What marks the change from prehistory to  history?

The beginning of writing marks the end of prehistory and the beginning of history. This extraordinary human milestone is thought to have taken place in Sumer and Egypt about 5500 years ago, around 3500 BC. The Sumerians and Egyptians had to keep track of the number of crops and animals they grew because they became more settled and needed a more complex social structure. As technology improved, they also had to keep track of a larger number of crops and animals.  Writing is one of the most extraordinary creations of mankind.