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Abstract:

Climatic change is widely acknowledged to have played a role in the dispersal of modern humans out of Africa, but the timing is contentious. Genetic evidence links dispersal to climatic change ~60,000 years ago, despite increasing evidence for earlier modern human presence in Asia. We report a deep seismic and near-continuous core record of the last 150,000 years from Lake Tana, Ethiopia, close to early modern human fossil sites and to postulated dispersal routes. The record shows varied climate towards the end of the penultimate glacial, followed by an abrupt change to relatively stable moist climate during the last interglacial. These conditions could have favoured selection for behavioural versatility, population growth and range expansion, supporting models of early, multiple dispersals of modern humans from Africa.

Abstract:

Ethiopia is rich in obsidian and prehistoric peoples were utilizing it to make artifacts since at least the Early Stone Age. The unique chemical compositions of obsidian are of considerable interest to archaeologists when obsidian artifacts are recovered at prehistoric sites, both in terms of determining provenance and cultural exchange. Here we present electron microprobe analyses to characterize the major and minor element compositions of a suite of obsidian samples from 45 volcanic source locations along a 700 km extent of the Main Ethiopian Rift and the Afar Triangle. Of the 62 analyzed obsidian, 50 are classified as rhyolite, with subordinate numbers of trachyte and dacite. The Main Ethiopian Rift and its extension into the Afar region to the north have produced obsidian with different chemical affinities which may prove useful in narrowing down possible source regions for artifacts for which sources have not yet been discovered and/or analyzed.

Abstract:

The study of human occupation and land use of high-altitude areas has been widely neglected in Ethiopia. This is probably due to the hypothetical assumption of general hostility which these areas may have represented. However, recent studies from different parts of the world have evidenced multiple human occupation of highly elevated areas during the late Pleistocene and Holocene periods. As a consequence, the exact environmental circumstances and the human strategies used to colonize high-altitude mountains and plateaus are now coming into closer focus. The Bale Mountains National Park, the study area of this research, is one of the most mosaic and bio-diverse areas in Ethiopia. It unites highly diverse vegetation zones in a comparably small area. It is a floral and faunal hotspot, characterized by high numbers of unique endemic species. In the case of the fauna, this refers to animals such as Ethiopian wolf (Canis simensis), Ethiopian highland hare (Lepus starcki), Bale monkey (Chlorocebus djamdjamensis), mountain nyala (Tragelaphus buxtoni), giant mole-rat (Tachyoryctes macrocephalus), not to mention many bird species as well. The Bale Mountains not only host the largest afroalpine areas, but also the largest spatial extent of high altitudes of the entire African continent. Before a survey in 2015, there were few paleoecological and botanical studies conducted in the area. The first archeological studies not only showed human MSA occupation and use of the afroalpine ecozone, but also led to the discovery of many rock shelters with occupation horizons. The Simbero rock shelter is one of the largest shelters in the Bale Mountains located in the northwest part of the park at 3,519 m asl elevations in an exceptional strategical location. Excavations at this site uncovered a stratigraphic sequence reaching back as early as c. 14,000 years until very recently, with a concentration of finds (fauna, charcoal, lithics) dating to between c. 5,000 and 2,000 years ago. Given the extraordinary number of faunal remains at this site, in-depth zooarcheological studies became mandatory as an ideal complement to the in-depth paleoenvironmental and archeological studies carried out at this site. Therefore, the first purpose of this research was to identify and investigate the agents of the faunal accumulations at the rock shelter. After human accumulation can be made sure, the identification of the predominantly exploited animals’ species should be achieved. Additionally, dietary variation and behavior of humans need to be investigated in relation to the identification of skeletal parts that were consumed predominantly. Finally, conclusions on the ecosystem and potential climatic changes on the base of faunal assemblage are desirable for the time of the human occupational periods at the rock shelter. In order to achieve these objectives, the faunal material of square K4 of the 2018 excavation at Simbero rock shelter was washed and dried for a better analysis of surface modifications. Each specimen was recorded separately and the information was stored into an Excel database, which formed the base for any statistical inquiry presented in this study. Consequently, more than 1,400 faunal remains were recorded and analyzed in terms of species abundance and skeletal part representation according to stratigraphic origin. By using the statistical means of the MNI, NISP and NSP values, it could be demonstrated that the prehistoric hunter-gatherers at Simbero rock shelter exploited a wide range of mammalian species. Abundant small mammals are followed by bovids of different size categories in the majority of studied levels. Hare, hyrax and rodents were among the commonly identified animals. In these cases, most elements of the body were recovered however, in the case of large and mid-sized mammals, most parts were represented by parts of long bones. Importantly, the vast majority of the faunal remains were burnt by humans, which forms the first and foremost anthropogenic modification of the bones, apart from distinct cut marks. As clear features for carnivores/owls or other non-anthropogenic agents are almost entirely missing, this study concludes that the faunal remains from Simbero rock shelter were hunted, transported, modified, and consumed by humans. With respect to skeletal part abundance, only small mammals are represented by a huge variety of body parts. This includes small, fragile part as well as large, robust long bones. This implies that there is a recurrent pattern of small mammals’ bones to have been locally captured, transported to shelter, and consumed there. This probably also includes small bovids (size classes I and II). In contrast, bovids and other mid- to large-sized mammals, represented mainly by parts of the long bones yielding large amount of meat, probably were dismembered at the killing places and only selected parts entered the rock shelter. It should be stressed that the bones were discovered in close association with stone tools and in charcoal-rich stratigraphic layers. This can be viewed as a good manifestation of humans using the tools to process the animal consumed and discovered in the rock shelter. The most surprising aspect of this study (requiring further investigations) is the unusual high amount of fire traces on bones (corresponding to those on lithic artifacts and sediments). These burnt bones came from all excavated levels. Some of them exhibited a very high degree of burning indicated by calcinated bones. Finally, due to the high fragmentation and resulting limitations in the identification of these bone fragments, in was not possible to include detailed analyses of the following two aspects: the identification of domesticates (especially from the younger top layers), and a more detailed paleoclimatic assessment. Therefore, further studies (e.g., by ZooMS) might contribute to the identification of domesticates. For an improved understanding the high-altitude land use and occupation in the Bale Mountains, this study proposes further analysis of zooarcheological remains of additional sites. As previously mentioned, only little work has been done on LSA faunal materials in Ethiopia. Thus, there are many sites identified in the park which might enable a regional study which could contribute to understanding the temporal and spatial patterns of site occupation, duration of occupation (seasonality), and the associated environmental changes and contrast these with other Holocene sites in Ethiopia.

