We observed the rest frame ultraviolet for 70 high redshift quasars (z ≥ 3.5). The fluxes of several ultraviolet emission lines were used to estimate the chemical composition of the line emitting gas and date the first star formation epoch. The line ratios were analysed within the frame work of the most recent photoionization models. We estimated an average abundance of Z/Z_⊙ = (5.1 ± 0.3) of the line emitting gas. Assuming an evolution time scale of ～ 0.5 Gyr, the first violent star formation epoch should start at a redshift of z_f approx.> 8 corresponding to an age of the universe of several 10~8 yrs (H_o approx.= 65 km s~(-1) Mpc~(-1), Ω_M/ approx.= 0.3, Ω_Λ approx.= 0.7). The high redshift quasars provide indications for increasing metallicity towards higher luminosities.
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