RICERCA ITALIANA     

TRACING HOMO ERECTUS ALONG THE WESTERN COAST OF THE RED SEA FROM ERITREA TO SUDAN: ENVIRONMENTS AND PEOPLING DURING THE PLEISTOCENE

Università degli Studi di Firenze

Abstract

Homo erectus was a highly successful species. From his African homeland he found favourable pathways to disperse during Pleistocene times, possibly in more than one phase, across Eurasia to the Far East. The clues of these dispersals, although clear within the origin region in the East Arican Rift, fade away between East Africa and the Middle East. The northernmost finding in East Africa is the cranium of Homo erectus from Buia in the Eritrean Dankalia, dating back to 1My.
The applicants for this research program plan to start with an in-depth analysis of the features of this cranium (by means of advanced techniques, such as a portable High resolution CT scanner devised on purpose) in order to clarify his morphological, paleoneurological, physiological placement within the evolutionary pattern towards Homo sapiens.
The Buia Homo cranium, as well as other dental and postcranial remains, were found thanks to the identification, within the Buia sedimentary succession, of fossiliferous key-beds depositionally connected with swampy or fluvio-lacustrine environments. Search for similarly characterised successions in nearby areas will be expanded with the aim of locating new hominid remains that, similar to Buia, will be possibly associated with abundant vertebrate remains and Paleolithic artefacts.
New fossiliferous/archaeological sites will be put into a chronostraigraphic context by magnetostratigraphy and radiometric dating on volcanic ashes. Paleoenvironmental and paleoclimatic conditions in selected sedimentary successions will be studied by detailed sedimentological analyses, by the paleoecologic study of mammal faunas and by the analyses of stable isotopes (O18, C13).
Taking into account the paleo-landscapes and the geological contexts characterising most of the East African Rift paleoanthropological sites, the dispersal of early humans seems to have been driven by a landscape within a scenario of diversified environments from highlands (rift shoulders) to lowlands (rift bottom) where lakes and perennial or seasonal rivers were scattered in wide savannahs.
On the basis of such background observations, we propose a research aimed at identifying possible areas of hominid dispersal routes towards Eurasia. For this reason, we plan to investigate areas from Eritrea northwards, along a belt that (according to preliminary field observation and bibliographic indications) could have been characterised by morphologies and environments comparable to the one observed in Buia or in other basins of the East African Rift.
One target area has been identified where Plio-Pleistocene fluvio-lacustrine sedimentary successions outcrop (e.g. the large Tokar delta), extending northward from Eritrea along the entire Sudan Red Sea coast. Another interesting target area in NE Sudan is represented by the Kassala region, characterized by outcropping sediments of the lake Sudd margins. In Plio-Pleistocene times, lake Sudd was a vast lake (occupying most of central Sudan) where some great African rivers (White and Blue Nile, Atbara etc.) debouched. Given the remarkable geographic extension of the target regions, small working areas will be selected on the basis of preliminary air-photos and satellite images analysis.
Paleoanthropological, archeological and paleontological sites, sedimentologic and stratigraphic logs, geological and geomorphological surveys, as well as samples for different analyses (stable isotopes, paleomagnetism, etc.) will be GPS geo-referenced, and acquired in a Geographic Informatics System (GIS) that will also record all data from laboratory analyses. The GIS system will simplify the handling, processing and interpretation of the data deriving from the wide range of disciplines involved in the project.
All phases and aspects of the proposed research have been submitted to academic institutions, museums and governmental organizations in Eritrea and Sudan and a scientific collaboration has been agreed. <<<

Principal Investigator

Ernesto ABBATE Università degli Studi di FIRENZE

Research Objectives

FOREWORD
The search for hominid remains is one of the objective of several international research teams. Such kind of research activities are plenty of difficulties and seldom result in new findings, the latter being precious due to their intrinsic rarity.
On the basis of relatively few remains, in most cases extremely fragmentary, the available modern technologies allow to derive crucial information for reconstructing phases and patterns of human evolution.
The reconstruction of paleo-environments and the study of Paleolithic artefacts (in most cases associated to fossil remains) both give us important information to evaluate the cultural placement of hominids and to understand factor that drove their dispersal across the African continent and over, in Eurasia. The research member of the units proposing the present research project are working on the above lines. They compose the only Italian group, active in East Africa, who has on his credit paleoanthropological findings: the Homo erectus cranium (with associated teeth and pelvis) published in Nature (Abbate et al., 1998) and a second finding in 2003 (a pubic symphysis of a male individual). Thanks to these results this Italian team can be aligned to other teams (from United States, United Kingdom and France) having a long tradition in researches on paleoanthropological sites and their geological context.
Our team includes specific expertises on the study of physical and (paleo-) biological environment in several areas of east Africa, on chronologic placement of sedimentary successions and geologic events, on physical anthropology and paleoanthropology, on setup and use of high resolution CT scanner devices aimed to the analysis of fossil remains, and on Paleolithic archaeology.

