Initial upper Palaeolithic on the Iranian Plateau: Sorheh Rockshelter, Southern Alborz mountains

The Late Pleistocene of southwestern Asia witnessed hominin diversification, admixture, and adaptation to new environments. The Iranian Plateau in southwestern Asia lies at the crossroads between Africa, Europe, Central Asia, and the Far East, and therefore, has contributed substantially to the history of hominin migration. On the Iranian Plateau, the Middle to Upper Palaeolithic transition is a puzzling phase that lacks chronological precision and stratified archaeological materials. The timing and geographical context of this transition are essential for understanding the spread of modern humans and their interactions with other species, including the Neanderthals. Sorheh Rockshelter in the southern piedmonts of the Alborz Mountains on the northern Iranian Plateau is a newly discovered site on high altitude of 1903 m asl., with the potential to answer some of these questions. In 2019 and 2022, excavations at Sorheh revealed distinct hominin behavioural and settlement systems, falling under the description of the Initial Upper Palaeolithic in the Levant, eastern Europe, Siberia, and Mongolia. In the chronological window covered at Sorheh (∼50–35 ka), the Upper Palaeolithic cultures had already been developed in other regions of the Iranian Plateau. The new data we obtained from Sorheh determines, for the first time, a physiogeographic, chronostratigraphic, and anthropogenic picture of the Initial Upper Palaeolithic on the Iranian Plateau, filling the gap in the distribution of this techno-complex between the Levant and eastern Eurasia. Deciphering the Initial Upper Palaeolithic in Sorheh indicates the complex and diverse nature of hominin behaviours during the transitional Middle-Upper Palaeolithic phase and reveals the critical role of the northern Iranian Plateau in hominin expansion towards Central Asia.