The Neutral Hydrogen Cosmological Mass Density at z=5

We present the largest homogeneous survey of redshift > 4.4 damped Lya systems (DLAs) using the spectra of 163 quasars that comprise the Giant Gemini GMOS (GGG) survey. With this survey we make the most precise high-redshift measurement of the cosmological mass density of neutral hydrogen, Omega(HI). After correcting for systematic effects using a combination of mock and higher-resolution spectra, we find Omega(HI) = 0.98(-0.18)(+0.20) x 10(-3) at < z > = 4.9, assuming a 20% contribution from lower column density systems below the DLA threshold. By comparing to literature measurements at lower redshifts, we show that OHI can be described by the functional form Omega(HI)(z). (1 + z) 0.4. This gradual decrease from z = 5 to 0 suggests that in the galaxies which dominate the cosmic star formation rate, H i is a transitory gas phase fuelling star formation which must be continually replenished by more highly-ionized gas from the intergalactic medium, and from recycled galactic winds.