At certain periods during the Pleistocene Epoch, the temperatures turned cold enough to freeze much of the earths water into ice. The sea level dropped as much as 90 m (300 ft) and the shallow Bering Strait between Alaska and Siberia became a natural land bridge on which grazing animals, and the humans who stalked them, passed. Most archaeologists and anthropologists believe that Native Americans descend from Asian peoples who moved into North America by way of this land bridge.
  Archaeology, scientific study of past human culture and behavior, from the origins of humans to the present. Archaeology studies past human behavior through the examination of material remains of previous human societies. These remains include the fossils (preserved bones) of humans, food remains, the ruins of buildings, and human artifactsitems such as tools, pottery, and jewelry. From their studies, archaeologists attempt to reconstruct past ways of life. Archaeology is an important field of anthropology, which is the broad study of human culture and biology. Archaeologists concentrate their studies on past societies and changes in those societies over extremely long periods of time.
  With its focus on the ancient past, archaeology somewhat resembles paleontology the study of fossils of long-extinct animals, such as dinosaurs. However, archaeology is distinct from paleontology and studies only past human life. Archaeology also examines many of the same topics explored by historians. But unlike historythe study of written records such as government archives, personal correspondence, and business documentsmost of the information gathered in archaeology comes from the study of objects lying on or under the ground.
  Archaeologists refer to the vast store of information about the human past as the archaeological record. The archeological record encompasses every area of the world that has ever been occupied by humans, as well as all of the material remains contained in those areas. Archaeologists study the archaeological record through field surveys and excavations and through the laboratory study of collected materials.
  Many of the objects left behind by past human societies are not present in the archaeological record because they have disintegrated over time. The material remains that still exist after hundreds, thousands, or millions of years have survived because of favorable preservation conditions in the soil or atmosphere. For the most part, the only things that survive are durable items such as potsherds (small fragments of pottery), tools or buildings of stone, bones, and teeth (which survive because they are covered with hard enamel). Because many items disintegrate over time, archaeologists get an incomplete view of the past that they must fill in with other kinds of information and educated reasoning. On rare occasions, however, delicate objects have been preserved. For example, fabrics and flowers were found in the celebrated tomb of Tutankhamun, an Egyptian pharaoh who was buried in 1323 BC.
  Archaeology became established as a formal discipline in the 19th and early 20th centuries. At that time, most archaeological work was confined to Europe, to the so-called cradle of civilization in southwestern Asia, and to a few areas of the Americas. Today, archaeologists study the great cultural diversity of humanity in every corner of the world.
  In 1987 and 1990 in Sipn, Peru, archaeologists discovered the tombs of royal lords of the ancient Moche culture. Buried in deep shafts beneath adobe pyramids, the lords were surrounded by goods indicating their wealth and status, including ceramics, masks, headdresses, and jewelry of gold and turquoise. The Moche civilization occupied the northern coastal region of Peru from about AD 100 to 800.
  THE SCOPE OF ARCHAEOLOGY  Archaeological study covers an extremely long span of time and a great variety of subjects. The earliest subjects of archaeological study date from the origins of humanity. These include fossil remains believed to be of human ancestors who lived 3.5 million to 4.5 million years ago. The earliest archaeological sites include those at Hadar, Ethiopia; Olduvai Gorge and Laetoli, Tanzania; East Turkana, Kenya; and elsewhere in East Africa. These sites contain evidence of the first appearance of bipedal (upright walking), apelike early humans. Laetoli even reveals footprints of humans from 3.6 million years ago. Some sites also contain evidence of the earliest use of simple tools. Archaeologists have also recorded how primitive forms of humans spread out of Africa into Asia about 1.8 million years ago, then into Europe about 900,000 years ago.
  The first physically modern humans, Homo sapiens sapiens, appeared in tropical Africa between 200,000 and 150,000 years agodates determined by molecular biologists and archaeologists working together. Dozens of archaeological sites throughout Asia and Europe show how people migrated from Africa and settled these two continents during the last Ice Age (100,000 to 15,000 years ago). Archaeological studies have also provided much information about the people who first arrived in the Americas over 12,000 years ago.
