To see why altruism is a problem, imagine an animal predisposed to sacrificing itself for the good of others. If you give up life and limb to help others, it is those others who will have a greater opportunity to reproduce. And in natural selection, reproduction is the coin of the realm. Thus, it would seem, that selection would tend to weed out altruism. More altruism, fewer offspring. Sacrificing yourself for the good of the community or the species, seems like a fool’s errand. Wouldn’t it be much better for your reproductive fitness to be the recipient of altruism rather than the donor? In the words of Garrett Hardin, “we must not forget that we are descended from an unbroken line of egoistic ancestors.” And yet, examples of altruism, self-sacrifice for others, abound. In fact, we can reliably find evidence of human altruism in the laboratory.
Economists have devised an experimental procedure called the ultimatum game. This is a simple two person game. One player is given a sum of money and is told to offer some of the money, at least $1, to the other player. The second player can either accept or reject the offer. If the proposal is accepted, the money is paid out according to the offer. If it is rejected, then no money is paid out and both players get nothing. Usually the game is played anonymously and only one time.
If people were purely selfish, then we would expect that the first player would offer the smallest amount possible, $1, and that the second player would always accept. After all, within the terms of the game, the first player would lose the least and the second player would be a little bit richer. But this rarely happens. The most common offer is half of the available money, and when the offer is below 40%, it is often rejected.
It is clear from this and similar experiments that humans are more altruistic than we might expect from evolutionary and economic theory. The question is why?