Abstract:

A large variety of remote sensing-based land use/land cover (LULC) products are currently available on national and global scales. This literature review and in situ validation study evaluate the suitability of these products for local scale applications in the complex terrain of the Ethiopian mountains. For the review, 146 research papers are analyzed. Most studies (73%) have been published since 2013 and are based on individually computed maps. Not a single study relied on readily available LULC products. Nine readily available LULC products with 20-, 30-, 300-, 500-, and 1000-m spatial resolution have been identified at national and global scales. To complement and extend this body of research, the recent (since 2013) LULC products are validated using 185 ground truth points collected in the Bale Mountains National Park between 1500 and 4385 m a.s.l. The results indicate a rather poor overall accuracy (<50%).

Abstract:

Erica is a dominant vegetation type in many sub-afroalpine ecosystems, such as the Bale Mountains in Ethiopia. However, the past extent of Erica is not well known and climate versus anthropogenic influence on altitudinal shifts are difficult to assign unambiguously, especially during the Holocene. The main objective of the present study is to chemotaxonomically characterize the dominant plant species occurring in the Bale Mountains using lignin phenols and n-alkane biomarkers and to examine the potential of those biomarkers for reconstructing vegetation history. Fresh plant material, organic layer and mineral topsoil samples were collected along a northeastern and a southwestern altitudinal transect (4134–3870 and 4377–2550ma.s.l., respectively). Lignin-derived vanillyl, syringyl and cinnamyl phenols were analyzed using the cupric oxide oxidation method. Leaf-wax-derived n- alkanes were extracted and purified using Soxhlet and aminopropyl columns. Individual lignin phenols and n-alkanes were separated by gas-chromatography and detected by mass spectrometry and flame ionization detection, respectively. We found that the relative contributions of vanillyl, syringyl and cinnamyl phenols allow us to chemotaxonomically distinguish contemporary plant species of the Bale Mountains. Erica in particular is characterized by relatively high cinnamyl contributions of > 40 %. However, litter degradation strongly decreases the lignin phenol concentrations and completely changes the lignin phenol pat- terns. Relative cinnamyl contributions in soils under Erica were < 40 %, while soils that developed under Poaceae (Festuca abyssinica) exhibited relative cinnamyl contributions of > 40 %. Similarly, long-chain n-alkanes extracted from the leaf waxes allowed for differentiation between Erica versus Festuca abyssinica and Alchemilla, based on lower C31 =C29 ratios in Erica. However, this characteristic plant pattern was also lost due to degradation in the respective O layers and Ah horizons. In conclusion, although in modern-day plant samples a chemotaxonomic differentiation is possible, soil degradation processes seem to render the proxies unusable for the reconstruction of the past extent of Erica on the Sanetti Plateau, Bale Mountains, Ethiopia. This finding is of high relevance beyond our case study.

