Archeology, study of the past through identification and interpretation of the material remains of human cultures. Archeology uses the knowledge and techniques of such disciplines as anthropology, history, paleography, and philology. Its keystone is fieldwork. Archeology began in the early 18th century with excavations of Roman and other sites. The famous Rosetta Stone, which provided the key to Egyptian hieroglyphics, was discovered in 1799 and deciphered in 1818. In the 19th century archeology became a systematized science through the work of Heinrich Schliemann, Arthur Evans, C. L. Woolley, Howard Carter, and others. In the United States archeologists have studied the culture of early Native Americans as well as settlements of colonial America—an example of historic archeology, which deals with peoples who left behind written documents.
Suitable sites may be revealed as a result of war damage or during construction of buildings and roads. Because unusually shaped hills or mounds are sometimes artificial, they are often investigated. Ancient writings may help in locating sites. Aerial photography has sometimes revealed the existence of buried structures. The archeological team then recovers objects or fragments lying loose on the ground or inside caves, or, more often, excavates (digs) to find the artifacts. Great care is required not to damage any object or trace of an object. Small hoes, spades, trowels, penknives, brushes, and fingers are used. Archeologists record the spatial relationships artifacts have to one another and to the layers in which they are found. Notes and drawings are made, each item is numbered, and photographs are taken.
Archeologists use 2 dating systems: absolute dating and relative dating. Early inscriptions, and especially, mention of an eclipse or other astronomical phenomena, make it easy to date a monument or site. Tree-ring chronology can help date wood remains. Pollen, an extraordinarily durable organic substance, is also a useful date indicator. Radiocarbon dating uses the known half-life of radioactive carbon-14, found in all organic matter, as a yardstick. Stratigraphy, the most important method for relative dating, uses the principle that objects found near the surface are more recent than those found lower within the ground. Because pottery styles sometimes overlap on several sites, information gained from one site can be applied to another. Chemical changes in bones can also help differentiate younger ones from older ones.