Orrorin tugenensis is the name given to a old Hominidé of approximately 6 million years, defined starting from a disparate whole of fossils of which some were officially discovered in October and November 2000 in the formation of Lukeino, in the hills of Tugen, with the Kenya, by Ezra Kiptalam Cheboi. Orrorin is the local name of a mythical character, “the original Man”. Orrorin tugenensis was also called Millennium Man , or Man of the millenium. He became temporarily the principal applicant with the statute of biped first Hominidé, granted since 1993 to Ardipithecus ramidus (4 to 5 M of years), followed closely by Australopithecus afarensis (Lucy, 3,2 M of years). He was however évincé in 2002 by Toumaï ( Sahelanthropus tchadensis ), old from 6 to 7 million years.
Fossils
First discovered, a fragment of jaw, was identified by Brigitte Senut and Martin Pickford of the national Muséum of natural history of Paris, in collaboration with the Community museums of Kenya. Twelve fragments of fossils made surface in three localities in October and November 2000; thereafter, was added to the list a thirteenth fossil found in 1974 in a close locality, the geological formation of Ngorora (average Miocène, 12,5 million years). The phylogenetic statute of this last until had been the center of varied and not corroborated speculations there.
Orrorin tugenensis was thus defined starting from thirteen fossil remainders corresponding at least to five distinct individuals (photographs of the unit) and including:
- 1 Humérus (arms)
- 3 Femur S, including 1 piece of small size (thigh)
- 1 phalange (hand)
- 2 mandible S
- 6 Tooth S
Detailed description of the fossils
Teeth present “morphological and metric affinities” with both anthropoïdes current. The right molar lower found than Ngorora (12,5 M years) resembles those of the Chimpanzé. The molars point out those of the later Hominidé S, like the Australopithèque S or the representatives of the kind Homo .
Dating
The various fossils of Orrorin were not the subject of direct datings but their age could be evaluated thanks to their context:- Sill Dolérite of Rormuch (5,62 ± 0,5 M years) passes through the Lukeino Formation.
- the lower levels of basalts Kararaina (5,65 ± 0,13 million years) recover the Formation of Lukeino.
- the higher levels of trachytes of Kabarnet (6,2 ± 0,13 million years) pass just below the Formation of Lukeino.
- Of the crystals vulcanogenic coming from the Formation of Lukeino was gone back with 6,06 ± 0,13 million to years;
- the fossils of other animal species accompanying Orrorin are similar to those found in layers whose dating is not any doubt. The common age indicated is the end of the Miocène, 6 million years.
Main features
Its face was relatively punt. According to the size of the bones available and especially of the femurs, Orrorin could measure 1,40 m for a weight of 50 kg. One does not know the degree of variability of the weight among members of the same kind and it is possible that it is important - only other fossils can inform us about this point. By holding account only material available, Orrorin would thus have been larger than A.L. 288-1 (Lucy), which makes an exception of it among the primitive Hominides.
Locomotion
The only thing on which everyone seems to agree without too many reserves is that the morphology of Orrorin makes the bipédie possible. This does not make for all that him a strict Bipède, being held and going mainly upright.Certain fossils present indeed indices of Adaptation to climbing:
- the phalange (BAR 349 ' 00) is bent in a permanent way; the hands of O. tugenensis those of one were hominidé arboricolous.
- the side peak of the distal humérus (BAR 1004 ' 00) is right, as in the modern chimpanzees like at A. afarensis , and is related to the existence of powerful muscles: it is on this peak that the muscle Mr. brachioradialis sticks.
Environment and food
Mainly fossils of Bovidae of small and average size, and small monkeys wads were found. Impala S indicate sparse forests; wads of spaces of dense forest.
The majority of the fossils of Kapsomin are covered with a fine layer coming from algae and bacteria indicating a stay in water before the bodies are not hidden under the sediments. There was thus water, in sufficient quantities to drown a whole group, before or after their death or causing it even.
Others, like the two fragments of mandible, are severely cracked; they were probably desiccated by exposure to the elements before finding itself buried.
With Orrorin one did not find tools, it probably did not use any.
Orrorin lived among the trees in sparse forest or borders wet forest. Its food was that of a Omnivore: fruits, almonds of cores, seeds, bays, insects, and occasionally meat.
See too
Sources
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