Damped Ly \alpha galaxies provide a sample of young galaxies where chemical abundances can be derived throughout the whole universe with an accuracy comparable to that for the local universe .
Despite a large spread in redshift , HI column density and metallicity , DLA galaxies show a remarkable uniformity in the elemental ratios rather suggestive of similar chemical evolution if not of an unique population .
These galaxies are characterized by a moderate , if any , enhancement of \alpha -elements over Fe-peak elemental abundance with [ S/Zn ] \approx 0 and [ O/Zn ] \approx 0.2 , rather similarly to the dwarfs galaxies in the Local Group .
Nitrogen shows a peculiar behaviour with a bimodal distribution and possibly two plateaux .
In particular , the plateau at low N abundances ( [ N/H ] < -3 ) , is not observed in other atrophysical sites and might be evidence for primary N production by massive stars . abstract