  Archaeologists have documented that the development of agriculture took place about 10,000 years ago. Early domesticationthe planting and harvesting of plants and the breeding and herding of animalsis evident in such places as the ancient settlement of Jericho in Jordan and in Tehuacn Valley in Mexico. Archaeology plays a major role in the study of early civilizations, such as those of the Sumerians of Mesopotamia, who built the city of Ur, and the ancient Egyptians, who are famous for the pyramids near the city of Giza and the royal sepulchers (tombs) of the Valley of the Kings at Thebes. Other sites that represent great human achievement are as varied as the cliff dwellings of the ancient Anasazi (a group of early Native Americans) at Mesa Verde, Colorado; the Inca city of Machu Picchu high in the Andes Mountains of Peru; and the mysterious, massive stone portrait heads of remote Easter Island in the Pacific.
  Archaeological research spans the entire development of phenomena that are unique to humans. For instance, archaeology tells the story of when people learned to bury their dead and developed beliefs in an afterlife. Sites containing signs of the first simple but purposeful burials in graves date to as early as 40,000 years ago in Europe and Southwest Asia. By the time people lived in civilizations, burials and funeral ceremonies had become extremely important and elaborate rituals. For example, the Moche lords of Sipn in coastal Peru were buried in about AD 400 in fine cotton dress and with exquisite ornaments of bead, gold, and silver. Few burials rival their lavish sepulchers. Being able to trace the development of such rituals over thousands of years has added to our understanding of the development of human intellect and spirit.
  Archaeology also examines more recent historical periods. Some archaeologists work with historians to study American colonial life, for example. They have learned such diverse information as how the earliest colonial settlers in Jamestown, Virginia, traded glass beads for food with native Algonquian peoples; how the lives of slaves on plantations reflected their roots in Africa; and how the first major cities in the United States developed. One research project involves the study of garbage in present-day cities across the United States. This garbage is the modern equivalent of the remains found in the archaeological record. In the future, archaeologists will continue to move into new realms of study.
  FIELDS OF ARCHAEOLOGY  Archaeology covers such an enormous span of time that archaeologists specialize in different time periods and different cultures. They also specialize in particular methods of study. Some archaeologists study human biological and cultural evolution up to the emergence of modern humans. Others focus on more recent periods of major cultural development, such as the rise of civilizations. Some study only the ancient or classical civilizations of the Middle East or Europe. Others research later historical subjects and time periods, using both written and archaeological evidence. Many archaeologists have expertise in other fields that are important to archaeological study, including physical anthropology (the study of human biology and anatomy), geology, ecology, and climatology (the science of weather patterns).
  The Chauvet cave paintings in southeastern France are some of the oldest and most spectacular examples of Ice Age art ever found. The red and black drawings and engravings depict a wide range of animals, from the more common horses and bison to the rarer lions and rhinoceroses. The paintings have been dated to between 20,000 and 30,000 years ago.
  Prehistoric Archaeology  Prehistoric archaeology is practiced by archaeologists known as prehistorians and deals with ancient cultures that did not have writing of any kind. Prehistory, a term coined by 19th-century French scholars, covers past human life from its origins up to the advent of written records. Historythat is, the human past documented in some form of writingbegan 5000 years ago in parts of southwestern Asia and as recently as the late 19th century AD in central Africa and parts of the Americas. Because there are no written records for prehistory, prehistorians rely entirely on material remains for evidence.
  British-Kenyan paleoanthropologist Louis Leakey examines the skull of the early human species Australopithecus boisei (originally known as Zinjanthropus boisei), right, next to the skull of a chimpanzee. British paleoanthropologist Mary Leakey, wife of Louis, discovered the 1.8-million-year-old skull in the Olduvai Gorge of northern Tanzania in July 1959. It was the first Australopithecus boisei skull ever found. The species earned the nickname "Nutcracker Man" because of its especially massive face, jaws, and molars.
  Discoveries of early human ancestors have changed the way many people think about what it means to be human. For instance, researchers working in southern Ethiopia and northern Kenya have found evidence that some human ancestors who lived about 2 million years ago were scavengers. They used stone tools to butcher game taken from the kills of predators such as lions. In 1978 at Laetoli, Tanzania, paleoanthropologist Mary Leakey discovered a fascinating early human site: sets of hominid footprints left in now-hardened volcanic ash. This find provides some of the strongest evidence that hominids walked upright as early as 3.6 million years ago.
