From their research, it seems that there is some evolutionary, positive attribute for this social phenomena. It appears to glue groups, as small as a pair and as large as civilizations.
It's too bad that Nature magazine couldn't have been more COOPERATIVE and released this research as a free web article, then more of us would have access to it and could CHOOSE to learn more about Nature and its peer reviewed research mission.
Explaining the rise and maintenance of cooperation is central to our understanding of biological systems1, 2 and human societies3, 4. When an individual's cooperativeness is used by other individuals as a choice criterion, there can be competition to be more generous than others, a situation called competitive altruism5.
evolution of cooperation between non-relatives can then be driven by a positive feedback between increasing levels of cooperativeness and choosiness6
in a situation where individuals have the opportunity to engage in repeated pairwise interactions, the equilibrium degree of cooperativeness depends critically on the amount of behavioural variation that is being maintained in the population by processes such as mutation.
important role of lifespan in the evolution of cooperation.