bones", and is dated to approximately 5.6 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 specific name comes from the Afar word for "basal family ancestor". Classification Due to several shared characteristics with chimpanzees, its closeness to ape divergence period, and due to its fossil incompleteness, the exact position of Ardipithecus in the fossil record is a subject of controversy. Primatologist Esteban Sarmiento had systematically compared and concluded that there is not sufficient anatomical evidence to support an exclusively human lineage. Sarmiento noted that Ardipithecus does not share any characteristics exclusive to humans, and some of its characteristics (those in the wrist and basicranium) suggest it diverged from humans prior to the human–gorilla last common ancestor. His comparative (narrow allometry) study in 2011 on the molar and body segment lengths (which included living primates of similar body size) noted that some dimensions including short upper limbs, and metacarpals are reminiscent of humans, but other dimensions such as long toes and relative molar surface area are great ape-like. Sarmiento concluded that such length measures can change back and forth during evolution and are not very good indicators of relatedness (homoplasy). However, some later studies still argue for its classification in the human lineage. In 2014, it was reported that the hand bones of Ardipithecus, Australopithecus sediba and A. afarensis have the third metacarpal styloid process, which is absent in other apes. Unique brain organisations (such as lateral shift of the carotid foramina, mediolateral abbreviation of the lateral tympanic, and a shortened, trapezoidal basioccipital element) in Ardipithecus are also found only in the Australopithecus and Homo. Comparison of the tooth root morphology with those of the earlier Sahelanthropus also indicated strong resemblance, also pointing to inclusion to the human line. Evolutionary tree according to a 2019 study: Paleobiology The Ardipithecus length measures are good indicators of function and together with dental isotope data and the fauna and flora from the fossil site indicate Ardipithecus was mainly a terrestrial quadruped collecting a large portion of its food