Archaeology

B

Recreating the Record

Archaeologists may also try to recreate the artifacts and patterns they find in excavated sites in order to understand how artifacts were made and how patterns formed. In experimental archaeology, archaeologists perform controlled experiments to help interpret finds such as abandoned fire hearths, accumulations of waste from stone toolmaking, and collapsed buildings.

In experiments conducted in the 1980s, American paleoanthropologists Nicholas Toth and Kathy Schick reconstructed the simple stone toolmaking techniques of early humans through controlled replication. They and their research teams used the same types of stones that the first toolmakers used and even collected them from the same areas. They tried making tools in a variety of ways. By making tools using both their right and left hands, and then comparing the resulting patterns in their tools with those from prehistoric sites, Toth and Schick learned that some early humans were left-handed. In addition, the stone flakes left by ancient toolmaking allow an expert to reconstruct minute details of stone technology, such as whether (and even how many times) a tool was retouched to give it a new, sharp edge. Toth and Schick and their research teams also butchered animal carcasses with stone tools to see what the resulting cuts look like. This information has helped archaeologists determine the extent to which ancient peoples hunted or scavenged for meat.

Some of the most ambitious experimental archaeology projects have involved long-term trials with prehistoric farming methods in Europe. Since 1972 archaeologists have experimented with prehistoric agricultural methods at Butser in southern England. Using only ancient tilling implements, they plant and grow varieties of grains used in prehistoric times. Other research at Butser involves breeding animals that were bred in prehistoric times. Researchers also have experimented with storing food supplies in covered pits in the ground, a practice that was common around 300 bc during the Iron Age. Using this technique, ancient farmers could keep food supplies over long winters and store seed to plant each spring.

VI

Establishing Archaeological Sites

Before archaeologists excavate, they locate potential sites and test them to determine if the sites will yield artifacts and other remains. Until about the late 1960s, many archaeologists favored large-scale excavations, arguing that the more ground they cleared the more they would discover. Today, archaeologists know that any disturbance of an archaeological site, however scientific, actually destroys an irreplaceable record of the past. For this reason, modern excavations are usually done on a more limited scale.

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Once excavated, archaeological sites are gone forever. Good survey techniques are crucial for minimizing damage to the record and for locating sites that contain objects of interest. Increasingly, archaeologists are also using less intrusive ways of investigating the past. Advanced technologies that can provide archaeological data without digging—such as various kinds of radar, magnetic sensors, and soil electric-resistance detectors—can keep actual excavation to a minimum.

A

Knowing Where to Dig

How do archaeologists know where to find what they are looking for when there is nothing visible on the surface of the ground? Typically, they survey and sample (make test excavations on) large areas of terrain to determine where excavation will yield useful information. Surveys and test samples have also become important for understanding the larger landscapes that contain archaeological sites.

Some archaeological sites have always been easily observable—for example, the Parthenon in Athens, Greece; the pyramids of Giza in Egypt; and the megaliths of Stonehenge in southern England. But these sites are exceptions to the norm. Most archaeological sites have been located by means of careful searching, while many others have been discovered by accident. Olduvai Gorge, an early hominid site in Tanzania, was found by a butterfly hunter who literally fell into its deep valley in 1911. Thousands of Aztec artifacts came to light during the digging of the Mexico City subway in the 1970s. In Israel in 1947, two Bedouins discovered the Dead Sea Scrolls by accident in a cave.

Most archaeological sites, however, are discovered by archaeologists who have set out to look for them. Such searches can take years. British archaeologist Howard Carter knew that the tomb of the Egyptian pharaoh Tutankhamun existed from information found in other sites. Carter sifted through rubble in the Valley of the Kings for seven years before he located the tomb in 1922. In the late 1800s British archaeologist Sir Arthur Evans combed antique dealers’ stores in Athens, Greece. He was searching for tiny engraved seals attributed to the ancient Mycenaean culture that dominated Greece from the 1400s to 1200s bc. Evans’s interpretations of these engravings eventually led him to find the Minoan palace at Knossos (Knosós), on the island of Crete, in 1900.

To find their sites, archaeologists today rely heavily on systematic survey methods and a variety of high-technology tools and techniques. Airborne technologies, such as different types of radar and photographic equipment carried by airplanes or spacecraft, allow archaeologists to learn about what lies beneath the ground without digging. Aerial surveys locate general areas of interest or larger buried features, such as ancient buildings or fields.

Ground surveys allow archaeologists to pinpoint the places where digs will be successful. Most ground surveys involve a lot of walking, looking for surface clues such as small fragments of pottery. They often include a certain amount of digging to test for buried materials at selected points across a landscape. Archaeologists also may locate buried remains by using such technologies as ground radar, magnetic-field recording, and metal detectors.

Archaeologists commonly use computers to map sites and the landscapes around sites. Two- and three-dimensional maps are helpful tools in planning excavations, illustrating how sites look, and presenting the results of archaeological research.

Surveys can cover a single large settlement or entire landscapes. Many researchers working around the ancient Maya city of Copán, Honduras, have located hundreds of small rural villages and individual dwellings by using aerial photographs and by making surveys on foot. The resulting settlement maps show how the distribution and density of the rural population around the city changed dramatically between ad 500 and 850, when Copán collapsed. Archaeologists believe the people of Copán may have overfarmed the surrounding land, depleting their primary food supply and forcing them into the countryside in search of fertile land.

