Climatic Hazards of Fourth Millennium BC and Cultural p Responses of Human Societies Case Study: Tehran Plain and Qomroud-Gharachay Basin

Climatic conditions have dried up since the late 5th millennium BC as if Paleoclimate research in the northern hemisphere, particularly Iran and neighboring countries, shows unfavorable climatic conditions and several periods of severe drought during 4th millennium BC. Also, based on environmental sedimentological studies on archaeological sites such as Mafin Abad of Islamshahr and Meymanat Abad of Robat Karim in Tehran province and Ghara Tepe of Qomroud in Qom province, it has been determined that all three sites were flooded by neighboring rivers in the mid and late 4th millennium BC. The occurrence of these floods coincided with the severe droughts in the 4th millennium BC. The enormous floods caused by severe centralized rains are, in principle, one of the main features of climate change and droughts. As the drought intensified, especially since the late-4th millennium BC, human populations in the cultural region of North Central Iran have decreased, leading to a cultural decline during the Bronze Age. This research tries to study the destructive impacts of climate change on ancient societies of the Tehran plain and the Qomroud-Gharachay basin, located in the western part of the North Central region of Iran. For this purpose, paleoclimate research of the Holocene Age and environmental sedimentological studies of ancient sites contemporary with Sialk III period have been used. Also, during environmental surveys of the Mafin Abad site, evidence of an ancient stream (possibly one of the branches of the Karaj River) belonging to the mid-4th millennium BC, was discovered. It is probable that the uprising of the same river destroyed the ancient village. The XRD analysis on the sediments of this river indicates the deliberate selection of this location for establishment of the important settlement in 5th and 4th millennium BC. According to the sedimentology, the ancient stream has been one of the most valuable mine of pottery clay in the whole of North Central Iran. Previously, there was one of the largest ceramic factories near Mafin Abad, which uses peripheral soil. Also, the existence of very fine and excellent pottery of Mafin Abad, belonging to the Cheshmeh Ali Culture with 3mm thickness is another reason to support this hypothesis. Thus, Mafin Abad has great environmental potential for attracting human communities, but has failed to reach the threshold of urbanization. Mafin Abad and Ghara Tepe in the mid-4th millennium BC and Meymant Abad in the late-4th millennium BC ended their lives. Although it is not yet known exactly where the Meymanat Abad settlement was formed after the Mafin Abad collapse, but because the most recent Mafin Abad cultural material belongs to the early Sialk III phase and the oldest Meymanat Abad cultural material belongs to the same period, it is likely that after the end of Mafin Abad due to the flooding of the ancient stream which was a branch of the Karaj River, Meymanat Abad has been established. Since the absolute dating of Meymanat Abad indicates the oldest settlement at around 3700 BC, it may be possible to attribute this date time to the flood in Mafin Abad. As noted, most of the paleoclimate researches confirm the occurrence of a climate change and drought in about 3700-3500 BC. Also, the eventual collapse of Meymanat Abad in the late 4th millennium BC overlaps with the 5.2 ka BP drought event (3200 BC) that continued until the early 3rd millennium BC. Since then, the long cultural decline began in the North Central Iran region and covered the whole Bronze Age. Perhaps one of the most important reasons for the significant decreased of settlements and the existence of only one to two layers of settlement after the Sialk III period was severe climate change. These natural hazards have undoubtedly had profound impacts on the subsistence system of the North Central societies of Iran.