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Abstract:

This dissertation presents complex cultural adaptations to the largest Afroalpine ecosystem of the continent: the high-altitude Bale Mountains in the Southeastern Ethiopian Highlands. Human occupation of African tropical highland environments is considered a relatively recent development due to the general perception of high altitude environments as unfavorable for human subsistence. Moreover, these environments are believed to have functioned as a migration barrier in the past, due to their physiological challenges, such as high-altitude hypoxia, higher energy demand, cold stress, or UV radiation. As a consequence, the high-altitude regions remained among the least researched areas in several disciplines. Archaeological research in Ethiopia is still today largely concentrated on the main Rift Valley and on the landscapes and ecosystems of elevations below 2500 m above sea level. Thus, the western part of the Southeastern Ethiopian Highlands, particularly the Arsi-Bale complex landmass, is one of the most neglected regions for the study of Middle and Later Stone Age cultural changes. Only recently, an interdisciplinary research unit (DFG FOR 2358, The Mountain Exile Hypothesis) was established to reconstruct the coupled landscape and human history of the Bale Mountains. In contrast to the general perception, it is hypothesized that especially during arid Quaternary climate phases, the well-watered and stable ecosystems of the Bale Mountains might have even acted as a glacial refuge for plants and animals, but humans as well. As part of the contribution of this research group, the goal of this dissertation is to investigate the evidence of prehistoric hunter-gatherer settlements and cultural responses to high-altitude environments. Archaeological survey and excavations on three selected rock shelters in the upper Web Valley in the northwest of the Bale Mountains provided evidence of prehistoric hunter-gatherer’s occupations dating back to 47 ka cal. BP and continuing until the end of the Holocene around 2 ka cal. BP. At least four major Paleolithic occupational events were identified and documented, based on the stratified deposits of the selected rock shelters. The earliest phase of human occupation at the Bale Mountains is associated with a late Middle Stone Age assemblage at Fincha Habera rock shelter (3469 m asl). These Late Pleistocene occupations were connected with the extraordinary exploitation of a large rodent, the giant root-rat (Tachyoryctes macrocephalus). A total of 1026 lithic, around 2306 faunal remains, and 86 coprolite samples were analyzed to understand the late MSA cultural adaptations at the Bale Mountains. Excavations at Simbero and Mararo rock shelters also show that the high altitudes of the Bale Mountains were repeatedly occupied by LSA cultural groups from 15 to 2 ka cal. BP. While the Terminal Pleistocene settlements were represented by limited archaeological records, later hunter-gatherer occupations during the Middle and Late Holocene show a dramatic subsistence change in response to the high-altitude environments. The LSA cultural phase at these sites contains the lithic assemblages of around 6900 lithic artifacts and 1479 faunal remains. The latter include birds and fishes, and hint at the exploitation of a heterogeneous spectrum of wild animals. The lithic assemblages show a high frequency of microliths and additional tools classes such as borers, probably related to the subsistence to the high-altitude environments. Almost all lithic artifacts were made on locally available obsidian from the Wasama Ridge around the central Plateau of the Bale Mountains. The presence of a few exotic materials such as non-local obsidian and chalcedony in the lithic assemblages show the existence of regional contacts among hunter-gatherers in South and Southeastern Ethiopia. This study also suggests that the Bale Mountains lithic industries represent local specificities stone tool production as a long-term technological change in adapting to the high-altitude environments. Since the Bale Mountains complex was an open system, the typology and technology of the late MSA and LSA lithic assemblages show a notable technical similarity to the sites in the southern Ethiopian Rift Valley and the Southeastern Ethiopian Highlands. Based on the identified lithic composition and the technological changes, in association with the exploitation of abundant high-altitude resources including indigenous resources and raw material, the high-altitude regions of the Bale Mountains probably functioned as a paleoenvironmental refuge during environmental changes between OIS 3 to OIS 1. More archaeological data from the Arsi-Bale Mountain complex and other high-altitude regions are needed to support the contribution of this study.