ALTRUISTIC BEHAVIOR IN DICTYOSTELIUM-DISCOIDEUM EXPLAINED ON THE BASIS OF INDIVIDUAL SELECTION

It is often argued that natural selection acting at the level of the i ndividual may not be sufficient to explain the evolution of altruism. We suggest that before accepting such a point of view in any specific instance, the parsimonious course would be to examine all possible way s in which individual-level selection might act and rule out its suffi ciency only when the postulated means for its action are either inhere ntly improbable or experimentally disproven. As an illustration we pro pose an evolutionary model, based on the individual cell as the unit o f selection, for the maintenance of 'altruistic' behaviour by pre-stal k cells in the social amoeba Dictyostelium discoideum.