  Under the assumptions that $SU(3)_c\times U(1)_Y \times G^{\prime}$ with
$G^{\prime}$ simple is a local symmetry group at high energies, that color is
parity-conserving, and the Y-charges are irreducible, we show that anomaly
constraints imply the minimal set of fermions is fifteen in number. Given this
minimal set, we further show that $G^{\prime}$ must be $SU(2)$ and the unbroken
gauge symmetry is {\it either} color {\it or} the product of color with
electric charge.