Abstract:

Low‑altitude lakes in eastern Africa have long been investigated and have provided valuable information about the Late Quaternary paleohydrological evolution, such as the African Humid Period. However, records often suffer from poor age control, resolution, and/or ambiguous proxy interpretation, and only little focus has been put on high‑ altitude regions despite their sensitivity to global, regional, and local climate change phenomena. Here we report on Last Glacial environmental fluctuations at about 4000 m asl on the Sanetti Plateau in the Bale Mountains (SE Ethiopia), based on biogeochemical and palynological analyses of laminated lacustrine sediments. After deglaciation at about 18 cal kyr BP, a steppe‑like herb‑rich grassland with maximum Chenopodiaceae/Amaranthaceae and Plantago existed. Between 16.6 and 15.7 cal kyr BP, conditions were dry with a desiccation layer at ~ 16.3 cal kyr BP, documenting a temporary phase of maximum aridity on the plateau. While that local event lasted for only a few decades, concentra‑ tions of various elements (e.g. Zr, HF, Nb, Nd, and Na) started to increase and reached a maximum at ~ 15.8–15.7 cal kyr BP. We interpret those elements to reflect allochthonous, aeolian dust input via dry northerly winds and increasingly arid conditions in the lowlands. We suggest an abrupt versus delayed response at high and low altitudes, respectively, in response to Northern Hemispheric cooling events (the Heinrich Event 1). The delayed response at low altitudes might be caused by slow negative vegetation and monsoon feedbacks that make the ecosystem somewhat resilient. At ~ 15.7 cal kyr BP, our record shows an abrupt onset of the African Humid Period, almost 1000 years before the onset of the Bølling–Allerød warming in the North‑Atlantic region, and about 300 years earlier than in the Lake Tana region. Erica pollen increased significantly between 14.4 and 13.6 cal kyr BP in agreement with periodically wet and regionally warm conditions. Similarly, intense fire events, documented by increased black carbon, correlate with wet and warm environmental conditions that promote the growth of Erica shrubs. This allows to conclude that biomass and thus fuel availability is one important factor controlling fire events in the Bale Mountains.

Abstract:

The endangered giant root-rat (Tachyoryctes macrocephalus, also known as giant mole rat) is a fossorial rodent endemic to the afro-alpine grasslands of the Bale Mountains in Ethiopia. The species is an important ecosystem engineer with the majority of the global population found within 1000 km2. Here, we present the first complete mitochondrial genome of the giant root-rat and the genus Tachyoryctes, recovered using shotgun sequencing and iterative mapping. A phylogenetic analysis including 15 other representatives of the family Spalacidae placed Tachyoryctes as sister genus to Rhizomys with high support. This position is in accordance with a recent study revealing the topology of the Spalacidae family. The full mitochondrial genome of the giant root-rat presents an important resource for further population genetic studies.

Abstract:

Compound-specific oxygen isotope (?18O) analysis of sugar biomarkers in lacustrine sediments – rationale, first applications and perspectives for future research

Abstract:

Archaeological findings, numerical human dispersal models and genome analyses suggest several time windows in the past 200 kyr (thousands of years ago) when anatomically modern humans (AMH) dispersed out of Africa into the Levant and/or Arabia. From close to the key hominin site of Omo-Kibish, we provide near continuous proxy evidence for environmental changes in lake sediment cores from the Chew Bahir basin, south Ethiopia. The data show highly variable hydroclimate conditions from 116 to 66 kyr BP with rapid shifts from very wet to extreme aridity. The wet phases coincide with the timing of the North African Humid Periods during MIS5, as defined by Nile discharge records from the eastern Mediterranean. The subsequent record at Chew Bahir suggests stable regional hydrological setting between 58 and 32 kyr (MIS4 and 3), which facilitated the development of more habitable ecosystems, albeit in generally dry climatic conditions. This shift, from more to less variable hydroclimate, may help account for the timing of later dispersal events of AMH out of Africa.

