UR 501

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UR 501 (original), the oldest known, complete lower jaw of the genus Homo
Excavation manager Friedemann Schrenk , 2007

UR 501 (also: HCRP UR 501 ) is the scientific name for the lower jaw of Homo rudolfensis . After the lower jaw fragment LD 350-1 , which resembles it, the very well preserved fossil is considered to be the second oldest find that has been assigned to the genus Homo .

UR 501 was Tyson Mskika, an employee of the German on 11 August 1991 paleoanthropologist Friedemann Schrenk American US and his colleague Timothy Bromage , as part of the corridor project hominid ( Hominid Corridor Research Project , HCRP) in Malawi discovered. The archive number UR 501 stands for the location near Uraha (hence: UR), a village near Karonga on the west bank of Lake Malawi and alludes to the jeans model Levi's 501 . Bromage and Schrenk had been searching specifically for hominini fossils in Malawi since 1983 , as they suspected that "primitive men " had not only lived in southern Africa and in East Africa , but also in the region in between.

features

The lower jaw was broken into two parts in the area of ​​the " chin " when it was found and covered by an iron crust, which is why it was very well preserved despite having been stored on the earth's surface for many years. The front teeth ( incisors and canines ) are missing, but four molars - the third and fourth premolars and the first and second molars - have been preserved on both the left and right . A quarter of the second molar on the right was initially missing, but was recovered after seven tons of earth had been sifted through for weeks. Only now was it possible to assign it to the genus Homo , because the back molars have six or seven cusps ( "tubercula" ), whereas the older australopithecines have fewer (see Dryopithecine pattern ). Numerous other features of the surviving tooth crowns - including in particular the arrangement of the tooth cusps and the fine structure of the enamel - are similar to the features of other finds from early representatives of the Homo genus . In particular, the features of the strong teeth and the strong lower jaw bone of UR 501 are similar to those of the lower jaw KNM-ER 1802, which was discovered in close proximity to the type specimen of Homo rudolfensis at Koobi Fora in Kenya . Nevertheless, the fossil shares some characteristics with Australopithecus africanus and Australopithecus afarensis as well as with Paranthropus .

Age and habitat

On the basis of biostratigraphic analyzes, an age of 2.4 million years was shown for the lower jaw in 1993 in the journal Nature ; in later publications the age of the find was corrected slightly upwards to 2.5 to 2.4 million years. UR 501 was therefore until the description of the lower jaw fragment LD 350-1 in March 2015 as the oldest fossil assigned to the genus Homo .

So far, the lower jaw could not be dated absolutely , but only relatively , based on the fossils of primeval giraffes ( Giraffa stillei and Giraffa pygmaea ), baboons ( Parapapio and relatives of the Dschelada ), horses ( Equus and Hipparion ), which were recovered in the same find horizon , elephants and mammoths ( Elephas Recki and mammuthus subplanifrons ), various antelopes and gazelles , black rhinos , hippos , turtles and crocodiles , which are also known from absolutely datable layers of Kenya.

The composition of the animal species found together with UR 501 indicates a tropical habitat for Homo rudolfensis in which open savannahs were crossed by river systems. The first appearance of Homo rudolfensis around 2.5 million years ago occurs in an era in which East Africa - as a result of a strongly growing ice sheet in the northern polar region - became noticeably drier and cooled. It is possible that the species evolved from representatives of the Australopithecus genus due to this climate change and the associated fragmentation of the previously contiguous rainforests in Africa .

Importance of the find

In 1993, when it was first presented in Nature, Bernard Wood described the find as three-fold significant. On the one hand, it proves that around 2.5 million years ago, in addition to Paranthropus, there was a second representative of the hominini in its habitat; On the other hand, that this second species - Homo rudolfensis - as evidenced by its strong teeth and its strong lower jaw, was adapted to relatively hard-fibred food (although much less strongly than Paranthropus ), which correlates temporally with the climate change in this epoch and a frequent stay in grasslands suggests. From this it can be deduced that both Paranthropus and Homo did not emerge from Australopithecus species before this climate change began 2.5 million years ago . Thirdly, the composition of the accompanying finds shows that the fauna of Malawi had closer ties to East Africa than to southern Africa . This in turn has an impact on the question of the region in which the genus Homo originated.

The fossil was allowed to be brought to Germany for further processing on the basis of personal approval from the Malawi minister of culture. It has since been kept at the Senckenberg Research Institute in Frankfurt am Main .

Web links

Commons : Homo rudolfensis  - collection of images, videos and audio files

Remarks

  1. ↑ The counting of the premolars (P 3 and P4) relates to the original set of teeth in primates with four premolars; P1 and P2 were lost in the course of tribal history.

Individual evidence

  1. ↑ Friedemann Schrenk , Timothy Bromage : The hominid corridor of Southeast Africa. In: Spectrum of Science . No. 8, 2000, p. 49. - At the same point it is explained that the lower jaw was the 499th find registered by Uraha.
  2. ^ Friedemann Schrenk et al .: Early Hominid diversity, age and biogeography of the Malawi-Rift. In: Human Evolution. Volume 17, No. 1-2, 2002, pp. 113-122, doi : 10.1007 / BF02436432
  3. ↑ Friedemann Schrenk in: Spectrum of Science. , No. 9, 2010, p. 69
  4. ↑ Fernando V. Ramirez Rozzi, Tim Bromage and Friedemann Schrenk: UR 501, the Plio-Pleistocene hominid from Malawi. Analysis of the microanatomy of the enamel. In: Comptes Rendus de l'Académie des Sciences - Series IIA - Earth and Planetary Science. Volume 325, No. 3, 1997, pp. 231-234, doi : 10.1016 / S1251-8050 (97) 88294-8
  5. ↑ Timothy G. Bromage, Friedemann Schrenk and Frans W. Zonneveld: Paleoanthropology of the Malawi Rift: An early hominid mandible from the Chiwondo Beds, northern Malawi. In: Journal of Human Evolution. Volume 28, No. 1, 1995, pp. 71-108, doi : 10.1006 / jhev.1995.1007
  6. ^ Friedemann Schrenk, Timothy Bromage et al .: Oldest Homo and Pliocene biogeography of the Malawi Rift. In: Nature . Volume 365, 1993, pp. 833-836, doi : 10.1038 / 365833a0
  7. ↑ For example in: Friedemann Schrenk, Die Frühzeit des Menschen. The way to Homo sapiens. CH Beck, 1997, p. 68
  8. ↑ "We therefore suggest that Homo rudolfensis arose during, and partly as a result of, the 2.5 Myr climatic cooling event in eastern Africa and remained endemic there ..." Quoted from: Friedemann Schrenk, Timothy Bromage et al., Oldest Homo and Pliocene biogeography of the Malawi Rift , p. 835
  9. ^ Bernard Wood: Rift on the record. In: Nature. Volume 365, 1993, pp. 789-790, doi : 10.1038 / 365789a0
  10. ^ Friedemann Schrenk, Timothy G. Bromage: Adam's parents. Expeditions into the world of early humans. CH Beck, 2002, p. 149