Altruism, the idea that animals, including apes such as ourselves, can act in unselfish ways, even to their own apparent detriment is often misunderstood by those who accept the Theory of Evolution and religious believers alike.
The problem stems from an inability to see the evolutionary value of altruism and a belief that doing good must be divinely driven.
Altruism is required for co-operative and social animals and may be the basis for the overall guiding moral that predates religious belief and is even apparent across species - Treat others as you would have them treat you. It has been observed in many species to date with chimps displaying a high level of it. There is the hope/ expectation that the gift/kindness will be reciprocated in some way.
One of the best documentaries, now quite old, was presented by Richard Dawkins and called 'Good Guys finish last'. It may be available on Google video/ You tube. In the example I remember well, the evidence shows altruism works both ways. In an example of grooming apes, if an animal only takes and does not reciprocate it is shunned after a time and needs to try extra hard if it is going to be accepted again.