retrogression
re.tro.gres.sion \-'gresh-*n\ n 1: REGRESSION 2: a reversal in development or condition; esp : a passing from a h igher to a lower or from a more to a less specialized state or type in the course of development
Webster's English Dictionaryre.tro.gres.sion \-'gresh-*n\ n 1: REGRESSION 2: a reversal in development or condition; esp : a passing from a h igher to a lower or from a more to a less specialized state or type in the course of development