why human beings are willing to do good to others?

Human beings, like many other mammals, are social animals and we progress when we do good to others. I believe the underlying reason why human beings are willing to do good to others is that we hope to be treated well when we are in troubles. If we have helped others in need, they will most likely reciprocate by helping us in need also. Therefore, I believe that the reason why human beings are willing to do good to others is that we want others to do good to us also, and none of us is completely selfless even when we are helping others.