We use gravitational lenses from the Cosmic Lens All-Sky Survey ( CLASS ) to constrain the evolution of galaxies since redshift z \sim 1 in the current \Lambda { CDM } cosmology .
This constraint is unique as it is based on a mass-selected lens sample of galaxies .
Our method of statistical analysis is the same as in Chae ( 2003 ) .
We parametrise the early-type number density evolution in the form of ( 1 + z ) ^ { \nu _ { n } } and the velocity dispersion as ( 1 + z ) ^ { \nu _ { v } } .
We find that \nu _ { n } = -0.11 ^ { +0.82 } _ { -0.89 } ( 1 \sigma ) if we assume \nu _ { v } = 0 , implying that the number density of early-type galaxies is within 50 % to 164 % of the present-day value at redshift z = 1 .
Allowing the velocity dispersion to evolve , we find that \nu _ { v } = -0.4 ^ { +0.5 } _ { -0.4 } ( 1 \sigma ) , indicating that the velocity dispersion must be within 57 \% and 107 \% of the present-day value at z = 1 .
These results are consistent with the early formation and passive evolution of early-type galaxies .
More stringent limits from lensing can be obtained from future large lens surveys and by using very high-redshift quasars ( z \gtrsim 5 ) such as those found from the Sloan Digital Sky Survey .