  Large-scale peculiar motions are commonplace in our universe. Nevertheless,
their origin, evolution and implications are still largely unknown. It is
generally assumed that bulk motions are a relatively recent addition to the
universal kinematics, triggered by the increasing inhomogeneity and anisotropy
of the post-recombination epoch. In this work, we focus on the linear evolution
of peculiar velocities prior to recombination, namely in the late radiation era
and also during a phase of de Sitter inflation. We begin by showing/confirming
that bulk motions are triggered and sustained by the non-gravitational forces
developed during structure formation. Since density and therefore
peculiar-velocity perturbations cannot grow in the baryonic sector before
recombination, we consider drift motions in non-baryonic species, which can
start growing in the late radiation era. Using relativistic linear cosmological
perturbation theory, we find that peculiar motions in the low-energy dark
component exhibit power-law growth, which increases further after
equipartition. Turning to the very early universe, we consider the evolution of
linear peculiar velocities during a phase of de Sitter inflation. We find that
typical slow-roll scenarios do not source peculiar motions. Moreover, even if
the latter were to be present at the onset of the de Sitter phase, the
subsequent exponential expansion should quickly wash away any traces of
peculiar-velocity perturbations.
