Dividing time into discrete chronological periods like those that organize the chapters here is a mixed blessing. On one hand, such divisions reflect real differences in the archaeological record, differences that tell us about important changes in the past. On the other, they often overemphasize those differences, as if massive changes occurred instantaneously. Looking for dividing lines teaches us to divide time into segments even though we know that it flowed continuously and it focuses our attention on archaeologically visible shifts, often blinding us to important patterns of continuity.