Australopithecus anamensis

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Australopithecus anamensis
Left: 3 fragments of the forearm bone KNM-ER-20419; Top center: shin KNM-KP-29285A and B; Lower middle: upper jaw KNM-KP-29283; top right: humerus fragment KNM-KP-271; bottom right: lower jaw (= type specimen) KNM-KP 29281 (replicas, Museo de Ciencias Naturales de Madrid)

Left: 3 fragments of the forearm bone KNM-ER-20419;
Top center: shin KNM-KP-29285A and B;
Lower middle: upper jaw KNM-KP-29283;
top right: humerus fragment KNM-KP-271;
bottom right: lower jaw (= type specimen ) KNM-KP 29281
(replicas, Museo de Ciencias Naturales de Madrid)

Temporal occurrence
Pliocene
4.2 to 3.8 million years
Locations
Systematics
Human (Hominoidea)
Apes (Hominidae)
Homininae
Hominini
Australopithecus
Australopithecus anamensis
Scientific name
Australopithecus anamensis
M. Leakey , Feibel , McDougall & Walker , 1995

Australopithecus anamensis is a species of the extinct genus Australopithecus . Fossils that have been assigned to this species come from found layers in East Africa around 4 million years old.

Australopithecus anamensis is considered to be the oldest species of the Australopithecines and at the same time the oldest undisputed species of hominini . It is also very likely that Australopithecus anamensis and the younger Australopithecus afarensis are consecutive sister species due to anagenesis .

Naming

Australopithecus is an artificial word . The name of the genus is derived from Latin australis ("southern") and Greek πίθηκος, old Gr. pronounced píthēkos ("monkey"). The epithet anam means "lake" in the Turkana language and refers to the place where it was found on Lake Turkana ; Australopithecus anamensis means "southern monkey from the lake".

Initial description

In the first description in 1995, the lower jaw KNM-KP 29281 from the Kanapoi site was described as the holotype of Australopithecus anamensis , all of the teeth of which have been preserved, but the jaw joints are missing . Other finds used to define the species (paratypes) include: a. the two related mandibular fragments KNM-KP 29283 and the two fragments of the tibia KNM-KP 29285 (see images of all three fossils in the head of the article); the abbreviations KNM-KP stand for the depository of the fossils, the Kenya National Museum , and for the location Kanapoi.

Finds

The humerus fragment KNM-KP 271 from the area of ​​the elbow joint was recovered as early as 1965, but was initially not assigned to a specific species.

The first fossil , later related to Australopithecus anamensis , a fragment of the lower end of a left humerus , was discovered in 1965 by Bryan Patterson in Kanapoi and initially archived under the name KNP 271 (later: KNM-KP 271). Two years later it was described in the journal Science as probably belonging to the genus Australopithecus , but not assigned to a specific species. In 1982, a similarly old, single left molar (KNM-ER 7727) was discovered at the Allia Bay site, which has been known since 1968 , further molar teeth in 1988, and finally several upper and lower jaw fragments in Kanapoi in 1994 . These teeth and a fragment of the lower jaw were scientifically described for the first time in 1994 and cautiously placed in the relationship of Australopithecus afarensis .

A precise analysis of the jaws and in particular the discovery of the upper and lower end of a right tibia (KNM-KP 29285) from almost the same layers of finds, which was interpreted to mean that its owner habitually moved on two legs , prompted the researchers working with Meave Leakey and Alan Walker on a changed view of these fossils: In 1995 the first description of Australopithecus anamensis was published in Nature on the basis of 21 finds .

Between 1995 and 1997 further fossils were recovered from both Kenyan sites, which were assigned to Australopithecus anamensis . It was also deduced from them that Australopithecus anamensis had "more primitive" anatomical features than Australopithecus afarensis and could therefore be classified as the earliest species of the genus Australopithecus .

Since 2006, in the course of several excavation campaigns in the Afar Triangle ( Ethiopia ), numerous fragments of at least eight individuals, whose age is comparable to the Kenyan finds, and which have therefore also been assigned to Australopithecus anamensis , including the largest known canine tooth and the oldest thigh -Bones of an Australopithecus .

One of the most important finds is a skull (MRD-VP-1/1) with a partially preserved upper jaw, which was discovered in February 2016 in the Ethiopian excavation site Woranso-Mille , which was ascribed an age of around 3.8 million years.

