  For a number of starless cores, self-absorbed molecular line and column
density observations have implied the presence of large-amplitude oscillations.
We examine the consequences of these oscillations on the evolution of the cores
and the interpretation of their observations. We find that the pulsation energy
helps support the cores and that the dissipation of this energy can lead toward
instability and star formation. In this picture, the core lifetimes are limited
by the pulsation decay timescales, dominated by non-linear mode-mode coupling,
and on the order of ~few x 10^5--10^6 yr. Notably, this is similar to what is
required to explain the relatively low rate of conversion of cores into stars.
For cores with large-amplitude oscillations, dust continuum observations may
appear asymmetric or irregular. As a consequence, some of the cores that would
be classified as supercritical may be dynamically stable when oscillations are
taken into account. Thus, our investigation motivates a simple hydrodynamic
picture, capable of reproducing many of the features of the progenitors of
stars without the inclusion of additional physical processes, such as
large-scale magnetic fields.
