BACKGROUND TO PALEOANTHROPOLOGY IN ETHIOPIA
WIC Nov 15, 2000
What is Paleoanthropology? The study of the prehistoric human past is called "paleoanthropology." Anthropology itself refers to the study of human beings. Paleoanthropology is the study of human ancestors in the distant
past. Since we can't travel back in time to observe these ancestors, scientists must use other kinds of evidence to understand what happened in the past. Today, paleoanthropologists study all aspects of the human
past. They pay particular attention to the biological and cultural dimensions of human ancestors. To study these dimensions, paleoanthropologists rely on evidence in the form of artifacts, fossilized bones of ancestors,
and the contexts that these things are found in. This is very difficult work. In general, the older something is, the greater the chance that the forces of nature have destroyed it. For this reason, most evidence
from the prehistoric past has disappeared. Paleoanthropologists actively search for traces of the past that have not disappeared, and they work to infer what happened by using these clues. There are three basic
sciences that contribute most data to paleoanthropology. Geology is the study of the earth. Geologists are scientists whose studies provide the dating of the fossils and artifacts. By studying the rocks and
sediments, geologists can assist in finding the fossils and artifacts needed for paleoanthropology. Once these antiquities are found, geologists are responsible for dating them and interpreting what the ancient landscapes
were like. The second major science involved in modern paleoanthropology is paleontology, the study of fossils. Fossils are traces of past life, ranging from bones of tiny mammals and birds, to footprints left by
dinosaurs,or human ancestors. In this sense, paleontologists are biologists of the past, visiting worlds that have almost disappeared except for the fossils that have been preserved. The third science comprising
modern paleoanthropology is archaeology. Before the invention of metals, most early human ancestors made and used stone tools. Archaeologists study these artifacts, and their contexts, in their efforts to understand how
human ancestors lived and behaved and died in the distant past. Archaeologists, geologists, and paleontologists work closely together in paleoanthropological research, each contributing vital information necessary to
understand human origins and evolution.
Paleoanthropology in Ethiopia
Ethiopia is
one of the best places in the world for conducting the science of paleoanthropology. This is because of the country's unique geological history. The Great Rift Valley is the most prominent feature of Ethiopian geology,
and this feature has been present for millions of years. Because of this, parts of the deep past have been preserved in the Main Ethiopian and Afar rifts. The artifacts and fossils contained in the rift's ancient lake
beds and riverbeds are the ingredients that paleoanthropologists need to explore the ancient past. Modern paleoanthropological research in Ethiopia is conducted by teams of geologists, paleontologists, and archaeologists
who work together in the field and in the laboratory. This research is conducted in Ethiopia under the Authority for Conservation of the Cultural Heritage (ARCCH) of the Ethiopian Ministry of Information and Culture.
The 'headquarters' for paleoanthropological research has traditionally been the National Museum of Ethiopia, located at Amist Kilo, in Addis Ababa. Here, Ethiopia's antiquities are studied, curated, and protected for
posterity. The paleoanthropological collections housed in Addis Ababa are unparalleled in their time depth and importance in human evolutionary studies, and these collections grow each year as different research projects
proceed. The Paleoanthropology Laboratory at the National Museum is the prime repository for Ethiopian fossils and paleolithic artifacts. It was built in the 1980s with funding from the National Science Foundation of
the U.S.. Since then this laboratory has been the focal point for paleoanthropology in Ethiopia. Field projects begin and end in this laboratory. Study of the objects and data collected by field projects is
conducted in this laboratory, and scientists from around the world come here to conduct comparative studies.
