Friday, January 18, 2013

A conversation with Dr. Amanuel Beyin

Part II

 Dr. Amanuel Beyin at an excavation site.

Issayas: What is the importance and evidences of first human exploitation in the marine resources at the coast of the Red sea such places as Asfet, Gelealo NW, Mise East (the sites where you studied for your PhD research), Abdur  and etc.?

Dr. Amanuel: As we all know, Eritrea was at war during most of the seminal years in the history of archaeological research in East Africa, 1960’s to the 80’s. As such, much of Eritrea’s coastal territories had seen little prior research due to protracted political instability and environmental adversity of the region.  The first archaeological evidence for prehistoric human adaptation along the Eritrea coast has come from the site of Abdur (eastern coast of the Gulf of Zula), where a geological survey in the late 1990’s documented stone tools embedded in a coral reef deposit dating to ~125,000 years ago. The Abdur evidence suggests the presence of coastal adaptation by African hominids along the Red Sea coast prior to the generally accepted date for Homo sapiens dispersal out of Africa. The association of artifacts with oysters, shellfish and terrestrial mammals at Abdur has suggested to researchers a mixed subsistence strategy, involving beach-combing, and hunting terrestrial game along the shorelines of the Gulf.  Stimulated by the Abdur discovery, in May 2005, my adviser and I set out to conduct a pilot archaeological exploration on the southern peripheries of the Gulf of Zula and interior plains of the Buri Peninsula, to further assess the archaeological potential of the landscapes outside of the Abdur proximity. The survey documented more than a dozen sites from near coastal and inland contexts representing different age ranges. In two subsequent field seasons, my team (all Eritreans) conducted intensive survey and excavation at three sites: Asfet, Gelalo NW and Misse East. The Asfet site produced stone tools, based on typological attributes, are believed to date to between 100,000 – 50,000 years ago. The other two sites, Gelalo and Misse produced stone tools in association with mollusk shells (presumably food refuse) dated to between 8000 and 5000 years ago.

Asfet setting off the coast of the Gulf of Zula

Gulf of Zula and Buri Peninsula

Dr. Amanuel surveying

Asfet, Eritrea. 2006.


Public outreach with local elders at Gelalo.

Eritrean field crew at Gelalo site, Eritrea in 2006.

All in all, the evidence suggests the presence of intermittent human settlement in the area, ranging in age 100,000 - 5000 years ago. The Asfet stone tool assemblage is particularly important because it represents an archaeological culture (referred to as Middle Stone Age) associated with the Homo sapiens populations that are believed to have launched successful dispersal out of Africa. The evidence reinforces the Abdur discovery in confirming the presence of coastal adaptation by African hominids along the Red Sea coast prior to their dispersal out of Africa. Whether the Asfet and Abdur hominids had directly dispersed to Arabia or Eurasia is difficult to prove. It is still possible that these hominids had returned to the hinterlands of the Horn once living around the coast became precarious for any reason, but at least one of the contemporary or descendant hominids must have made the long trek to Asia.  In a broader anthropological context, the evidence attests the degree of our ancestors’ adaptive acuity in occupying such a strategic area where they could maximize their survival chance by exploiting both marine and terrestrial resources. This acuity was a necessary prerequisite for our ancestors’ subsequent evolution into a culturally more complex species, capable of colonizing all of earth’s frontiers…and possibly other planets, soon!

Issayas:  If I am not mistaken, you are studying the stone industries and varied shell types from the above sites in coastal Eritrea to understand the Human behavior, the paleo-environment and paleo-ecology. How does one understand the behavior and why do one need to understand the aforementioned?
Dr. Amanuel: Yes, in my dissertation I reported on a thorough description of the stone tool industries documented at the three sites I mentioned above. The results of my work have been published in peer reviewed journals and as a monograph (see a link to my personal website below to find out more about my scholarly work). The paleoenvironmental and paleoecological aspects have not been examined yet. The diversity of stone tools at the sites is quite striking. We have artifacts that look like they were used for butchering, as arrow points and for piercing/slicing purposes. Often times, stone tools represent the most common surviving evidence of human behavior at archaeological sites, not just because they were the only tools humans made, but they preserve better. By virtue of being rocks, they are less susceptible to decomposition and alteration by weathering, unlike wood, hide or fabric, which can easily decay. One way to reconstruct past human behavior using stone tools is by examining the sources of the raw materials used and the design aspects of the final products (variability in shape and size of the tools). Stone tool making requires selecting suitable raw materials and an understanding of the fracture mechanics of each rock type. The Asfet inhabitants utilized about seven rock types, each of which has its advantages and disadvantages. For example, obsidian, a modestly utilized rock at Asfet, is brittle and can produce flakes with sharp edges. However, it is a very dangerous rock during knapping. The sharp flakes and shatters can cut through the skin of one’s hand at a split of a second if you don’t understand how to manipulate it. Other rocks are not as brittle as obsidian, but are safer to manipulate and endure edge damage better (remember those tools can get worn after repeated use). The majority of the rocks utilized at Asfet appear to have been procured from the local exposures, meaning the inhabitants did not transport the raw nodules for longer distances (they were lucky!).


Asfet artifacts

Gelalo and Misse artifacts

In addition to utilizing a broad range of raw materials, the Asfet humans produced a variety of tools, presumably to meet their daily survival needs. For example, among the common tools we observe at Asfet are the triangular points (see figure), which are usually associated with making arrow points that could be used for hunting. Likewise, while the large almond shaped hand axes are often interpreted as characteristic of meat butchering and scraping activities, the pointed perforators (see figure) are typically associated with piercing and drilling. The younger sites of Gelalo and Misse are characterized by different toolkits, collectively referred to as microliths because of their diminutive nature. These tools appear to have been used as knives and inserts into wooden shafts for making spears. The discovery of abundant stone tools with design aspects indicative of hunting activity and a variety of mollusk shells (large enough to be consumed as food) indicates that the inhabitants of the Eritrean sites employed a broad subsistence strategy, involving hunting terrestrial game and gathering aquatic resources from the shoreline.  By all accounts, we are looking at hunter-gatherers that lived off of the blessings of nature. The same is true of those hominids that spread out of Africa. It took several millennia after these settlements for domestication/agricultural innovations to set off in the region.

