How you define ancient history may not be the same as the way it is defined for the purposes of this site.
For the purposes of this Ancient / Classical History site, ancient history begins with the earliest writing and ends with the end of the Roman Empire.
Because the Fall of the Roman Empire is unclear, for the purposes of this site, it is the point Gibbon chose, 476 A.D., when the Western Roman Empire fell to Odoacer. During this time period, civilizations with writing arose in Mesopotamia, which is the land between the Tigris and Euphrates Rivers, in China, in the Indian Subcontinent, in Egypt, and around the Mediterranean -- most notably, Greece and Rome.
Occasionally, Byzantine history and some events in early British history are included, although those are more properly the domain of the Medieval History site. Writing is taken as the starting point because artifacts can more properly be appreciated by the archaeologists of the Archaeology site at About.com.
Please note, we know very little about the ancient world. Most of the writing has been lost. Dating is imprecise and subject to revision when evidence proves existing theories wrong.