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Background, Disciplines, Current ControversyField methods

The term archaeology refers, in part, to the study of human culture and of cultural changes that occur over time. In practice, archaeologists attempt to logically reconstruct human activities of the past by systematically recovering and examining artifacts or objects of human origin. However, archaeology is a multi-faceted scientific pursuit, and includes various specialized disciplines and subfields of study. Depending on the specific field of interest, archaeological artifacts can encompass anything from ancient Greek pottery vessels to disposable plastic bottles at modern dump sites. Thus, studies in archaeology can extend from the advent of human prehistory to the most recent of modern times. The two most common areas of study in archaeological research today, particularly in the United States, are prehistoric and historic archaeology.

Prehistoric archaeology

Everything that is currently known about human prehistory is derived through the excavation and study of ancient materials.

Prehistoric archaeology encompasses the study of humankind prior to the advent of written languages or written history. In effect, the job of the prehistoric archaeologist is to discover and write about the histories of ancient peoples who had no written history of their own.

However, prehistory lasted for different times in different parts of the world. In Europe, primitive written languages made their appearance around 2500 B.C., thus technically ending Old World prehistory. On the other hand, American prehistory came to a close only 500 years ago when explorers such as Christopher Columbus (c. 1451-1506) visited the New World for the first time. By returning to their homelands with written reports of what they had seen, those explorers ushered in the early historic era of the Western Hemisphere.

Historic archaeology

As opposed to prehistoric archaeological studies, historic archaeology is a discipline that focuses on a more detailed understanding of the recent past. Typically, any site or building over 50 years old but younger than the regional area's prehistory is considered historic. For example, Civil War battlefields are historic landmarks. Because most historic sites and buildings were used during times when records were kept, the historic archaeologist can review written documentation pertaining to that time and place as part of the overall study.

Artifactual material discovered during an historic archaeological excavation adds specific detailed information to the knowledge already gathered from existing historic documents.

A relatively new sub-discipline of historic archaeology, known as urban archaeology, attempts to quantify our current culture and cultural trends by examining material found at modern dump sites. Urban archaeology has been primarily used as a teaching aid in helping students of cultural anthropology and archaeology develop interpretive skills.

Classical archaeology

The classical archaeologist is perhaps the most popular public stereotype—the "Indiana Jones" movie character, for example, is based on the fantastic exploits of a classical archaeologist. The roots of classical archaeology can be traced to the European fascination with Biblical studies and ancient scholarship. Classical archaeologists focus on monumental art, architecture, and ancient history. Greek mythology, Chinese dynasties, and all ancient civilizations are the domain of the classical archaeologist.

This field is perhaps one of the most complex areas of the study of human culture, for it must utilize a combination of both prehistoric and historic archaeological techniques. In addition, classical studies often employ what is referred to as underwater archaeology to recover the cargo of sunken ancient sailing vessels that carried trade goods from port to port.

Archaeological excavation, Eldon Pueblo, Coconino National Forest, Arizona. Photograph by Tom Bean. Stock Market. Reproduced by permission.

Cultural resource management

Beginning in the 1940s, a number of state and federal laws have been enacted in the United States to protect archaeological resources from potential destruction that could be caused by governmental developments such as highway construction. In the 1970s, additional legislation extended these laws to cover development projects in the private sector. Other countries have also passed similar laws protecting their antiquities. As a result, archaeology has moved from a purely academic study into the realm of private enterprise, spawning hundreds of consulting firms that specialize in contract archaeology or what is commonly known as cultural resource management (CRM).

CRM work has become a major economic industry in the United States, generating an estimated 250 million dollars a year in annual business through government and private contracts. Most archaeological studies conducted in the United States today are a direct result of compliance with antiquities laws.

Construction projects such as the building of dams, highways, power lines, and housing developments are a recognized and accepted pattern of human growth. It is also recognized that these activities sometimes have a detrimental affect on the evidences of human history. Both historic buildings and prehistoric sites are often encountered during the course of new construction planning. However, various steps can be taken to insure that such sites are acknowledged and investigated prior to any activities that might damage them.

The two most common measures that can be taken when a site lies in the path of development include (1) preservation by simple avoidance or (2) data recovery. Preservation by avoidance could mean re-routing a highway around an archaeological site, or moving the placement of a planned building to a different location. On the other hand, when avoidance is not possible, then data recovery by excavation becomes the next alternative.

In the case of historic structures, for example, data recovery usually includes a thorough recordation of the building. This might include photographs, scale interior and exterior drawings, and historic document searches to determine who designed and built the structure or who might have lived there. For prehistoric resources, sampling the contents of the subsurface deposit by excavation is perhaps the only method by which to determine the significance of a site.

Archaeological survey/field reconnaissance

Prior to any archaeological excavation, whether it be prehistoric or historic, a survey or field reconnaissance must be conducted. In general terms, a survey systematically inspects the surface of a site to determine whether or not it is significant and may warrant further investigation. Although the determination of significance is somewhat subjective, most researchers agree that it hinges on a site's potential to yield useful information. Significance may include the ability of a site to produce new, previously unknown information, or additional data to add to what is currently known about the site's original inhabitants and their culture.

Surveys are also conducted on undeveloped properties where no sites have been previously recorded. These types of surveys are performed to verify that no sites are on the subject property, or if one is found, to record its presence and document its location, condition, size, and type. All records pertaining to archaeological surveys and sites are permanently stored at either government or university clearing houses for future reference by other archaeologists.

Test excavation

The term test excavation refers to the intermediate stage of an archaeological investigation between surveying and salvage excavation or full data recovery program. It generally incorporates the digging of units or square pits in order to sample the contents and depth of an archaeological site. Test units can be randomly located on a site or placed in specific locations. The use of test units helps the archaeologist determine what areas of a site will yield the highest quantity of artifacts or most useful information before committing time and resources to a more intensive study.

Typically, test units are measured metrically, such as in a one meter by one meter square, and excavated through the archaeological deposit to sterile soil, or soil which fails to produce any additional finds. Depending on the project and the type of site, various methods and techniques are used during an excavation. Sometimes the artifact-bearing soils (called midden) are excavated from units in 2–4 in (5–10 cm) levels, carefully peeling one layer of soil and then the next. This is known as arbitrary excavation.

In instances where natural soil layering can be observed, excavation comprises removal of each layer or strata regardless of its thickness. The purpose in both cases is to maintain a vertical control of where artifacts were recovered, as well as separating the shallow, younger materials from deeper, older materials.

Each layer or level of soil recovered from unit excavations is sifted through a wire mesh or screen. Soil falls through the screen while artifacts and other material are left on top, where they are then washed, sorted according to type, bagged, and labeled. In this way, archaeologists not only record from what unit a particular artifact was found but also at what depth.

Thus, archaeologists can reconstruct a three-dimensional view of a site layout.

Salvage excavation

Salvage excavations, or what is referred to as rescue archaeology outside the United States, generally represent the final data recovery program of an archaeological site. Although the methods used in salvage excavations are similar to those of test excavations, there are some distinctions with regard to objectives.

Whereas the term test implies an initial investigation to be followed by further study, the term salvage generally denotes that no additional research may be undertaken once the excavation is complete. This is particularly true for archaeological sites that will be destroyed as a result of construction activities.

Unfortunately, it is an accepted fact in archaeology that recovery of 100% of the contents of a site is impractical due to either time or budget constraints. In actuality, that number is estimated from less than 1% to as much as 7%, leaving the remaining bulk of the deposit unstudied. Thus, archaeologists are forced by necessity to make determinations on the most appropriate mode of data recovery and what avenues of research would best benefit from the excavation.

Traditional methods of excavation typically include the use of picks, shovels, trowels, and hand-held shaker screens.

However, archaeologists have realized that although laboratory techniques have taken full advantage of the latest technologies, field methods have not made a corresponding advancement, and in fact have not changed dramatically since the 1930s. To tackle this problem, researchers have begun to experiment with various alternative methods of data recovery. These alternatives are designed to increase sample size, lower costs to sponsors, and at the same time maintain careful scientific control over the recovery process.

One of these alternatives includes the use of earthmoving machinery. For decades, machines such as backhoes or tractor-mounted augers have been employed during test excavations to aid in determining the boundaries and depths of archaeological deposits. Recently, however, machines have been used to actually salvage excavate sites by simulating traditional digging methods, or digging level by level. As a result, new methods of hydraulic water screening have been developed to process large amounts of midden soils. Although machines have been successfully utilized in salvage excavations, the use of mechanized earth-moving machinery in archaeology is not widely practiced and cannot be applied to all sites.

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