  The standard picture holds that giant elliptical galaxies formed in a single
burst at high redshift. Aging of their stellar populations subsequently caused
them to fade and become redder. The Canada-France Redshift Survey provides a
sample of about 125 galaxies with the luminosities and colours of passively
evolving giant ellipticals and with 0.1 < z < 1. This sample is inconsistent
with the standard evolutionary picture with better than 99.9% confidence. The
standard Schmidt test gives <V/V_{max}> = 0.398 when restricted to objects with
no detected star formation, and <V/V_{max}> = 0.410 when objects with emission
lines are also included. A smaller sample of early-type galaxies selected from
tha Hawaii Deep Survey gives equally significant results. With increasing
redshift a larger and larger fraction of the nearby elliptical and S0
population must drop out of of the sample, either because the galaxies are no
longer single units or because star formation alters their colours. If the
remaining fraction is modelled as F=(1+z)^{-\gamma}, the data imply gamma = 1.5
+- 0.3. At z=1 only about one third of bright E and S0 galaxies were already
assembled and had the colours of old passively evolving systems. We discuss the
sensitivity of these results to the incompleteness corrections and stellar
population models we have adopted. We conclude that neither is uncertain enough
to reconcile the observations with the standard picture. Hierarchical galaxy
formation models suggest that both merging and recent star formation play a
role in the strong evolution we have detected.
