Martin, otto and I had a rather interesting discussion last night in the IRC chat about altruism. I mentioned that altruism was a survival trait (something I remembered from college), but I had some trouble articulating my argument because I had been working on my car while conference calling a local food distributor all day (not to mention seeing The Dark Knight at the midnight showing on Thurs).
Altruism develops in many animals of higher intelligence that are more social as a sort of "I'll scratch your back" arrangement only for survivability. For some animals, living in a pack or tribe instead of on one's own vastly increases their odds of survival because the individuals can pool their respective strengths and they can team up to fight off danger. In the development of these societies, the ability to work together was of paramount importance. A pack that can work together more efficiently had a higher survivability rate. This is where altruism came in. Trust has to be developed, which means that emotions like guilt, embarrassment, an pride took center stage to help build the mutual trust between members of a pack. This trust lead to behavior that was in the interest of the whole pack even over the individual. When a soldier bravely dives on a grenade, he is doing so in order to save his friends so that they may continue on. This same behavior can be seen in many higher primates, like chimpanzees. I would certainly trust someone who did something selflessly for me, and I'd be more inclined to return the favor.
Here is some further reading:
http://www.eurekalert.org/pub_releas...-teo012207.php
http://www.livescience.com/animals/0..._altruism.html