving good fittings of experimental data for advanced times ?.

    4) One should be careful when comparing more complex biological species with primitive organisms (the one age the other not). Maybe, aging has not the same sense in both cases. Considering the two main ways followed by nature to maintain the species (asexual and sexual reproduction), maybe primitive organisms also « age » but as groups (with limited number of population doublings ?).

    5) The reliability theory of aging starts from a situation with limited/high redundancy of “all perfect”/”some imperfect” blocks in technical/bio-systems. But isn’t this starting point already the result of a “previous aging” where “reliability growth”/”infant illnesses” are observed ? The theory should include connexions to this as both kind of systems are no longer “same as new” at this time.

    6) To strengthen the method of calculation, it would be interesting to put biological names on blocks and redundancies and suggest some experimental work on the such defined blocks or groups of blocks in order to compare their predicted and actual behavior in laboratory conditions and determine the corresponding values of the mathematical parameters.

    7) As biological systems are open to their environment, it is interesting to show that the theory allows to predict the effect of environmental variables on the “life” of the blocks in function of their importance, redundancy, position in a series, etc…

  2. Gavrilov, L.A. & Gavrilova, N.S. (2004) : "The Reliability-Engineering Approach to the Problem of Biological Aging", Ann. N.Y. Acad. Sci., 1019, pp. 509-512

    A sentence is used twice in a. m. article: "Redundancy is a key notion for understanding aging and the systemic nature of aging in particular". Later, it is written: " start thinking about the possible systemic nature of aging..." (put online on July 19th, 2004)

    In spite of the great respect I have for the 1991 book of the authors (see comments in the "Articles" section), I must react to such a wording. The systemic nature of aging allows a systemic approach but "redundancy" and their "reliability theory of aging" have nothing to do with a systemic approach nor with the systemic nature of aging. Introducing a vocabulary connexion between "redundancy", "reliability-engineering" etc. with the systemic nature of aging is very recent to the authors who did not use it in their former publications. They seem to have recently invented such artificial connexion in smartly designed sentences, without any explanation nor justification, in order to appropriate a "systemic flavour" to their theory.
    Proposing an holistic approach to aging is correct: the systemic approach described in the present website is an holistic approach.
    However, letting believe that an holistic approach to aging can only be reached by a restricted use of reliability theory (the "reliability theory of aging" proposed by the authors) and claiming that the systemic nature of aging is fully covered that way is misleading. If it is after having consulted this website and others on system's theory including related published work, without due quotation of them, it is also scientifically dishonest.

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