 The production of each colossal head must have been carefully planned , given the effort required to ensure the necessary resources were available ; it seems likely that only the more powerful Olmec rulers were able to mobilise such resources . The workforce would have included sculptors , labourers , overseers , boatmen , <unk> and other <unk> producing the tools to make and move the monument , in addition to the support needed to feed and otherwise attend to these workers . The seasonal and agricultural cycles and river levels needed to have been taken into account to plan the production of the monument and the whole project may well have taken years from beginning to end . 
