  Most young stars in nearby molecular clouds have estimated ages of 1-2 Myr,
suggesting that star formation is rapid. However, small numbers of stars in
these regions with inferred ages of >= 5-10 Myr have been cited to argue that
star formation is instead a slow, quasi-static process. When considering these
alternative pictures it is important to recognize that the age spread in a
given star-forming cloud is necessarily an upper limit to the timescales of
local collapse, as not all spatially-distinct regions will start contracting at
precisely the same instant. Moreover, star-forming clouds may dynamically
evolve on timescales of a few Myr; in particular, global gravitational
contraction will tend to yield increasing star formation rates with time due to
generally increasing local gas densities. We show that two different numerical
simulations of dynamic, flow-driven molecular cloud formation and evolution 1)
predict age spreads for the main stellar population roughly consistent with
observations, and 2) raise the possibility of forming small numbers of stars
early in cloud evolution, before global contraction concentrates the gas and
the bulk of the stellar population is produced. In general, the existence of a
small number of older stars among a generally much-younger population is
consistent with the picture of dynamic star formation, and may even provide
clues to the time evolution of star-forming clouds.
