| Ardipithecus kadabba | |
|---|---|
 | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Primates |
| Suborder: | Haplorhini |
| Infraorder: | Simiiformes |
| Family: | Hominidae |
| Subfamily: | Homininae |
| Tribe: | Hominini |
| Genus: | †Ardipithecus |
| Species: | †A. kadabba |
| Binomial name | |
| †Ardipithecus kadabba Haile-Selassie, 2001 | |
Ardipithecus kadabba is the scientific classification given to fossil remains "known only from teeth and bits and pieces of skeletal bones",[1] originally estimated to be 5.8 to 5.2 million years old, and later revised to 5.77 to 5.54 million years old.[2] 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 "probablechronospecies" (i.e. ancestor) ofA. ramidus. Although originally considered a subspecies ofA. ramidus, in 2004 anthropologistsYohannes Haile-Selassie,Gen Suwa, andTim D. White published an article elevatingA. kadabba to species level on the basis of newly discovered teeth fromEthiopia. These teeth show "primitive morphology and wear pattern" which demonstrate ...................................................thatA. kadabba is a distinct species fromA. ramidus.
The specific name comes from theAfar word for "basal family ancestor".[3]
Fossil remains were first described in 2001 by Ethiopian paleoanthropologistYohannes Haile-Selassie based on bones collected from five localities in theMiddle Awash, Ethiopia. Haile-Selassie initially classified them asArdipithecus ramidus kadabba, withkadabba deriving from theAfar language meaning "basal family ancestor".[4] In 2004, he, along with Japanese paleoanthropologistGen Suwa and American paleoanthropologistTim D. White, elevated it to species level asA. kadabba based on apparently primitive features compared toA. ramidus.[5]A. kadabba is considered to have been the direct ancestor ofA. ramidus, makingArdipithecus achronospecies.[6]
Along with elevating it to species level, they suggested thatArdipithecus,Sahelanthropus, andOrrorin could potentially belong to the same genus.[5] In 2008, American paleoanthropologists Bernard Wood and Nicholas Lonerga said that the larger ape-like canines ofA. kadabba cast doubt on its assignment to the human line,[7] but the position ofArdipithecus near humans has been reaffirmed by the discoverers and colleagues. They see a lineage of apes whose teeth continually reduce in size:A. kadabba–A. ramidus–Australopithecus anamensis–Au africanus, though they are unsure ifArdipithecus were the ancestors to theseAustralopithecus species, or were only closely related.[8]
Evolutionary tree according to a 2019 study:[9]
A. kadabba is known from nineteen specimens which reveal elements of the teeth, jaw, feet, and hands and arms. Theholotype specimen, ALA-VP-2/10, is a right lower jaw fragment with a third molar, discovered in December 1997, and five associated left lower jaw teeth or root fragments collected in 1999.
This correction of the initial allocation of the fossil record was based on the argument thatArdipithecus kadabba had more "primitive" features than otherArdipithecus fossils.Ardipithecus kadabba thus also has a greater similarity with the generaSahelanthropus andOrrorin. 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 ofArdipithecus ramidus has been used for the allocation of discoveries in that line of development of great apes that led to the australopithecines and the genusHomo.
The first description suggested thatArdipithecus kadabba lived in a habitat that consisted of forests, wooded savannas, and open water areas, as had been described forSahelanthropus.[10]