American archaeologists René Million and George Cowgill spent years systematically mapping the entire city of Teotihuacán in the Valley of Mexico near what is now Mexico City. At its peak around ad 600, this city was one of the largest human settlements in the world. The researchers mapped not only the city’s vast and ornate ceremonial areas, but also hundreds of simpler apartment complexes where common people lived. Million and Cowgill found evidence in distinctive potsherds that foreign merchants, from areas such as Veracruz on the Gulf of Mexico and the Valley of Oaxaca, lived in small enclaves, apart from the main community of Teotihuacán.

B

Aerial Survey Methods

Archaeologists rely on a wide variety of aerial survey methods, all of which are commonly referred to as remote sensing. Remote sensing involves using photography, radar, and other imaging technologies to detect potential sites. The technology was developed largely as a tool for military reconnaissance. During World War I (1914-1918) American military pilots took photographs from the air that revealed previously unknown archaeological sites in France and the Middle East. Archaeologists have used aerial survey techniques ever since.

Aerial photography is especially useful for detecting archaeological sites that are difficult to see from the ground. Aerial photographs reveal human-made geographical features such as earthworks; these giant earthen mounds were erected by prehistoric peoples in many parts of the world, including Britain and North America (Mound Builders). Aerial photos have also revealed entire Roman road systems in northern Africa that are almost invisible from the ground. Some sites appear in aerial photographs as distinctive marks running through agricultural fields and deserts. For instance, at Chaco Canyon, New Mexico, a combination of aerial photographs and other techniques revealed the full extent of an elaborate road system that led to the pueblos and sacred sites of the Anasazi people whose society centered on the canyon between about ad 850 and 1130. The Chaco road system was almost invisible on the ground without the help of air photographs. See also Chaco Culture National Historical Park.

Archaeologists also use other airborne technologies that record information about the earth’s surface and subsurface. Aerial photographs of infrared radiation can detect minute differences in ground temperatures. Using infrared photography, archaeologists identify soils that have been disturbed or manipulated in the past, as well as other ground features that are normally invisible. Infrared photographs and thermal scanners also detect the presence of subsurface stone and variations in soil moisture. Subsurface stone may indicate the presence of buried buildings, and soil moisture differences can reveal ancient crop fields.

Sideways-looking airborne radar (SLAR) is an advanced aerial technology that sends and receives pulses of radiation. These pulses are used to form a detailed picture of the terrain below and around an aircraft’s flight path. SLAR is commonly used for geological mapping and oil exploration; archaeologists find it useful for locating sites under the dense canopy of rain forests.

The excellent imaging capabilities of SLAR helped archaeologists solve the mystery of how the Classical Maya civilization supported its enormous population. This civilization dominated the Yucatán Peninsula region—primarily in what are now Mexico, Belize, and Guatemala—from about the 4th to the 10th century ad. SLAR revealed formerly invisible, gray, crisscrossed grids in the swampy lowlands of the Maya region. Subsequent ground surveys identified these grids as ancient moat-and-field systems, called chinampas, which Maya farmers used to grow large quantities of maize and other staple crops.

Archaeological sites have also been located from space. Imaging radar systems carried on U.S. space shuttle flights in 1981 and 1994 revealed ancient river valleys buried under the sands of the Sahara in northern Africa. American archaeologist C. Vance Haynes discovered 200,000-year-old stone axes in the subsurface deposits of one of these valleys. These tools provide evidence of human habitation in the Sahara when it was a fertile area with plenty of vegetation.

C

Ground Survey Methods

Much archaeological research still takes place on the ground. Most ground surveys involve long days of walking and looking for telltale signs of ancient human habitation. Various objects may remain on the surface for long periods of time. Archaeologists may find pot fragments or stone tools, light-colored ash from ancient fires, and piles of shells accumulated by people who ate shellfish. Other objects come up to the surface when previously built-up sediments are eroded by weather, or they may be brought up by burrowing animals.

The ruins of a few ancient Asian cities—including Jericho in the present-day West Bank, Nineveh in present-day Iraq, and Mohenjo-Daro in Pakistan’s Indus Valley—were easily visible above ground at the time of their discovery. Archaeological sites are usually inconspicuous, however.

When an archaeologist has reason to believe that there is something to be found in a particular area, systematic and patient searching sometimes pays rich dividends. British archaeologist Francis Pryor spent many months searching the banks of drainage canals in the flatlands of eastern England. In 1992 he finally found some waterlogged timbers at Flag Fen, a bog near the present-day city of Peterborough. These timbers were the remains of a submerged 3,000-year-old Bronze Age settlement and field system. The marshland preserved a long set of posts, the remainder of 50,000 such posts that held up a platform stretching for 1 km (0.6 mi). Beneath the platform Pryor’s excavation team found bones, plant materials, and bronze implements that the inhabitants had thrown into the shallow water, perhaps as religious offerings. Researchers also retrieved the oldest-known wheel in England from the marsh.

Ground-penetrating radar can detect objects and impressions left by decayed remains beneath the earth’s surface. It is a powerful tool for examining buried features at archaeological sites. For instance, in 1989 American archaeologist Payson Sheets used such radar to locate hut floors at the Maya village of Cerén, in what is now El Salvador. The village was buried under volcanic ash in the 6th century ad. Using computers, researchers created a three-dimensional map of the landscape as it appeared before it was buried.

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