Advertisement

Journal of Paleolithic Archaeology

, Volume 1, Issue 4, pp 302–313 | Cite as

When Hominins Conquered Highlands—an Acheulean Site at 3000 m a.s.l. on Mount Dendi/Ethiopia

  • Ralf Vogelsang
  • Olaf Bubenzer
  • Martin Kehl
  • Svenja Meyer
  • Jürgen Richter
  • Bahru Zinaye
Report

Introduction

High-altitude mountain habitats are regarded as unfavorable for human occupation (e.g., Aldenderfer 2014) and basic findings of high altitude human physiology research impressively illustrate this: e.g., prevalence of high-altitude hypoxia, increased UV radiation, increased loss of water, and higher basal metabolic rates (Beal 2001; Berghold and Schaffert 2009). Therefore, it seems reasonable that hominins would only be pushed into such conditions by decreasing land resources in the lowlands following rapid population increase or ecological changes (Basell 2008; Foerster et al. 2015). In fact, the scarce archeological evidence for a pre-Holocene occupation of high mountain ranges hypothesized a late colonization of these environments. Archeological investigations on Mount Dendi (3270 m a.s.l.) located on the Ethiopian Plateau question this assumption.

The Dendi caldera is situated about 110 km west from Addis Ababa in the Western Central Highland Plateaus of Ethiopia (Fig. 1a, b). It is among the central volcanoes along the Yerer-TulluWellel volcano tectonic lineament (YTVL) that begins at the western margin of the Main Ethiopian Rift (MER) and extends to the west as far as the Sudan border (Abebe 2014). The volcano is part of the upper volcanic sequence of the Ethiopian Plateau, where the volcanic activity started during the Late Miocene with formation of the YTVL, with volcanic activity ceasing less than 1 myr ago (Abebe et al. 1998; Abbate et al. 2015).
Fig. 1

Mount Dendi. (a) View of Mount Dendi (looking west). (b) View of the two crater lakes within the caldera. (c) Map showing the location of archeological sites (The basic digital elevation model (DEM) was extracted using ENVI software and panchromatic images of Pléiades (1A) stereo pair satellite imagery (date: 2014-12-28: cloud cover: 0%; cell sizes: 0.5 m × 0.5 m; coordinate system: WGS 84)

Dendi is a large silicic volcanic complex constituted by both trachytic and rhyolitic lava flows and domes. The rhyolites and trachytes are pale gray and have an aphanitic or microporphyritic texture with Sanidine phenocryst. Obsidian lava flows on top of these deposits have been an important raw material source for the production of stone artifacts. The lava flows are overlain by younger pyroclastic deposits dominated by pyroclastic surge lapilli tuffs and minor ignimbrite and volcanic ashes. These products mainly constitute the floor of the caldera except the volcanic ash which is found everywhere in the caldera (Zinaye 2014).

A notable feature is the presence of two connected lakes formed within the central depression (Fig. 1) surrounded by the caldera rim rising up to 440 m above lake surface. A large number of springs in the steep slopes of the caldera drain into the lakes, with the exception of some tributaries of the Huluka River, which joins the Blue Nile (Abay) Basin. During high water levels, the lakes flow out to this basin. The current abundance of water is recharged primarily during the main rainy season from June to September (annual mean precipitation: ~ 1400 mm) (Degefu et al. 2014; Adimassu et al. 2014).

Research Background

Archeological prospections concomitant to coring activities on the crater lakes by a CRC 806 research group in 2012 (Wagner et al. 2018), led to the first discovery of Stone Age sites. Further archeological surveys in 2013 and 2015 resulted in the recording of a total of 71 archeological sites from all Stone Age periods. A test-excavation in a small rockshelter (DEN12-A01) yielded four Holocene Later Stone Age layers with a tool spectrum dominated by backed microliths (Schepers et al. in prep.). The Middle Stone Age is mainly represented by single finds of obsidian points that might have been lost during hunting trips. Of outstanding importance are ten Early Stone Age (ESA) sites with large obsidian bifaces that demonstrate the presence of hominins at high altitudes already during the Middle Pleistocene. This short report will focus on one of these sites, DEN-12-A02 that is located at an altitude of 3000 m a.s.l. and yielded finds in stratigraphic context. The altitude has been the same at time of the deposition, given that the impact of tectonic uplift was insignificant during the last 500 ka in the southeastern Ethiopian Plateau (Pik et al. 2003; Xue et al. 2018).

