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.
The earliest archaeological sites include those at Hadar, Ethiopia; Olduvai Gorge and Laetoli, Tanzania; East Turkana, Kenya; and elsewhere in East Africa.
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 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.
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.Laetoli even reveals footprints of humans from 3.6 million years ago.