  Fantappi\'e-Arcidiacono projective relativity, also known as "de Sitter
relativity", provides a formulation of mechanics according to which it is
possible to identify an inertial frame of reference by means of kinematic
methods. This article presents the hypothesis that inertial frames of reference
originated during the so-called "archaic era" of the Universe. A simple
mechanism is proposed for this process. Such a process could leave behind
cosmic fluid granulation, which could manifest itself in the present Universe
as a clustering of dark matter in galaxies.
