The Prehistory reference article from the English Wikipedia on 24-Jul-2004
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Prehistory

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Prehistory is the period of human history prior to the advent of writing, which marks the beginning of recorded history. More precisely, prehistory is the period from which no known written records (including later copies) have been preserved. In Egypt, prehistory would end around 3500 BC. In New Guinea, prehistory would end around 1900. Still earlier periods of time are usually known as geological history.

When did prehistory begin? People disagree. Some would begin it with the first known tools, c. 2.5 million years ago (Olduway). The first Homo erectus, around 1.5 million years ago is another possibility. Others would begin it around 40,000 BC, with the Cro-Magnons. If however, human prehistory is defined, as presumably it should be if we are talking of the prehistory of man, as the pre-literate history of Homo sapiens sapiens then at least the matter can be resolved in principle, and the recent pace of progress in understanding the evolution of Homo sapiens suggests the answer will not be long in coming. Current best estimates are in the range of 100,000 to 200,000 years ago.

Prehistory is often subdivided by a three-age system: