Orrorin

Orrorin tugenensis

• Virtues Hills (Kenya )

Orrorin tugenensis is an extinct species of apes, which occurred in the upper Miocene in Kenya. Their fossilized remains have been dated to around 6 million years. They are probably close to Ardipithecus and Sahelanthropus tchadensis and how these by many researchers attributed to the circle form the australopithecines. Due to its discovery in 2000 Orrorin is tugenensis also referred to as the "Millennium Man".

Since Orrorin tugenensis probably could walk upright, he was asked by its discoverers in the ancestors of the genus Homo; because of the few, fragmentary finds this is controversial.

Fund Description

1974 was Martin Pickford in the virtues Hills near the village Cheboit, 250 km west of Nairobi, a molar, which was scientifically described in the following year along with other finds. It was not until 26 years later, in October 2000, discovered a French -Kenyan research group further fossils, those of the already known tooth was assigned. The new finds were made of two associated mandibular fragments with three molars (archive number BAR 1000a'00 and BAR 1000b'00; BAR stands for the Kenyan district of Baringo ), the Kiptalam Cheboi discovered and in 2001 in the scientific first description of Orrorin tugenensis have been designated as the holotype. In addition, a further five were discovered with the mandible unassociated teeth, a finger bone, a fragment of a right humerus, and three fragments of the femur; later was added the final link of a finger.

These finds were recovered from four different deposits, so their assignment to a single species is not mandatory; the finger bones (BAR 349'00 ) such as that coming from a fund- layer, the more than 300,000 years younger than the layers may be of the other finds. The dental findings come from different age strata, but can at least conclude that they came from a creature that is mainly fed on plants. The age of the Fund layers could, as stored both above them and below them rocks of volcanic origin, be dated reliably in the time between 6.2 to 5.65 million years.

From the construction of the thigh bone, the researchers deduced that Orrorin had gone tugenensis upright. Since a similar thickness of the outer layer of bone but also exists in baboons, this interpretation was initially very controversial. The same was true for the statement from the construction of the upper arm bone to let the ability to carry heavy loads derived. Secured however, can be derived from the size of the arm and leg bones that Orrorin tugenensis was about 50 percent larger than Lucy, the most famous Hominidenskelett the much younger kind Australopithecus afarensis.

Associated finds of various animal and plant species can be concluded that the Fund layers come from a habitat in which woodland, wet grasslands and lakeside alternated (gallery forests).

The genus name is derived from the word Orrorin, which means in the language of virtues " primitive man, fossil"; the epithet tugenensis refers to the locality, the virtues Hills, Baringo District in Kenya; Orrorin tugenensis thus means roughly " primitive man of virtues ". The fossils are preserved in the Kenyan National Museum in Nairobi.

Controversy

Although the fossils are preserved only fragmentary and come from different sites and time horizons, led their discoverers far-reaching conclusions from out of them. So they wrote in the 2001 South African Journal of Science prior to the classification of the fossil as a new species, their findings stood " in terms of size and morphology of the still living hominids closer than the much younger Australopithecus and Ardipithecus ramidus ." This said they were extinct sidelines; instead they put their own Kenyan fossils found at the base of that line of development that eventually emerged and explained in this way Kenya to the actual cradle of mankind to modern man. To these theses immediately, a heated scientific debate, which is still ongoing.

A recent study of the best preserved femur BAR1002'00 by Brian Richmond of George Washington University and William Jungers of Stony Brook University confirmed in March 2008 that Orrorin could go tugenensis upright. The construction of the bone differs both from that of the apes and from which the genus Homo; he resembles most closely the femur of Australopithecus and Paranthropus. Computer-assisted analysis of 300 fossil and now temporal comparison pieces also revealed that is very similar, in particular the biomechanics of the hip that of the australopithecines. The two researchers suggest, therefore, that these features developed already in the common ancestor of these species had almost four million years in hand and only in the late Pliocene - were modified - with the emergence of the genus Homo. Therefore, the Fund designated specifically as a hominin, although their analysis was based at the same time the thesis of the majority of paleoanthropologists that the development of modern people not directly tugenensis emanated from Orrorin, but from the australopithecines.

In February 2011, Bernard Wood and Terry Harrison criticized in a review article, the assignment of Orrorin of Ardipithecus and Sahelanthropus and to the taxon Hominini premature. Walking upright is by no means an exclusive feature of the Hominini, but also for example for Oreopithecus bambolii occupied, the - was initially made ​​on the basis of the Hominini, but later filed because of other characteristics unequivocally off the Hominini - as Ramapithecus punjabicus. Do not rule is therefore that the similarity of the characteristics of Orrorin with those of the oldest as undoubtedly hominin species Australopithecus anamensis is applicable to evaluate as synapomorphy and refers to convergent developments.

The following year, Martin Pickford replied that Orrorin homo in three separate features stand closer than Australopithecus: hand ( thumb), leg (thigh bone ) and dental apparatus ( tooth size and ratio ).