Dating

The majority of all fossils found in the vicinity of Lake Turkana can be reliably and absolutely dated , as volcanic eruptions have occurred repeatedly in this region. Most of the fossils related to Australopithecus anamensis are found between a basalt stream and a layer of ash ( tuff ), radiometrically dated to 4.35 and 3.89 million years ago. If the position within the - between basalt and tuff - altogether 37 meter high find layer is taken into account, then the fossils of Allia Bay and Kanapoi are around 3.95 million years old. The finds from Ethiopia could also be absolutely dated radiometrically, they are around 4.2 to 4.1 million years old.

features

Hypothesis on the evolution of the australopithecines , as represented by Friedemann Schrenk , for example, based on the current finds .
Site plan of the two sites of Australopithecus anamensis on Lake Turkana in Kenya

nutrition

Australopithecus anamensis differs significantly from the older Ardipithecus ramidus , but also - especially with regard to the structure of the teeth - from the younger Australopithecus afarensis . Its skull is similar to that of the chimpanzee , the rows of teeth in the lower and upper jaw are almost parallel to each other. Its large canine teeth are at an angle to the chewing surface, and the molars are also quite large, which suggests the consumption of relatively coarse vegetable food. In 2013, an isotope analysis of the teeth of finds from the Turkana basin showed that Australopithecus anamensis consumed a high proportion of relatively soft C 3 plants , while Australopithecus afarensis primarily consumed C 4 plants . In a study published in 2019, the proportion of C 4 plants in the diet of Australopithecus anamensis was estimated to be at least 15 percent.

anatomy

The attachment points of muscles, tendons and ligaments as well as the curvature and orientation of the articular surfaces of the arms "can best be compared with the corresponding bones of an orangutan." The "chimpanzee-like curvature of the finger bones" suggests that Australopithecus anamensis is common in trees hung on branches or walked on the knuckles (in the ankle duct ). The shape of the face - the nose clearly behind the upper lip - suggests an appearance that could have resembled an orangutan.

The paleoanthropologist Friedemann Schrenk describes the appearance as follows:

“While the skull looks more like an ape, the structure of the extremities is difficult to distinguish from that of modern humans. In contrast to the later species Australopithecus afarensis, the upright gait in the earlier Australopithecus anamensis was apparently already fully developed. There are only two possible explanations for this paradoxical situation: Either the thighbones found in Kanapoi do not belong to Australopithecus anamensis or Australopithecus anamensis is not a direct ancestor of Australopithecus afarensis. In the second case, the most exciting prospect opens up that the first members of the genus Homo may even be directly traced back to Australopithecus anamensis. "

Habitat

Similar to the much older Sahelanthropus , the accompanying finds of the individuals initially discovered at Lake Turkana (including fossil antelopes , especially kudu ) indicated that Australopithecus anamensis lived in a habitat that consisted partly of scrubland and partly of savannah, typical for so called gallery forests ; no fossils were found that suggest open water surfaces.

The findings from the Afar region were interpreted by Tim White's researchers to the effect that Australopithecus anamensis stands between Ardipithecus ramidus and Australopithecus afarensis in terms of many anatomical features . The relatively large teeth were also interpreted in these finds as an adaptation to relatively hard plant food, as is to be expected from a species that primarily lives in forests, but is at least native to the edge of a steppe landscape.

criticism

The assignment of all of these finds to a single species is controversial, mainly because the size and appearance of the molars vary widely and the fossils from Ethiopia are "incomplete, worn and damaged"; In addition, the Ethiopian tooth finds come from the upper jaw and can therefore not be directly compared with the holotype (a lower jaw). According to some researchers, the chimpanzee-like premolars and the narrow auditory canals speak in favor of assigning the fossils to the genus Ardipithecus instead of Australopithecus ; The orangutan-like snout, in conjunction with other original features, may also indicate that the fossils known as Australopithecus anamensis are to be classified before the lineages of hominini and chimpanzees split up .

Even the 30 fossils from the Kenyan site of Allia Bay have so far only been "temporarily" combined with the 50 fossils from the location of the holotype in a single species.