  Some prehistorians specialize in studying various periods of the Stone Age. This period of human cultural development began about 2.5 million years ago, when humans learned to make simple stone tools. The Stone Age ended at different times in different parts of the world, roughly within the last 10,000 years.
  Important Stone Age archaeological sites include the 30,000-year-old rock paintings of the Grotte de Chauvet cave in southeastern France and Syrias 10,000-year-old Abu Hureyra farming village in the Euphrates Valley. By analyzing plant remains at Abu Hureyra in the 1970s and 1980s, British archaeologist and botanist Gordon Hillman showed that the inhabitants of this village were among the earliest people to cultivate wild cereal grasses, ones that evolved into what we know today as wheat and barley.
  These life-size terra-cotta figures are a small part of more than 6000 figures and horses that were made for the tomb of Emperor Shihuangdi of the Chinese Qin dynasty in 210 BC. They were originally painted in bright colors. The burial mound, in the northwestern province of Shanxi, was discovered in 1974.
  Archaeology of Early and Classical Civilizations  At their height, ancient civilizations centered on magnificent cities with large buildings and tombs. Some of these cities also had roads and human-made waterways. Archaeologists who study this period of the human past investigate how sufficient political and economic power developed to create and maintain early civilizations, and what factors led to the decline of such large and powerful societies.
  Located on the west bank of the Nile River on the outskirts of Cairo, the pyramids at Giza, Egypt, rank as some of the best-known monuments in the world. The ancient Egyptians constructed the pyramids to serve as royal tombs. Built without the use of cranes, pulleys, or lifting tackle, the massive structures stand as testaments to the engineering skills of their makers.
  Archaeologists who study ancient civilizations also often concentrate on particular regions. Egyptologists, for instance, study the civilization of ancient Egypt. Generations of Egyptologists have studied the numerous finds from the well-preserved tomb of the pharaoh Tutankhamun. This tomb is located in the Valley of the Kings at Thebes and was found by British archaeologist Howard Carter in 1922. Other archaeologists have recorded architectural details, paintings, and inscriptions from the many other tombs in the Valley of the Kings. These works are in danger of eroding in Egypts harsh desert environment. Egyptological research projects also study numerous other important sites along the Nile River valleyincluding the city of Memphis and the Old Kingdom mortuary complex of Gizaas well as north to the Mediterranean Sea, east to the Sinai Peninsula, and south into the Nubian Desert.
  This painted limestone bust of the ancient Egyptian queen Nefertiti dates from about 1350 BC (Staatliche Museen, Berlin). Wife of Akhenaton, Nefertiti supported and assisted her husband in implementing new religious ceremonies during the mid-14th century BC.
  Classical archaeology examines ancient Greek and Roman civilization. During the late 1800s German-born American archaeologist Heinrich Schliemann conducted expeditions in Greece and Turkey, near the coasts of the Aegean Sea. Schliemann first excavated in Hissarlik, Turkey, revealing what he claimed were several distinct periods of the great city of Troy, which is described in the Iliad, an epic tale by Homer. Schliemann also excavated in Mycenae, Greece, searching for the tomb of the Greek leader Agamemnon, who campaigned against Troy in the Trojan War. Schliemann conducted quick excavations, destroyed large portions of his sites, which earned him the suspicion and anger of the Turkish government.
  German archaeologist Heinrich Schliemann discovered remnants of ancient Aegean civilizations that lent historical evidence to ancient legends. In the early 1870s Schliemann excavated a site he believed to be Troy, near present-day Hissarlik in Turkey. He found objects made of gold, bronze, and silver, including the artifacts in this photo. Scientists later determined that these artifacts are some 1000 years older than the city described in Homers Iliad,.
  A French officer of Napoleons engineering corps found this stone near the city of Rashd (Rosetta), Egypt, in 1799. Known as the Rosetta Stone, it provided the key to the translation of ancient Egyptian hieroglyphs. The Rosetta Stone, inscribed in 196 BC, contains the same messagea decree praising the Egyptian King Ptolemy Vcarved in three different scripts: Egyptian hieroglyphs, Egyptian demotic, and Greek. Scholars deciphered the hieroglyphic and demotic versions by comparing them to the Greek translation.
