The idea that we gain from helping others existed long before we could witness how the brain functions. Researchers pointed out that the sense of self-satisfaction we receive from helping another, along with the idea that we "bank" favors by helping others is evidence that humans are selfish. In a sense, we've confused long-term selfish acts for altruism [source: Gintis, et al].
Over time, different competing explanations for altruism have taken shape. It became clear that human generosity may be context-specific. There also may be more than one type. Reciprocal altruism, where we give under the assumption that we'll receive in return, is different from kin selection, where our altruism favors our relatives over strangers. What is sure is that altruism is a motivator, just like our emotions, our sense of curiosity, and any behaviors that our brains can activate, reward or punish. If we believe that altruism is a motivator, we still arrive back at the same question: What purpose does it serve?
There are essentially two domains that altruism can serve: the self or the group. It's also entirely possible that it serves both.
If altruism is a motivator, then we can compare them to emotions. While the debate continues over the nature of emotions, it appears that humans may have a lower set of basic emotions like fear, joy and anger that serve the self. The other set of "higher" or "moral" emotions, like pride and embarrassment, that are specific to our interactions with others, allows us to live in groups [source: Simons].
If altruism follows this model, then we have a set of basic, self-serving altruistic behaviors as well as another, higher type that evolved as we came to live in larger groups. This would explain why we see altruistic behavior in other animals, yet can't reconcile our own altruism entirely through evolution.
The full explanation of altruism remains elusive, and one man stands as a cautionary tale for those who seek to understand it. In the 1960s, evolutionary biologist George Price created a mathematical formula for altruism -- called the Price equation -- that showed that over time, those individuals who acted exclusively in their own self interest would succumb to natural selection. Price's equation also showed that altruistic acts benefit the giver. After he completed his equation, he became a "radical altruist," donating all of his possessions to the needy and ultimately becoming destitute himself [source: Khan]. He committed suicide in a squat in London just after Christmas, in 1974.
For more information on human behavior and emotion, take a look at the links on the next page.