Re species sensecence

Date: Fri Apr 20 2001 - 06:46:07 EDT

  • Next message: Geoff Bagley: "RE:senescence"


    You raised the question about species senescence, but for some reason your
    post disappeared into hyperspace and I no longer have it in my archives. Let
    me address what I think your question is. And in so doing perhaps I will
    address some of the issues and questions that others have posted.

    (Incidentally can someone tell my why my postings are so often transmitted in
    duplicate, and why responses to them are also in duplicate?)

    I am interested in the process of aging not only in its individual
    manifestation, but also in what I believe is its phyletic appearance as well.
     We should not be surprised if we find that phyletic groups go through the
    process of aging. Aging is ubiquitous, (but not universal) in nature. A few
    organisms are immune from it, e.g., cancer cells, some trees, and some early,
    simple organisms. The earliest and simplest organisms to appear seem to be
    more immune from the process than are later, more morphologically complex
    ones. In general, however, the process of aging is a pervasive feature of
    the organic world.

    What is it that becomes senescent in phyletic groups? I believe it is the
    phyletic germ line. The germ line is what is continuous from generation to
    generation in a phyletic group. What reason have we to believe that the germ
    line is not subject to the process of aging? It accumulates detrimental
    mutations, it loses its ability to correct errors, genes become
    dysfunctional, all of which accumulate and are passed on to future
    generations. The aging germ line produces individual organisms in the
    phyletic group which, which show the characteristics associated with aging.
    Some of these appear in the fossil record.

    It should be noted that there is no satisfactory, widely accepted definition
    of aging. All we can do is refer to its characteristics. What are they? At
    the individual level they are as follows: decrease in size, especially in
    linear, skeletal dimensions rather than mass; loss of morphological
    structures; decrease in strength, robustness, speed, coordination;
    decreasing mobility, geographic range, retreat to less demanding
    environments; decreasing functionality of all systems; decline in population
    size and density; increasing incidence of degenerative diseases, such as
    those of the skeleton; increasing incidence of tumors and malignancies;
    increasing incidence of infectious diseases; increasing vulnerability to
    environmental trauma, such as accidents. These may be summed up in two
    words, increasing decline and disorder. I think we can all visualize these
    characteristics in ourselves as we grow older,
     and in others.

    Unlike the process of development and growth, the process of aging is less
    "determined". One aging individual may display one suite of characteristics,
    another individual may show a rather different suite. Yet both are aging

    The virtue of this list of characteristics of individual aging is that it is
    independent of biological processes in groups of animals, i.e., species, and
    thus avoids the problem of circularity. Thus these characteristics can be
    applied not only to data from the fossil record, but in some cases to extant
    groups of animals.

    That is what I have done. With this list of characteristics in hand, I made
    an unsystematic_search of paleontological and biological literature, looking
    for studies of groups of animals that show one or preferably more of these
    characteristics. Since most such studies are conducted in the evolutionary
    framework, the data were often incomplete for what I wanted. Moreover, I am
    an amateur at this game, and do not have at my fingertips a well stocked
    research library. In brief, what I found is as follows:

    Decline in Devonian Brachiopods Fenton (1935) Fenton, C. L. 1935. Factors
    of evolution in fossil series. Amer. Nat., 69:139-173.

    Phyletic Decline and Aging in Extinct Eocoelia (brchiopods) M. Ziegler
    (1966) Ziegler, . M. 1966. The Silurian brachiopod, Eocoelia Hemisphaerica
    (J. de C. Sowerby) and related species. Palaeontology, 9:523-43.

    Decline and Aging in Corals Moore, et. al. (1952) Moore, R. C., Lalicker, C.
    G., Fischer, A. G. 1952. Invertebrate Fossils. McGraw-Hill, New York.

    Progressive Degeneration in Corals (Carruthers, 1914) Carruthers, R. G.
    1910. The evolution of Zaphrentia delanouei in Lower Carboniferous times.
    Quart J. Geol. Soc. London. 66:523.

    Decline of Morphological Characters in the Lungfish Westoll (1949) Westoll,
    T. S. 1949. On the Evolution of the Dipnoi. In Jepsen, G. L., Mayr, E.,
    Simpson, G. G., Eds. Genetics, Paleontology, and Evolution. Princeton
    University Press, Princeton.

    Bone Disease in Mosasaurs Rothschild and Martin (1987) Rothschild, B.,
    and Martin, L. D., 1987. Avascular necrosis: occurrence in diving Cretaceous
    mosasaurs. Sci. 236:75-7.

    Evidence of Decrease in Size in the Extinct Irish Elk Barnosky (1985)
    Barnosky, A. D. 1985. Taphonomy and herd structure of the extinct Irish
    elk, Megalocerous giganteous. Sci. 228:340-3.

    Ancestral and Derived Species of Caddisflies Alstad (1982, 1987) Alstad, A.
    J. 1982. Current speed and filtration rate link caddisfly phylogeny and
    distributional patterns on a stream gradient. Science, 216:533-4.
        , 1987. A capture rate model of net-spinning caddisfly communities.
    Oecologia, 71:532-6.

    Decrease in Genetic Variability in Sonoran Topminnows, by Vrijenhoek,
    Douglas, and Meffe (1985). Vrijenhoek, R. C., Douglas, M. E., Meffe, G. K.
    1985. Conservation genetics of endangered fish populations in Arizona.
    Science, 229:400-2.

    Symmetry asymmetry in other animals. Pennisi (1995a, 1995b). Pennisi, E.,
    1995a. Not simple symmetry. Science News. 147:46-7.
        , 1995b. Imperfect match. Science News. 147:60-61.

    Phylogenetic Decrease in Body Size and Loss of Carpal Bones in Salamanders
    Hanken (1985a, 1985b). Hanken, J. 1985a. Morphological novelty in the limb
    skeleton accompanies miniaturization in salamanders. Science, 229:871-4.
        , 1985b. Small wonders. The Sciences, 25:40-3.

    Reduction in Limbs and Locomotion of Lizards Rensch (1960) Rensch, B. 1960.
     Evolution Above the Species Level. Columbia University Press, New York.

    Patterns of Lineal Aging in Cheetahs (O’Brien, et. al., 1985). O’Brien, 1985. Genetic basis for species vulnerability in the cheetah.
    Science, 227:1428-34.
        , 1986. . Proc. Nat’l. Acad. Sc. (Vol. 84, No. 2). In, 1987,
    Two bottlenecks for cheetahs? Sci. News, 131:88.

    I have identified 19 extant animal groups that are smaller than their
    Pleistocene relatives which I interpret as evidence of aging in modern
    species. Peters, D., 1986. Giants of Land, Sea & Air, Past & Present.
    Sierra Club, San Francisco. National Geographic Society. 1983. Giants from
    the Past. Washington, DC.

    Granted that many of these studies are rather old, it must be born in mind
    that the study of phyletic aging is pretty much taboo in the evolutionary
    community, and no current biologist or paleontologist is likely to waste his
    or her time on such problems.

    I have completed a booklength MS on the topic of phyletic development, which,
    of course, includes phyletic aging, and submitted a publishing proposal of it
    to every university, commercial and religious publisher in the country that I
    could locate. To no avail.

    I hope this helps.


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