  Pareto selective forces optimize several targets at the same time, instead of
single fitness functions. Systems subjected to these forces evolve towards
their Pareto front, a geometrical object akin to the thermodynamical Gibbs
surface and whose shape and differential geometry underlie the existence of
phase transitions. In this paper we outline the connection between the Pareto
front and criticality and critical phase transitions. It is shown how, under
definite circumstances, Pareto selective forces drive a system towards a
critical ensemble that separates the two phases of a first order phase
transition. Different mechanisms implementing such Pareto selective dynamics
are revised.
