Australopithecus africanus

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Australopithecus africanus
Original of the skull of an A. africanus ("Mrs. Ples") in the Transvaal Museum in Pretoria

Original of the skull of an A. africanus (" Mrs. Ples ") in the Transvaal Museum in Pretoria

Temporal occurrence
Pliocene
3.0 to 2.1 million years
Locations
Systematics
Human (Hominoidea)
Apes (Hominidae)
Homininae
Hominini
Australopithecus
Australopithecus africanus
Scientific name
Australopithecus africanus
Dart , 1925

Australopithecus africanus is a species of the extinct genus Australopithecus . Fossils that have beenassigned to Australopithecus africanus mostly come from around 3 to 2.5 million year old layers in South Africa ; however, some finds may be a little older and others a little younger.

From which precursor species Australopithecus africanus descends and how close it is to the immediate ancestors of humans is not known. The species is often referred to as the graceful Australopithecus - as the opposite of the so-called "robust Australopithecines" .

Naming

Australopithecus is an artificial word . The name of the genus is derived from the Latin australis 'southern' and the Greek  πίθηκος (old Greek pronounced) píthēkos 'monkey'. The epithet africanus refers to the site in Africa ; Australopithecus africanus therefore means "southern monkey from Africa". Australopithecus africanus is the type species of the genus Australopithecus .

Find history

Initial description

The child of Taung ( replica )

The holotype of Australopithecus africanus and thus at the same time for the entire genus Australopithecus is the "child of Taung" discovered in 1924. It was also the first find of the genus introduced by Raymond Dart in 1925 . The facial skull with lower jaw and milk teeth , the forehead region and a natural skull cast have been preserved . This fossil was discovered in the autumn of 1924 by a quarry worker near the small town of Taung in what was then British Bechuanaland (now South Africa ) and handed over to Raymond Dart, who named it in 1925 with the genus and species name he had newly created, Australopithecus africanus .

More finds

After the assignment of the genus Australopithecus to the pre-humans was controversial for decades, the finding of the skull of Mrs. Ples (who was possibly a "Mr. Ples") was able to confirm this assignment. The skull discovered at Sterkfontein is now dated to an age of around 2.1 million years, making it the youngest find for Australopithecus africanus .

The most complete skeleton to date, which in its first description was cautiously assigned to “ Australopithecus africanus or another early hominid species”, also came to light in one of the Sterkfontein caves from 1995 onwards. It was given the inventory number StW 573 and the nickname Little Foot because initially (1994) only four bones were discovered from the left foot. In 1997, Ronald J. Clarke discovered more bones in the cave and, in 1998, a well-preserved skull. The bones have not yet been fully exposed due to their concrete-like, solid embedding in breccia . Very contradicting dates have been published, varying between 2.17 and 3.5 million years ago.

"Plesianthropus transvaalensis"
(today Australopithecus africanus )

Some hominini finds discovered in Sterkfontein from 1936 onwards , which are today attributed to Australopithecus africanus , were first introduced by Robert Broom in 1937 as Australopithecus transvaalensis , but renamed Plesianthropus transvaalensis ("Fast man from Transvaal ") the following year . Broom chose this generic name because he assumed that the fossils are close to man's ancestors. Broom also assigned the find published by Mrs. Ples in 1947 to Plesianthropus transvaalensis . Ernst Mayr, however, referred to such old finds in 1950 as Homo transvaalensis . Some finds that are now assigned to Australopithecus africanus , Raymond Dart had initially identified as Australopithecus prometheus , named after the Greek god Prometheus ("the forerunner"), who brought fire to people; Dart had mistakenly concluded from blackened animal bones in Makapansgat that the early pre-humans already ruled fire.

Besides Sterkfontein, Makapansgat is the most important site for finding fossils of Australopithecus africanus , some teeth come from the Gladysvale cave ; only the child's skull is known from Taung.

anatomy

The upper jaw Sts 52a with an added lower jaw

The occipital hole of Australopithecus africanus , discovered exclusively in South Africa , through which the rearmost part of the brain extends to the beginning of the spinal cord , is located below the skull, close to the center of gravity . From this it can be concluded that Australopithecus africanus could walk upright. However, Australopithecus africanus still had relatively long arms, so that its gait could have been comparable to that of modern baboons , although it may have walked upright more often than these. From the relatively abundant bone finds it could be deduced that the individuals of this species probably stayed in trees more often than other species of the genus Australopithecus . Australopithecus africanus also had relatively large molars , so its skull looked relatively ape-like. The canines , however, are much smaller than those of fossil and modern monkeys.

