Humans are dual creatures by nature. We are capable of horrific cruelty, corruption and greed yet we have the unique ability to do genuinely selfless deeds.
In most cases humans have a tendency to altruistic behavior towards relatedness. Close family member protect and support each other against outside impacts.
However humans can to good without any selfish motivation, simply aiding others. An explanation for this might be that people have a tendency to behave better when they think that they are being watched. They want to leave a good impression and gain a respectable reputation. There is a universal code amongst humans to value and reward virtues like generosity, fairness and conscientiousness.
Another interesting fact is the benefit of reciprocity. Exchanging things with others for mutual profit provides a safety net. People do not forget who was kind towards them. In times of need, they will always take care and protect those members of their group. The same happens vice versa.
The flipside to this phenomenon is nastiness displayed towards outsiders. The very system that enforces a unity and altruism in a group promotes atrocities such as racism, genocide and war.
People are not born with morals, they are taught the morality codes of their culture. This results in morality being flexible. Moving neighborhoods means people will try to adapt their behavior to fit the local culture. As a result if a person wants to be prosocial and does not receive back, their prosocial behavior will gradually disappear to a similar level of their environment. In toxic cultures the evil sides of human beings are enforced. A good social environment brings out the good side in humans.
Cultural context is key for virtue. Virtue is key for altruism.
Image1: (Fahey, Christian, Compassion, you got to feel it, published on the 05. June 2012, available at christiandfahey.wordpress.com accessed 10.11.2012)
Image2: (Unknown, British troops in Iraq, published 12. Oct. 2012, available at http://www.howmanypeopledied.net accessed 10.11.2012)
Image3: (Training for Travel, Support Group, available at vle.trainingfortravel.com accessed 10.11.2012)