It appears that the Ly forest is becoming thick at a redshift of about 5.5,
cutting off the higher redshift intergalactic medium from view in neutral
hydrogen. However, the effects of star formation at higher redshift are sti
ll readable in the intergalactic metal lines. In this Letter, I use observa
tions of 32 quasars with emission redshifts in the range 2.31-5.86 to study
the evolution of the intergalactic metal density from to z = 1.5 to z = 5.
5. The C IV column density distribution function is consistent with being i
nvariant throughout this redshift range. From direct integration, I determi
ne Omega (C IV) to be in the range and (2.5-7) x 10(-8) and Omega (Si IV) i
n the range (0.9-3) x 10(-8) between z = 1.5 and z = 5. The metallicity at
z = 5 exceeds 3.5 x 10(-4), which in turn implies that this fraction of the
universal massive star formation took place beyond this redshift. This is
sufficient to have ionized the intergalactic medium.