Galaxy Evolution From the Dark Side

Evolution in galactic gas kinematic, ionization, and chemical conditions can provide a window on galaxy evolution, since stellar populations and galaxy morphology are connected to the gas reservoir and the efficiency of star formation. I will argue that observing Mg II absorption in quasar spectra is the best way to build a large, complete, and uniform database for galaxy evolution to z=4; for example, Mg II absorption is known to arise in a wide range of galaxy environments and the sensitivity is not a function of redshift; we are not limited to only the very bright end of the luminosity function as are present studies of high redshift galaxies. The present status of Mg II absorbers will be reviewed, including much unpublished work on the high ionization phases, the population of "weak" systems, and an argument that weakens, and may rule out, the controversial Blitz-Spergel model for high velocity clouds. Near-future plans to build a complete sample to z=4 using the 9-m Hobby-Eberly Telescope will be presented.