Archaeologists dig, pick and sift through archaeological sites
and examine very carefully whatever material remains they find to
gain an understanding of prehistoric human behavior. Artifacts such
as stone tools and pottery remains from a prehistoric site—perhaps
hundreds or even thousands of years old—are fascinating not only
to archaeologists but to many others because these artifacts are
often our only guide to recognizing the activities of early humans.
Since there is no written history, the artifacts are scrutinized
to glean whatever we can about the people who made and used them.
Many times they are our only connection to those ancient peoples,
and are among the few items that reflect their daily lives.
By employing various physical and chemical techniques to examine
artifacts, archaeologists systematically can collect, evaluate and
analyze data to try to imagine and visually recreate what life might
have been like. Archaeologists call it modeling, testing, and
theorizing the nature of past human activity. The application
of physical and chemical techniques for archaeological study is
commonly known as archaeometry.
One of the most powerful archaeometric techniques is the method
of neutron activation analysis (NAA), which uses thermal
neutrons from a nuclear reactor to determine the chemical make-up
of artifacts. When we put a small sample of the artifact in our
reactor for a very brief time, the neutrons produced in the reactor
"activate" the sample—make it radioactive. Every radioactive
element gives off a specific radioactivity signature that can be
read (detected) by special instruments. Thus when activated, the
artifact emits unique gamma rays in proportions that correspond
to its chemical composition. In this way we learn about the chemical
ingredients in the artifact—which elements there are and how
much of each. A tabulation of this compositional data for an artifact
is known as its chemical fingerprint.
Sourcing involves matching the artifact with the original
site, quarry or outcropping it came from by comparing chemical fingerprints.
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University of Missouri-Columbia
