How did the climate of the Indus River Valley change, between 6000 BCE and 2500 BCE?

The time before the development of writing is known as Prehistory. Humans developed stone tools about 2,000,000 years ago, beginning what is known as the Stone Age. The Stone Age can be divided into two basic periods: the Paleolithic era, or Old Stone Age, and the Neolithic era, or New Stone Age