Parent-Offspring Interactions in Anthropoid Pri1nates: An Evolutionary Perspective

RoM an evolutionary viewpoint what is special about parentoffspring interactions? Most behavior that is performed at a reproductive or survival "cost" by one animal and that "benefits" (both terms sensu Hamilton, 1964) a recipient by increasing its chances of survival is thought to be done at some direct, usually immediate, cost to the actor. Generally such behavior will be selected against unless the cost is recouped, either through reciprocity or through inclusive fitness effects. The case of behavior directed by parents toward their offspring is an exceptional one because increases in the offspring's survival directly increase the parent's current reproductive success. Any effective parental care that is costly for the parents also, simultaneously, directly increases the parents' reproductive success. However, this increment to the parents' reproductive success is not as great as the benefit to the offspring; the increment in the parents' current repro. ductive success must be weighed against the cost to the parents' future reproduction. Another feature of the benefits and costs involved in parental behavior is that any cost incurred by the parent also entails a cost for the recipient or beneficiary of the act. It does so through inclusive fitness effects, or directly through reduced parental ability to continue investment or even to survive. This self-inflicted cost places limitations on the evolution of selfishness or exploitation on the part of the offspring. However, the cost to the parent, in terms of future reproduction, will be greater than the cost to the off<ipring, through inclusive fitness (frivers, 1974). Because of these asymmetries in costs and benefits to each participant, a "conflict of interest" can arise between parent and off-