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Zab basin is in the south part of Urmia Lake. The little Zab River in northwestern Iran rises at the Piranshehr mountains and flows from the northwest to the southeast to join Iraq through Alan passage. The river basin contains many ancient settlements. Based on pot sherds it can be inferred that this basin has been a residential zone since the prehistoric period. A noteworthy feature of this basin is the presence of Uruk pottery, including the beveled-rim bowl, at 5 sites in Zab basin. This pottery has not been seen either in the northwest of Iran or in the higher regions of Hamadan. For the first time this material is identified in the Little Zab basin. This pottery belongs to the late Uruk period, i.e. late fourth millennium BC. Geographical position and settlement patterns could be signs of commercial and cultural relations between societies of Northwestern Iran and northern Mesopotamia in late Chalcolithic.
 

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According to the studies conducted by western archaeologists in a number of plains in Iran such as Doroodzan and Shahabad Plains, they have estimated population of the nuclear villages in the above plains between 100 and 150 people per hectare. This estimation is mostly related to large sedimentary plains with agricultural and animal husbandry livelihood. It seems, the condition in highland is different with those villages in lowlands due to differences in their lifestyle.  Accordingly, Laran County, which is located in the highland with nomadic lifestyle and animal husbandry, was studied to estimate its population in each period and assess its population changes during long period.  By applying Descriptive-Analytical and statistical methods such as SPSS, it was attempted to have a better understanding of the population changes. To estimate population of the area, population census of the modern day villages during year 2012 and ethno-archaeological activities such as study of 21 modern campsites were applied in this study. Finally, it was estimated that each person occupies 5/6 sq. m in village houses and 6/5 sq. m in campsites. Consequently, based on our studies in village houses and surrounding areas, it seems 51 persons are living in each hectare.  For campsites, which are located close to the village houses, it was estimated to 27 persons per hectare. Then the prehistoric population of Laran County was estimated in both site and region scales.

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In March 2004, a fluxgate gradiometer survey was conducted over Tepe Ghabristan, covering approximately 6ha of ground. It identified further areas of the Iron Age cemetery with possible grave pits (Areas B and C). In addition, an irrigation channel was discovered which could be contemporary to these Iron Age graves (Area D). The anomalies in Area E can be interpreted as buried structural remains, possibly linked to metalworking.

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The little Zab River in northwestern Iran rises from the mountains Piranshehr and flows from the northwest to the southeast direction to join Iraq from Alan passage. The River basin contains a large number of ancient settlements, and its lower area that is close to the Zab River has been the most interesting place for people in the Neolithic Age. An increasing population during Chalcolithic Age led to the dispersion of settlements. These sites are located in the north of this basin, in a valley and a little plain.

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Lorestan’s Balageriveh, is a lowland passage area, located in between two rivers, Dez and Kashkan in South Central Zagros; the area itself is divided into three parts, northern, southern and central. In previous studies in Lorestan, a form of complete shift was depicted from sedentary lifestyle to a mobile one, in transition between the Late Chalcolithic and the Middle Bronze Age. Central Balageriveh is important to be studied on this matter due to its central position among Susiana (Elam), Central Zagros, Bakhtiyari region, Posht Kouh and Mesopotamia, as well as paleoclimatology and archaeological studies conducted over there. Due to the above reasons, the present study has taken into account paleoclimatology and archaeological data, the transition process from Chalcolithic Cultures to the Bronze Age, a change in settlement patterns and the role of socio-economic and environmental changes in this pattern alteration. The findings indicated that long-time climatic change which occurred in the middle of 4th millennium B.C. in the region cannot be regarded as the cause of the complete cultural gap and the change of settlement pattern at the time. Instead, it seems that with the collapse of the Uruk System and its commercial organization, the areas like Balageriveh which were intermediary in this commercial network, lost their charm. When people like Kura-Araxes, on whom some would put the blame of the Uruk collapse as they were mobile pastoralists, settled in some areas which the previous power had lived, the commercial paths withered and Balageriveh’s intermediary role diminished and instead due to socio-political reasons, the lowland characteristics of the area became highlighted and the change in settlement pattern occurred.

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The Central Plateau of Iran, which has been called by various names until now, has special place in terms of Archaeological developments from the fifth millennium BC to the beginning of the third millennium BC. Archaeological evidence indicates the desolation, destruction, displacement, moving, and formation of sites during that period. Despite the dominance of this situation in the field of settlement, the analysis of pottery data in the first place, followed by architecture, metallurgy, and burial, indicates that there was an ongoing cultural continuity. The sites in the area did not have high sustainablity due to environmental factors. Therefore, the analysis of relevant data based on chaos and complexity theories as well as the general theory indicates that the communities in the region followed a particular pattern from the Transitional Cholcolithic to the Early Bronze Age 1. They would survive with a movement. While the continuity of social life was guaranteed by the abandonment of one site and the formation of a new one, technological, architectural, and economic revolution took place at the new site. It is often observed that this life continuity was accompanied by technological developments and innovations. In fact, the aforementioned societies did not collapse but leaving a site ensured their social and economic life. In the Central Plateau of Iran, we encounter with communities that have pursued the process of endogenous development while at the same time expanding inter-regional communication.