Abstract:

Garba Guracha is a cirque lake located at 3950 m altitude in the Bale Mountains National Park, Ethiopia, at the boundary between the Afro-alpine and sub-alpine Ericaceous vegetation belts. Jean-Jacques Tiercelin and Mohammed Umer cored its sediments in about 2002, leading to publication of one of the longest, best-dated, and most continuous Late Pleistocene-Holocene palaeoenvironmental records from above 3000 m in Africa. Their 2007 and 2008 papers document the vegetation and deglaciation history of the Bale Mountain plateau, which supports the most extensive area of Afro-alpine vegetation on the planet, and an exceptionally rich endemic biodiversity. However, those publications revealed little about human exploitation of the Bale Mountain environment. We again cored Garba Guracha (‘Black Lake’ in the Oromo language) in February 2017, as part of a major DFG-funded research unit (“The Mountain Exile Hypothesis - How humans benefited from and re-shaped African high altitude ecosystems during Quaternary climate changes”) that aims to test the hypothesis that human settlement of the Bale Mountains dates from at least the late Pleistocene. We also drilled cores from seven other sites in the area in early 2018, in partnership with archaeological, glacial geological and pedological investigations. Here we attempt an early synthesis of the results of ?XRF geochemistry, stable isotope, biomarker, pollen and charcoal analyses of the Garba Guracha sediments with a new age model based on radiocarbon and 210Pb ages, and suggest an initial interpretation of anthropogenic impact on the Bale Mountains.

Abstract:

The lakes of the eastern Africa Rift often contain great thicknesses of sediment that may provide continuous records of environmental change over decadal to million-year timescales. However interpretation of these changes is greatly compromised without a reliable chronology. Luminescence dating has not been used extensively in lacustrine settings; instead previous studies have often relied upon radiocarbon dating, using extrapolation beyond the upper limit of that technique, and employing opportunistic sampling of tephra and palaeomagnetic signatures where possible. This study from Lake Tana, Ethiopia, demonstrates that recent advances in luminescence methodology can provide long chronologies for lake sediments that are not dependent on the intermittent presence of dateable material, as is the case for radiocarbon and tephra-based methods. Specifically, this study generates luminescence ages that agree with independent chronology based on radiocarbon dating in the upper part of the core, and extends significantly beyond the range of radiocarbon dating to provide one of the longest independently dated lacustrine sediment records in eastern Africa, thus demonstrating the tremendous potential of luminescence for constructing lacustrine sediment chronologies over 100,000 year timescales.

Abstract:

This first survey of rock shelters and settlements in the Bale Mountains in Ethiopia is a baseline assessment for further research into the settlement history of Africa’s largest alpine highlands. Extensive GPS-based mapping and interviews resulted in two detailed maps, a catalogue of profiles, and complete photographic documentation. In total, 331 rock shelters (four permanently inhabited, 51 seasonally inhabited, and 276 currently uninhabited) and 870 settlements (207 permanently inhabited, 449 seasonally inhabited, 214 uninhabited) were recorded together with information about the activities and livelihoods of the inhabitants of the current settlements. This 2015 study was part of the Ethiopian-European research project “The mountain exile hypothesis – how humans benefited from and re-shaped African high-altitude ecosystems during Quaternary climate changes” (DFG FOR 2358). It was designed to support future management plans in this internationally important conservation area that has recently faced increasing land-use pressure and the threat of degradation.

Abstract:

The Bale Mountains were one of the three extensively glaciated higher elevation areas in Ethiopia during last glacial maximum (Osmaston et al, 2005). After deglaciation, several small depressions on the Sanetti Plateau turned into shallow lakes. Today, some of these lakes dry out seasonally due to the alternation between monsoonal precipitation in summer and dry north-easterlies in winter. Drastically decreasing of Erica vegetation at higher altitude was recorded on the study area (Umer, 2007; Miehe and Miehe 1994). But the driving causes of this vegetation change is still unclear. Therefore, with this study we aim at contributing to the reconstruction of the Late Glacial and Holocene environmental evolution of the Bale Mountains, particularly sedimentation, fire and vegetation evolution by studying depression sediments based on the hypothesis that any process in the catchment of the depression, initiated by climate fluctuations, human impact and natural fires disturbing the vegetation cover, soil stability, run off and erosion should be documented in the physical, chemical and biological properties of depression sediments.

Abstract:

The high-altitude regions of African tropical environments are among the least studied areas regarding the dispersal and colonization of anatomically modern humans across and out of Africa. Human colonization of high altitude regions is considered a relatively recent process, not least as high-altitude environments are usually perceived as unfavorable for human subsistence and are believed to have functioned as a migration barrier due to their physiological and ecological challenges, including high-altitude hypoxia, cold stress and lack of sufficient resources. Although it is not yet clear when and how human population dispersed into the high-altitude mountains of tropical Africa, our new findings suggest that specialized hunter-gatherer successfully colonized and exploited a wide range of ‘harsh’ landscapes of the Bale Mountains (>3800m asl) in the southeastern Ethiopian Highlands during the Late and Terminal Pleistocene up to Middle and Late Holocene. Moreover, ongoing archaeological research in the northwestern part of the Bale Mountains provides new perspectives on human colonization of high-altitude tropical environments and the relationship between human adaptation and climate changes at least during three separate time periods between 31,000 cal. BP and 4,000 cal BP.