Middle Awash Project

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The Middle Awash Project is an international research expedition conducted in the Afar Region of Ethiopia with the goal of determining the origins of humanity. The project has the approval of the Ethiopian Culture Ministry and a strong commitment to developing Ethiopian archaeology, paleontology and geology research infrastructure. This project has discovered over 260 fossil specimens and over 17,000 vertebrate fossil specimens to date ranging from 200,000 to 6,000,000 years in age. Researchers have discovered the remains of four hominin species, the earliest subspecies of homo sapiens as well as stone tools. All specimens are permanently held at the National Museum of Ethiopia, where the project’s laboratory work is conducted year round.

Contents

Geography

The Afar Region of Ethiopia Ethiopia-Afar.png
The Afar Region of Ethiopia

The Middle Awash Project takes place in a semi arid, rather remote part of the Afar rift. Between 5.8 and 4.4 Ma, the region was grassland and wetland. [1] Today, the rift is a basin divided by fault lines and filled with volcanoes. [2] Also called the Afar Depression, it has long been inhabited by the nomadic Afar people of Ethiopia. The Ethiopian Plateau lies to the west of the depression, the Danakil block to the northeast, the Ali-Sabieh block to the southeast, and the Somalian Plateau to the south. [2]

The study area is bounded in the south by Gewane town and the Arso River and the north end touches the Talalak River. The rift margin marks the western end of the study area, while the Gewane-Adaitu highway lies on its east.

Middle Awash is much larger than other nearby sites, such as Olduvai Gorge and Hadar. This is because the fossil potential is spaced out across the area. In fact, not even a quarter of the area contains any possibility of bearing fruit. Fossils found in the Middle Awash are located in small, scattered windows. Therefore, the fossil record is more fragmented as opposed to a continuous view of the past.

To accurately date fossils and artifacts, researchers use “geology and structural, geomorphological, sedimentological, volcanological, paleomagnetic, tephrochemical, isotopic, and radiometric dating studies.” [3]

Project history

Jon Kalb Jon Kalb (cropped).jpg
Jon Kalb

The recognition of Middle Awash as a site of value to the field of paleontology was a gradual process. Some sources say that the first European exploration was led by a British mining engineer. [4] Since he failed to see anything of note in the area, there is less of a record of this. In 1938 two Italian geologists Michele Gortani and Angelo Bianchi, conducted a geological survey of the area. The Italians also did not see anything of potential importance in their survey. The first European to take paleontological interest in Middle Awash was a French professor named Maurice Taieb who surveyed the area in the 1960s. Ultimately, Taieb decided to focus his studies on an area North of Middle Awash called Hadar. Taieb recruited Yves Coppens, Don Johanson and Jon Kalb among others to help him with his work at Hadar (work is still taking place at Hadar to this day). This research team in 1972 and within 10 years found the first fossil hominids in the Afar Rift.

In 1975 Jon Kalb decided to leave the Hadar team to start the Rift Valley Research Mission in Ethiopia (RVRME for short). The next year, the RVRME team discovered a Middle Pleistocene era hominid at a site known as Bodo. While fieldwork on this mission only went on until 1978, RVRME laid the groundwork for the Middle Awash Project, even going so far as to propose nomenclature for the entire Southern Afar Region. Though the nomenclature served as the basis of the past several decades of research, on their official website the Middle Afar Project had this to say: “the RVRME stratigraphic nomenclature impossible to apply because descriptions of beds and marker horizons were imprecise, upper and lower contacts were undefined, there was no valid mapping of a reference area, and boundaries between formations were set systematically at fault contacts. Radiometric dating and tephrachemistry were not done by the RVRME”. [5]

J. Desmond Clark talking with a colleague at an airport in West Africa. DesmondClark.jpg
J. Desmond Clark talking with a colleague at an airport in West Africa.

In 1981 Professor J. Desmond Clark, a prominent African prehistory expert of the 20th century, initiated the Middle Awash Project with the approval of the Ethiopian Culture Ministry. During the Project’s initial run researchers including Professor and paleontology expert Tim White explored both sides of the river. Clark recapped their time in his 1984 paper as when the “Archaeological excavations were undertaken at Bodo and Hargufia, the first radiometric dates for the area were determined, and the first Pliocene hominids were recovered”. [5]

Clark and White were planning to continue their research in Middle Awash however circumstances made this impossible. In October 1982 the Ethiopian government banned all foreign prehistory expeditions while they reformulated their policies on international researchers. It was a response to foreign expeditions perceived inability to incorporate locals into their teams, tension between the Cultural Ministry (who had the authority to give foreign expedition permits since before the end of the monarchy in 1974) and the University of Addis Ababa (who wanted a greater role in expeditions), and the circumstances leading to the forced departure of RVRME lead researcher Jon Kalb in 1978 due to later disproven rumors that he was a CIA agent. [6] Clark and White went to Addis Ababa to try and persuade the government to change their position. They were unsuccessful and had to submit a report to the National Science Foundation. The Middle Awash Project did not make it back to Ethiopia until 1990 when research resumed.

