What is the reason for and what should be the results of human cooperation?

Both, but also a new reason, because people are groupish.  It's just natural behavior, maybe even more natural than not-cooperating.  Based on Haidt's new book: http://www.amazon.com/The-Righteous-Mind-Politics-Religion/dp/0307455777

very few people co-operate purely for altruistic reasons, recognizing this and being able to see even the tiniest bit of self gratification in what we are doing is no bad thing and denying that it is there is a best counterproductive and at worst self defeating

Preserving life on this planet and in the future hopefully on other planets.

Win-win (and "happiness") as opposed to win-lose (and "hate").

Society is the outcome of conscious and purposeful behavior. This does not mean that individuals have concluded contracts by virtue of which they have founded human society.. The actions which have brought about social cooperation and daily bring it about anew do not aim at anything else than cooperation  with others for the attainment of definite singular ends.. The total complex of the mutual relations created by such concerted actions is called society.. It substitutes collaboration for the--at least conceivable--isolated life of individuals. Human society is an intellectual and spiritual phenomenon.. It is the outcome of a purposeful utilization of a universal law determining cosmic becoming the higher productivity of the division of labor.  As with every instance of action, the recognition of the laws of nature is put into the service of man's efforts to improve his conditions.