IRANIAN JOURNAL OF ARCHAEOLOGICAL STUDIES 6 (2016) Introduction T he ecosystem is a collection of animals and the environment, which are in a permanent interaction with each other and affect the condition of one another (Asadian, 1384: 7). Ecosystems are continuously changing. More often, a new ecosystem may appear because of such changes. A group of plants, animals and micro-organisms may be gradually substituted by other groups so that the whole collection of living beings may change (Kardavani, 1389: 241-242). The culture of human communities appears by a specifc ecosystem, grows and dies out at last. The ecosystem is in close connection with Palaeoclimate, since the condition of an ecosystem depends more on the climate than morphology. Consequently, in archaeology, the climate impact on the communities is signifcant. Prehistoric archaeological sites in North Central Iran suddenly disappeared around the end of the 4 th millennium BCE. At Tepe Sialk, near Kashan, the last cultural period, namely Sialk IV - probably established around 3400 BCE after the last settlements of Sialk III 6-7b - was abandoned approximately after 500 years. The material culture of this period, known as Proto-Elamite period, is very different from the previous one, showing similarities with Susa III. This period belongs to the same horizon of Uruk III in Mesopotamia and similar evidences were discovered also at sites such as Sofalin, Shoghali, Pardis, Chaltasian, Meymanat Abad, Gholi Darvish, Maral Tepe (Uzbeki), Ghabristan, Arisman and Hissar. With the abandonment of Sialk IV, cultures affected by Uruk in Near East were simultaneously abandoned. This trend of abandonment documented in North Central Iran continued for about 500- 1500 years. Paleoclimate research show that this period coincides with a cold and dry period dated approximately between 3200 and 2700 BCE. Apparently, these climatic changes threatened life more at North Central Iran than in Mesopotamia and Khuzestan, by virtue of the presence of overfowing and permanent rivers in these territories (Euphrates and Tigris above all), probably forcing the migration of people from North Central Iran to more favour- able areas. The present comparative study suggests that climate changes were the main reason for the cultural col- lapse attested in the region. Keywords: North Central Iran, Sialk IV, Middle-Holocene, Late Holocene, Climate Change. On the Possible Correlation between the Collapse of Sialk IV and Climatological Events during the Middle–Late Holocene Babak Shaikh Baikloo Islam 1 , Ahmad Chaychi Amirkhiz* , 2 and Hamid Reza Valipour 3 1 Department of History and Archaeology, Science and Research Branch, Islamic Azad University, Tehran, Iran. 2 Archaeological Research Centre, Tehran, Iran. 3 Department of Archeology, Shahid Beheshti University, Tehran, Iran. (Received: 05/ 02/ 2015; Received in Revised form: 08/ 05/ 2015; Accepted: 04/ 07/ 2015) Weather system is a collection of stratosphere, hydrosphere, biosphere, lithosphere and atmosphere and their mutual effects on each other. These fve spheres involve in a permanent energy transmission. Climate promotion, sensitiveness and feedback can positively or negatively affect the climate system (Mohammadi et al. 1395: 49). The Earth has always experienced climate changes in the long run; however, climate changes occur for a short time (Moghimi, 1391: 102-103). Gradual effects of climate change on nature do not affect human settlements the same way abrupt changes do, since humans have enough time to adapt themselves to the environment. By the end of the last Ice Age, the Holocene began, and after 40,000 years of a challenge with coldness, more favourable conditions for a sedentary and food production lifestyle appeared. Compared to Pleistocene, the Holocene Age imposed severe * Corresponding author. E-mail address: a.chaychi@richt.ir