  The ruins of the ancient city of Corinth have provided a rich treasure-trove of ancient artifacts, such as this ointment jar dated from 400 BC depicting the Goddess Aphrodite. With two excellent harbors, Corinth was one of the major commercial centers of ancient Greece.
  Many other archaeologists followed Schliemann, conducting more methodical and scientific excavations of lands surrounding the Aegean. Recent archaeology of the classic civilizations of Europe has concentrated on the lives of common citizens. American archaeologist David Soren, for example, led a research team in the 1980s in southwestern Cyprus. Soren and his team reconstructed the events of a powerful earthquake that struck the Roman port of Kourion in AD 365. Sorens team uncovered collapsed buildings in which entire families had been buried in their sleep.
  One of the best-preserved ruins of the Roman Empire, this aqueduct, named El Puente (Spanish for "The Bridge"), stretches from Spains Fro River to the city of Segovia. Built during the rule of Roman Emperor Trajan in the 1st century AD, the aqueduct runs both above and below the ground and stretches for a total of 16 km (10 mi). These two tiers of arches, at the center of an aboveground portion of the aqueduct, reach a height of 28.5 m (93.5 ft).
  Although much is known about life in colonial Williamsburg, Virginia, from the writings of the city's residents and visitors, excavations have provided additional information. In this photo, archaeologists excavate an 18th-century tavern found beneath a Williamsburg house.
  Historical Archaeology  Historical archaeology examines past cultures that used some form of writing. Although writing was invented thousands of years ago in some parts of the world, many historical archaeologists study only the past few hundred years. Historical archaeologists use written documents as part of their research, and they may work in collaboration with historians. This kind of archaeology first developed in North America and England. It continues to thrive in both of those places but is also practiced in many other parts of the world. Historical archaeologists have studied a wide variety of subjects, such as relations among settlers and Native Americans in colonial North America, Spanish religious missions in the southern United States, medieval villages in England, and early factories of the Industrial Revolution in Europe and North America.
  Underwater archaeology is a growing field. Underwater surveys and excavations of sunken ships and their cargo provide a wealth of information about ancient systems of trade. Sunken artifacts are often well preserved, protected by layers of silt in a stable environment of salt or fresh water.
  Underwater Archaeology  Underwater archaeology uses special methods to study shipwrecks and other archaeological sites that lie beneath water. Archaeologists who work under water rely on sophisticated diving and excavating equipment and employ special techniques to preserve perishable materials that have been submerged for long periods. In an extensive underwater archaeological project from 1983 to 1994, a team led by American archaeologist George Bass and Turkish archaeologist Cemal Pulak recovered the cargo of a heavily laden Bronze Age ship at Uluburun, off the southern coast of Turkey. The ship, which was wrecked in a storm around 131O BC, carried enough copper and tin ingots to forge weapons for a military regiment of several hundred people.
  Among the earliest inhabitants of the southwestern United States, the Anasazi flourished in parts of New Mexico during the 1st millennium AD. Marvelous multistoried homes built by the Anasazi serve as reminders of their fascinating culture and architectural skills. The homes shown here are at the Bandelier National Monument near Los Alamos.
  Other Fields Some archaeologists learn skills from other disciplines to form specialized fields of study. For instance, experts in zooarchaeology study animal bones found in and around human habitations, from which much can be learned about human subsistence methods. Archaeologists who specialize in paleoethnobotany study the plants used by ancient people for food, medicine, and other purposes. Some archaeologists also have expertise in such subjects as radiocarbon dating methods or the techniques used in ancient metallurgy (the making of metals from mineral ores).
  Another archaeological specialty, geoarchaeology, determines what ancient environments and landscapes were like. Geoarchaeologists use many sources of information and specialized techniques to learn about environmental conditions of the past. For example, they learn about past global and regional temperature changes by examining changes in the composition of the air, water, and sediments in large cores of the earth taken from the deep-sea bottom or the polar ice caps.
  Some geoarchaeologists also have expertise in zooarchaeology or paleoethnobotany. They may use this expertise to examine millions of tiny fossil pollen grains preserved in old layers of sediment. By noting the differences in the fossils, geoarchaeologists can chart how the earths vegetation changed over time.
