Based on the population synthesis results1 for the nuclear region of the elliptical galaxy NGC5044, possible theoretical Age Metallicity Relations (AMR) have been derived, reproducing the stellar luminosity distribution over age A and metallicity Z. A self-consistent method, used to constrain the star formation history and chemical evolution of a galaxy directly from its spectrum (i.e. from 3000 – 10000 å) is presented. This method is predominantly based on the modelling of stellar luminosity contributions obtained by spectral decomposition methods with those theoretically calculated using a conventional galactic evolution model, incorporating a parametrised Star Formation Rate (SFR) and Initial Mass Function (IMF). Related model parameters were constrained by minimizing the λ2– test defined by the corresponding luminosity distributions.