Reading the Evidence

When archaeologists are at work, they are essentially acting a sort of scientific "historical interpreter." Using material culture — the tangible remnants of the past — archaeologists take the pottery, rocks and buttons from the days of yore and translate them into information about the life and times of the people who made and used them.

Get a Clue
While it may look like just playing in the dirt, archaeologists are in fact looking for evidence in the form of artifacts, features or ecofacts. An artifact can be anything that has been made, altered or used by humans. So a rock is just a rock, but a rock that has been used as a tool becomes an artifact. Some artifacts are easy to spot — such as broken dishes, bottles or projectile points — while objects like stone tools can be a little trickier to identify. Years of training go into deciphering whether that rock we were just talking about was in fact, a rock, or a 5,000 year old version of a ball-peen hammer.

A feature is another important clue for archaeologists. It is essentially an artifact that cannot be taken back to the lab. Features are fixed in place, like rock walls or foundations, and can be very fragile, like a charcoal stain from a cooking hearth. Features are very exciting to archaeologists because, unlike an artifact that can be carried, eroded or transported by a busy gopher, a feature sits right where it was put by those who made it.

While ecofacts were not made by humans, they still provide relevant information about what humans were eating or what their environment was like. Ecofacts can be anything from acorns, to pollen, to wild animal bones. Understanding what the world was like around humans can sometimes help to explain the archaeology they left behind.

A Dirty Job
In order to decipher the meaning behind archaeological finds, archaeologists rely on investigative tools that help them figure out how and why a site was formed. Almost more important than the artifact itself is its context, or where an artifact is located in space and time. Context can be established by recording the 3-dimensional placement, or provenience, of the artifact (usually depth, and horizontal measurements), and how it is associated with the other archaeological finds in the deposit. By establishing the context of archaeological material, you can figure out events or activities that led to the placement of the artifact in the archaeological record. Artifacts removed from their original context contain only a fraction of their original data.

Stratigraphy is another important way archaeologists make sense of what they are excavating. By examining the different strata, or layers, of the soil, archaeologists can begin to piece together a map of the archaeological site over time. Stratigraphy can be used to figure out which soil was associated with human occupation (and therefore likely to contain archaeological materials), but it can also illustrate certain events (like a fire) or natural disasters (like a flood). Stratigraphy is also a useful excavation guide as it can show archaeologists which layers are sterile and in which layers they should be keeping an eye out for cultural materials.

Back at the Lab
For every hour archaeologists spend in the field, they will spend several more back at the lab washing, cataloging, and analyzing artifacs, and processing all of the archaeological data. All of the detailed information gathered during excavation is put to use as the artifacts are identified and patterns begin to emerge. Diagnostic artifacts like a penny, bottle or an item with an identifiable age range can be used to date an archaeological deposit. The type and style of artifacts found associated together can indicate what the site was used for. An abundance of slate tablets and pencils could suggest schoolhouse; tableware, chamberpots, and medicine bottles could suggest a household; hundreds of chert flakes and broken tools could indicate the location of a quarry. When all of the materials are analyzed and interpreted, the archaeologists can then share the results of their hard-earned data in the form of a report, article or book.

The Dating Game
Archaeologists work with two types of dating: relative and absolute. Relative dating, which can establish an older than/younger than chronology, can be achieved with stratigraphy. For example, a cluster of artifacts at the bottom of the unit, is likely older than material found on the surface. This is a quick and dirty way to organize archaeological material and is sometimes the only dating method available to archaeologists. Absolute dating can provide a specific calendar age — 10,000 years old, for example — for an object or deposit. Historical artifacts sometimes come with datable traits, while artifacts such as charcoal, bone, or other organic materials can be assigned an absolute date using techniques such as radiocarbon dating. It is always ideal to be able to date a site or archaeological deposit with multiple dating techniques that are in agreement.

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