Orrorin

Orrorin tugenensis of O. tugenensis The first part of the holotype, a lower molar, was discovered by Martin Pickford in 1974 and described by Pickford (1975). The team that found the rest of the holotype of O. tugenensis was led by Brigitte Senut and Martin Pickford from the French National Museum of Natural History. Orrorin tugenensis was named and described by Senut et al. (2001). and Ward & Hill (1988), and was initially described as Homo antiquus praegens by Ferguson (1989) based on specimen KNM-TH 13150, a mandible discovered in the Pliocene Mabaget Formation of Kenya during the early 1980s. The mandible is known as the Tabarin mandible, which was previously classified within Ardipithecus ramidus (or cf. A. cf. ramidus), "Ardipithecus" praegens or "Praeanthropus" praegens. Several referred remains of O. praegens were collected between 2005 and 2011 by the Franco-Kenyan Kenya Palaeontology Expedition and they, alongside the Tabarin mandible, were classified by Pickford et al. (2022) as being separate from Homo, so they were classified within Orrorin as O. praegens. == Etymology ==

The name of genus Orrorin (plural Orroriek) means "original man" in Tugen, and the epithet of O. tugenensis derives from Tugen Hills in Kenya, where the first fossil was found in 2000. The epithet of O. praegens means roughly “group of people who came before.” ==Fossils==

The 20 specimens belonging to O. tugenensis are believed to be from at least five individuals. They include: the posterior part of a mandible in two pieces; a symphysis and several isolated teeth; three fragments of femora; a partial humerus; a proximal phalanx; and a distal thumb phalanx. In the femur, the head is spherical and rotated anteriorly; the neck is elongated and oval in section and the lesser trochanter protrudes medially. While these suggest that Orrorin was bipedal, the rest of the postcranium indicates it climbed trees. While the proximal phalanx is curved, the distal pollical phalanx is of human proportions and has thus been associated with toolmaking, but should probably be associated with grasping abilities useful for tree-climbing in this context. In 2017, impressions resembling human-like footprints were reported on the island of Crete in Greece. These "Trachilos footprints", found in fossilized beach sediments near the west Cretan village of Trachilos, have been dated to a similar time period as Orrorin tugenensis, being 6.05 million years old. However, there is no consensus that these impressions are distinct enough to confidently assign to a primate or even a vertebrate, or that they are indeed footprints at all. ==Classification==

If Orrorin proves to be a direct human ancestor, then according to some paleoanthropologists, australopithecines such as Australopithecus afarensis ("Lucy") may be considered a side branch of the hominid family tree: Orrorin is both earlier, by almost 3 million years, and more similar to modern humans than is A. afarensis. The main similarity is that the Orrorin femur is morphologically closer to that of Homo sapiens than is ''Lucy's; there is, however, some debate over this point. This debate is largely centered around the fact that Lucy was female and the Orrorin'' femur it has been compared to belonged to a male. Another point of view cites comparisons between Orrorin and other Miocene apes, rather than extant great apes, which shows instead that the femur shows itself as an intermediate between that of Australopiths and said earlier apes. Other fossils (leaves and many mammals) found in the Lukeino Formation show that Orrorin lived in a dry evergreen forest environment, not the savanna assumed by many theories of human evolution. == Evolution of bipedalism ==

The fossils of Orrorin tugenensis share no derived features of hominoid great-ape relatives. In contrast, "Orrorin shares several apomorphic features with modern humans, as well as some with australopithecines, including the presence of an obturator externus groove, elongated femoral neck, anteriorly twisted head (posterior twist in Australopithecus), anteroposteriorly compressed femoral neck, asymmetric distribution of cortex in the femoral neck, shallow superior notch, and a well developed gluteal tuberosity which coalesces vertically with the crest that descends the femoral shaft posteriorly." Based on the structure of its femoral head it still exhibited some arboreal properties, likely to forage and build shelters. An analysis of the BAR 10020' 00 femur showed that Orrorin is an intermediate between Pan and Australopithecus afarensis. ==See also==