Some Biological Underpinnings of the Self-Image

The hypothesis of genetic control (regulation) ascribed to (Chitty 1960, 1967) explains the causes of fluctuations in population numbers in terms of genetic composition. In periods of decrease in population numbers, the competitiveness between individuals is reduced and therefore there occurs a type of selection called selection r. In periods of peak population growth competitiveness is intense and a shift toward a different type of selection, selection K, takes place. Directional changes of selection are connected with population density and are self-regulatory. A corollary is that the average phenotype never totally represents the individual best fitted to specific population conditions, since those conditions are constantly changing. Consequently, the genetic pool of a group of individuals is always changing from generation to generation (Pianka, 1970, 1972).

MacArthur and Wilson (1967) denoted the two, opposed types of selection, with letters r and K, derived from two parameters in the logistic equation of population growth. One cannot say of any species that it is subject either to selection r or to selection K, because each species takes an intermediate position between these two extreme types. The r-selection and K-selection, the two opposing selective forces, are defined by Pianka (1974) as follows: “In a ‘competitive vacuum’ (or an extensively rarefied environment) the best reproductive strategy is often to put maximal amounts of matter and energy into reproduction and to produce as many total progeny as soon as possible. Because there is little competition these offspring often can thrive even if they are quite small and therefore energetically inexpensive to produce” (r-selection = K.W.). “However, in a ‘saturated’ environment, where density effects are pronounced and competiton is keen, the best strategy may often be to put more energy into competition and maintenance and to produce offspring with more substantial competitive abilities. This usually requi