Archaeologists use various methods for finding out how old various settlements are. Marshall concluded that the Harappa civilization was about 5000 years old and not 1000 years as believed by Cunningham. According to Marshall the seal, sealing, written script and works of art found in Harappa were totally different from those with which scholars were already familiar and which belonged to a much later period.
Similar finds were reported in another place called Mohenjo-Daro in Sind. In Mohenjo-Daro the settlement lay underneath a Buddhist monastery belonging to the Kushan period. It has been found that in ancient times if a house were destroyed for some reason people would generally use the brick or mud of the house to prepare a plinth and make another house on top of it. Thus if an archaeologist excavates an area and find remains of a house beneath another house he can figure out that the one below is older than the one above. Marshall could find out that the houses below the Buddhist monastery must be older than the Kushan period. Then, there was the evidence that people living in these settlements did not know the use of iron. This meant that these cities were part of an age when iron was unknown. Iron came in use in the beginning of the second millennium BC.
When these discoveries were going on some archaeologists’ found objects similar to those of Harappa and Mohenjo-Daro in Mesopotamia. Mesopotamian ties came into existence in the early 3rd millennium BC.It indicated that the people in Harappa lived at the same time. With these evidences scholars could figure out that the conclusions of the local population and Cunningham were incorrect. Marshall’s chronology of Harappa has been further supported by methods such as carbon dating etc.
The earliest evidence for the emergence of agricultural communities comes from a place called Mehrgarh near the Bolan Pass in the Baluchistan province of Pakistan between 5500 BC and 3500 BC. The place turned into settled village by 5th millennium BC.People were growing wheat, barley, cotton etc. and tending sheep, goat and cattle. People of Mehrgarh lived in mud houses with 5-6 rooms. By the middle of the 3rd millennium BC many small and large villages had sprung up around Indus, Baluchistan and Afghanistan area. The better-known settlements among them are Kili Ghul Mohammad in Baluchistan and Mundigak in Afghanistan. In the Indus flood plains villages like Jalilpur near Harappa had come into existence. Once the agriculturists learnt to exploit the Indus plains and the to control the flooding of the Indus there was a sudden expansion in the size and number of villages. They also managed to exploit stone quarries and mines useful to them. There are indications of the existence of pastoral nomadic communities in form of seasonal settlements. The interactions with these groups seem to have helped agriculturists exploit resources from other regions .All this led to the development of small towns. The period of this new development is called the early Harappan because of certain uniformities found all over the Indus.
Between 3500 BC and 2600 BC many more settlements were established. Use of copper, wheel and plough began. Extraordinary range of pottery showing the beginning of many regional traditions emerged. Evidences of granary, defensive walls and long distance trade emerged. Emergence of uniformities in the pottery tradition through out the Indus valley. Also emerged the motifs such as pipal, humped bulls, snake, horns etc. in the seals.
The period between 2600 BC and 1900 BC saw emergence of large cities, bricks, weights, beads, and pottery. The period also saw planned township and long distance trade. The mature phase of the Harappan civilization lasted from 2300 BCE to 1900 BCE.1900 BC onwards many Harappan sites were abandoned. Interregional exchange declined. The village cultures of Punjab-Sutlej Yamuna and Gujarat imbibe the Harappan crafts and pottery traditions.
The early Harappan, Mature Harappan and Late Harappan phases are also called the regionalization, Integration and localization respectively with the regionalization era reaching back to the Neolithic Mehrgarh II period. Discoveries at Mehrgarh changed the entire concept of the Indus Civilization.