  Modified Newtonian Dynamics has one free parameter and requires an
interpolation function to recover the normal Newtonian limit. We here show that
this interpolation function is unnecessary in a recently proposed covariant
completion of Erik Verlinde's emergent gravity, and that Verlinde's approach
moreover fixes the function's one free parameter. The so-derived correlation
between the observed acceleration (inferred from rotation curves) and the
gravitational acceleration due to merely the baryonic matter fits well with
data. We then argue that the redshift-dependence of galactic rotation curves
could offer a way to tell apart different versions of modified gravity from
particle dark matter.