Fieldwork in Paleoanthropology
The artifacts and fossils needed by paleoanthropologists to study and understand the past are embedded in geological contexts where they have often lain undisturbed,
protected for millions of years. These deposits may be found where sediments accumulate, in the basins within the Ethiopian Rift Valley and Afar. As these sediments are deposited, they pile up and sometimes entomb parts
of animals, particularly the bones and teeth, which are most resistant to decay and can actually turn to stone, or fossilize. Cultural artifacts such as stone tools can also sometimes be found in these deposits. But all
of these paleoanthropologically important deposits are geological deposits, so paleoanthropological research must begin with geology. Geological deposits with paleoanthropological resources like stone artifacts and fossils
are very rare. Indeed, in Africa, most of these sites are confined to the rift valleys because it is here that sediments accumulated--elsewhere the continent's surface is eroding, and little can be preserved for millions of
years under these conditions. In contrast, rift valleys and their lakes and rivers are places that can 'capture' evidence from the past and preserve it by burial through time. Because these rift environments are
also geological active, the ancient sediments can return to the surface and begin to erode, exposing their precious antiquities and allowing their discovery by paleoanthropologists. However, even in the best circumstances,
these antiquities from the distant past are extremely rare. For example, even though the Ethiopian Rift Valley is known as one of the world's most important paleoanthropological research areas, its floor offers only
relatively small windows of exposed sediment. In fact, most of the rift floor has no paleoanthropological resources at all. Rather, the rift floor is most usually covered with recent volcanic rocks like lava flows, or
recent alluvium or grass cover. Ancient sediments are exposed only in small patches in the rift, and these patches are often called sites or study areas. Sites can be different sizes. Some cave sites like Porc
Epic are only a few tens of square meters, whereas some large open-air paleoanthropololgical sites such as the famous Omo locality in southern Ethiopia are hundreds of square kilometers in extent, with fossiliferous sediments
spanning millions of years exposed to modern erosion with each passing rainstorm. Paleoanthropological sites are found in different ways. Prior to the late 1980s when Dr. Berhane Asfaw launched a national inventory of
Ethiopia, several sites were found by accidental discovery. However, the modern approach is for geologists to use satellite images to identify good potential areas for survey (See Figure 1). This is done by
carefully studying the structure of the modern earth's surface to predict where sediments may have accumulated. By using the refection of ground surfaces monitored by the satellite's sensors, scientists can identify and
target potential study areas. Ancient sediments that are exposed to erosion on the modern landscape represent good targets for paleoanthropological exploration. Once such patches of sediment are identified, teams of
geologists, archaeologists, and paleontologists visit them to inspect their potential in person. Initial survey of a potential site is usually conducted carefully, with little collection of antiquities until the geology of
the site is understood. Paleontologists, geologists, and archaeologists work closely jointly as they traverse the sediment patches by vehicle and by foot, noting the sediment type and any surface antiquities. Most
exposed sedimentary patches contain no fossils or artifacts. For the few cases of sediments that do, it is essential that their position on the landscape and their relationships to the sediment layers be determined
precisely. Fossils or artifacts have little meaning unless their time and space relationships are accurately and precisely recorded at the time of collection. Today, such collection usually involves using the
satellite-based Global Positioning System (GPS) for precise spatial placement. This locates the discoveries geographically, but these antiquities are also of very different ages, so fieldworkers pay close attention to the
geological layers in which they are found. This is the key to determining the age of the fossils and artifacts. After the potential of a paleoanthropological study area has been established by survey, a research
strategy is developed by the research team to match the resources of the study area. A permit application is made to the ARCCH, and the research team seeks funding. Because paleoanthropology is a non-commercial,
scientific and educational enterprise, the work cannot be done as a business. Rather, basic research is supported by grant support from various agencies such as the U.S. National Science Foundation, the National Geographic
Society, the L.S.B. Leakey Foundation, the French CNRS, and the Wenner-Gren Foundation for Anthropological research. Because of the nature of paleoanthropological research, a long-term approach is most likely to yield the
most reliable and complete information about the past. Various specialists in geology, archaeology and paleontology are assembled in the field to extract different sorts of data necessary to fully explore the past. For
