We find that the observed stacked Lya line profile evolves with redshift. At lower z the stacked line profile exhibits a strong red peak accompanied by a weaker blue peak. This blue peak decreases its luminosity at higher z, as the IGM and CGM become denser. interestingly, we find that the stacked Lya line profile produce by the ISM is constant though redshift. This suggests that the galactic escape channels of Lya photons are fixed though the Universe evolution. We measure the mean IGM escape fraction as a function of redshift which evolves from 0.95 at z=0.0 to 0.5 at z=6.0.