At www.telegraphindia.com?100406/jsp/others/print.html The Telegraph of India says a study of 100s of Indus Valley civilisation towns and cities have revealed factors previously unsuspected – growth and decline does not show a gradual eastward expansion (from Baluchistan outwards). The study instead showed three epicentres of the civilisation, i) Baluchistan ii) Gujarat, and iii) an ancient channel of the Indus that dried up, located in Haryana and the Punjab. In other words, they are contradicting the idea that farming and urban societies was driven by ‘a wave of advance’ moving from Baluchistan towards the Ganges flood plain – and they also say the civilisation did not collapse suddenly. The site of Mehrgarh in Baluchistan dates back to 7000BC and has the earliest evidence of wheat and barley. However, rice cultivation, at around the same point in time, was introduced from SE Asia. The Indus Valley was densely populated in the 3rd millennium BC, and C14 dates appear to locate it’s most thriving period of settlement between 2500-1900BC – described as a phase of mature culture and high stability. It is not known what kind of political organisation contributed to this uniformity – in the design of seals, use of scrip, and weights and measures etc. There was however a catastrophic reduction in the number of sites along the river around 1900BC – which as been attributed by some commentators to tectonic activity. The decline in Baluchistan and Gujarat occurred differently and much more slowly and it seems that sites in the Ganges Plain directly succeeded those in the Indus Valley.
Note … the shelf life 2500-1900BC is presumably derived from C14 dating methodology but in Mesopotamia at the same time it was far from stable – does this imply the dates require adjustment?