4000-1900 BCE: Indus valley civilisation (IVC) - the beginning of a new era

6000-7000 BCE: Agriculturalists from Zagros region of today’s Iran (eastern extent of the then Mesopotamian civilization) likely mixes with South Asian Hunter Gatherers in North Western India. They start and grow agricultural practices and further domestication of wild animals. 

We know what they grew. What did they speak ? Probably one of the languages could have been proto-Elamite family of languages including proto- Acadian (These languages has some linkages to present day Dravidian languages of India especially Tamil). 

Elamite was Zagros urban civilization originating around 2500 BC. Indus valley civilisation would latter export Sesame to Mesopotamia / Zagros – Acadian (proto Elamite language) and Dravidian language have same word for Sesame, Ellu.

4000-3000 BCE

They push further ahead on agriculture and trade with Mesopotamia. The surpluses thus generated helps lay the foundation for one of the greatest, most well structured and sophisticated societies of its time by around 4000 BC - the Indus Valley civilization (IVC)  -thus named after the river Indus around which many of its settlements are found. The alluvial, fertile soil of Indus valley helps create huge agri surpluses, leading to establishment of major urban centres like Harappa (Indus upstream) and Mohenjo Daro (lower Indus) by 2900-3000 BC. 

 Similar to other neolithic civilization (Egyptian around river Nile, Mesopotamian around Tigris-Euphrates) originated and grew around a semi arid region - which meant no iron tools were needed to cut dense trees to build their cities while at the same time the river helped in irrigation and fertilizing the plains. 

3000-1900 BCE

Indus valley civilisation peaks around 2900-1900 BC. They establish trade routes with Egypt and Mesopotamian region (the region between the rivers Tigris and Euphrates in current Iraq). They had well established, well planned urban centres, underground draining systems, houses with wells and bathrooms. They grew wheat and barley, had dogs, cats, sheep/goat, fowls as pets. 

At its peak, IVC was home to 4-5 Million people - by far the largest civilization of its time (more than sum of Egypt and Mesopotamia) and in size comparable to one-third of today's India. This would easily be more than one-forth of the total global population which was around 15-25 Mn at this time. They had time for art and sculpture. Had complex writing that is still undecipherable.