Tim White with a cast of "Ardi", a well known Ardipithecus Ramidus fossil Tim White 2010-01.JPG
Tim White with a cast of "Ardi", a well known Ardipithecus Ramidus fossil

Upon the revival of the Middle Awash Project in 1990 there were a few slight changes in leadership. It was at this point that Tim White succeeded J.Desmond Clark as lead researcher. The other notable change that happened was by 1992 Dr.Giday WoldeGabriel joined the expedition as the Head of Geographical Studies and helped them finish the bulk of their work on the East Side of the Awash River.

Key discoveries

Middle Awash contains fossils existing from about 6 million years ago to 200 thousand years ago. [7]

Ardipithecus kadabba

Ardipithicus kadabba was discovered in 1997 on the Western Side, at site Asa Koma, [8] by Yohannes Haile Selassie and Giday WoldeGabriel. Ardipithecus kadabba is one of the earliest known hominids from the Late Miocene period. It was first announced in 2001, and further remains were announced in 2004. [8] The Specimens found represent at least 7 individuals and were dated to 5.8-5.2 Ma. Primarily dental fossils were found but they do include a clavicle, a hand phalanx, ulna fragments and humerus fragments.

Ar. Kadabba was originally considered a part of Ar. ramidus but was differentiated due to significant difference in their teeth. The presence of self sharpening upper canines was one such difference. Postranial evidence is less conclusive, as conflicting evidence both supports and opposes bipedalism. [9]

Ardipithecus ramidus

Ardipithecus ramidus was discovered by Tim White in 1992 at Aarmis in Middle Awash. The initial assemblage was made up of 13 dental fragments, some cranial fragments, some postcranial fragments, including from the radius and ulna. Since, over 100 total specimens have been discovered from 36 individuals.

While originally considered a new species of Australopithecus, this changed due to difference in the size of the molars and premolars, which fell outside the range of Australopithecus. It was then given a new genus, Ardipithecus. Ardipithecus ramidus was first recognized as a new genus and species in 1994 and 1995. [8]

In 2009, a complete description of a partial skeleton called “Ardi” was published in the journal Science. It was dated to approximately 4.4 Ma and was 120 cm tall and weighed 50 kg. The fossil was extremely fragmented and required much reconstruction, but eventually proved valuable for the knowledge of Ar. Ramidus.

Similar to chimpanzees, Ar. Ramidus shows no signs of sexual dimorphism. Its reconstructed cranium is smaller than those of later hominins, and stable isotope analysis suggests a more omnivorous diet than great apes. Additionally, canines and third premolars set Ar. Ramidus apart from modern African Apes. These differences present evidence that canines were not as necessary for fighting and intimidation in Ar. Ramidus. Ar. Ramidus has a more primitive postcrania than subsequent hominins (had a primitive fully abductable big toe), but also demonstrated evidence of bipedalism, such as an inflexible midfoot. The pelvis has both primitive traits and traits closer to later hominids. While the ilia is relatively broad and representative of later hominids, the ischium is essentially identical to those of the Apes. Finally, the flexibility of the wrist suggests bipedalism. [7]

Australopithecus anamensis

Australopithecus anamensis was found at Asa Issie and Aramis 14, both located in Middle Awash. Fossils found at Asa Issie include “2 partial maxillary dentitions, a partial metatarsal shaft, a foot phalanx, a hand phalanx, 4 vertebral fragments, and a proximal femur” [7] belonging to at least 2 specimens.

The cheek teeth of Au. anamensis are much larger than that of Ar. Ramidus, but approximately equal to Au. afarensis. Both individuals have relatively large canines and thicker molar enamel than Ar. Ramidus.

There is little postcranial evidence for Au. Anamensisfound at Asa Issie. The hand phalanx is similar to those of Australopithecus and the femur is on the more primitive side of the range in Au. Afarensis. Postcrania found outside of Asa Issie suggests bipedalism and strong, tree-climbing arms.

Australopithecus garhi

A reconstructed Australopithecus Garhi skull from the National Museum of Ethiopia. Musee national d'Ethiopie-Australopithecus garhi (2).jpg
A reconstructed Australopithecus Garhi skull from the National Museum of Ethiopia.

