You may have heard the expression that it's nice to be nice. Well there is now scientific evidence that suggests it is in your best interests to cooperate with others. I have long maintained that it wasn't climbing down from the trees that led to the ascent of humankind. Rather it was the cooperation with others who stayed in the trees and warned of any predators that made the difference.
Yes I know there were other more complex interactions, but at the end of the day, we only have the society that we have today because someone is watching your back.
Here's link to the article...http://phys.org/news/2013-08-evolution-youre-selfish.html