Site DEN-12-A02

Road construction work, creating artificial terraces in three successive levels at the shoulder of the crater rim, exposed the site of DEN-12-02 (Fig. 2a). Obsidian is the exclusive raw-material used for the production of the 65 artifacts (33 flakes, 8 cores, 5 blades, 8 large bifacial tools, 7 small facially retouched points). On the upper artificial terrace, characteristic stone tools are typologically attributed to the Middle Stone Age (MSA), while on the surface of the middle artificial terrace artifacts appear to be from the Early Stone Age (ESA) with only a number of probably displaced MSA artifacts. A thin scatter of artifacts from both periods on the lower terrace is interpreted as having been redeposited. The assumed origin of the ESA artifacts from the wall above the middle artificial terrace was verified in 2015 by the excavation of an archeological horizon in this part of the sequence that included one handaxe and two flakes in situ (Fig. 2c).
Fig. 2

The Acheulean site DEN12-A02. (a) View of the three artificial terraces and location of profile B (white rectangle, humans as scale). (b) Profile DEN15-A02 with four different soil horizons. The in situ handaxe was found in the Bt horizon ( Open image in new window ). The surface horizon A is a silty clay loam containing roots and showing a high total organic content (TOC; 4%). TOC and grain size decrease with depth. The lower horizons Bwt, Btg, and Bt all classify as clays and have TOC-values < 1%. These horizons show blocky soil structure and firm soil consistence. Furthermore, strong accumulation of siliceous clay with voids of manganese-oxides and iron hydroxides in the matrix are evident, also in characteristic micromorphological features such as intact coatings and nodules (d). (c) Handaxe in situ

Stratigraphy and Micromorphology

The hand axe was found 2 m below the actual surface in the uppermost level of the terrace embankments that was further excavated. The profile DEN15-A02 prepared at this location exposed dark reddish colored clayey slope deposits, more than 2 m thick (Fig. 2b) interspersed with heavily weathered pyroclastic rock fragments. Features of sediment redeposition such as sharp boundaries between soil horizons, bedding, laminations, or rotational features were not apparent. Pronounced pedogenesis resulted in a sequence of A/Bwt/Btg/Bt horizons, with all horizons containing at least 37% clay. The lowermost Bt with 54% clay shows a particularly strong pedogenic alteration. This is reflected by several generations of illuvial clay coatings, frequent manganese oxide and iron hydroxide nodules and coatings as well as by a strongly developed soil structure. Stagnic color pattern in the Btg horizon (46% clay) indicates reduction/oxidation processes caused by seasonal water saturation. Micromorphological evidence and granulometric composition suggest that an eluvial horizon is lacking, probably due to erosion of the upper part of the profile. The lower part of the sequence, however, does not show any characteristic feature of reworking along the slope, hence, an in situ preservation of the lower part of the sediment sequence is suspected. Considering the different generations of illuvial clay coatings and intercalation by manganese coatings (Fig. 2d), it is highly likely that formation of the lower Bt horizon started a long time ago and was polygenetic, i.e., it continued during several glacial/interglacial cycles. Radiocarbon dating of organic samples has a maximum age limit of around 50,000 years, while a much higher age of several 100,000 years is expected for the find horizon. As luminescence dating of vulcanogenic minerals has proven unreliable (e.g., Tsukamoto et al. 2007), we did not carry out these radiometric methods. In addition, palaeomagnetic measurements yielded no results.

Lithic Assemblage

The analysis of all archeological finds from Mount Dendi is ongoing and a large contextual study, which will present detailed data from all sites, is planned for a comprehensive research article. Despite the preliminary stage of this work, we wanted to share a few observations about the DEN-12-A02 assemblage.

