Some view the three-age system as over-simple; that is, it neglects vital detail and forces complex circumstances into a mold they do not fit. Rowlands argues that the division of human societies into epochs based on the presumption of a single set of related changes is not realistic:But as a more rigorous sociological approach has begun to show that changes at the economic, political and ideological levels are not 'all of apiece' we have come to realise that time may be segmented in as many ways as convenient to the researcher concerned.