Gompertz survival kinetics: Fall in number alive or growth in number dead?
Basing their conclusion on impressively large numbers, \textit{J. R. Carey} et al. [Science 258, 457-461, 398 (1992)] \((> 1.2\) million medflies, Ceratitis capitata) and \textit{J. W. Cursinger} et al. [ibid., 461-463 (1992)] (hundreds of Drosophila melanogaster of different genotypes) suggest that the classical Gompertz model of survival is deficient in that it predicts for the older individuals a higher mortality rate than is observed, specifically for fruit flies and, possibly, other organisms. However, it appears that the survival of the older individuals is ``exceptional'' only because the standard survivorship equation (Gompertz, 1825) is not, at least for Mediterranean fruit flies (Carey et al., 1992), an appropriate application of Gompertz kinetics. In generalized Gompertz kinetics, the rate coefficient, \(r\), of an exponentially increasing or decreasing process \(dy/dx = \pm r \cdot y\) may itself change exponentially in a positive or negative direction, i.e., \(dr/dt = \pm k \cdot r\). When the appropriate form of this model is used, the proportional demise of the older subjects in the Carey et al. (1992) data follows the same rule as the rest of the population.
scientific article; zbMATH DE number 797078