premise: The advent of the Bronze Age ( about 3200 b.c . ) , and the spread of city-states ruled by kings , is marked by the appearance of royal tombs containing bronze objects in such places as Troy in the west , and Alacah ? ? y ? ? k near Ankara .
hypothesis: Ww know the Bronze Age started around 3200 b.c . because royals were starting to be buried with bronze treasure .