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

Artifacts as time markers

[photo] Soda 
                bottles (Mia Parsons)

Soda bottles recovered at Manassas National Battlefield Park can be dated by designs embossed on the glass. (Mia Parsons)

Changing technology has created a vast number of artifacts that mark specific time periods in archeology. These are called diagnostic artifacts because they allow archeologists to pinpoint relatively specific time periods during which they were produced. Archeologists studying prehistoric cultures use stone and bone tools to understand technological changes and assign approximate dates to sites. Historical archeologists have found increasingly detailed ways to partition time on their sites. For example, archeologists can date a glass bottle based on attributes that demonstrate how it was made. A hand-blown wine bottle made of thick, olive green glass is much earlier than a machine-molded medicine bottle made of clear glass and embossed with the manufacturer's name and logo. Documented patterns in manufacturing technology allow archeologists to determine the absolute dates for most glass bottles, ceramics, nails and other artifacts found at historic sites. The most common diagnostic artifacts are described below.