example, there are more than 50 Ph.D. level scientists from a dozen countries working on the Middle Awash study area in the Afar rift today. This large team of specialists is led by five co-investigators, Professor. Desmond
Clark and Dr. Yonas Beyene (archaeologists), Dr. Giday WoldeGabriel (a geologist), and Professor Tim White and Dr. Berhane Asfaw (paleontologists). These leaders coordinate the research of the other specialists in the field
and laboratory. Paleoanthropological study areas represent non-renewable resources, and as research work proceeds in the field and laboratory, new questions arise and new research strategies are constantly evolving as a
result. Most of these areas are found in the rift system, and access is often difficult because of a lack of roads, a problem that gets worse during the rainy season. Therefore, depending on local climatic conditions,
field research is usually scheduled for periods of a few months each year. The research team usually sets up a field camp from which equipment and scientists are taken by vehicle each day to the excavation or survey
sites. Different specialists working simultaneously on different research problems need different amounts of field time. Some field sites are remote, and the logistics operation required to sustain a team in the field
can be a major undertaking. Each day of fieldwork is different, with parts of the research team undertaking different tasks such as mapping of localities, work with aerial photographs, collection of fossils, excavations of
archaeology sites or fossils, screening with water for microscopic teeth from small mammals like bats and mice, sampling of geological horizons for dating, excavation of trenches for sedimentary isotopic studies, and more basic
survey (walking the surface of the sediments and searching for newly-exposed fossils and artifacts). All of this is difficult, time-consuming work, and this is why research in any one area can continue for decades. For
example, work in the Hadar and Middle Awash sites has gone on since the early 1970s, and at Olduvai Gorge in Tanzania, excavations have been underway since the 1930s. Many of these important research study areas will continue
to produce important new information as new generations of researchers are trained. The training of future paleoanthropologists is another function of the ongoing research, with students from Ethiopia and elsewhere working
closely with senior scientists to learn the techniques, research problems, and field logistics necessary to conduct this kind of research. One of the most important steps in the process comes when an important hominid fossil
has been found. In paleontological research, contrary to popular belief, paleoanthropologists virtually never find whole skulls on the surface. Fossil bone has lost all of its organic matter, and is very
brittle. When fossils reach the actively eroding surface, they tend to shatter into small pieces which are scattered across the outcrop. Recognizing important fossils under these conditions of erosion, scatter, and
fragmentation is a very specialized activity requiring detailed knowledge of the skeleton of all kinds of mammals. When an important fossil is found, the scatter of pieces is assessed and plotted. Excavations aimed at
recovering more of the usually fragmentary specimen are then undertaken, and these can last for weeks as no effort is spared to recover precious tiny pieces of tooth or skeleton. Some fossils are found in very precarious
positions, just eroding out of soft sediment like sand or silt. These require very special extraction techniques designed to rescue the fossil without further damage occurring, and special chemical consolidation of the
fossils is often necessary. In archaeological research, contrary to popular belief, the paleoanthropologists do not dig at random, hoping to find something interesting. Rather, they identify likely places to recover
artifacts by carefully searching the surface and finding telltale traces of ancient habitation--mostly in the form of bits of bone or stone that have eroded to the surface as witnesses of what is buried below. As excavation
begins, a grid is established over the site to make sure that each fragment found is plotted precisely. A complete documentation of what is found is completed by the team of excavators, and no clues are overlooked. As
in the paleontological collection, each antiquity is entered into field catalogs and later updated into computer databases.
Paleoanthropological Research in the Laboratory
When paleontological collection and archaeological excavation is complete, the collected antiquities are carefully
packed and returned to the National Museum in Addis Ababa. As the field equipment is cleaned, repaired, inventoried and stored, work on the collected antiquities really begins. Very important fossil discoveries are
often announced to the Ethiopian and international media as soon as they are found. However, such announcement usually only mentions the discovery of the fossil, because to understand the significance of each discovery, it
must be carefully cleaned, molded, photographed, and studied comparatively. Most of the artifacts and fossils collected in the field require some form of cleaning. Often, these antiquities are embedded in very hard stone
that must be carefully cleaned from their surfaces. Some fossils are so fragile that matrix must be moved slowly and carefully, under a binocular microscope, with chemical hardening proceeding with the cleaning process.