Issayas:  How does your study contribute to the current knowledge of the Human evolution researches and dispersal?

Dr. Amanuel: As I mentioned earlier, by virtue of its strategic location along the Red Sea basin (one of the potential dispersal corridors for early humans) and being part of the East African tropical ecosystem (where Homo sapiens are believed to have first appeared), Eritrea represents a critical region of East Africa in the ongoing human origins research. Unfortunately, much of the coastal region had not seen adequate research in the past. This has hindered a well-informed assessment of the contribution of the region to human origins and dispersal theories. The plain question I asked myself when developing the project I described above was: what would be the contribution of Eritrea to human origins and dispersal research?  Of all the sites I examined so far, the Asfet assemblage is particularly important in the context of human origins or dispersal research. As noted above, the assemblage broadly dates to 100,000 – 50,000 years ago, which is a critical period in the evolution and dispersal of anatomically modern humans out of Africa. The evidence exhibits reasonable affinity with northeast African, the Nile Valley and Southern Arabian Middle Stone Age Industries, which means that the inhabitants of Asfet had cultural and biological (?) relationships with the hominids that left cultural and fossil traces in those regions. We do not have hominid fossil remains from Asfet or Abdur yet, but the artifacts are comparable with cultural findings at other East African sites that yielded Homo sapiens fossils (eg. Omo Kibish and Herto in Ethiopia).  While much needs to be done to fully understand the chronological and paleoenvironmental contexts of Asfet, the evidence corroborates the plausibility of the region as a potential refugium and departure point for early human dispersal. Hunter-gatherers successfully adapted to coastal habitats along the Eritrean coast may have served as source populations for the early inhabitants of Arabia and Southeast Asia. Given the paucity of Stone Age record from the western side of the Red Sea basin, the finding provides a much needed reference datasets for future research in the region. Even though there are only a few known coastal sites from the African side of the Red Sea, it is likely the case that the coastal territories of Eritrea and its neighboring regions (Sudan, Somalia and Djibouti) were continuously visited by our early ancestors. Finally, the discovery of the Asfet and Abdur Middle Stone Age sites from the Gulf of Zula attests that numerous sites can be discovered along the African side of the Red Sea basin by future systematic survey.

Issayas: How and when did the first human species spread from the African side of the Red Sea to the Asian side?

Dr. Amanuel: It is not yet well understood as to how exactly early humans dispersed from the African side to the Arabian side of the Red Sea, but there are some hypotheses worth sharing. One hypothesis is that, they may have used canoes or floating rafts to navigate the narrowest section of the basin, which is located across the Strait of Bab el Mandeb. The problem is that wood doesn’t preserve for a long time, so we can’t prove this hypothesis. Alternatively, early humans could have swum the narrow strait during periods of extreme low sea-level-stand. But, given the violent wind currents across the strait, this view does not seem plausible. Others have suggested the presence of episodic land-bridges between the two sides of the basin. There is tangential evidence supporting this view. A recent study of mtDNA variation among southwestern Arabian and Horn of African baboon populations (Papio hamadryas hamadryas) shows that the ancestral lineage of this species originated in the Horn of Africa and entered Arabia in the time range of 200,000 – 80,000 years ago. The striking finding from the study is that the SW Arabian hamadryas baboons are not related to any other baboon populations in the northern parts of Arabia (meaning they don’t have close relatives in the Middle East or northern Arabia). Based on this observation, scientists suspect that the only way the ancestors of the Arabian baboons could have reached the region is via temporary land bridges formed during glacial maxima across the Red Sea (eg. Bab el Mandeb). Hypothetically, the same route or land-bridge that the baboons have used to enter Arabia must have been equally accessible to early modern humans. One caveat with this scenario is that, marine isotopic data shows that the Red Sea has not been severed from the Indian Ocean for the past 400,000 years, which means, either the isotopic data is not picking up some short-lived periods of disconnections between the two bodies of water or there is something else we should know. Perhaps, early humans used no other route except the Sinai land-bridge to disperse out of Africa. Like any other scientific enterprise, the issue of early human dispersal is full of unresolved riddles.

Front cover of Dr. Amanuel's new book.

When did humans reach Arabia? I don’t have a definitive answer to the question, but we know that human ancestors have continuously lived in that region at least for the last one million years. Early humans and their ancestors could have arrived there in waves, through either of the potential routes mentioned above. Based on current genetic evidence, the most successful wave of Homo sapiens migration into Arabia is believed to have occurred ~ 75,000 years ago via the Bab el Mandeb. Some researchers dispute this time frame in favor of earlier dispersal dates. The artifacts from Arabian sites do show close resemblance with their African counterparts, but it is not possible to determine dispersal or arrival events based on cultural affinity alone. One culture can disperse to a new environment after several millennia of its first appearance at the source region. This topic being one of the hotly debated issues in paleoanthropology, I rather not waste the reader’s time with too many conjectures.

Issayas: Thank you for spending time from your busy schedule to answer my questions. Much appreciated.

Dr. Amanuel: Thank you for inviting me to offer my perspectives on this fascinating scientific topic.  

All pictures are courtesy of Dr. Amanuel.

Below are links to various works of Dr. Amanuel and his website.