  Using a single dilaton field, a unified model of the Universe is proposed,
which evolves from the radiation-like dominance in the Big Bang, to the
dark-matter-like dominance in the early Universe, to the coexistence of both
dark-matter-like and dark energy today, and finally to the dark energy
dominance in the infinite future. This model is consistent with current results
on the age of the Universe, the transition redshift from deceleration to
acceleration, BBN and evolution of dark energy. Future higher quality data may
constrain the cosmic evolution of dark matter, dark energy and Hubble constant
more precisely and make critical tests on our model predictions.
