A cladistic analysis on samples of low-z quasars (z<0.7) separates sources radiating at higher Eddington ratios values, as well as radio-quiet from radio-loud quasars. The analysis properly distinguishes also core-dominated and lobe-dominated quasars, in agreement with the basic tenet of Unification schemes, and suggests a black hole mass threshold for powerful radio emission. Considering that the black hole mass then provides a sort of "arrow of time” of nuclear activity, an evolutionary interpretation becomes possible if cladistic trees are rooted on black hole mass. More massive radio-quiet Population B sources at low-z become a more evolved counterpart of Population A i.e., wind dominated sources, to which at least part of the “local” Narrow-Line Seyfert 1s belong. In this scheme, powerful radio-loud sources may be seen as sources belonging to a most evolved quasar population.