  The purpose of this paper is to propose an extension to Lee Smolin's
hypothesis that our own universe belongs to a population of universes evolving
by natural selection. Smolin's hypothesis explains why the parameters of
physics possess the values we observe them to possess, but depends upon the
contingent fact that the universe is a quantum relativistic universe. It is
proposed that the prior existence of a quantum relativistic universe can itself
be explained by postulating that a process of cosmogenic drift evolves
universes towards stable ('rigid') mathematical structures.
