  In this Letter we discuss a natural general relativistic mechanism that
causes inhomogeneities and hence generates matter perturbations in the early
universe. We concentrate on spikes, both incomplete spikes and recurring
spikes, that naturally occur in the initial oscillatory regime of general
cosmological models. In particular, we explicitly show that spikes occurring in
a class of G_2 models lead to inhomogeneities that, due to gravitational
instability, leave small residual imprints on matter in the form of matter
perturbations. The residual matter overdensities from recurring spikes are not
local but form on surfaces. We discuss the potential physical consequences of
the residual matter imprints and their possible effect on the subsequent
formation of large scale structure.