  The bones of some animals, including rodents and many invertebrates, can also provide clues about ancient climates. For example, in the 1950s and 1960s American archaeologist Hallam Movius gathered such data from the Abri Pataud rockshelter of the late Ice Age in the Dordogne Valley of southwestern France. His research showed how hunter-gatherer bands living there 18,000 years ago adapted to constantly changing climatic conditions, which alternated between bitter cold and warmer periods.
  Archaeologists working with botanists have also learned about prolonged drought cycles that affected the Anasazi Pueblo peoples of the North American Southwest. Because of the effects of such drought cycles on food production, these peoples abandoned large towns and dispersed into small villages about 700 years ago. Since the 1960s, American tree-ring expert Jeffrey Dean has examined wooden beams from ancient pueblos (dense villages of adobe and stone houses). Dean has used dendochronology (the study of annual growth ring sequences in tree trunks) to determine when droughts occurred and how long they lasted.
  THE GOALS OF ARCHAEOLOGY  Modern archaeological studies have three major goals: (1) chronology, (2) reconstruction, and (3) explanation. Chronologies establish the age of excavated materials. Reconstructions are models of what past human campsites, settlements, or citiesand their environmentsmight have looked like, and how they might have functioned. Explanations are scientific theories about what people living in the past thought and did.
  Chronology  Archaeologists carefully record their excavations in a way that allows them to piece together culture historieschronologies (time perspectives)of past cultures. Excavations reveal the order in which remains were deposited, while laboratory analyses can give the actual age of remains. Archaeologists also document how each artifact or fossil lies in the ground in relation to other artifacts or fossils. This task involves careful recording of geological and artifact layers, or strata.
  Chronological data can provide information such as how the use of a new style of pottery or type of weapon spread from one region to another over time. By analyzing this information for several related archaeological sites, archaeologists assemble long sequences of past human cultures.
  For example, in the 1920s American archaeologist Alfred Kidder created a culture history at Pecos Pueblo, near Santa Fe, New Mexico. Kidder excavated human occupations at the pueblo going back more than 2000 years. (Occupations are clearly defined layers of artifacts and fossils created by people who lived at a site.) He also collected pottery passed down through many generations of pueblo inhabitants. From these collected items, he was able to establish a continuous record of pottery styles from 2000 years ago to the 1920s. Kidder then analyzed trends and changes in pottery styles through time. He associated each stylistic change in pottery with a change in the peoples culture, just as people today associate changes in clothing styles, for example, with changes in the culture. Archaeologists have since used the Pecos pottery sequence to assign approximate dates to dozens of sites throughout the Southwest and to determine cultural ties and differences among them.
  By perhaps 5000 BC the indigenous peoples of southern Mexico first domesticated a wild variety of corn. The earliest corn plants bore only a few kernels on each stalk. By selectively breeding these plants over thousands of years, Native Americans developed a variety of types of domesticated corn, or maize, which bore large cobs holding hundreds of kernels. This illustration shows several varieties of maize.
  Reconstruction  Building on information about the chronology and composition of sites and their environments, archaeologists reconstruct how life might have looked in particular places at particular times. The reconstruction of past ways of life depends on interpretation of well-documented material remains and environmental remains in their chronological contexts. Environmental remains may include animal body partssuch as bones, skins, and feathersas well as parts of plants, such as seeds, pollens, and spores.
  In the 1960s American archaeologist Richard MacNeish and a group of archaeologists and scientists from other fields reconstructed the subsistence patterns (ways of obtaining and producing food) of people who once lived in Mexicos Tehuacn Valley. In the 1980s teams of later researchers refined MacNeishs reconstructions. These researchers analyzed the chemical composition of materials from MacNeishs studies and newly collected samples, including human bones and plant and animal remains found near those bones. The analyses revealed a shift in subsistence patterns over a 9000-year period. During this time, the inhabitants of the valley shifted from a pattern of seasonal migration and a diet of wild plants and game animals to a more stable pattern of settlement and a diet based on cultivated maize (corn), beans, and squash.
