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.
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.
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.
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.
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.
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.
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.