Patterns of human behavior change continually. As behavior changes, so do its material products. We all notice changes in clothing styles, car design, music and art. Sometimes we are able to assign a particular item in its approximate time period based on its style or other distinctive characteristics.
Seriation chart. (Heather Hembrey, University of Maryland)
The artifacts and features of past societies also exhibit changes through time. By observing and studying their attributes, archeologists can usually discover trends. By identifying attributes that change most rapidly—such as a pot shape or the images carved on gravestones—archeologists can construct a sequence that accurately reflects the passage of time. Studying how attributes become popular, then lose popularity and are replaced by new attributes reveal much about a culture's creation, use, and consumption of material goods.
Look at the chart to the right. The frequencies of three artifact types at five sites are graphed to illustrate seriation. The wider the line, the more frequent a particular artifact type occurred at that site. Only Artifact Type A exists at Site 1, while Types A, B, and C exist at Site 4. At Site 5, Artifact Type A is absent and the frequency of Artifact B decreases while the frequency of Artifact Type C increases.
Although an archeologist may be able to arrange artifacts in a sequence, he or she cannot assume that the trend of change is always from the simple to the complex or that it implies progress as our own culture defines that term (Ashmore and Sharer 1996:147). Because deposits or artifacts will reveal change in style or frequency over time, archeologists must use other dating methods (usually absolute) to determine which end of the seriation is earlier and which is later.