Age, Years

Figure 5.6. Compensation Law of Mortality. Convergence of mortality rates in different populations at advanced ages. Death rates (with removed age-independent external mortality component) are plotted in a log scale as a function of age in the following countries: 1 - India, 1941-1950, males. 2 - Turkey, 1950-1951, males. 3 - Kenya, 1969, males. 4 - Northern Ireland, 1950-1952, males. 5 - England and Wales, 1930-1932, females. 6 - Austria, 1959-1961, females. 7 - Norway, 1956-1960, females. Adapted from Gavrilov and Gavrilova, ''The Biology of Life Span,'' 1991.

term A (see Gavrilov and Gavrilova, 1991; Golubev, 2004). Parameter B is called the species-specific lifespan (95 years for humans), and parameter M is called the species-specific mortality rate (0.5 year-1 for humans). These parameters are the coordinates for convergence of all the mortality trajectories into one single point (within a given biological species), when extrapolated by the Gompertz function (Gavrilov and Gavrilova, 1979; 1991). This means that high mortality rates in dis-advantaged populations (within a given species) are compensated for by a low apparent ''aging rate'' (longer mortality doubling period). As a result of this compensation, the relative differences in mortality rates tend to decrease with age within a given biological species (Figure 5.6).

In those cases when the compensation law of mortality is not observed in its strong form, it may still be valid in its weak form—i.e., the relative differences in mortality rates of compared populations tend to decrease with age in many species. Explanation of the compensation law of mortality is a great challenge for many theories of aging and longevity (Gavrilov and Gavrilova, 1991; Strehler, 1978).

There are some exceptions from both the Gompertz law of mortality and the compensation law of mortality

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