A PCA Analysis of the Impacts of Environmental Factors on Prehistoric Settlement Patterns in Sarfiroozabad, Kermanshah, Iran

This paper explores man-environment relationships during the prehistoric periods. It calculates the main factors affecting the establishment of prehistoric settlements in Sarfiroozabad rural dis-trict, south of Kermanshah County, which is south-eastern extension of Mahidasht. The research has been done on the basis of Environmental archaeology according to archaeological surface surveying data. The Principal Component Analysis method has been used to investigate the measure of natural and cultural factors involve in the prehistoric settlement patterns of the region. The general patterns of settlement distribution of the studied region are mainly unchanged through the long-term processes of man-environment relationship. The results also show that the impacting factors on settlement distribution patterns were different in every prehistoric period. The results could be used to reconstruction of man-environment interactions of the region to apply it in contemporary environmental management of it.. An important achievement of the project was dis-covering very earlier occupational evidences than what which was revealed from Mahidasht; re-sulting to a reconsideration of the origins of Neolithic settlements of the region such as Tepe Sar-ab.. In such a way, it could be possible to take into account attributes other than natural ones and consider potential cultural factors affecting settlement locating during prehistoric times. It is not to overleap the natural and environmental factors, but to examine site distributions according to their relations as well; as if each of them is a node on the complicated network of occupying the valley through different periods. it should probably be impossible to get a comprehensive understanding of prehistoric settlement conditions of the region unless the excavations carried out to establish secure chronology. The current results are mainly based on relative chronology of surface sherds compared to the same material recovered accurately in temporal order from the stratigraphic de-posits of Mahidasht. However there is necessity to have absolute datings of prehistoric evidences of the valley.
Keywords: Environmental Archaeology, Principal Component Analysis, Geomatics, Correlation, Sarfiroozabad.
 
Introduction
The relationship between human culture and the environment, and their interactions and mutual impacts have been the focus of intense scholarly attention in environmental anthropology and archeology (see Dove & Carpenter, 2008; Evans & OʼConnor, 1999; Dincauze, 2000). Environmental archeology deals with the role of the environment in the genesis and historical evolution of cultures and human societies. Mounds or ancient sites represent the primary data for environmental archeology. Archaeologists may reconstruct the cultural and environmental factors involved in past and present environmental processes through conducting surface surveys and identifying archeological sites over a specific geographic area as well as using chronological techniques and the paleoclimatic and paleoenvirnomental findings. The concept of “settlement systems” implies that human settlements (even in prehistory) by no means arose from some random, serendipitous or arbitrary choices, and that they were rather subject to specific patterns stemming from best decisions of their occupants attain a most stable dwelling to the possible extent. In individual geographic areas, thus, the distribution of archaeological sites, environmental conditions and contexts, and the developmental level of societies are characterized by significant relations, which are in turn contingent on specific, examinable patterns.
 
Conclusion
Having examined the three influential factors on the distribution and location of the prehistoric settlements of Sar Firuzabad, we can now more easily embark on appraising the environmental patterns for that distribution and positioning as well as their chronological evolution. Two issues are to be addressed in this respect: one is the evolution of the subsistence and economic systems of prehistoric inhabitants of Sarfiroozabadbased on environmental capacities, and the other is the evolution of the local settlement patterns in different prehistoric periods.
The results suggest that “environment” and environmental factors were among the major determinants in the distribution of prehistoric sites. The main river of the valley, Ab-e-Mereg, was the core of rapid changes in the settlement schemes of the prehistoric populations from the Neolithic to the end of the Bronze Age. It is clear that the earliest settlement systems (consisting of a group of settlements with partially superimposed boundaries and spatial relationships) appeared along the river in the eastern parts of the valley in the Chalcolithic period.
In light of our findings, the isolated and clustered settlements exhibit contrasting distribution patterns: the former are concentrated along the main lines of communication, higher elevations, close to the foothills, and remote from the earlier settlements, while the latter lie far from the main lines of communication, in the lower parts of the valley, next to the main river and within the precincts of the past settlements. Another differentiating point is the frequency of painted sherds, which occur in higher abundance on the clustered settlements.
Mortensen, with regard to Mahidasht of Kermanshah, points out that the distribution of the Neolithic settlements show a tendency for clustering (Hole, 2002). Yet, our findings suggest that the bunched positioning of the prehistoric settlements depended on the environmental circumstances. In the case of Sar Firuzabad, the clustering occurs only in the eastern parts of the valley and near the main river, while in the remaining parts the Neolithic sites are detached and spaced apart.
During the Chalcolithic period, the population of the valley experienced a sudden increase due to the influx of new peoples (Hole, 2002). The incidence is attested in the archeological record by the appearance of two distinct pottery traditions, viz. Dalma Ware and Ubaid Ware (Young, 1963) in northern and western Iran. This population surge leads to two different distribution patterns in the region: one is the advent of settlement systems characterized by sites with overlapping boundaries and arranged in a “circular” outline in the proximity of the main river of the plain, invoking an agriculture-based subsistence. And, the second is the “linear” distribution of settlements along the southern foothills, which contain auspicious natural pastures for livestock. The Chalcolithic settlements along the main river display a higher average expanse than those arranged linearly along the southern slopes.
As a hallmark typical to the prehistoric intermountain valleys of the Central Zagros (Wilkinson, 2003: 184-185), including Mahidasht, the arrival of the mid-Holocene climatic regime associated with an increase in the average annual temperature since about 5, 000 years ago and the predominance of warmer, drier conditions in the region led to the replacement of farming with the specialized livestock raising as the underlying subsistence strategy at the dawn of the Bronze Age. In the previous Chalcolithic period, settlement systems had formed along the permanent river of Sarfiroozabadand relied on plant cultivation by means of permanent water resources. However, due to the climatic change coupled with the population rise in the Middle and Late Chalcolithic, most of the permanent settlements across the valley were abandoned, giving way to temporary nomad camps. The scarce surviving permanent sites (about 5 of which were identified) were not but isolated settlements that could have functioned as chiefdoms or seasonal marketplaces.
Henrickson (2002) suggested that with the advent of the Bronze Age communities on the highlands (Central Zagros) became politically independent of the lowlands (Khuzestan and Mesopotamia). As already indicated by Nissen and Lutzeier (1990), during this period many settlements would vanish despite the persistence of a small number of them. This meant the emergence on the highlands of a different political system based on nomadism, on which environmental factors still left deep impressions.
Thus, in the Neolithic period, first a mixed economic and subsistence pattern was established in landscapes characterized by the diversity of natural resources, causing a sprinkled distribution of settlements. In the Chalcolithic period, two specialized subsistence patterns would develop from that mixed pattern: one was the specialized agriculture in the lower parts of this intermontane valley with sustainable resources that gradually led to complex settlement clusters; and the other was the specialized nomadic pastoralism in the higher elevations that gave rise to the temporary, detached settlements. The same patterns would endure, albeit in a more limited extent, during the Bronze Age, with the only discernible difference that the settlement systems established in the previous period now either disappeared or assumed a novel configuration that is yet to be grasped by scholars.