Hadar, Ethiopia

Hadar (also spelled Qad daqar, Qadaqar; Afar "white [qidi] stream [daqar]")[1] is a paleontological site 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 (Adayitu kebele).[2]

Administrative Zone 1 (Afar Region), Ethiopia

It is situated on the southern edge of the Afar Triangle (part of East Africa's Great Rift Valley), along the left banks of the Awash River, between two minor tributaries, the eponymous Kada Hadar and the Kada Gona.[2] In 1972, Taieb organized a small, exploratory reconnaissance of the Afar region to investigate more paleontological finds there. After six weeks of exploration, the party focused on the Hadar site.[3] The site has yielded some of the most well-known hominin fossils, including "Lucy." These hominin fossils range from the age of approximately 3.42 to 2.90 million years ago. These finds give us a greater understanding of hominin evolution between the years of 3.45 to 0.8 million years ago.

It is postulated that the specimens in the region were deposited by way of a fluvial large river system with associated crevasse channels/splays, deltas, and distributary channels, as well as periodic transgressions of paleolake Hadar located east of the research area (Aronson and Taieb, 1981, Tiercelin, 1986, Campisano and Feibel, in press) possibly related to geological activity or climatic cycles in at least the Kada Hadar Member (Yemane et al., 1996, Yemane, 1997, Campisano and Feibel, in press)."

According to Jon Kalb, early maps show caravan routes passing within 10 to 15 km of Hadar but not through it. The British explorer L.M. Nesbitt passed 15 km west of Hadar in 1928.[1]

Paleontology
"Lucy," one of the most famous hominin fossils, is a 3.2 million-year-old Australopithecus afarensis fossil discovered in Hadar, Ethiopia by Donald Johanson in 1974.

The first paleo-geological explorations of the Hadar area were conducted by Maurice Taieb. He found Hadar in December 1970 by following the Ledi River, which originates in the highlands north of Bati to empty into the Awash River. Taieb recovered a number of fossils in the area and led a party back to Hadar in May 1972. In October 1973, 16 individuals with the International Afar Research Expedition (IARE) arrived at Hadar and camped there for two months during which the first hominin fossil was found. (Taieb claims in his 1985 book Sur la Terre des premiers Hommes to have discovered the Hadar fields in 1968, but Kalb argues that claim of an earlier find to be incorrect.)[4] The IARE party examined a series of sedimentary layers called the Hadar Formation, which was dated to the late Pliocene to early Pleistocene epochs (3.5 to 2.3 million years ago).[5]

The anthropologist Donald Johanson, a member of the 1973 expedition to Hadar, returned the next year and discovered the fossil hominin "Lucy" in the late fall of 1974.[6] He spotted a right proximal ulna in a gully, followed by an occipital bone, a femur, some ribs, a pelvis, and a lower jaw. Within two weeks, nearly 40% of the hominoid skeleton had been identified and cataloged.[7] Lucy is the most famous fossil to have been found at Hadar. Lucy is among the oldest hominin fossils ever discovered[6] and was later given the taxonomic classification Australopithecus afarensis. (The name 'Lucy' was inspired by the song "Lucy in the Sky with Diamonds" by The Beatles, which happened to be playing on the radio at base camp.)

In 1975, Donald Johanson made another discovery at a nearby site in Hadar: 216 specimens from approximately 17 individuals, most likely related and varying in age, called AL 333 (colloquially referred to as the "First Family").

About thirty years later in nearby Dikika, another Australopithecus afarensis fossil skeleton was found in a separate outcrop of the Hadar Formation across the Awash River from Hadar. The skeleton is of a three-year-old girl later named "Selam," which means peace in Amharic Ethiopian languages.

Hadar Geology

The region consists mainly of mudstones, stiltstones, fine-grained sandstones and volcanic tuffs. The region has been divided into 4 geologic members: Hadar Formation: Basal (∼3.8–3.42 Ma), Sidi Hakoma (∼3.42–3.26 Ma), Denen Dora (∼3.26–3.2 Ma), and Kada Hadar (<∼3.2 Ma) with the three tufts: Sidi Hakoma Tuff (SHT), the Triple Tuff (TT) and the Kada Hadar Tuff (KHT) separating the four members.

The Sidi Hakoma member tends towards high rainfall and low seasonality. The overlying Denan Dora Member was a grassland habitat. Finally, the Kada Hadar Member was an even more open and arid habitat as seen in the high abundance of antilopins, an animal that frequents these types of terrains.[8]


Hadar Specimens and Inferences

In 1973 and 1974 when the first anatomical discoveries were made, their size and shape pointed towards a variety of taxon present, but further research has confirmed that only one hominin taxon is present here. The first find there was a fossil knee joint estimated to have lived 3.4 million years ago. Since then, the Hadar research area has yielded 370 specimens of A. afarensis, one specimen of Homo, and 7571 additional vertebrate specimens.

Based on the specimens recovered, there were a variety of different primitive cranial post features, which indicate A. afarensis is distinct from other species of Australopithecus: small cranial capacity, palate similar to African apes (parallel tooth rows, shallow, long from antero-posteriorly, narrow from side to side), primitive occipital, basal cranium anatomy, high frequency of unicuspid third premolars, prognathic face, and primitive mandibular anatomy. Postcranially, the pelvis, knee, ankle and foot indicate habitual, terrestrial bipedalism, but ape-like curved finger and foot bones are retained ancestral ape-like features.[9]

See also

References
  1. Jon Kalb Adventures in the Bone Trade (New York: Copernicus Books, 2001), p. 83
  2. E. N. Dimaggio et al., "Tephrostratigraphy and depositional environment of young (<2.94 Ma) Hadar Formation deposits at Ledi-Geraru, Afar, Ethiopia", Journal of African Earth Sciences 112A (December 2015), pp. 234–250 (Figure 2), doi:10.1016/j.jafrearsci.2015.09.018.
  3. Johanson, Donald (1 March 2017). "The paleoanthropology of Hadar, Ethiopia". Comptes Rendus Palevol. Des gènes à la culture / From genes to culture. 16 (2): 140–154. doi:10.1016/j.crpv.2016.10.005. ISSN 1631-0683.
  4. Halstead, L. B. (1984). A la recherche du passé: la vie sur Terre, des origines aux premiers hommes. Hachette. ISBN 2010096029. OCLC 25125386.
  5. Feibel, Craig S.; Christopher J. Campisano (2004). "Sedimentary Patterns in the Pliocene Hadar Formation, Afar Rift, Ethiopia". {{cite journal}}: Cite journal requires |journal= (help)
  6. Hogenboom, Melissa. "The 'Lucy' fossil rewrote the story of humanity". Retrieved 25 October 2018.
  7. "Lucy's Story | Institute of Human Origins". iho.asu.edu. Retrieved 25 October 2018.
  8. Johanson, Donald (1 March 2017). "The paleoanthropology of Hadar, Ethiopia". Comptes Rendus Palevol. Des gènes à la culture / From genes to culture. 16 (2): 140–154. doi:10.1016/j.crpv.2016.10.005. ISSN 1631-0683.
  9. Johanson, Donald (1 March 2017). "The paleoanthropology of Hadar, Ethiopia". Comptes Rendus Palevol. Des gènes à la culture / From genes to culture. 16 (2): 140–154. doi:10.1016/j.crpv.2016.10.005. ISSN 1631-0683.

This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.