  Our recent minimal model of cooperation (P. Gawronski et al, Physica A 388
(2009) 3581) is modified as to allow for time-dependent altruism. This
evolution is based on reputation of other agents, which in turn depends on
history. We show that this modification leads to two absorbing states of the
whole system, where the cooperation flourishes in one state and is absent in
another one. The effect is compared with the results obtained with the model of
indirect reciprocity, where the altruism of agents is constant.
