  Cold dark matter models for galaxy formation predict that low-mass systems
will be the first sites of star formation. As these objects have shallow
gravitational potential wells, the subsequent growth of their stellar
populations may be halted by heating and gas loss due to reionization. This
effect has been suggested to have profoundly influenced properties of
present-day dwarf galaxies, including their stellar populations and even
survival as visible galaxies. In this Letter we draw on results from
quantitative studies of Local Group dwarf galaxy star formation histories,
especially for Milky Way satellites, to show that no clear signature exists for
a widespread evolutionary impact from reionization. All nearby dwarf galaxies
studied in sufficient detail contain ancient populations indistinguishable in
age from the oldest Galactic globular clusters. Ancient star formation activity
proceeded over several Gyr, and some dwarf spheroidal galaxies even experienced
fairly continuous star formation until just a few Gyr ago. Despite their
uniformly low masses, their star formation histories differ considerably. The
evolutionary histories of nearby dwarf galaxies appear to reflect influences
from a variety of local processes rather than a dominant effect from
reionization.