IN ERITREA AND SUDAN: WHY?
We feel worth to anticipate, to complete what will be exhaustively exposed in the next points, that both countries are actually unexplored (or under-explored) for what concerns Quaternary paleontology and paleoanthropology. This could be surprising, specially due to their geographic location in proximity to regions, like Ethiopia or Kenya, well known for their celebrated paleoanthropological record. As a matter of fact, we have to take into account that long-lasting conflicts or fighting have been solved since about ten years in Eritrea, and even more recently (and only partially) in Sudan.
In Eritrea, the recent documented findings by the applicants, have identified the region of the northern Danakil depression as an extremely promising area. The occurrence of comparable geological contexts outcropping along the Red Sea coastal region in Sudan let to hypothesize favourable conditions also in these areas.
Both in Eritrea and in Sudan, the applicants have discussed and formalised collaboration agreements with academic institutions, museums and governmental organizations.
Field work in Eritrea and Sudan are carried out in difficult areas, far away from main roads and principal town/villages. For this reason each mission has an high cost in term of all-terrain vehicles rental for personnel and equipment transportation and in term of the setup and logistic of working camps for Italian and local researchers.

PROGRAM OBJECTIVES
The applicants plan to:
- perform an in-depth analysis of the anatomical features of the one-million-year-old Buia Homo erectus cranium, as well as of other human remains from the same site. The study will be carried out also by means of advanced techniques, such as a portable High resolution CT scanner (devised on purpose) in order to clarify his morphological, paleoneurological, physiological placement within the evolutionary pattern towards Homo sapiens.
- to explore the Eritrea Plio-Pleistocene basins, nearby the Buia basin, by using the same research criteria that in the previous activities led to the individuation of sedimentary layers (and physical environments) more suitable for the conservation of fossil remains (vertebrates, including humans) and Paleolithic artefacts.
Field survey and detailed analyses will include: basin analysis, sequence stratigraphy, megnetostratigraphy, biostratigraphy and biochronology, stable isotopes analyses on organic carbonates, radiometric dating on volcanic ashes and fission tracks dating for landscape evolution, characterization of technocomplexes of Paleolithic artefact assemblages.
Conclusions derived from previous studies will be checked and verified. It has been hypothesised, in agreement to evidences from geological contexts characterising most of the East African Rift paleoanthropological sites, that the dispersal of early humans has been driven by a landscape within a scenario of diversified environments from highlands (rift shoulders) to lowlands (rift bottom) where lakes and perennial or seasonal rivers were scattered in wide savannahs.
- extend our exploratory field work to the Red Sea coastal region of Sudan. This new research is aimed at identifying Plio-Pleistocene sedimentary succession that may yield new hominid remains and/or associated vertebrate faunas and Paleolithic artefacts, along an hypothesised area of hominid dispersal route towards Eurasia.
We plan to investigate areas from Eritrea northwards, along a belt that (according to preliminary field observation and bibliographic indications) could have been characterised by morphologies and environments comparable to the one observed in Buia or in other basins of the East African Rift.
One target area has been identified where Plio-Pleistocene fluvio-lacustrine sedimentary successions outcrop (e.g. the large Tokar delta), extending northward from Eritrea along the entire Sudan Red Sea coast. Another interesting area in NE Sudan is represented by the Kassala region, characterized by outcropping sediments of the lake Sudd margins. In Plio-Pleistocene times, lake Sudd was a vast lake (occupying most of central Sudan) where some great African rivers (White and Blue Nile, Atbara etc.) debouched.
- to setup a Geographic Information System (GIS) where will be acquired GPS geo-referenced data for Paleoanthropological, archaeological and paleontological sites, sedimentologic and stratigraphic logs, geological and geomorphological surveys, as well as samples for different analyses (stable isotopes, paleomagnetism, etc.). The GIS system will also record all data from laboratory analyses. <<<

