  In this paper we shall relate computational complexity to the principle of
natural selection. We shall do this by giving a philosophical account of
complexity versus universality. It seems sustainable to equate universal
systems to complex systems or at least to potentially complex systems. Post's
problem on the existence of (natural) intermediate degrees (between decidable
and universal RE) then finds its analog in the Principle of Computional
Equivalence (PCE). In this paper we address possible driving forces --if any--
behind PCE. Both the natural aspects as well as the cognitive ones are
investigated. We postulate a principle GNS that we call the Generalized Natural
Selection principle that together with the Church-Turing thesis is seen to be
in close correspondence to a weak version of PCE. Next, we view our cognitive
toolkit in an evolutionary light and postulate a principle in analogy with
Fodor's language principle. In the final part of the paper we reflect on ways
to provide circumstantial evidence for GNS by means of theorems, experiments
or, simulations.
