  We constrain the evolution of the dark energy density from Cosmic Microwave
Background, Large Scale Structure and Supernovae Ia measurements. While
Supernovae Ia are most sensitive to the equation of state $w_0$ of dark energy
today, the Cosmic Microwave Background and Large Scale Structure data best
constrains the dark energy evolution at earlier times. For the parametrization
used in our models, we find $w_0 < -0.8$ and the dark energy fraction at very
high redshift $\Omega_{early} < 0.03$ at 95 per cent confidence level.