Australopithecus garhi was discovered by Tim White in the Bouri Peninsula area of Middle Awash. It was announced in 1999. [8] Au. Garhi has a holotype of a fragmented skull. The skull has all teeth but the left second and third molars, and additionally contains fragments of the frontal, parietal, and maxilla.

Similarities in the cranial morphology to Au. Afarensis include the shape of the braincase and the relatively small brain size. The canines and incisors fall into the size range of Au. Afarensis, but the premolars and molars are comparatively very large. Pa. Boisei is the only hominin with larger post canines. Au. Garhi additionally has a thinner plate and cheekbones that flare less than usual. Additionally, Homo has wear patterns in cheek teeth like Au. Garhi.

Limb fossils, such as a left femur, right humerus, radius, and ulna, parts of the fibula, and pieces of the foot, are located 278 meters from the skull. Some argue that these limb bones belong to the same specimen as the skull.

This postcranial evidence cannot be ascribed with complete certainty to Au. Garhi. It does, however, possess attributes of both australopiths and homo. The phalanx is identical to that of Au. Afarensis. The limbs are a strange combination of resemblances to humans and australopiths, possibly implying a combination of bipedalism and climbing. [7]

Homo sapiens idaltu

These earliest known Homo sapiens [8] were discovered in 1997 at Herto Bouri by Tim White. It is dated to 0.16 Ma (160,000 years). It was first announced as a subspecies "idaltu" in 2003, [8] but is often called “Herto Man.” The skull of Herto Man has features too archaic to be Homo sapiens, but is considered a direct ancestor of today’s humans. [10]

Current project focus

The work of the Middle Awash Project is currently focused on the sites West of the Awash River because while there has been a long tradition of field work taking place on both sides, the Eastern side has been more thoroughly investigated. Lab work is primarily focused on fossils dated to approximately 4.4 million years ago as well as assembling additional Ardipithecus ramidus evidence for publication. [5]

Related Research Articles

<i>Ardipithecus</i> Extinct genus of hominins

Ardipithecus is a genus of an extinct hominine that lived during the Late Miocene and Early Pliocene epochs in the Afar Depression, Ethiopia. Originally described as one of the earliest ancestors of humans after they diverged from the chimpanzees, the relation of this genus to human ancestors and whether it is a hominin is now a matter of debate. Two fossil species are described in the literature: A. ramidus, which lived about 4.4 million years ago during the early Pliocene, and A. kadabba, dated to approximately 5.6 million years ago. Initial behavioral analysis indicated that Ardipithecus could be very similar to chimpanzees, however more recent analysis based on canine size and lack of canine sexual dimorphism indicates that Ardipithecus was characterised by reduced aggression, and that they more closely resemble bonobos.

<span class="mw-page-title-main">Homininae</span> Subfamily of mammals

Homininae, also called "African hominids" or "African apes", is a subfamily of Hominidae. It includes two tribes, with their extant as well as extinct species: 1) the tribe Hominini ―and 2) the tribe Gorillini (gorillas). Alternatively, the genus Pan is sometimes considered to belong to its own third tribe, Panini. Homininae comprises all hominids that arose after orangutans split from the line of great apes. The Homininae cladogram has three main branches, which lead to gorillas and to humans and chimpanzees. There are two living species of Panina and two living species of gorillas, but only one extant human species. Traces of extinct Homo species, including Homo floresiensis have been found with dates as recent as 40,000 years ago. Organisms in this subfamily are described as hominine or hominines.

<i>Orrorin</i> Postulated early hominin discovered in Kenya

Orrorin is an extinct genus of primate within Homininae from the Miocene Lukeino Formation and Pliocene Mabaget Formation, both of Kenya.

<i>Australopithecus</i> Genus of hominin ancestral to modern humans

Australopithecus is a genus of early hominins that existed in Africa during the Pliocene and Early Pleistocene. The genera Homo, Paranthropus, and Kenyanthropus evolved from some Australopithecus species. Australopithecus is a member of the subtribe Australopithecina, which sometimes also includes Ardipithecus, though the term "australopithecine" is sometimes used to refer only to members of Australopithecus. Species include A. garhi, A. africanus, A. sediba, A. afarensis, A. anamensis, A. bahrelghazali and A. deyiremeda. Debate exists as to whether some Australopithecus species should be reclassified into new genera, or if Paranthropus and Kenyanthropus are synonymous with Australopithecus, in part because of the taxonomic inconsistency.

