Several explanations for the lack of cooperation in previous studies have been put forward such as high impulsiveness of non-human animals [35].
Traditional explanations of the evolution of cooperation cannot explain this typical form of human cooperation (Henrich 2004).
This theory offers explanations for the development of cooperation in social systems, which imply a (risk of) loss for the decision- maker in the short-term compared to alternative behavioural options [ 29].
In this regard, it is worth noting that recent experiments by Fischbacher and Gächter [27] led to an explanation of the decline of cooperation in public goods games in which heterogeneity seemed to matter only at the end of the experiment.
A major cornerstone of evolutionary biology theory is the explanation of the emergence of cooperation in communities of selfish individuals.
In artificial lab settings, where there are no expectations of future interactions, the concept of social identity seems less persuasive as an explanation of the observed rates of cooperation.
This explanation rests on the proposed mechanism of cooperation between monocytes and cytophilic IgG in mediating parasite growth inhibition [2], [7], and the evidence for a functional role of anti-GLURP antibodies in such a process [47], [48].
But as highlighted by the author in [18] there is still "a lack of clear explanation of the mechanisms necessary for the evolutionary origin of cooperation, particularly between species".
Why, and under what conditions, presumptively selfish individuals cooperate is a prevailing question in social science that has stimulated an extraordinary range of explanations, many of which have focused on the strategic benefits of cooperation.
This property provides a potential explanation on how PCD can evolve as an extreme form of cooperation, although many questions remain to be addressed.