Many tools are available for this cleaning, depending on the preservation of the fossil and the type of embedding matrix. Some preparation is as simple as scraping away matrix with a hand-held dental pick. Other
preparation requires powerful air compressors that drive tiny air hammers that are used to chip away the harder matrix without damaging the bone below. Preparation of a single hominid skull can take up to two years to
complete. The Paleoanthropology Laboratory at the National Museum is the ideal venue for the cleaning activities because all the necessary equipment is there. There is also the possibility of comparison with casts and
other original fossils to help guide the processing and reconstruction of fossils. And a fully-equipped casting facility allow the precious original fossils and artifacts to be accurately replicated, minimizing handling of
original fossils and allowing comparison with other fossils in different countries. These comparisons are very important in working out the evolutionary and functional implications of the fossils found in the field.
Publications about Paleoanthropology
Once the studies are completed (studies may
take several years of comparisons), they are submitted by the scientific teams to research journals. For particularly important fossils, the top world journals of Science (US) and Nature (UK) often form the venue for the
first announcement of the significance of the fossils. A week before publication, these journals inform the global journalistic community, under a promise of secrecy (an embargo) so that reporters have time to check their
stories with the discoverers and scientists who have written about them, and have time to file accurate stories on the day of publication. Once the publication of the paper has been made, important paleoanthropological
stories may appear in newspapers, and on electronic media. In this way, the world has come to see Ethiopia as the major contributor to paleoanthropology over the last decade, culminating with the publication of an Ethiopian
fossil, Australopithecus garhi on the cover of the 1999 TIME magazine. Meanwhile, the study of the fossil does not end with this first announcement. The research team is already at work preparing more comprehensive
papers, far longer than the simple announcements that Science and NATURE allow. These papers, often published as monographs or in specialty journals, are important to scientists in their research. Once the fossils and
their anatomies and dimensions have been described, illustrated, and analyzed comprehensively by the research teams which find them, these antiquities become available to the entire global scientific community, and as a result,
many specialists from arround the world travel to the Paleoanthropology Laboratory to conduct further work on Ethiopia's most important fossils and artifacts. It is important to realize that modern
paleoanthropology is not simply a search for human ancestors. It is a search for knowledge about our biological and technological origins and evolution. It is a search for every clue, no matter how small, about the now
vanished worlds that these ancestors, and the ancestors of all the other living plants and animals occupied. This is enormously complex, time-consuming, and detailed research conducted by many researchers at many centers of
higher learning worldwide. Ethiopia's paleoanthropological heritage is expanding by each field season, and many new discoveries are being worked on in the laboratory at the present time. Readers of WALTA'S website will
be able to follow this research as it takes place, and to see behind-the-scenes reports on work in progress that will be tomorrow's headlines worldwide.
Figure Captions
Figure 1. The Paleoanthropology Inventory of Ethiopia field team uses satellite imagery in order to identify targets for ground survey. Photograph by T. White, 1989.
Figure 2. Geologist Dr. Giday WoldeGabriel on an outcrop of basaltic tuff, a layered volcanic deposit that accumulated in a shallow lake about 4.3 million years ago in the Middle Awash. The foundation of all paleoanthropological research is geology. Photograph by T. White, 1996.
Figure 3. Hamed Elema of the Bouri Modaitu Afars, examines a fossilized skull of a rhinoceros found eroding last year from 3.4 million-year-old sands at the Maka site, Middle Awash study area, Ethiopia. Another rainstorm and this fragile specimen would have broken into pieces and tumbled down the slope. It is very rare to find specimens this complete, and when they are found, it is slow and difficult work to preserve them, transport them to the National Museum in Addis Ababa, and clean and study them there to learn about evolution and environment of the distant past. Photograph by T. White, 2000.
Figure 4. Dr. Berhane Asfaw and Professor Tim White conducting comparative work on the new species Australopithecus garhi in the Paleoanthropology Laboratory at the National Museum of Ethiopia. Photograph courtesy of David Brill, 1999.