<i>Australopithecus afarensis</i> Extinct hominid from the Pliocene of East Africa

Australopithecus afarensis is an extinct species of australopithecine which lived from about 3.9–2.9 million years ago (mya) in the Pliocene of East Africa. The first fossils were discovered in the 1930s, but major fossil finds would not take place until the 1970s. From 1972 to 1977, the International Afar Research Expedition—led by anthropologists Maurice Taieb, Donald Johanson and Yves Coppens—unearthed several hundreds of hominin specimens in Hadar, Ethiopia, the most significant being the exceedingly well-preserved skeleton AL 288-1 ("Lucy") and the site AL 333. Beginning in 1974, Mary Leakey led an expedition into Laetoli, Tanzania, and notably recovered fossil trackways. In 1978, the species was first described, but this was followed by arguments for splitting the wealth of specimens into different species given the wide range of variation which had been attributed to sexual dimorphism. A. afarensis probably descended from A. anamensis and is hypothesised to have given rise to Homo, though the latter is debated.

Paleoanthropology or paleo-anthropology is a branch of paleontology and anthropology which seeks to understand the early development of anatomically modern humans, a process known as hominization, through the reconstruction of evolutionary kinship lines within the family Hominidae, working from biological evidence and cultural evidence.

Hadar or Hadar Formation is a paleontological fossil site located in Mille district, Administrative Zone 1 of the Afar Region, Ethiopia, 15 km upstream (west) of the A1 road's bridge across the Awash River.

<i>Australopithecus anamensis</i> Extinct hominin from Pliocene east Africa

Australopithecus anamensis is a hominin species that lived approximately between 4.2 and 3.8 million years ago and is the oldest known Australopithecus species, living during the Plio-Pleistocene era.

<span class="mw-page-title-main">Afar Triangle</span> Geological depression caused by the Afar Triple Junction

The Afar Triangle is a geological depression caused by the Afar Triple Junction, which is part of the Great Rift Valley in East Africa. The region has disclosed fossil specimens of the very earliest hominins; that is, the earliest of the human clade, and it is thought by some paleontologists to be the cradle of the evolution of humans. The Depression overlaps the borders of Eritrea, Djibouti and the entire Afar Region of Ethiopia; and it contains the lowest point in Africa, Lake Assal, Djibouti, at 155 m (509 ft) below sea level.

<i>Australopithecus garhi</i> Extinct hominid from the Afar Region of Ethiopia 2.6–2.5 million years ago

Australopithecus garhi is a species of australopithecine from the Bouri Formation in the Afar Region of Ethiopia 2.6–2.5 million years ago (mya) during the Early Pleistocene. The first remains were described in 1999 based on several skeletal elements uncovered in the three years preceding. A. garhi was originally considered to have been a direct ancestor to Homo and the human line, but is now thought to have been an offshoot. Like other australopithecines, A. garhi had a brain volume of 450 cc (27 cu in); a jaw which jutted out (prognathism); relatively large molars and premolars; adaptations for both walking on two legs (bipedalism) and grasping while climbing (arboreality); and it is possible that, though unclear if, males were larger than females. One individual, presumed female based on size, may have been 140 cm tall.

<span class="mw-page-title-main">Tim D. White</span> American paleoanthropologist

Tim D. White is an American paleoanthropologist and Professor of Integrative Biology at the University of California, Berkeley. He is best known for leading the team which discovered Ardi, the type specimen of Ardipithecus ramidus, a 4.4 million-year-old likely human ancestor. Prior to that discovery, his early career was notable for his work on Lucy as Australopithecus afarensis with discoverer Donald Johanson.

<span class="mw-page-title-main">Gawis cranium</span> Hominin fossil

The Gawis cranium is a portion of a fossil hominin skull discovered on February 16, 2006 near the drainage of Gawis, a tributary of the Awash River in the Afar Depression, Ethiopia. Despite the presence of volcanic ash layers that are key to dating, the cranium is only generally dated between 200,000 and 500,000 years ago due to taphonomic issues.

<span class="mw-page-title-main">Middle Awash</span> UNESCO World Heritage Site in Ethiopia

The Middle Awash is a paleoanthropological research area in the northwest corner of Gabi Rasu in the Afar Region along the Awash River in Ethiopia's Afar Depression. It is a unique natural laboratory for the study of human origins and evolution and a number of fossils of the earliest hominins, particularly of the Australopithecines, as well as some of the oldest known Olduwan stone artifacts, have been found at the site—all of late Miocene, the Pliocene, and the very early Pleistocene times, that is, about 5.6 million years ago (mya) to 2.5 mya. It is broadly thought that the divergence of the lines of the earliest humans (hominins) and of chimpanzees (hominids) was completed near the beginning of that time range, or sometime between seven and five mya. However, the larger community of scientists provide several estimates for periods of divergence that imply a greater range for this event, see CHLCA: human-chimpanzee split.