The DEN-12-A02 ESA assemblage is characterized by varied tool type forms, including elongated hand axes (n = 2), ovate hand axes (n = 3), one cordate hand axe, leaf-shaped scrapers (n = 2), one backed biface (“Keilmesser”), and one cleaver (Fig. 3). In contrast to the diverse tool-types, the operational sequences (chaines opératoires) are similar (standardized analysis after Richter 2004; 2018 p.78–95). In the majority of cases, the platy natural surface of the obsidian slabs is partly preserved and sometimes used as a naturally backed edge. Facial shaping was first completely finished on one face and then on the other. In a last step, lateral thinning and edge retouch were performed for the preparation of the working edge (Fig. 4).
Fig. 3

DEN12-A02 bifacial tools. (1) Flat cordate hand axe, (2) bifacial scraper, (3) ovate hand axe, (4) cleaver-like biface, (5) elongated hand axe, and (6) bifacial knife (“Keilmesser”)

Fig. 4

Two examples for the operational sequence analysis after Richter (2004); 2018 p.78–95; Online resource 1) of bifaces from the site DEN12-A02. c Classification of the steps of procedure

The technological similarity of the production processes indicates a consistent association of the assemblage, which would most probably represent one temporary occupational event. Tool types, their heterogeneous spectrum and the shaping method, indicating a high level of knapping skill, i.e., bifacial retouch extending over whole surfaces, lateral thinning, and edge retouch point to a Middle to Late Acheulean age classification of the site (Chazan 2015, Gallotti & Mussi 2017, Schick and Toth 2017, Shipton 2018). Working on one face and then on the other has also been documented in India, where it was argued to relate to increased hierarchical complexity at the transition from the Acheulean to the Middle Paleolithic (Shipton et al. 2013, 101). Inter assemblage variability of tool size might be explained by functional variability, geographic distinctions, different raw-material usage, or chronological differences. Therefore, a comparison of mean length/breadth measurements from DEN12-A01 with other Ethiopian ESA sites as a chronological indicator has to be considered with care. However, there seems to be a general trend of miniaturization that supports the Late Acheulean chronological classification (Fig. 5). The most resembling assemblage, not only in the relatively small size of the artifacts, but also in the typological diversity and technological aspects, such as marginal trimming, is Mieso 31. The Mieso Acheulean is dated around 212 ka ago and is one of the latest evidences of this period in Eastern Africa (de la Torre et al. 2014). A similar Late Acheulean chronological classification can be assumed for DEN-12-A02, indicating an age between 500 and 200 ka ago.
Fig. 5

Mean length-breadth ratio of Ethiopian hand axe assemblages (Gadeb: de la Torre 2011; Clark and Kurashina 1979. Konso: Beyene et al. 2013. Melka Kunture: Gallotti et al. 2010, 2014; Piperno et al. 2004. Mieso: de la Torre et al. 2014)

To our knowledge, the site DEN12-A02 is the highest-located Acheulean site (Table 1). Such sites are extremely rare and “modern behavior” connected to the advance of early Homo sapiens sapiens seemed to be the precondition for the successful colonization of such harsh environments. Indeed, the systematic occupation of Europe’s high-relief upland regions began as late as the Mesolithic (Biagi and Starnini 2015). Only few earlier exceptions came to our knowledge such as Neanderthal presence at 1477 m (Wildkirchli) and at Salzofen (2007 m) in the Central Alps (Richter 2006). But there are also only rare examples of modern Homo sapiens presence exceeding 1000 m.a.s.l. from the Upper Paleolithic period in Europe, e.g., in the southeastern Alps (Verpoorte 2012). Indeed, it is striking that with a single exception all Acheulean sites in high-altitude environments are located in Ethiopia (Chavaillon and Piperno 2004; de la Torre 2011).
Table 1

Finds of bifaces in high-altitudes. Single finds from northwest Iran (Biglari and Shidrang 2006) and Namibia (Breunig 2003) are not included

Name

Location

~ Altitude m a.s.l.

Finds

References

Tsona

Caucasus

2150

134 Lithics including at least 18 Acheulean bifaces, dating to the end of OIS 7

92% bones Ursus spelaeus

Doronichev 2008

Melka Kunture

Ethiopia

2020

More than 70 sites ranging from the Oldowan to the Late Stone Age. Besides few Early Acheulean sites, especially a later phase of the African Acheulean is well-represented (Gombore II, dated to ~ 0.8 myr ago, Garba I, dated to ~ 0.5 myr ago)

Chavaillon and Piperno 2004

Gadeb

Ethiopia

2300

Eight localities dated between 1.45 and 0.7 myr ago with more than 50 hand axes/large cutting tools (LCT)

de la Torre 2011

Conclusions

The site DEN12-A02 shows that hominins might have settled in high-altitude regions already before the advance of Homo sapiens sapiens. This would question the concept of modern humans’ superiority in a wide range of domains, such as subsistence strategies and hunting equipment in comparison to extinct hominins (for a critical discussion of this concept see: Villa and Roebroeks 2014). In any case, for millennia modern Homo sapiens seemed to have no reasons to colonize high mountains in Europe.