See also

literature

  • Carol Ward, Meave Leakey, and Alan Walker: The new hominid species Australopithecus anamensis. In: Evolutionary Anthropology. Volume 7, No. 6, 1999, pp. 197-205, doi : 10.1002 / (SICI) 1520-6505 (1999) 7: 6 <197 :: AID-EVAN4> 3.0.CO; 2-T
  • Peter S. Ungar et al .: Molar microwear textures and the diets of Australopithecus anamensis and Australopithecus afarensis. In: Philosophical Transactions of the Royal Society B. Online publication of September 20, 2010, doi: 10.1098 / rstb.2010.0033
  • Margaret J. Schoeninger, Holly Reeser and Kris Hallin: Paleoenvironment of Australopithecus anamensis at Allia Bay, East Turkana, Kenya: evidence from mammalian herbivore enamel stable isotopes. In: Journal of Anthropological Archeology. Volume 22, No. 3, 2003, pp. 200-207, doi: 10.1016 / S0278-4165 (03) 00034-5
  • CV Ward, FK Manthi and JM Plavcan: New fossils of Australopithecus anamensis from Kanapoi, West Turkana, Kenya (2003-2008). In: Journal of Human Evolution. Volume 65, No. 5, 2013, pp. 501-524, doi: 10.1016 / j.jhevol.2013.05.006

Web links

Commons : Australopithecus anamensis  - Collection of images, videos and audio files

Individual evidence

  1. ↑ a b c Meave Leakey, Craig S. Feibel, Ian McDougall and Alan Walker: New four-million-year old hominid species from Kanapoi and Allia bay, Kenya. In: Nature. Volume 376, 1995, pp. 565-571, doi: 10.1038 / 376565a0 , full text (PDF) ( Memento from July 22, 2018 in the Internet Archive )
  2. ↑ Bernard Wood , Terry Harrison : The evolutionary context of the first hominins. In: Nature . Volume 470, 2011, pp. 347-352, doi: 10.1038 / nature09709
  3. ^ William H. Kimbel, Charles A. Lockwood, Carol V. Ward, Meave Leakey , Yoel Rak and Donald Johanson : Was Australopithecus anamensis ancestral to A. afarensis? A case of anagenesis in the hominin fossil record. In: Journal of Human Evolution . Volume 51, No. 2, 2006, pp. 134-152, doi: 10.1016 / j.jhevol.2006.02.003
  4. ↑ Bryan Patterson and William W. Howells: Hominid Humeral Fragment from Early Pleistocene of Northwestern Kenya. In: Science . Volume 156, No. 3771, 1967, pp. 64-66, doi: 10.1126 / science.156.3771.64
  5. ↑ Katherine Coffing, Craig Feibel, Meave Leakey, and Alan Walker : Four-million-year-Old hominids from East Lake Turkana, Kenya. In: American Journal of Physical Anthropology. Volume 93, No. 1, 1994, pp. 55-65, doi: 10.1002 / ajpa.1330930104
  6. ↑ Meave G. Leakey, Craig S. Feibel, Ian McDougall, Carol Ward and Alan Walker: New specimens and confirmation of an early age for Australopithecus anamensis. In: Nature. Volume 393, pp. 62-66, 1998, doi: 10.1038 / 29972
  7. ↑ Tim White et al .: Asa Issie, Aramis and the origin of Australopithecus. In: Nature. Volume 440, 2006, pp. 883-889, doi: 10.1038 / nature04629 , full text
    Neue Affenmenschen. On: heise.de from April 14, 2006
  8. ↑ Yohannes Haile-Selassie et al .: A 3.8-million-year-old hominin cranium from Woranso-Mille, Ethiopia. In: Nature. August 28, 2019, doi: 10.1038 / s41586-019-1513-8
    A face for Lucy's ancestors. On: mpg.de from August 28, 2019
  9. ↑ Thure E. Cerling et al .: Stable isotope-based diet reconstructions of Turkana Basin hominins. In: PNAS . Volume 110, No. 26, 2013, pp. 10501-10506, doi: 10.1073 / pnas.1222568110
  10. ↑ Rhonda L. Quinn: Isotopic equifinality and rethinking the diet of Australopithecus anamensis. In: PNAS. Advance online publication of May 3, 2019, doi: 10.1002 / ajpa.23846
  11. ↑ Gary J. Sawyer, Viktor Deak: The Long Way to Man. Life pictures from 7 million years of evolution. Spektrum Akademischer Verlag, Heidelberg, 2008, pp. 24-25, ISBN 978-3827419156
  12. ↑ Friedemann Schrenk : The early days of man. The way to Homo sapiens. CH Beck, 1997, p. 44 f.
  13. ↑ Gary J. Sawyer, Viktor Deak, Long Road to Humans, pp. 27–28
  14. ↑ Carol V. Ward, Meave G. Leakey and Alan Walker: Morphology of Australopithecus anamensis from Kanapoi and Allia Bay, Kenya. In: Journal of Human Evolution. Volume 41, No. 4, 2001, pp. 255–368, doi: 10.1006 / jhev.2001.0507 , full text (PDF)