In archaeology, it is important to either have a working knowledge (or colleagues involved) in geology, biology, and chemistry. In particular, chemistry is very important in painting as complete of a picture of past cultures and people as possible, since much of the artifact collection involves basic elements like carbon (as in wood, charred/burned seeds), strontium (bones, teeth), and isotopes of these elements (like carbon-14). These elements help in determining approximate age of objects and can give insight into how old a settlement was or where an individual came from geographically.
Archaeology and Radiocarbon Dating
Carbon is a common element in the environment. It can be found in all living things, even once they have died. The breakdown of carbon from the carbon 14 (C-14) isotope occurs at a relatively even pace each year; this number is called a half-life. The cycle of breaking down carbon 14 begins when a living object dies. The measurement of C-14 remaining in an object lets an archaeologist know approximately how long ago it ceased to live. Although the precise date of death cannot be conclusively determined most of the time, carbon 14 (or more commonly called radiocarbon) dating) can help archaeologists assign an approximate age.
They can do this because other living objects like trees also log a history of past environmental conditions, including the level of C-14 in the area each year. Scientists use dendrochronology and carbon 14 dating together in an equation to determine a date of death. Since this date is an approximate, it always has a plus/minus number. This plus/minus number is a standard deviation to show that any inaccuracies in measurement could throw this date off by a number of years.
C3 and C4 Plants at Archaeological Sites
A second way carbon is useful is in dietary analysis, since not only do humans burn or cut down living objects (trees, plants) as necessary, but they also consume carbon in different ways. One of the most investigated areas in archaeology is the transition in diet, including the advent of agriculture. Within the plants around the world, there are two many types: C3 and C4 plants. The C refers to the carbon chain in the plant. C3 plants are older plants, while C4 plants are a more recent adapted plant type.
C3 plants are most of the plants growing around the world, as they are quite flexible in what type of environments they need, as long as the temperatures and rainfall totals are moderate. C3 plants include potatoes, rice, and wheat.
C4 plants include most grasses, sugar cane, maize, and millet. C4 plants have a different outer protection layer of plant fibers. These help keep in moisture in times of dry spells. They also may have a higher starch content.
This is where archaeologists find carbon levels useful. Knowing the carbon fixation of a plant helps determine the likely foods eaten in the past.
Archaeology and Strontium Isotopes
In diet reconstruction, strontium levels are also significant in archaeological research. Strontium levels vary across the world, and in some areas, are distinctive to specific smaller regions. Strontium levels vary in nature, and end up in humans who reside in the region.
The fact that the human has a similar isotopic signature to strontium levels of a geographic location means that person very likely was born or lived in that area for a length of time and was exposed to the strontium there. Strontium adheres to bones and teeth given its likeness to calcium.
As a result, the bones found at an excavation site may be taken to a laboratory and analyzed for strontium levels. The area this person lived in for a long time may be discernible, although not all of the time. This information may help in identifying someone as a longtime resident (or conversely, as a transient or visitor).
Although at first glance archaeology and chemistry seem very separated, with one being a social science and the other being a physical science, there is a great deal of overlap when it comes to how humans interact with their surroundings. Carbon studies help in determining relative age of a site, as well as possible diets. Strontium helps determine place of origin or homeland of a long-deceased individual. All of this gleans more information about a past society and its environment when it comes to the final archaeological site report.
Alison Diefenderfer - Hold a B.A. (anthropology) and an M.S. degree (social science) Work experience in higher education environments *I have gone ...
