This article from the New York Times uses observation of primates to explore the origins of our generosity.
"The researchers designed an experiment that could provide strong evidence that bonobos could give things to each other simply out of generosity — rather than being pressured into doing so, or expecting some sort of immediate payback” … “Would they do it if there was no benefit to them?” asked Brian Hare, a primatologist at Duke University who helped run the study.