We present observations of 11 high redshift quasars ( 3.9 \la z \la 5.0 ) observed with low spectral resolution in the restframe ultraviolet using FORS 1 at the VLT UT 1 .
The emission-line fluxes of strong permitted and intercombination ultraviolet emission lines are measured to estimate the chemical composition of the line emitting gas .
Comparisons to photoionization calculations indicate gas metallicities in the broad emission line region in the range of solar to several times solar .
The average of the mean metallicity of each high-z quasar in this sample is Z / Z _ { \odot } = 4.3 \pm 0.3 .
Assuming a chemical evolution time scale of \tau _ { evol } \simeq 0.5 - 0.8 Gyrs , we derive a redshift of z _ { f } \simeq 6 ~ { } { to } ~ { } 8 for the onset of the first major star formation episode ( H _ { o } = 65 km s ^ { -1 } Mpc ^ { -1 } , \Omega _ { M } = 0.3 , \Omega _ { \Lambda } = 0.7 ) , corresponding to an age of the universe of several 10 ^ { 8 } yrs at this epoch .
We note that this epoch is also supposed to be the era of re-ionization of the universe .