The timeline starts at 1970 because the original article seems to have been written by someone who doesn t recognize the existence of the Bronze Age which runs roughly 1970 1985 The statement that the period begins in the mid 80 s was added changed by someone who does recognize the Bronze Age That s why the inconsistency What we should do is create a Bronze Age article and just get rid of the references to 1970 in here But it s too easy for naysayers to kill the article by selectively demanding references that aren t demanded for Gold Silver Modern