Why hominins conquered the tropical high-altitude habitat already at this early time is still an open question. Was the area a common habitat or was it only used as a refugium during times of environmental stress? Is the case of Dendi, an exception from the general settlement scheme or is the absence of sites the result of a research deficit in high-altitude regions? It is striking that with only one exception, all Acheulean sites in high-altitude environments are located in Ethiopia. Under certain environmental conditions, high mountains in tropical zones might have been favorable ecological niches despite the general stress factor for hominins in high altitudes. Fresh water availability may have played a key role. Modern circulation patterns suggest the Ethiopian Highlands are likely to have received more rainfall than surrounding regions of northern Africa and the Horn during prehistoric times. The region receives moisture from both the Atlantic and Indian Ocean system (Umer et al. 2004) and as a major topographic feature, the highlands capture high orographic rainfall. In the case of Mount Dendi, the crater lakes, if they already existed, might have been important water reservoirs during arid periods.

The ongoing analysis of lacustrine and terrestrial sediment cores from the crater lakes and the caldera deposits hopefully will elucidate the climate history and environmental conditions of the area and might help to answer these questions.

Notes

Acknowledgments

We thank the local residents of Mt. Dendi for their support and participation in field research. The Ethiopian Authority for Research and Conservation of Cultural Heritage (ARCCH) and regional and zonal cultural bureaus facilitated fieldwork and museum studies. We thank all participants of the fieldwork, which had to stand the sometimes-harsh environmental conditions. Special thanks to Asfawossen Asrat Kassaye and Tamrat Endale for their support during the fieldwork and fruitful discussion, Wei Chu for his helpful comments, Ingrid Koch for the lithic drawings, and Lutz Hermsdorf-Knauth for help with the figures. We are grateful to the University of Cologne for administrative support, especially Dr. W. Schuck from the office of the CRC 806. Finally, we are grateful to the two anonymous reviewers for their very helpful comments and suggestions that significantly improved the manuscript.

Funding information

Funding was provided by the Deutsche Forschungsgemeinschaft (DFG) in frame of the Collaborative Research Center 806 at the University of Cologne.

Compliance with Ethical Standards

Conflict of Interest

On behalf of all authors, the corresponding author states that there are no conflicts of interest.

