  We point out that, in the context of the SM, $|V^2_{13}| + | V^2_{23}|$ is
expected to be large, of order one. The fact that $|V^2_{13}| + |V^2_{23}|
\approx 1.6 \times 10^{-3}$ motivates the introduction of a symmetry S which
leads to $V_{CKM} ={1\>\!\!\!\mathrm{I}} $, with only the third generation of
quarks acquiring mass. We consider two scenarios for generating the mass of the
first two quark generations and full quark mixing. One consists of the
introduction of a second Higgs doublet which is neutral under S. The second
scenario consists of assuming New Physics at a high energy scale , contributing
to the masses of light quark generations, in an effective field theory
approach. This last scenario leads to couplings of the Higgs particle to
$s\overline s$ and $c \overline c$ which are significantly enhanced with
respect to those of the SM. In both schemes, one has scalar-mediated flavour-
changing neutral currents which are naturally suppressed. Flavour violating top
decays are predicted in the second scenario at the level $ \mbox{Br} (t
\rightarrow h c ) \geq 5\times 10^{-5}$.
