"When I went to the apt today there was a small bird huddled by the back door. From his looks and behavior he was probably very young and lost. I took a small bun from your freezer, thawed it out and left it for him. He immediately went over and started to eat. When I returned an hour later he was gone. If humans only act in their selfish interests, why did I bother? Humans are also motivated by altruistic interests!"