References

  1. Abbate, E., Bruni, P., & Sagri, M. (2015). Geology of Ethiopia: a review and geomorphological perspectives. In P. Billi (Ed.), Landscapes and landforms of Ethiopia. World geomorphological landscapes (pp. 33–64). Dordrecht: Springer.Google Scholar
  2. Abebe, T. (2014). The occurrence of a complete continental rift type of volcanic rocks suite along the Yerer-Tullu Wellel volcano tectonic lineament, Central Ethiopia. Journal of African Earth Sciences, 99, 374–385.CrossRefGoogle Scholar
  3. Abebe, T., Mazzarini, F., Innocenti, F., & Manetti, P. (1998). The Yerer-Tullu Wellel volcanotectonic lineament: a transtensional structure in central Ethiopia and the associated magmatic activity. Journal of African Earth Sciences, 26, 135–150.CrossRefGoogle Scholar
  4. Adimassu, Z., Mekonnen, K., Yirga, C., & Kessler, A. (2014). Effect of soil bunds on runoff, soil and nutrient losses, and crop yield in the central highlands of Ethiopia. Land Degradation & Development, 25, 554–564.CrossRefGoogle Scholar
  5. Aldenderfer, M. (2014). Altitude environments in archaeology. In C. Smith (Ed.), Encyclopedia of global archaeology (pp. 163–168). New York: Springer.CrossRefGoogle Scholar
  6. Basell, L. S. (2008). Middle Stone Age (MSA) site distributions in eastern Africa and their relationship to Quaternary environmental change, refugia and the evolution of Homo sapiens. Quaternary Science Reviews, 27, 2484–2498.CrossRefGoogle Scholar
  7. Beal, C. (2001). Adaptation to altitude: a current assessment. Annual Review of Anthropology, 30, 423–456.CrossRefGoogle Scholar
  8. Berghold, F., & Schaffert, W. (2009). Handbuch der Trecking- und Expeditionsmedizin. München: DAV.Google Scholar
  9. Beyene, Y., Katoh, S., WoldeGabriel, G., Hart, W. K., Uto, K., Sudo, M., Kondo, M., Hyodo, M., Renne, P. R., Suwa, G., & Asfaw, B. (2013). The characteristics and chronology of the earliest Acheulean at Konso, Ethiopia. PNAS, 110(5), 1584–1591.CrossRefGoogle Scholar
  10. Biagi, P., & Starnini, E. (2015). Human settlement and environmental exploitation of Valcamonica-Valtrompia watershed from the beginning of the Holocene to the Middle Ages. Natura bresciana, 39, 249–259.Google Scholar
  11. Biglari, F., & Shidrang, S. (2006). The lower Paleolithic occupation of Iran. Near Eastern Archaeology, 69, 160–168.Google Scholar
  12. Breunig, P. (2003). Der Brandberg. Köln: Heinrich-Barth-Institut.Google Scholar
  13. Chavaillon, J., & Piperno, M. (Eds.). (2004). Studies on the early Paleolithic site of Melka Kunture, Ethiopia. Florence: Instituto Italiano di Preistoria e Protostoria.Google Scholar
  14. Chazan, M. (2015). Technological trends in the Acheulean of Wonderwerk cave, South Africa. African Archaeological Review, 32, 701–728.CrossRefGoogle Scholar
  15. Clark, J. D., & Kurashina, H. (1979). An analysis of Earlier Stone Age Bifaces from Gadeb (locality 8E), northern bale highlands, Ethiopia. South African Archaeological Bulletin, 34(130), 93–109.CrossRefGoogle Scholar
  16. Degefu, F., Herzig, A., Jirsa, F., & Schagerl, M. (2014). First limnological records of highly threatened tropical high-mountain crater lakes in Ethiopia. Tropical Conservation Science, 7(3), 365–381.CrossRefGoogle Scholar
  17. Doronichev, V. B. (2008). The lower Paleolithic in Eastern Europe and the Caucasus: a reappraisal of the data and new approaches. PaleoAnthropology, 2008, 107–157.Google Scholar
  18. Foerster, V., Vogelsang, R., Junginger, A., Asrat, A., Lamb, H. F., Schaebitz, F., & Trauth, M. H. (2015). Environmental change and human occupation of southern Ethiopia and northern Kenya during the last 20,000 years. Quaternary Science Reviews, 129, 333–340.CrossRefGoogle Scholar
  19. Gallotti, R., Collina, C., Raynal, J. P., Kieffer, G., Geraads, D., & Piperno, M. (2010). The early middle Pleistocene site of GomboreII (Melka Kunture, upper awash, Ethiopia) and the issue of Acheulean bifacial shaping strategies. African Archaeological Review, 27, 291–322.CrossRefGoogle Scholar
  20. Gallotti, R. & Mussi, M. (2017). Two Acheuleans, two humankinds: From 1.5 to 0.85 MA at Melka Kunture (Upper Awash, Ethiopian highlands). Journal of Archaeological Science s 95, 1–46.Google Scholar
  21. Gallotti, R., Raynal, J.-P., Geraads, D., & Mussi, M. (2014). Garba XIII (Melka Kunture, Upper Awash, Ethiopia): a new Acheulean site of the late Lower Pleistocene. Quaternary International, 343, 17–27.CrossRefGoogle Scholar