  In another classic study of an archaeological site in its ecological setting, British archaeologist Grahame Clark excavated a tiny Stone Age hunting site in 1949. The site at Star Carr in northeastern England dated as far back as 10,700 years ago. By analyzing animal bones and tiny pollen grains, Clark determined that the site was at one time set amid reeds at the edge of a glacial lake and had been surrounded by a dense birch forest. The site yielded a wide variety of tools made of stone, bone, and antler. In the 1980s and 1990s archaeologists have returned to the site with more refined methods of analysis. They have been able to reconstruct the details of a yearly springtime habitation of the site over many centuries.
  Explanation  Archaeologists commonly use theoretical models, experiments, and observations of the world as it is today to try to explain what happened in the past. They have attempted to explain, for example, why people first began to walk upright and why civilizations that once flourished suddenly collapsed. Good explanations come from well-thought-out theoretical models that propose ways in which the existing archaeological record might have been formed. Explanations can include factors such as environmental changes, demographic shifts (changes in population makeup and size), migrations, and patterns of thought and behavior. Whereas reconstructions use physical remains to create a picture of the past, explanations are attempts to answer questions about the past. For instance, the reconstruction of changes in settlement and subsistence patterns of the inhabitants of the Tehuacn Valley does not explain why these changes took place. They might be explained by any one factor or a combination of factors, such as a dramatic change in weather patterns, an increase in the population, or a conscious decision to take advantage of a new discoveryagriculture. To be persuasive, an explanation has to fit with the existing archaeological data and stand up to scrutiny over time.
  Australian Aborigines have made mysterious and beautiful rock paintings for tens of thousands of years. This prehistoric rock painting from Alice Springs in the Northern Territory depicts a large serpent and precisely drawn geometric shapes on a background of red ochre, a natural pigment. The meaning of such symbols from the past is not entirely clear, but Aborigines continue to make rock paintings today with similar themes.
  GAINING INSIGHTS ON THE PAST  It would be extremely difficult for archaeologists to interpret the archaeological record if they thought that people and cultures of the past bore no resemblance to those of today. Because they assume that there has been some continuity through time, archaeologists commonly use information from the present to interpret the past. One way they accomplish this is by doing archaeological research on present-day societiesstudying the ways in which people live today and the material traces that their activities leave behind. This method is known as ethnoarchaeology. Archaeologists also try to experimentally recreate the patterns they find in their researcha technique known as experimental archaeology. Successful recreations can become plausible explanations for how the archaeological record was formed.
  An assortment of prehistoric tools provides evidence of the hunting and gathering methods of early peoples. Slabs of bark were often used to gather nuts and berries and functioned as crude dishes or bowls (top left). Reproductions of fishing tackle and arrows believed to have been used around 8000 BC are displayed on the lower left. Recovered tools for digging and cutting (right) are shown with recreated wooden handles. The heads of the adzes are made from flint, as is the fire-starter shown below them.
  Clues from the Present  Artifact and fossil evidence reveals that humans lived by hunting and gathering until relatively recently in human evolution. Archaeologists have tried to understand this way of life by studying living groups of hunter-gatherers, including the Aborigines of Australia, Inuit and other Eskimo peoples of the Arctic, and the San people of Botswanas Kalahari Desert. Through ethnoarchaeology, archaeologists cautiously deduce characteristics of past cultures based on their observations of living peoples. Archaeologists believe that present-day hunter-gatherers and people who lived throughout much of prehistory share some aspects of their ways of life.
  To document the lives of living peoples, archaeologists do a brief type of ethnographic research, the method of study usually practiced by cultural anthropologists. In this method, the archaeologists spend time among the people they are studying, keeping detailed records of the peoples daily activities and behaviors. They also make precise records of the peoples abandoned campsites and settlements, including discarded food remains and artifacts, to compare with patterns they see in archaeological sites. Ethnoarchaeological research can provide valuable clues for deciphering accumulations of artifacts and other remains found in archaeological sites, particularly accumulations that resulted from such activities as toolmaking or animal butchering.
  In an ethnoarchaeological study made from 1969 to 1973, American archaeologist Lewis Binford documented the caribou hunting methods of the Nunamiut Eskimo of Alaska. He followed the hunters, studied their butchering techniques, and mapped their kill and butchering sites. Binford collected information that proved extremely useful in interpreting distributions of animal bones in other archaeological sites.

