  There are theories which implement the idea that the constants of nature may
be "time dependent." These introduce new fields representing "evolving
constants," in addition to physical fields. We argue that dynamical matter
coupling constants can arise naturally in non-perturbative matter-gravity
theories, after a choice of global time is made. We illustrate the idea in
scalar field cosmology with spatial volume as a global clock, and compute the
time dependence of the scalar mass and self-interaction coupling constants.
