  Recently, our understanding of the origin of W UMa-type contact binaries has
become clearer. Initial masses of their components were successfully estimated
by Y{\i}ld{\i}z and Do\u{g}an using a new method mainly based on observational
properties of overluminous secondary components. In this paper, we continue to
discuss the results and make computations for age and orbital evolution of
these binaries. It is shown that the secondary mass, according to its
luminosity, also successfully predicts the observed radius. While the current
mass of the primary component is determined by initial masses, the current
secondary mass is also a function of initial angular momentum. We develop
methods to compute the age of A- and W-subtype W UMa-type contact binaries {in
terms of} initial masses and mass according to the luminosity of the
secondaries. Comparisons of our results with the mean ages from kinematic
properties of these binaries and data pertaining to contact binaries in open
and globular clusters, have increased our confidence on this method. The mean
ages of both A- and W-subtype contact binaries are found as 4.4 and 4.6 Gyr,
respectively. From kinematic studies, these ages are given as 4.5 and 4.4 Gyr,
respectively. We also compute orbital properties of A-subtype contact binaries
at the time of the first overflow. Initial angular momentum of these binaries
is computed by comparing them with the well-known detached binaries. The
angular momentum loss rate derived in the present study for the detached phase
is in very good agreement with the semi-empirical rates available in the
literature. In addition to the limitations on the initial masses of W UMa-type
contact binaries, it is shown that the initial period of these binaries is less
than about 4.45 d.
