  Cooperation is crucial for the remarkable evolutionary success of the human
species. Not surprisingly, some individuals are willing to bare additional
costs in order to punish defectors. Current models assume that, once set, the
fine and cost of punishment do not change over time. Here we show that relaxing
this assumption by allowing players to adapt their sanctioning efforts in
dependence on the success of cooperation can explain both, the spontaneous
emergence of punishment, as well as its ability to deter defectors and those
unwilling to punish them with globally negligible investments. By means of
phase diagrams and the analysis of emerging spatial patterns, we demonstrate
that adaptive punishment promotes public cooperation either through the
invigoration of spatial reciprocity, the prevention of the emergence of cyclic
dominance, or through the provision of competitive advantages to those that
sanction antisocial behavior. Presented results indicate that the process of
self-organization significantly elevates the effectiveness of punishment, and
they reveal new mechanisms by means of which this fascinating and widespread
social behavior could have evolved.
