We offer a game-theoretic proof of Hamilton's rule for the spread of altruism. For a simple case of siblings, we show that the rule can be derived as the outcome of a one-shot prisoner's dilemma game between siblings. -- evolution of altruism ; Hamilton's rule ; one-shot prisoner's dilemma game

Most private giving between living generations takes the form of "tied" transfers, such as help with housing downpayments. We argue that parents provide help with downpayments in order to encourage the production of grandchildren, and that such a subsidization emanates from the "demonstration...