Archaeological research indicates that early species of the genus Homo may have been the first human ancestors to eat meat on a regular basis. In the lower foreground of this artist's rendering, a mother and child share meat from an animal carcass. Rather than hunting prey themselves, these early humans often may have scavenged the kills of predatory animals, using simple stone tools to cut up carcasses.
  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.
  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.
  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 diggingsuch as various kinds of radar, magnetic sensors, and soil electric-resistance detectorscan keep actual excavation to a minimum.
  In 1947 Juma, a shepherd of the Taamireh tribe of the nomadic Bedouins, discovered ancient scrolls rolled up in leather and cloth in a cave to the northwest of the Dead Sea in the Qumrn Valley. A remarkable archaeological find, the scrolls formed the first part of a collection of Hebrew and Aramaic manuscripts that were discovered in quick succession after Jumas original find. These ancient texts, which include the Book of Isaiah in its entirety and fragments from all other books of the Old Testament except for the Book of Esther, turned out to be more than 1000 years older than any other known Hebrew texts.
  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.
  Little was known of the early Minoan civilization of Crete until British archaeologist Sir Arthur Evans began a series of excavations in 1894. Skilled in such fields as engineering and architecture, the Minoans constructed the palace at Knossos, shown here, in about 1700 BC.
  Some archaeological sites have always been easily observablefor 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.
  The Temple of the Sun at Teotihuacn, Mexico, was built between AD 50 and 200. The pyramidal structure is made of layers of clay faced with stone, and it stands about 61m (200 ft) high. Flights of stairs lead to the top, where a temple to the sun god Uitzilopochtli originally stood. The site is aligned with the rising and setting of the sun on the summer solstice.
  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. Evanss interpretations of these engravings eventually led him to find the Minoan palace at Knossos (Knoss), 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 Copn, 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 Copn collapsed. Archaeologists believe the people of Copn may have overfarmed the surrounding land, depleting their primary food supply and forcing them into the countryside in search of fertile land.
  American archaeologists Ren Million and George Cowgill spent years systematically mapping the entire city of Teotihuacn 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 citys 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 Teotihuacn.
  This radar image was taken over Cambodia in 1994 by the space shuttle Endeavor from its orbit around earth. It shows the 12th-century Angkor Wat, the largest temple complex in the world. It covers an area of roughly 81 hectares (about 200 acres).
  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.
  Archaeologists also use other airborne technologies that record information about the earths 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 aircrafts flight path. SLAR is commonly used for geological mapping and oil exploration; archaeologists find it useful for locating sites under the dense canopy of rainforests.
  The Watson Brake mound complex in northeast Louisiana consists of 11 earthen mounds connected by lower ridges. Archaeologists reported in September 1997 that these human-made structures are more than 5000 years old, making them the oldest large-scale earthworks in the Americas.
  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 Yucatn Peninsula regionprimarily in what are now Mexico, Belize, and Guatemalafrom 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.
  The ancient city of Nineveh was first settled in Neolithic times, before 6000 BC. The city, which is located in northern Iraq opposite the modern city of Mosul, was once the capital of the Assyrian empire. All that remains of Nineveh are two large mounds and the remains of the city walls. Shown here is a depiction of the royal palace of Assyrian king Sargon II that once stood in the city.
  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 the ancient city Mohenjo-Daro are found in the province of Sind, southern Pakistan. Dating to 2500 BC, the ruins are an important source of information about the Indus Valley civilization, which was one of the worlds first great civilizations.
  The ruins of a few ancient Asian citiesincluding Jericho in present-day Jordan, Nineveh in present-day Iraq, and Mohenjo-Daro in Pakistans Indus Valleywere 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 3000-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 Pryors 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 earths 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 Cern, 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.
  Computer-Aided Mapping In recent years, many archaeologists have begun to use geographic information systems (GIS) to aid in mapping sites. These computer-based systems allow the collection, storage, and manipulation of environmental, geographic, and geologic data, together with archaeological information, in a single database. Using this technology, archaeologists can create maps that simulate different environments and ways in which people might have used land, living space, and material goods.