Timescale

24 months

National and international background

East Africa is the region where started and developed most studies on early hominization, on Plio-Pleistocene peopling and early bio- and cultural human evolution. It is from this region that main phases of the so called "out-of-Africa" dispersal of our ancestors (Anton & Swisher 2004) started, and possibly were repeated during time (Aguirre & Carbonell 2001).
The latest Pliocene to Early Pleistocene interval represents a time span when crucial evolutionary phases in human evolution occurred, but the paleoanthopological record of this time span still is relatively scarce (cfr. Wood 1991).
The last few years have seen remarkable new findings across Europe (Italy, Spain) or at the gates of Europe (Georgia) yielding new clear evidences of a human dispersal out of the African continent since the latest Pliocene, at about 1,8 Ma (Gabunia et alii 1999; Oms et alii 1997; Ascenzi et alii 1996). Remarkable in this respect are the Early Pleistocene Paleolithic artefacts found in the Guadix-Baza basin (Spagna; Oms et alii 2002). Even more important are the 1,8 Ma human remains and Paleolithic artefacts from Dmanisi (Georgia) (Gabounia et alii 1999; Lordkipanidze et alii 2005; Vekua et alii 2002).
These new data allow the drawing of a new scenario for the understanding of early human dispersal(s) out of Africa towards the Eurasia, in a wider context of vertebrate fauna dispersal (and also paleoecological and paleoclimatological evolution).
The 1995-2003 discoveries in Buia (Eritrea) of a well preserved cranial (UA 31), dental, and postcranial remains, dated approximately 1 My and excellently preserved, referred to Homo aff. H. erectus (Abbate et al. 1998; Rook et al. 1998, 1999; Macchiarelli et al. 2002, 2004a, b; Bondioli et al. 2005) are of extreme relevance.
UA 31 represents an almost complete adult cranium, lacking the mandible. The new estimate of endocranial volume is 950 cc (cfr. Conroy et al. 2000; Asfaw et al. 2002). This specimen preserves most of the facial anatomy, a striking fact in the African and Asiatic human fossil record, (cf. Rightmire 1998; Anton 2002, 2003). The cranial base is incomplete, and all dental crowns are missing, despite the presence in situ of some upper roots. From the same site, a few human postcranial remains were also discovered. Two associated pelvis fragments, and a portion of a pubis bone with symphysis. These remains are extremely useful for individual body size and sex determination (Macchiarelli et alii 2002, 2004b). Still unsatisfactory is the Buia cranium CTscan record, whose quality is of a very rough resolution, far from comparative data available in literature for other specimens (Thomson & Illerhaus 1998).
International interest in the geo-paleontological and paleoanthropological research developed in Eritrea, and in particular for the morpho-architectural characters and potential taxonomic status of the UA 31 specimen (cfr. Asfaw et al. 2002; Anton 2003) is increasing. As a matter of fact, the recent discovery at Bouri (middle Awash, Ethiopia) of a calvarium very close (morphologically, chronologically and geographically) to the Buia remain (Asfaw et alii 2002), further increased the international interest for the Buia fossils.
During the Early Pleistocene, up until one million years BP, Homo genus is represented in North-Eastern Central Africa by some specimens, commonly referred to as H. erectus/ergaster (or erectus s.l.), which seem characterized by a relevant morphological and anthropometric variation (Anton 2002, 2003; Macchiarelli et al. 2004a). The definition of a unique politipic taxon seems still more difficult (cf. Asfaw et al. 2002; Gilbert et al. 2003) as new discoveries from Ileret (KNM-ER 42700) and Olorgesaile (KNM-OL 45500) are added to known specimens such as OH 12 from Olduvai Gorge. They confirm the co-inhabitancy of small adults, with inferior to 800 cc cranial capacity, and more robust individuals (e.g., OH 9, Daka). This potential morpho-dimensional "dichotomy" highlights the importance of the Eritrean fossils as "evolutionary transition" between Early-Middle Pleistocene. The results of the analyses of the potential paleobiological relations between Buia and Daka specimens (Asfaw et al. 2002) and the characterisation of the respective paleoecological scenarios are deputed to have a key role in paleoanthropology, in order to comprehend the origins and the early evolutionary phases of H. heidelbergensis/sapiens.
Buia site represents the northernmost evidence of the East African Plio-Pleistocene paleoanthropological record, located about 500 km Nord to Daka (Bouri). It represents thus a key locality for the study of timing and patterning human dispersal pathways out of the African continent. North of Buia, the first Plio-Pleistocene evidence available is at Ubeidiya and Gesher Benot Ya'aqov, in the southernmost portion of Eurasiatic continent in Israel. Here, the Levantine corridor is well known for the occurrence of mammal faunas and hominids dispersing out of Africa towards Eurasia (e.g. Tchernov 1992; Ron & Levi, 2001). In fact, the documentation of human activity in these Pleistocene Israel sites is an evident proof of actual dispersal routes from African continent throughout the Dead Sea graben. Acceleration in the vertical tectonism which produced present physiography of the region, began slightly before man had started his way out of Africa northwards (Ben-Avraham et al. 2004). The first human dispersal began around 1.8Ma, in coincidence with the intense climatic and environmental changes, that started at the Plio-Pleistocene transition (de Menocal 1995).
A different route for early human dispersal out of Africa into Eurasia hypothesized in literature is across Gibraltar (Martinez 2005). This hypothesis is based on the occurrence of European carnivores like Ursus or Nyctereutes in a Late Pliocene / Early Pleistocene site in Morocco (Geraads 1997). Gibraltar strait however has been probably crossed occasionally and probably never acted as an effective dispersal pathway.
The most likely Homo erectus dispersal routes out of the African continent are traceable along the northernmost East African Rift (including the Danakil Depression and the Buia site) throughout northeastern Sudan and the Red Sea coastal regions until the Dead Sea and the Levantine corridor. These are actually the northernmost sector of a longer pathway that, starting from Tanzania, across Kenya and Ethiopia is detected along the east African rift by a well known documentation of celebrated archaeological and paleoanhropological sites. As a matter of fact, morpho-tectonics and climatic-environmental conditions that favoured northward dispersion occur noticeably within the complex of African rifts. African rifts are characterised by a frequent tectonic activity (Mohr 1967; Morley et al. 1992; Ghebreab 1998; Bonini et al. 2005) by the sinking of the rift floor and by the uplift of the margins. Thus, the main river drainages are controlled by structures and along the longitudinal axes of these tectonic depressions form and develop river systems, lakes and humid areas (Frostick & Reid 1989, 1990; Feibel 1999). The occurrence of transverse tectonic structures and/or volcanic structures accentuate the environment differentiation within each basin, determining high environmental variability and, consequently, favouring the increase in biodiversity. The continuous uplift of rift shoulders creates orographic barriers favouring the condensation of humid air-masses. Morphological difference in height and the intense atmospheric precipitations thus cause erosive processes producing in rapid sedimentation of detrital successions which have a good preservation potential for fossils.