  22. Pik, R., Marty, B., Carignan, J., & Lavé, J. (2003). Stability of the Upper Nile drainage network (Ethiopia) deduced from (U–Th)/he thermochronometry: implications for uplift and erosion of the Afar plume dome. Earth and Planetery Science Letters, 215(1), 73–88.CrossRefGoogle Scholar
  23. Piperno, M., Bulgarelli, G. M., Gallotti, R. (2004). Prehistoric archaeology. The site of Garba IV. The lithic industry of Level D. Tools on pebble and percussion material. In: Chavaillon, J. & Piperno, M. (eds.) Studies on the Early Paleolithic of Melka Kunture, Ethiopia, 545–580.Google Scholar
  24. Richter, J. (2004). Copies of flakes: operational sequence of foliate pieces from buran-Kaya III level B. In V. B. Chabai, K. Monigal, & A. E. Marks (Eds.), The Middle Paleolithic and Early Upper Paleolithic of eastern Crimea (pp. 233–248). Liege: ERAUL.Google Scholar
  25. Richter, J. (2006). Neanderthals in their landscape. In: Demarsin, B. & Otte, M. (eds.) Neanderthals in Europe. Liège – Tongeren, ERAUL 117 & ATVATVCA 2, 51–66.Google Scholar
  26. Richter, J. (2018). Altsteinzeit. Der Weg des frühen Menschen von Afrika bis in die Mitte Europas. Stuttgart: Kohlhammer.Google Scholar
  27. Schick, K., & Toth, N. (2017). Acheulean industries of the Early and Middle Pleistocene, Middle Awash, Ethiopia. L’anthropologie, 121, 451–491.CrossRefGoogle Scholar
  28. Shipton, C. (2018). Biface knapping skill in the east African Acheulean: progressive trends and random walks. African Archaeological Review, 35, 107–131.CrossRefGoogle Scholar
  29. Shipton, C., Clarkson, C., Pal, J. N., Jones, S. C., Roberts, R. G., Harris, C., Gupta, M. C., Ditchfield, P. W., & Petraglia, M. D. (2013). Generativity, hierarchical action and recursion in the technology of the Acheulean to Middle Palaeolithic transition: a perspective from Patpara, the Son Valley, India. Journal of Human Evolution, 65(2), 93–108.CrossRefGoogle Scholar
  30. de la Torre, I. (2011). The Early Stone Age lithic assemblages of Gadeb (Ethiopia) and the developed Oldowan/early Acheulean in East Africa. Journal of Human Evolution, 60, 768–812.CrossRefGoogle Scholar
  31. de la Torre, I., Mora, R., Arroyo, A., & Benito-Calvo, A. (2014). Acheulean technological behavior in the Middle Pleistocene landscape of Mieso (East-Central Ethiopia). Journal of Human Evolution, 76, 1–25.CrossRefGoogle Scholar
  32. Tsukamoto, S., Murray, A. S., Huot, S., Watanuki, T., Denby, P. M., & Bøtter-Jensen, L. (2007). Luminescence property of volcanic quartz and the use of red isothermal TL for dating tephras. Radiation Measurements, 42, 190–197.CrossRefGoogle Scholar
  33. Umer, M., Legesse, D., Gasse, F., Bonnefille, R., Lamb, H.F., Leng, M.J., Lamb, A.A. (2004). Late Quaternary climate changes in the Horn of Africa. In: Battarbee, R.W., Gasse, F., Stickley, C.E. (Eds.) Past climate variability through Europe and Africa (pp. 159–180). Dordrecht: Springer.Google Scholar
  34. Verpoorte, A. (2012). Caching and retooling in Potočka Zijalka (Slovenia). Implications for Late Auragnacian land use strategies. Archäologisches Korrespondenzblatt, 42, 135–151.Google Scholar
  35. Villa, P., & Roebroeks, W. (2014). Neandertal demise: an archaeological analysis of the modern human superiority complex. PLoS One, 9(4), 1–10.CrossRefGoogle Scholar
  36. Wagner, B., Wennrich, V., Viehberg, F., Junginger, A., Kolvenbach, A., Rethemeyer, J., Schaebitz, F., & Schmiedl, G. (2018). Holocene rainfall runoff in the central Ethiopian highlands and evolution of the River Nile drainage system as revealed from a sediment record from Lake Dendi. Global and Planetary Change, 163, 29–43.CrossRefGoogle Scholar
  37. Xue, L., Alemu, T., Gani, N. D., & Abdelsalam, M. G. (2018). Spatial and temporal variation of tectonic uplift in the southeastern Ethiopian plateau from morphotectonic analysis. Geomorphology, 309, 98–111.CrossRefGoogle Scholar
  38. Zinaye, B. (2014). Geological and geomorphological characterization of the Dendi caldera, west Central Ethiopia: implications for paleo-environmental reconstruction using lake sediment cores. MSc. Thesis University of Addis Ababa.Google Scholar

Copyright information

© Springer Nature Switzerland AG 2018

Authors and Affiliations

  1. 1.Institute of Prehistoric ArchaeologyUniversity of CologneCologneGermany
  2. 2.Institute of GeographyHeidelberg UniversityHeidelbergGermany
  3. 3.Institute of GeographyUniversity of CologneCologneGermany
  4. 4.School of Earth SciencesAddis Ababa UniversityAddis AbabaEthiopia

Personalised recommendations