Last updated: July 22, 2021
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How Do Archeologists Talk About Time?
In archeology, the date of production of an artifact, date of occupation of a site, or a cultural period can be described in several ways. We are taught history in grade school in terms of BC and AD, which are used to describe time in relationship to events in the Christian calendar. In the late 20th century, scholars began shifting to the use of BCE and CE, before common era and common era, which directly correlate to BC and AD but instead are secular. Archeologists often use these terms to describe time at the sites that they are researching, particularly sites that date from after the European colonization of the Americas, but they use other categorizations to talk about deeper time as well.
For time periods in the deep past, to be as specific as possible, archeologists can use radiocarbon dating analyses. Using samples of organic material found in archeological contexts, radiocarbon calibrated dates can be derived through detecting the remaining levels of Carbon-14 in the organic materials. Calibrated radiocarbon dates can be represented using BC/AD or BCE/CE, but are also described as years before present (BP). The “present” is the year 1950 because radiocarbon dating was invented during this year. Each of these dating conventions can be used interchangeably but figuring them out may require mathematical calculations!
Here is an example:
NPS Photo / Claire Norton
This projectile point from the Saugus Iron Works National Historic Site Museum Collections is a Levanna type triangle shaped projectile point, which archeologists have determined is from the Middle to Late Woodland Period. The Levanna type projectile point was popular from around 700-1350 CE (AD 700-1350), or about 1,250-600 years before present (BP). These date ranges may seem different, but they refer to the same period!
These various dating conventions are used throughout this website to discuss the history of Saugus Iron Works National Historic Site. The reference texts and typologies by archaeologists define cultural periods and artifacts correlating to those periods through radiocarbon dating and as such before present (BP) dates are often used to describe and discuss artifacts at precolonial and deep time archeological sites in New England. The Native American archeological collections that are a part of the Saugus Iron Works National Historic Site Museum Collections will be discussed in terms of years before present (BP).
Beyond radiocarbon dating, there are many different types of relative and absolute dating methods archeologists use to determine the date of artifacts and sites. Check out the information packed resource page created by the archeologists in the NPS Archeology program in the links below!
Resources
Taylor, R.E. (1997) Radiocarbon Dating. In Chronometric Dating in Archaeology. Advances in Archaeological and Museum Science, vol 2. Springer, Boston, MA: https://doi.org/10.1007/978-1-4757-9694-0_3.