SEDIMENTARY BASINS, PALEOANTHROPOLOGICAL AND ARCHAEOLOGICAL SITES ALONG THE EAST AFRICAN RIFT FROM TANZANIA TO ERITREA
This kind of morpho-tectonic and climatic-environmental conditions are typically found along the whole East African Rift, from Tanzania to Eritrea, where a number of hominid or Paleolithic sites are known within the rift sedimentary basins. We summarize here the main characteristic of these basin, from Tanzania to Eritrea in order to provide a regional reference frame.
In this context, the southernmost basin is Olduvai (Hay 1963). The celebrated Olduvai Gorge yielded a number of hominid remains and abundant Paleolithic industries. Beds I to IV cover the Plio-Pleistocene transition until about 0.7 Ma (Somi 1993). Bed I is made up by a fluvio-lacustrine succession rich in large mammals (including hominids) and birds. It passes to a clay-sandy succession (Bed II) representing depositional phases of rivers that, after flowing across wide savannahs were flowing into the lake. Bed III, characterized by reddish clays sands and conglomerates, testifies a climatic-environmental change towards more arid conditions and playa lakes. Bed IV, again, represents a depositional environment characterized by water abundance with rivers and lakes.
Moving northward, to the area of Turkana basin (northern Kenya), Early Pleistocene times are documented by sedimentary successions (rich in paleolithic industries) deposited in shallow lakes environments, passing to marginal lakes and eolic deposits (Brown & Feibel 1991).
The Omo basin, in southern Ethiopia, is located in the southern part of the Main Ethiopian Rift and is characterized by a series of semi-graben filled by fluvial, lacustrine and fan-delta depostis, with frequent interbedded volcanic layers. Hominids, including Homo erectus, and widespread mode I and mode II Paleolithic industries are known in this area (de Heinzelin 1983). Further North within the Main Ethiopian Rift, similar depositional conditions are reported at Gadeb (Williams et alii 1979) and Kesem-Kebena (Woldegabriel et alii 1992). Also in these sites, the occurrence of water bodies (rivers and lakes) seems to be a crucial aspect for human occupation in Early Pleistocene times. As a matter of fact, the high-standing level of water in the lakes and the widespread volcanism along the lowermost (topographic) rift parts may be responsible of the marginal distribution (in respect of the Rift axis) of some sites like Konso-Gardula (Asfaw et alii 1992) and Melka-Kunturè (Chavaillon & Piperno 2004).
Further North, in the Afar area (Tiercelin 1986) a number of Paleoanthropologic sites are reported in literature. Among them, we stress here the importance of the deposits outcropping at Daka/Bouri (middle Awash valley; Williams et alii 1986). Here, within the deltaic sand belonging to the Dakanihylo Member (Bouri Formation), a level dating back to 1 My, yielded the above mentioned Homo erectus calvarium, associated with Oldowan (mode I) and Acheulean (mode II) Paleolithic industries. The Bouri mammal assemblage, dominated by bovids, seems indicative of savannah open spaces with available water bodies.
The Buia basin sedimentary successions (more than 500 meters-thick) crops out in the Eritrean Danakil depression, about 500 km north of middle Awash, and covers a time span from the late Early Pleistocene to the early Middle Pleistocene (approx from 1,2 to 0,6Ma) (Abbate et alii 1998; 2004). Here, fluviatile sands, lacustrine clays and alluvial gravels are arranged in two lacustrine transgressive-regressive cycles. Buia human remains (referable to Homo cf. erectus and dated back to 1 My) and associated vertebrate faunas were living in savannah areas close to lake and rivers where permanent water resources were available and abundant. Paleolithic technocomplexes at Buia are dominated by Acheulean hand-axes (mode II) artefacts (Martini et alii 2004) and are comparable with the documentation of most East African Rift sites, especially with Bodo (Ethiopia) and Olorgesailie (Kenia) (Isaac 1977).
The sedimentary succession at Buia has been analysed for magnetostratigraphy. Four magnetozones have been recognised, and the level yielding the human remains has been correlated with the top of the Jaramillo sub-chron (Albianelli & Napoleone, 2004). Cyclostratigraphy detected within the magnetic signal, showing a relation with lithofacies alternancy, has been related to astronomic parameters driving climatic changes along the entire deposition history of the succession over a 500.000 years time across early and Middle Pleistocene.

