The model of Chapter IV argues that intergenerational altruism is not a universal constant but adjusts to circumstances. Chapters III - VIII motivate the model by arguing that such a model of altruism offers more accurate predictions for intergenerational mobility than do existing economic models. However, I believe that there are motivations for the model. One motivation comes from the field of sociobiology. Sociobiologists have argued that their analysis has a lot to say about the origins of social behavior in general and altruism in particular, but I show that their arguments have implications for the endogeneity of altruism. A theory of the origins of altruism is, in my view, is also a theory of the endogeneity of altruism.
Section A outline the merits and demerits of sociobiological reasoning. I then apply the reasoning to uncover determinants of altruism. The current chapter is more mathematical than preceding chapters. The mathematical models show exactly how biological and economic analysis might be integrated.