Aramis is a village and archaeological site in north-eastern Ethiopia, where remains of Australopithecus and Ardipithecus have been found. The village is located in Administrative Zone 5 of the Afar Region, which is part of the Afar Sultanate of Dawe, with a latitude and longitude of 10°30′N40°30′E, and is part of the, Carri Rasuk, Xaale Faagê Daqaara.

<span class="mw-page-title-main">Yohannes Haile-Selassie</span> Ethiopian paleoanthropologist (born 1961)

Yohannes Haile-SelassieAmbaye is an Ethiopian paleoanthropologist. An authority on pre-Homo sapiens hominids, he particularly focuses his attention on the East African Rift and Middle Awash valleys. He was curator of Physical Anthropology at the Cleveland Museum of Natural History from 2002 until 2021, and now is serving as the director of the Arizona State University Institute of Human Origins. Since founding the institute in 1981, he has been the third director after Donald Johanson and William Kimbel.

<i>Ardipithecus kadabba</i> Hominin fossil

Ardipithecus kadabba is the scientific classification given to fossil remains "known only from teeth and bits and pieces of skeletal bones", originally estimated to be 5.8 to 5.2 million years old, and later revised to 5.77 to 5.54 million years old. According to the first description, these fossils are close to the common ancestor of chimps and humans. Their development lines are estimated to have parted 6.5–5.5 million years ago. It has been described as a "probable chronospecies" of A. ramidus. Although originally considered a subspecies of A. ramidus, in 2004 anthropologists Yohannes Haile-Selassie, Gen Suwa, and Tim D. White published an article elevating A. kadabba to species level on the basis of newly discovered teeth from Ethiopia. These teeth show "primitive morphology and wear pattern" which demonstrate that A. kadabba is a distinct species from A. ramidus.

<i>Ardipithecus ramidus</i> Extinct hominin from Early Pliocene Ethiopia

Ardipithecus ramidus is a species of australopithecine from the Afar region of Early Pliocene Ethiopia 4.4 million years ago (mya). A. ramidus, unlike modern hominids, has adaptations for both walking on two legs (bipedality) and life in the trees (arboreality). However, it would not have been as efficient at bipedality as humans, nor at arboreality as non-human great apes. Its discovery, along with Miocene apes, has reworked academic understanding of the chimpanzee–human last common ancestor from appearing much like modern-day chimpanzees, orangutans and gorillas to being a creature without a modern anatomical cognate.

<span class="mw-page-title-main">Bouri Formation</span> Archeological area in Afar Region, Ethiopia

The Bouri Formation is a sequence of sedimentary deposits that is the source of australopithecine and Homo fossils, artifacts, and bones of large mammals with cut marks from butchery with tools by early hominins. It is located in the Middle Awash Valley, in Ethiopia, East Africa, and is a part of the Afar Depression that has provided rich human fossil sites such as Gona and Hadar.

Ardi (ARA-VP-6/500) is the designation of the fossilized skeletal remains of an Ardipithecus ramidus, thought to be an early human-like female anthropoid 4.4 million years old. It is the most complete early hominid specimen, with most of the skull, teeth, pelvis, hands and feet, more complete than the previously known Australopithecus afarensis specimen called "Lucy". In all, 125 different pieces of fossilized bone were found.

The savannah hypothesis is a hypothesis that human bipedalism evolved as a direct result of human ancestors' transition from an arboreal lifestyle to one on the savannas. According to the hypothesis, hominins left the woodlands that had previously been their natural habitat millions of years ago and adapted to their new habitat by walking upright.

References

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  2. 1 2 "Geology of Afar Depression". www.see.leeds.ac.uk.
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  4. Anthropology, The University of Texas at Austin, Department of. "Middle Awash | eFossils Resources". www.efossils.org. Retrieved 2018-10-28.{{cite web}}: CS1 maint: multiple names: authors list (link)
  5. 1 2 3 "Middle Awash history". middleawash.berkeley.edu. Retrieved 2018-10-28.
  6. Lewin, Roger (1983-01-14). "Ethiopia Halts Prehistory Research". Science. 219 (4581): 147–149. Bibcode:1983Sci...219..147L. doi:10.1126/science.219.4581.147. ISSN   0036-8075. PMID   17841665.
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  8. 1 2 3 4 5 6 "Middle Awash fossil hominids". middleawash.berkeley.edu.
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  10. "Homo sapiens idaltu". Bradshaw Foundation.