  We introduce a minimalist dynamical model of wealth evolution and wealth
sharing among $N$ agents as a platform to compare the relative merits of
altruism and individualism. In our model, the wealth of each agent
independently evolves by diffusion. For a population of altruists, whenever any
agent reaches zero wealth (that is, the agent goes bankrupt), the remaining
wealth of the other $N-1$ agents is equally shared among all. The population is
collectively defined to be bankrupt when its total wealth falls below a
specified small threshold value. For individualists, each time an agent goes
bankrupt (s)he is considered to be "dead" and no wealth redistribution occurs.
We determine the evolution of wealth in these two societies. Altruism leads to
more global median wealth at early times; eventually, however, the
longest-lived individualists accumulate most of the wealth and are richer and
more long lived than the altruists.
