The Data-Fitting concept presented is an efficient, method to analyze data from frequency sweep or relaxation experiments to determine viscoelastic properties of polymers. It can be used with profit by material developers and CAE-experts needing a rapid and comprehensive evaluation procedure. Master-curves in either time or frequency domain can be evaluated and the result may be a discrete line spectra of relaxation time constants. The applied data-evaluation software relies on a noval fitting strategy which makes use of the "mutation-selection" schema, well known in biology.