Children as Refrigerators: When Would Backward Altruism Appear?

Existing economic theories of the evolution of altruism between kinship members usually emphasize the role that altruism can play in facilitating coordination among kin to achieve an otherwise unachievable efficient (in terms of fitness) equilibrium. In this paper, we explore the background environment against which backward altruism was likely to appear. The instinct of sustaining one’s own life drives one to save for one’s old age. However, since social mechanisms were not sophisticated in a primitive society, the rate of return on savings was not high. As a consequence, the resources that remain for the children might be limited. Suppose a cultural menchanism or a mutation caused an individual to become backward-altruistic. She would then expect her children to adopt the same attitude as herself, and take care of her in her old age. With this expectation in mind, she would avoid inefficient savings voluntarily so that her children could obtain more resources. Thus, backward altruism in our model does not play a role of coordination, but helps parents to avoid inefficient resource disposition. We analyze the possible appearance of backward altruism as the rate of return on savings changes.