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. 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" (i.e. ancestor) 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.
The name of the genus, Ardipithecus, is partly derived from the Afar language (ardi = soil) and partly from the Greek language (from "πίθηκος," ancient Greek pronounced "píthēkos" = Simian). The epithet 'kadabba' comes from Afar and refers to the father of a family. Ardipithecus kadabba accordingly means mutatis mutandis "progenitor of the ground ape."
The type specimen is a right mandibular fragment with a resulting molar (M3) and five tooth or root fragments with the inventory number ALA-VP-2/10. The first description, in 2001, also relied on other bone finds that have been excavated since 1992 from five sites in the Afar Depression, Ethiopia, and are from ten other individuals. In the first description by Yohannes Haile-Selassie, Ardipithecus kadabba was, however, recognized as a subspecies of Ardipithecus ramidus termed "kadabba".[clarification needed] In 2004 Ardipithecus kadabba was designated in a joint publication of Haile-Selassie and Tim White.
This correction of the initial allocation of the fossil record was based on the argument that Ardipithecus kadabba had more "primitive" features than other Ardipithecus fossils. Ardipithecus kadabba thus also has a greater similarity with the genera Sahelanthropus and Orrorin. These statements were based on additional bone finds that came to light in November 2002 and were dated at 5.8 to 5.6 million years.
At the same time, it was emphasized that evidence could be found of a reduced "honing" complex, traces on the teeth that arise when the canines rub against each other when biting, constantly sharpening their peaks, which has been found in all older finds. The loss of this feature in the successor species of Ardipithecus ramidus has been used for the allocation of discoveries in that line of development of great apes that led to the australopithecines and the genus Homo.
Finally, it was noted in the same publication that Ardipithecus, Sahelanthropus, and Orrorin could potentially be associated with a single genus. In 2008 Bernard Wood and Nicholas Lonerga pointed out that the substantially different features of the dentition of Ardipithecus kadabba make its assignment to the early Hominini as less well justified than those of other taxa.
- Gibbons, Ann (2009). "A New Kind of Ancestor: Ardipithecus Unveiled" (PDF). Science. 326 (5949): 36–40. Bibcode:2009Sci...326...36G. doi:10.1126/science.326_36. PMID 19797636.
- Webseite von Yohannes Haile-Selassie Archived 2015-09-20 at the Wayback Machine
- Yohannes Haile-Selassie: Late Miocene hominids from the Middle Awash, Ethiopia.[full citation needed]
- Haile-Selassie, Yohannes; Suwa, Gen; White, Tim D. (2004). "Late Miocene Teeth from Middle Awash, Ethiopia, and Early Hominid Dental Evolution". Science. 303 (5663): 1503–1505. Bibcode:2004Sci...303.1503H. doi:10.1126/science.1092978. PMID 15001775.
- Ellis, Richard (2004). No Turning Back: The Life and Death of Animal Species. New York: Harper Perennial. p. 92. ISBN 0-06-055804-0.
- Giday WoldeGabriel et al.: Geology and palaeontology of the Late Miocene Middle Awash valley, Afar rift, Ethiopia.[full citation needed]
- Wood, Bernard; Lonergan, Nicholas (2008). "The hominin fossil record: Taxa, grades and clades". Journal of Anatomy. 212 (4): 354–76. doi:10.1111/j.1469-7580.2008.00871.x. PMC 2409102. PMID 18380861.