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| c. Time and Space |
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| Archaeologists date the past and study the ever-changing distributions of ancient cultures across the world by studying the context of archaeological finds, whether sites, food remains, or artifacts, in time and space. This is the study of culture history, the description of human cultures as they extend back thousands of years. | 1 |
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| 1. Time |
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| Human prehistory has a time scale of more than 2.5 million years and a vast landscape of archaeological sites that were occupied for long and short periods of time. Some, like the Aztec capital, Tenochtitlán, in the Valley of Mexico, were occupied for a few centuries. Others, like Olduvai Gorge in East Africa, were visited repeatedly over hundreds of thousands of years. The chronology of prehistory is made up from thousands of careful excavations and many types of dating tests. These have created hundreds of local sequences of prehistoric cultures and archaeological sites throughout the world. | 2 |
| Historical records provide a chronology for about 5,000 years of human history in Egypt and Mesopotamia, less time in other regions. For earlier times, archaeologists rely on both relative and absolute dating methods to develop chronological sequences. | 3 |
| Relative dating is based on a fundamental principle of stratigraphic geology, the Law of Superposition, which states that underlying levels are earlier than those that cover them. Thus any object found in a lower level is from an earlier time than any from upper layers. Manufactured artifacts are the fundamental data that archaeologists use to study human behavior. These artifacts have changed in radical ways with passing time. One has only to look at the simple stone choppers and flakes made by the first humans and compare them with the latest luxury automobile to get the point. By combining the study of changes in artifact forms with observations of their contexts in stratified layers in archaeological sites, the prehistorian can develop relative chronologies for artifacts, sites, and cultures in any part of the world. | 4 |
| The story of prehistory has unfolded against a backdrop of massive world climatic change during the Great Ice Age (See Prehistory and the Great Ice Age). Sometimes, when human artifacts come to light in geological strata dating to the Ice Age, one can place them in a much broader geological context. But in such cases, as with relative chronologies from other archaeological sites, determining the actual date of these sites and artifacts in years is a matter of guesswork, or of applying absolute dating methods. | 5 |
| Absolute chronology is the process of dating in calendar years. A whole battery of chronological methods have been developed to date human prehistory, some of them frankly experimental, others well established and widely used. The following are the best known ones. | 6 |
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| a. Historical Records and Objects of Known Age |
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| Historical documents can sometimes be used to date events, such as the death of an ancient Egyptian pharaoh or the Spanish conquest of Mexico in 1519–21 C.E. Clay tablet records in Mesopotamia and ancient Egyptian papyri provide dates going back to about 3000 B.C.E. The early Near Eastern civilizations traded many of their wares, such as pottery or coins with precise dates, over long distances. These objects can be used to date sites in, say, temperate Europe, far from literate civilization at the time. | 7 |
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