  The coherent rise and fall of the quasar population is discussed in terms of
gas accretion onto massive black holes, governed by the hierarchically growing
environment. The rise is related to plentiful accretion during the assemblage
of the host galaxies; the fall to intermittent accretion when these interact
with companions in a group. The LFs are computed out to z=6, and are related to
the mass distribution of relict BH found in local galaxies. The histories of
the QS and of the star light are compared.