The brain volume is given in the specialist literature as 400 to 500 cubic centimeters , which corresponds approximately to that of the chimpanzee . The height of adult individuals is estimated to be about 1.10 to 1.40 meters and their body weight to 30 to 60 kilograms, with males being significantly larger than females. Accompanying finds indicate that Australopithecus africanus - like other Australopithecines - preferred “wooded habitats” in the transition to savannahs and maintained “a close connection to the broad banks of rivers and lakes”.

One of the oldest human-like anatomical features, the shape of the anvil in the middle ear , which already for Australopithecus africanus (the Fossil Stw 255 from Sterkfontein ) and Paranthropus robustus is busy and probably even at the last common ancestor of the shape of the anvil with the chimps differed .

Diet and Lifestyle

The tooth STS 1881 from Sterkfontein , South Africa
Hypothesis on the evolution of the australopithecines , as represented by Friedemann Schrenk , for example, based on the current finds .

The molars, which are relatively large in comparison to humans, are interpreted as an adaptation to a relatively hard plant food - including, at least at times, hard-shelled seeds . A computer analysis of the fossils Sts 5 and Sts 52 a (of a well-preserved upper jaw ) showed that the teeth and the structure of the facial bones were able to withstand high pressure , similar to that of the crab monkeys living today .

For Australopithecus africanus , it was also proven, based on the texture of the teeth, that more than 50 percent of its daily caloric intake was fed by C 3 plants and a further significant proportion of C 4 plants . This food, consisting mainly of leaves, fruits and seeds, was supplemented by meat, possibly depending on the season. this combination of vegetable and animal food probably distinguished Australopithecus africanus both from Paranthropus robustus , which was much more specialized in hard vegetable foods, and from the early representatives of the genus Homo , which consumed a higher proportion of meat.

Mass spectrometric analysis of teeth indicated that newborns were breastfed for 12 months ; Furthermore, in the following years - presumably during dry seasons with little food - they were sometimes fed with breast milk again . In terms of their breastfeeding behavior, Australopithecus africanus therefore resembles that of the orangutans living in their natural environment , which repeatedly suckle their offspring for up to nine years .

Stone tools have not been discovered in those strata containing Australopithecus africanus fossils . However, a comparison of the metacarpal bones of Australopithecus africanus , Neanderthals , Homo sapiens and the tree-dwelling great apes that are still alive today indicated that the alignment of the fine trabeculae of the substantia spongiosa in particular was caused by frequent pressure that only then built up when the thumb is in opposition to the other fingers. From this it was deduced that the hands of Australopithecus africanus had the anatomical requirements for the use of stone tools and that its individuals may have already used tools. The opposing position of the thumb enables the fist to be closed and significantly improves the gripping function of the hand by enabling both a force grip and a precision grip .

The alignment of the trabeculae in the heel bone StW 352 was interpreted to mean that the locomotion of Australopithecus africanus was more similar to that of a gorilla living today than that of a chimpanzee . From this it was also deduced that Australopithecus africanus probably - similar to the gorillas - moved more frequently on the ground than the chimpanzees living today.

According to a study published in 2011, the males of Australopithecus africanus were largely localized from birth , while the females migrated from other populations , which was interpreted as an indication of exogamy ; Female exogamy and male local loyalty also exist in the chimpanzees , while in the gorillas male and female individuals migrate equally to other populations after sexual maturity.