  Italian archaeologists have used GIS technology to interpret life in the Roman city of Pompeii, which was buried by an eruption of Mount Vesuvius in AD 79. Researchers mapped thousands of computerized pictures of artifacts directly over floor plans of individual houses, matching specific artifacts to the exact locations where they were recovered. Using a database of artifacts, locations, and other information, archaeologists can quickly study a wide variety of interconnected topics about Pompeii, from relationships between peoples wealth and their lifestyles to differences among wall paintings from one dwelling to another.
  ARCHAEOLOGICAL EXCAVATION Many 19th-century archaeological excavations proceeded unscientifically. Archaeologists commonly rushed through disorderly searches for spectacular art works and buried treasure. During the 20th century, archaeologists developed precise, detailed methods of excavation and statistical sampling (mathematical ways of answering questions using relatively small amounts of data). Archaeologists today can often obtain more information from a small trench than they could recover from a large dig a generation ago.
  Celtic objects found in archaeological digs indicate the Celts inhabited what is now France and western Germany in the late Bronze Age, around 1200 BC. The bronze helmet (top center) probably belonged to a high-ranking Celtic warrior. Its hollow horns were made of riveted sheets of bronze, and the helmet was probably more for display than battle. The shiny sheath (third from left) also was made from sheets of bronze riveted together and had a birch-bark lining.
  Developing Research Questions Archaeologists decide where and how much to dig based, in part, on what questions they want to answer; they must also determine the best ways to answer these questions. They must decide, for instance, how much and what types of statistical sampling to use. These choices, as well as time and money limitations, affect archaeologists excavation plans. In addition, archaeologists attempt to limit excavations to leave intact as much of the archaeological record as possible. A dig should answer planned research questions while disturbing the archaeological record as little as possible.
  Between 1969 and 1988 British archaeologist Barry Cunliffe investigated a 2000-year-old Iron Age Celtic fort built on a hill (for defensive purposes) at Danebury in southern England. Cunliffe conducted minimal and careful stratigraphic examination of the hill, observing the layers of earth and the objects contained within the earth. From this information he developed a chronology of the site, establishing what happened there through time. He then conducted a few larger excavations of open areas in the interior of the fort to study the crowded settlement that flourished there. By keeping to his carefully formulated research strategy, Cunliffe left large areas of the site undisturbed for later generations to investigate.
  Minimizing the Size of a Dig Because of the high costs of excavation and concerns about conserving the archaeological record, most archaeologists today work on small projects in relatively short periods of time. Only rarely do modern-day excavations cover large amounts of land and last many years, as did some earlier digs.
  In the early years of scientific archaeology, grand excavations of important sites gave prestige to the archaeologists and institutions that conducted them. British archaeologist Sir Leonard Woolleys excavation from 1922 to 1934 of the Sumerian city of Ur, in present-day Iraq, typified these expansive and highly publicized digs. Woolley employed hundreds of workers, unearthed entire quarters of the city, and probed to the bottom of the city mound (the accumulation of many generations of inhabitants), the level at which a small farming village had flourished in about 4700 BC. He also excavated a spectacular royal burial site where a buried prince lay entombed. The prince was surrounded by the members of his court, all of whom were executed for the burial.
  In contrast, modern excavations can reveal significant amounts of information with a minimum of digging by a small team of people. For instance, in the 1970s and 1980s, American archaeologists Fred Wendorf and Angela Close excavated a series of tiny foraging camps by the Nile River in Egypt. These camps were occupied between about 16,000 and 15,000 BC. The researchers used a combination of wide but shallow excavations and small, narrow test pits to sample the densest concentrations of artifacts, fragments of animal and fish bones, and the remains of hearths. These small-scale excavations allowed the researchers to gain good insights into how foragers lived along the Nile at the end of the last Ice Age.
  The Maya, a Native American people of Mexico and the northern part of Central America, produced intricate relief carvings (sculpture in which the figures project from a background surface), such as this piece from the late classical period of Maya civilization (7th to 9th century). The relief art either adorned buildings or stood alone as stelae (inscribed stone slabs and pillars). Maya sculpture frequently depicted rulers and gave dates and other information about these rulers. Sculpture and other art forms were also used to record important events and to portray deities and their activities.
 
