Age, days

Figure 5.5. Mortality leveling-off in a population of 4,650 male house flies, Hazard rates were computed using life table of house fly, Musca domestica, published by Rockstein and Lieberman (1959). Source: Gavrilov and Gavrilova, 2005.

beetle Callosobruchus maculates (Tatar et al., 1993), fruit flies Anastrepha ludens, Anastrepha obliqua, Anastrepha serpentine and a parasitoid wasp Diachasmimorpha longiacaudtis (Vaupel et al., 1998).

Interestingly, the failure kinetics of manufactured products (steel samples, industrial relays, and motor heat insulators) also demonstrates the same "nonaging" pattern at the end of their "lifespan" (Economos, 1979). This phenomenon is presenting a theoretical challenge to many models and theories of aging. One interesting corollary from these intriguing observations is that there seems to be no fixed upper limit for individual lifespan (Gavrilov, 1984; Gavrilov and Gavrilova, 1991; Wilmoth, 1997).

This observation calls for a very general explanation of this apparently paradoxical ''no aging at extreme ages'' phenomenon, which will be discussed in this chapter.

Another empirical observation, the compensation law of mortality, in its strong form refers to mortality convergence, when higher values for the parameter a (in the Gompertz function) are compensated by lower values of the parameter R in different populations of a given species:

ln(R) = ln(M) - Ba where B and M are universal species-specific invariants. Sometimes this relationship is also called the Strehler-Mildvan correlation (Strehler, 1978; Strehler and Mildvan, 1960), although that particular correlation was largely an artifact of the opposite biases in parameters estimation caused by not taking into account the age-independent mortality component, the Makeham

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Staying Young

Staying Young

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