Is 'senescence' of diploid cells an ad hoc mechanism suppressing 'replicon' or not?

Mechanical optimization of bone

In bending, the mechanical strength of tubular bone can be estimated by the area moment of inertia (I) = 1/4 x pi x (R4 - r4) (R: external radius, and r: internal radius). Mechanical strength of bone is dissociated from bone density, since radiological density is different from inertia. When the cross-sectional area is constant (C = R2 - r2) in this equation, inertia can be expressed by the equation of (I) = 1/4 x pi x (2Cr2 + C2). Inertia increases with increases of the external and internal radii. According to the above equation, increase of inertia depending on the expansion of radii is inevitable 'optimization' of bone mass. Expansion of the radii of tubular bone with the decrease of wall thickness is an adaptation process rather than the 'decompensation' called osteoporosis. Senescence of individuals as manifested in conditions such as osteoporosis is a stampede of adaptations rather than decompensation of it.

Self and nonself: duality of immune system

From the viewpoint of evolution, mammalian immunity has been developed to prevent invasion by foreign bodies including parasites and microorganisms and not to survey oncogenesis. The surveillance system on oncogenesis has been lost in the evolutionary process from amphibians to mammals. The essential duality between developmental antigens and tumor specific antigens is important in explaining what the target of self-defense mechanisms is. This duality between self-defense and defense against foreign bodies originated from invertebrates as shown in insects. Immunity has been developed to survey retrodifferentiation of somatic cells and to drive the developmental process in organogenesis. Under these conditions, the clonal deletion theory of immunocyte differentiation will lose its teleological meaning. Also, the hypothesis explaining self reactivity of immunity by the immune system recognizing only an 'internal image' composed of an idio-antiidio network of immunocytes and antibodies is overly pedantic.