Ardi is elected by its discoverers nickname of a 4.4 million years old, largely preserved individual of the species Ardipithecus ramidus. The remains of the presumably female Fossils were recovered between 1994 and 1996 in the north- eastern Ethiopia in the Afar Triangle. The preservation of the skeletal remains was found due to their extreme fragility to be extremely difficult and time consuming, so that their comprehensive interdisciplinary approach was first made public in eleven simultaneously published professional articles in October 2009. The scientific term for this called the Ardi skeleton since 2009 Fund is ARA-VP-6/500.
The special importance of the fossil is found that were decades-old hypotheses about evolutionary history of man, according to which the knuckle-walking chimpanzees and gorillas is an original feature in question.
The name of the genus Ardipithecus is partly derived from the Afar language (from " ardi " = ground ), partly from the Greek (from " πίθηκος ", ancient Greek, pronounced " píthēkos " = monkey); Ardipithecus means according to the sense hence " Bodenaffe ".
The first two fossils of Ardi - two fragments of metacarpals - were discovered on November 5, 1994 by Yohannes Haile - Selassie in Aramis, about 100 km south of Hadar and west of Awash. They were on the surface of a slope of silty clay (English " silty clay" ) emerged. This reference was only 54 meters to the north of that locality, where ten months previously had been discovered the type specimen ARA -VP -6/ 1 of Ardipithecus ramidus. By carefully screening the superficially lying fine soil further fragments homininer finger bone were recovered. Then a phalanx, and the fragment of a femur and an almost completely preserved tibia were excavated in the emerging information - trough. Subsequently, a total of three square-foot space was removed millimeter by millimeter in the following months; In this way, more than a hundred more pieces of bone were secured, including several sesamoid bones and fragments from the area of the face.
The age determination of Ardi deemed highly reliable, since both immediately above and immediately below the fossil -bearing layer of volcanic material was deposited and both volcanic layers are 4.4 million years old, respectively. Both Ardi and the other finds of Ardipithecus ramidus from Aramis come from a three to six meters thick, fine-grained sediment that originated in a relatively short period of only 100 to a maximum of 10,000 years. Both the fine granularity of the sediment layer and the condition of the fossil bones suggest (the absence of signs of abrasion ) indicated that they were not or only slightly drifted by water.
The bones of Ardi are poorly fossilized. They are described by their discoverers as cream. The smaller bones of the hands and feet are largely undamaged, the larger bones of the legs and arms are however broken varies.
On the bone no signs of weathering or of bite marks were found. This is a phenomenon, as almost all other bone finds were gnawed from the same find horizon by hyenas and other carnivores. However, the bones of Ardi were scattered over a larger area and were found more in their natural arrangement in any case - a condition of the outer indications are that must have occurred prior to their embedding into the earth; The researchers suspect that the remains of Ardi were trampled by other animals.
Many bones were found to be so soft that they were already crumbled light touch. After a careful stress test toothpick or similar means, therefore, were the sediments that surrounded the bone, first moistened to prevent damage due to dehydration during the salvage of the finds. Then, it was several times on curing agent; only after the bone has been removed from the ground, packaged and transported for further processing to Addis Ababa. In many years of fine work all finds were finally cleaned and treated with the help of digital reconstructions in their putative natural position. The remains of Ardi are still fragile, which is why most research has been on Gipsabformungen or computerized, with the aid of computed tomography, performed despite various cures.
The skull of Ardi is indeed highly fragmented and deformed but the left half of the lower jaw, teeth, and almost all informative parts of the face, the cranial vault and base of the skull remained. With the help of computer -assisted procedures and the involvement of another Fossils - ARA-VP-1/500 from the base of the skull - could the Japanese paleoanthropologist Gen Suwa (University of Tokyo), the appearance of the skull from 65 fragments as a "pre- Australopithecus - like morphology " reconstruct. A separate analysis of the construction of the skull base ARA-VP-1/500 confirmed in early 2013, the morphological proximity to Australopithecus and Homo.
The reconstruction of the skull size resulted in a brain volume of 280-350 cubic centimeters, which in relation to body size a rather small brain - comparable to today's chimpanzees - equivalent; Australopithecus is attributed to a brain volume of 400 to 550 cubic centimeters. The skull of Ardi is similar to the larger and more powerful Sahelanthropus tchadensis, for a comparable intracranial volume was calculated. Numerous features distinguish the skull of Ardi from the skulls of extant gorillas and chimpanzees, but also of the Australopithecus skulls.
The exact position of the occipital hole was for lack of Ardi fossil evidence can not be determined, however, succeeded in its reconstruction of the skull fragment ARA-VP-1/500. The reconstruction german confirmed the previously expressed already in the original description of the species suggest that the occipital foramen of Ardipithecus ramidus was already moved to a position below the head, similar to that of later Hominini species, and its position is therefore " fully " ( " squarely " ) from the position in the chimpanzee is distinguishable.
The upper jaw of Ardi - ARA-VP-6/500-115 - has, unlike the living chimpanzees, not very far forward, so it has a merely weak prognathism ("a superoinferiorly short face and weak prognathism Compared with the common chimpanzee "). It is similar to the upper jaw of Sahelanthropus, but is slightly smaller overall than this. The incisors are relatively small, from their position, and from the position of the nostril can be inferred that Ardi had a slightly projecting snout. Together with other findings, the construction of the face by the authors is evaluated as an original feature of the early Hominini, so the last common ancestor of chimpanzees and Hominini resembling; the distinct, wide projecting snout of chimpanzees interpret them accordingly as a younger, more derived character. The lower jaw is also similar to that of Sahelanthropus and Ardipithecus of the kadabba. The construction of both jaws and the teeth can be preserved to any particular specialization include in food intake.
