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Archeology for Interpreters > 5. How Do Archeologists Figure Out How Old Things Are?

Artifacts as time markers

Mean ceramic dating

(photo) Polychrome delft charger with  hand painted flower motif.

Large delft forms like this charger from Charles Pinckney National Historic Site have a mean manufacture date of 1775. (NPS/Little 1995:72)

Mean ceramic dating dating technique is used in historic archeology to date sites based on the average age of recovered ceramics. European pottery manufacturers kept records on the ceramics they produced from the late sixteenth century onward. Therefore, archeologists know the start and end dates of manufacture for over one hundred pottery types that were used in America. Many manufacturers identified their work by pressing, painting, or using decals containing their name on the ceramic's surface. If an archeologist recovers a sherd containing one of these makers' marks, she or he may identify the ceramic's origin and date of manufacture.

During artifact analysis, the archeologist counts the fragments of each type of ceramic from a site. He or she then determines the mean manufacturing date for each type—the midpoint in the period when it was known to have been made. The mean dates are assigned importance according to the quantity of each pottery type at the site. An average of the mean dates is taken, and the date that results should approximate the middle period when the ceramics were deposited (Deetz 1996:25).

Between approximately 1765 and 1840 European ceramics manufacture changed rapidly. The predominant ceramics types introduced to the American market included creamware, pearlware, and whiteware—in that order. The dates of manufacture for these ceramics are documented, making this period optimal for dating ceramics.

Try it yourself

Mean Ceramic dating

You have recovered sixty-five ceramic sherds from Verysignificantsite. You wish to analyze these ceramic sherds to determine the midpoint of your site's occupation. You know the production ranges and median dates of the three types of ceramics you recovered. Your data is recorded below:

Ceramic Types Production Range Mean manufacturing date (x) # Sherds (f)
 
Transfer-printed pearlware 1795-1840 1818 5
Brown stoneware 1820-1910 1860 10
Creamware 1762-1820 1791 50
 
MEAN CERAMIC DATE = x (f)/ f

To determine your site's mean ceramic date, follow these steps:
1) For each ceramic type, multiply the mean manufacturing date (x) by the # of sherds (f). You'll have 3 numbers.
2) Add these three numbers for TOTAL 1
3) Add the three numbers of sherds (f) for TOTAL 2
4) Divide TOTAL 1 (x[f]) by TOTAL 2 (f)

What is the mean ceramic date for your site (round up to the nearest whole number if necessary)?

1762 1791 1804 1818 1850 1910

 

What does the mean ceramic date tell you about your site's occupation?

A. It could have been occupied as early as 1795
B. It could have been occupied as late as 1910
C. Your site was most heavily occupied between 1762 and 1820
D. All of the above

TSM/MJB