  We investigate the dependence of the nucleon-nucleon force in the deuteron
system on the values of coupling strengths at high energy, which will in
general depend on the geometry of extra dimensions. The stability of deuterium
at all times after nucleosynthesis sets a bound on the time variation of the
ratio of the QCD confinement scale to light quark masses. We discuss the
relation between this ratio, which is exponentially sensitive to high-energy
couplings, and fundamental parameters, in various classes of unified theory.
The binding energy of the deuteron is also expected to have an important effect
on nucleosynthesis and we quantify this effect.