PLIO-PLEISTOCENE SEDIMENTARY BASINS, PALEOANTHROPOLOGICAL AND ARCHAEOLOGICAL SITES ALONG THE RED SEA COASTS IN NORTHERN ERITREA AND SUDAN
Along the western Red Sea coast in northern Eritrea and Sudan, reports of paleoanthropological sites are rare if not absent. Despite this, some old geologic references (Baldacci 1891; Porro 1936) and recent large scale official geologic maps (Sudan Geological Research Authority, 1:1.000.000, 1981 e 1:2.000.000, 2004) give us interesting indications on the location and extension of Plio-Pleistocene successions.
Within this context it is worth to mention the finding of a Late Pleistocene fossil human cranium at Singa with associated lithics and mammals (Stringer 1979; Stringer et alii 1985; Mc Dermott et alii 1996). The site of Singa is located about 400 Km South of Kassala where crops out fluvio-lacustrine sediments deposited on the margins of the Plio-Pleistocene lake Sudd (Whiteman 1971; Said 1992), where White and Blue Niles debouched south of Khartoum.
In order to reconstruct the paleolandscape in these areas is essential to define the paleohydraulic and paleomorphological features deeply connected with the evolution of the fluvial systems and their wide terminal fans or fan-deltas. For example, the terminal fan of the Gash River (Abdullatif, 1989), a river nowadays flowing south of Kassala, was debouching into the lake Sudd. Also the Barca river is draining most of the northern Eritrean Plateau flowing into the Red Sea where, South of Port Sudan. has built-up the huge Tokar delta system.
No one of the above mentioned Plio-Pleistocene successions has been investigated for their archaeological, paleontological or paleoanthropological potential content. On the other hand, researches conducted for offshore petroleum exploration in the Sudanese continental shelf evidenced the occurrence of Oligo-Miocene to Pleistocene sediments along the Red Sea coasts North of Port Sudan (Carella & Scarpa 1962; Sestini 1965). The most recent portion of these successions has not been studied in detail but is reportedly made up by an alternation of fluviatile and paralic sands and gravels which can represent interesting successions for the aims of the present project.
This short review on Plio-Pleistocene East African sedimentary basins ends with a mention to the first basins yielding paleoanthropological evidences we find moving northward from East Africa. These are in Israel, along the Levantine corridor: Ubeidiya e Gesher Benot Ya'aqov sites (Ron & Levi 2001; Tchernov 1992; Bar-Yosief & Befer-Cohen 2001). Here the geological and paleoenvironmental context was by and large comparable with those occurring in the African Rift, being located within a rift depression within marginal lake context (Feibel 2001). <<<