Answer:
Prehistory was as long as about five hundred million years ago and ended when humans invented writing about 600 thousand years ago. Usually prehistory refers to anything which is before 3200BC.
Step-by-step explanation:
Prehistory is defined as the period in which humans did not know how to write. It ended when the humans were capable enough to write.
Prehistory is divided into three stages; Paleolithic stage, Neolithic stage, and metal age.
Prehistory usually refers to anything which was pre-human race. Every stage has its own significance where humans learnt something that revolutionized their existence.