  We investigate the evolutionary history of the Universe's metal content
focusing on the chemical abundance of several elements (N, O, S, Si, Fe, Cr,
Zn) taken from observational data and predictions from chemical evolution
models. The estimated abundances were observed in Damped Lyman alpha Systems
(DLAs) over a wide range of redshift (z ~ 0.5-4.5). These data are compared to
predictions of chemical evolution models. Since the nature of the DLAs is
uncertain, they are represented by two class of models: models with galactic
winds describing dwarf galaxies and with infall representing disk galaxies. In
order to settle constraints for star formation timescales in DLAs, we use the
ratios [alpha/Fe] and [N/alpha] in the comparison to the predictions of the
models. These ratios in DLAs are only partially reproduced by the disk and
dwarf galaxy models suggesting that the DLAs come from a variety of
morphological types of galaxies and not only one. They also imply a typically
long timescale for the star formation in these systems.