See also

Web links

Commons : Australopithecus africanus  - Collection of images, videos and audio files
Wiktionary: Australopithecus africanus  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. ^ A b c Raymond A. Dart : Australopithecus africanus: The man-ape of South Africa. In: Nature . Volume 115, 1925, pp. 195–199, doi: 10.1038 / 115195a0 , ( full text (PDF; 456 kB) )
  2. ^ A b Bernard Wood , Nicholas Lonergan: The hominin fossil record: taxa, grades and clades. In: Journal of Anatomy . Volume 212, No. 4, 2008, p. 358 f., Doi: 10.1111 / j.1469-7580.2008.00871.x , full text (PDF; 292 kB) ( Memento from October 20, 2012 in the Internet Archive )
  3. ↑ Primitive man gets an abdomen. On: stern.de from July 22, 2002
  4. ↑ Andy IR Herries, John Shaw: Palaeomagnetic analysis of the Sterkfontein palaeocave deposits: Implications for the age of the hominin fossils and stone tool industries. In: Journal of Human Evolution. Volume 60, No. 5, 2011, pp. 523-539, doi: 10.1016 / j.jhevol.2010.09.001 .
  5. ↑ Ronald J. Clarke , Phillip Tobias : Sterkfontein member 2 foot bones of the oldest South African hominid. In: Science. Volume 269, 1995, pp. 521-524, doi: 10.1126 / science.7624772 .
  6. ^ Robert Broom: On some new Pleistocene mammals from limestone caves of the Transvaal. In: South African Journal of Science. Volume 33, 1937, pp. 750–768, ( full text )
  7. ^ Ernst Mayr: Taxonomic categories in fossil hominids. In: Cold Spring Harbor Symposia on Quantitative Biology 1950. Volume 15, 1950, pp. 109-118, doi: 10.1101 / SQB.1950.015.01.013 .
  8. ↑ Steve Jones et al .: The Cambridge Encyclopedia of Human Evolution. Cambridge University Press, Cambridge 1992, p. 237
  9. ^ Friedemann Schrenk , Timothy G. Bromage : Adam's parents. Expeditions into the world of early humans. CH Beck, Munich 2002, p. 196.
  10. ^ Rolf M. Quam et al .: Early hominin auditory ossicles from South Africa. In: PNAS . Online advance publication of May 13, 2013, doi: 10.1073 / pnas.1303375110 .
  11. ^ Robert S. Scott et al .: Dental microwear texture analysis shows within-species diet variability in fossil hominins. In: Nature. Volume 436, 2005, pp. 693-695, doi: 10.1038 / nature03822
  12. ^ David S. Strait et al .: The feeding biomechanics and dietary ecology of Australopithecus africanus. In: PNAS . Volume 106, No. 7, 2009, pp. 2124–2129, doi: 10.1073 / pnas.0808730106
    Can you bite open a nut? On: idw-online from February 2, 2009.
  13. ^ Peter S. Ungar, Matt Sponheimer: The Diets of Early Hominins. In: Science . Volume 334, No. 6053, 2011, pp. 190–193, doi: 10.1126 / science.1207701 .
  14. ↑ Vincent Balter et al .: Evidence for dietary change but not landscape use in South African early hominins. In: Nature. Volume 489, 2012, pp. 558-560, doi: 10.1038 / nature11349 .
    Early human ancestors had more variable diet. Scientists reconstruct dietary preferences of 3 groups of hominins in South Africa. On: eurekalert.org of August 8, 2012
  15. ↑ Renaud Joannes-Boyau et al .: Elemental signatures of Australopithecus africanus teeth reveal seasonal dietary stress. In: Nature. Online pre-publication of July 15, 2019, doi: 10.1038 / s41586-019-1370-5 .
  16. ↑ Mother-child bond 2 million years ago. On: idw-online.de from July 15, 2019.
  17. ↑ Gary J. Sawyer, Viktor Deak: The Long Way to Man. Life pictures from 7 million years of evolution. Spektrum Akademischer Verlag, Heidelberg 2008, p. 64.
  18. ↑ Matthew M. Skinner et al .: Human-like hand use in Australopithecus africanus. In: Science. Volume 347, No. 6220, 2015, pp. 395-399, doi: 10.1126 / science.1261735 .
    Australopithecus africanus - strong hands for precise gripping. On: idw-online from January 22, 2015.
  19. ↑ Human ancestors got a grip on tools 3 million years ago. On: newscientist.com January 28, 2015; same text as The quiet rise of the first toolmaker. In: New Scientist. Volume 225, No. 3006, 2015, p. 14.
  20. ↑ Angel Zeininger et al .: Trabecular architecture in the StW 352 fossil hominin calcaneus. In: Journal of Human Evolution. Volume 97, 2016, pp. 145–158, doi: 10.1016 / j.jhevol.2016.05.009
    More gorilla than chimp. On: eurekalert.org of August 11, 2016.
  21. ↑ Sandi R. Copeland et al .: Strontium isotope evidence for landscape use by early hominins. In: Nature. Volume 474, No. 7349, 2011, pp. 76–78, doi: 10.1038 / nature10149
    Teeth reveal a lot about the life radius of early ancestors. On: mpg.de from June 1, 2011