Glial evolution still remains unknown, although this process should had required adaptations to the internal medium of the nervous system and to functional needs in the neuroaxis of each species. The hypothesis of the functional and adaptive importance of glia, based on the astrocytary functional multiplicity is supported here as the main objective. The number of glial cells increases in parallel with the encephalic complexity due to a possible activation of new genes associated with the formation of different cellular types; the reason for this cellular