Hand and foot
From Ardis hands and feet so many bones have been preserved, that a very reliable reconstruction of both extremities is possible. Their accuracy is at best equivalent to much younger fossil Littlefoot from South Africa, there are known even by Lucy only two metacarpals.
The construction of Ardis hands shows clear echoes of one of the earliest known representative of the anthropoids ( Hominoidea ), more than four times as old Proconsul. Ardis hand was in the medium wrists extremely movable so that they could embrace these on branches very good with their hands in the horizontal Moving. The other wrists were much more mobile than that of living chimpanzees and gorillas, and therefore differed greatly from their hands. These African apes have relatively long palms and long fingers, which - unlike Ardipithecus - especially good are able to powerfully up to pull her body into the higher regions of the trees. The associated forces - effects had the consequence that in them the joints between the fingers and palm are only slightly movable. This in turn has on the ground the ankle going to the sequence; for a comparable locomotion, there is no evidence at Ardi.
Also the foot of Ardi more closely resembles the foot of the macaques and gibbons as the foot of the great African apes. So when Ardi is still a special bone present (Os peroneum ), which is considered an original, that is phylogenetically old feature; also the reconstructed tendon to fibula muscle peroneus longus refers to an homology with these distant relatives of Hominini. However, the most striking feature of the foot is the most widely spreadable big toe. Ardi could therefore hold good also with the help of his big toes on those branches, which they climbed all fours. This anatomical feature is not known from any living primates and fossil occupied only by the Ethiopian recovered in excavation area Woranso - Mille Burtele -foot; it gave Ardipithecus unique among all known primates gait, because the big toes were likely to be in upright walking splayed.
Pool and walking upright
Although the arrangement of the bones of the foot and hands suggests that Ardi continues moving in the branches of the trees on all fours and the big toes were designed as prehensile organs, results in the reconstruction of the bones of the pelvis that she could walk upright on the floor. For example, the approach of the gluteal muscles compared to older fossil anthropoids thanks to a developed ilium for upright walking is so stabilizing low positioned so that Ardi could progressing without pivoting the body from side to side with each step. In contrast to Australopithecus afarensis, who already had all the essential adjustments for a permanent bipedalism, Ardis pelvic girdle is, however, described by investigators as a " mosaic of features " that made her both climbing and rapid running.
The few obtained from the foot bone fragments have been described as " a mixture of retained primitive characteristics and features of which are adapted for a habitual bipedalism ".
Sex determination, body weight and body size
Among the total of 21 preserved canines of Ardipithecus include the canine teeth of the smallest Ardi: The maxillary canine is the second smallest of 13, the mandibular canine is the second smallest of eight canines obtained. From this, the researchers infer that Ardi was female. Supported this interpretation by a small fragment of the Überaugenwulsts ( supraorbital torus ) whose thickness is also ranked in the lowest range.
Comparative measurements in living today primates have shown that the size of the head of the talus bone and very well correlated with the body weight of the primates. Thanks to this correlation could be derived for a Ardi body weight of 51 kg. Because Ardi was one of the larger individuals of its kind, could be regarded as typical of the entire species a weight of about 50 kg. The reconstruction of the height of Ardi was the inclusion of other fossils an estimate of 117-124 cm.
From the period before the appearance of Australopithecus anamensis few finds of fossil Hominini known to date. These findings are also - as Orrorin tugenensis - so fragmentary or - as the skull of Sahelanthropus tchadensis - deformed so that its position in the family tree of the apes is controversial and therefore unclear. The lack of conclusive fossil evidence had of the consequences is that the hypotheses on the evolution of the physique of the early Hominini were mainly from the appearance of the next of kin of the people, by the physique of chimpanzees derived. These models indicated, for example, to walk upright the Hominini in the sense of homology as a further development of a supposedly original ankle gangs, that is, as in chimpanzees and gorillas surviving intermediate stage of transition from a primarily arboreal lifestyle for permanent residence in the open savannah. Ardis hand skeleton yielded now but a proof that the early Hominini had relatively original gripping hands and - going on - that the hands of modern man " primitive " are (less strongly on the initial state different) than that of chimpanzees and gorillas. In addition, walking and pelvic girdle of Ardi show that Ardipithecus ramidus was already capable of walking upright, as the individuals of this kind with respect to many other anatomical features were regular tree dwellers. The Body of Ardi therefore falsified the historical savanna hypothesis that the upright gait had developed at quadrupedally living savannah inhabitants.
The editors of the journal Science said the description of Ardi and their environment the most important scientific publication of the year 2009, as this discovery " a major figure in the history of human evolution " is, pari passu with the discovery of the first Neanderthal man, the " child of Taung " and the skeleton of " Lucy ". In the journal Nature, they said, the fossil " enable the first comprehensive look at the biology of a species in temporal proximity to the last common ancestor of humans and other great apes "; carry it to the fact that the previous presentation of the early evolution of Hominini should be " rewritten ". The Frankfurter Allgemeine Zeitung supplemented this statement: " The idea that the ancestors of the people strongly million years ago, four or five were similar to chimpanzees and as they swung in the trees from branch to branch, it should have become obsolete now. "