Homo ergaster

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Homo ergaster
The fossil KNM-ER 3733

The fossil KNM-ER 3733

Temporal occurrence
Pleistocene
1.9 to 1.4 million years
Locations
Systematics
Human (Hominoidea)
Apes (Hominidae)
Homininae
Hominini
homo
Homo ergaster
Scientific name
Homo ergaster
Groves & Mazák , 1975
Lower jaw KNM-ER 992 (replica)

Homo ergaster is an extinct species of the genus Homo from the Old Pleistocene . Only fossils from Africa that are 1.9 to 1.4 million years old and were discovered in Koobi Fora ( East Africa ) and in Swartkrans ( South Africa ) are assigned to this chronospecies . However, some of the finds attributed to the species also come from younger strata and are possibly only 1 million years old.

Naming

The name of the genus Homo is derived from the Latin homo [ ˈhɔmoː ] = German human. The epithet ergaster comes from the Greek and means " worker "; Homo ergaster thus means “the working man”, which refers to the use of stone tools that is ascribed to this type. The oldest stone tools, at 2.4 million years old, are much older than the fossils of Homo ergaster and were probably made by Homo rudolfensis and Homo habilis .

Initial description

Holotype of Homo ergaster is a well-preserved and almost completely dentate lower jaw (archive number KNM-ER 992, see illustration) consisting of two fragments that belong together. It was discovered by Richard Leakey in Koobi Fora ( Kenya ) in 1971 and its age is approximately Had been dated 1.5 million years; Leakey published the find in 1972 and assigned it to the genus Homo , but not assigned it to a specific species. The name was given in 1975 by Colin Groves and Vratislav Mazák in a Czech trade journal. A dozen mandibular and maxillary fragments with some preserved teeth, which had also been discovered by Richard Leakey in Kenya on the east bank of Lake Turkana, were added as paratypes to the type specimen in the first description . It is noteworthy that these finds were delimited from Australopithecus africanus and Homo habilis , but not from Homo erectus .

All of the finds from South Africa placed in the immediate vicinity of Homo ergaster in the first description were discovered by John T. Robinson in 1949 and named by him as Telanthropus capensis .

In the first description it was noted that the fossils used to define Homo ergaster had been discovered by Richard Leakey and that "under normal circumstances" the epithet leakeyi would have been chosen; however, this designation Homo leakeyi had already been given in 1963 by Gerhard Heberer for a variant of Homo erectus .

The finds from Koobi Fora are kept in the Kenyan National Museum in Nairobi , the finds from Swartkrans in the Transvaal Museum in Pretoria .

features

Since Homo ergaster has been assigned numerous fossils that other researchers consider earlier Homo erectus , the characteristics of the two species hardly differ. As typical for the head is u. a. an uninterrupted and moderately wide bony bulge above the widely spaced eyes that protrude from - in the upper area of ​​the face - almost vertical bones. The upper jaw still protrudes far forward so that the jaws form a kind of snout ; the distance between the mouth and the nostril is quite large. “The morphological characteristics of H. ergaster compared to H. erectus include: generally more delicate skeletal structure, longer and narrower molars , complex roots of the premolars , thinner skull bones, no bone keel on the skull, weaker ocular bulge , higher skull bulge , lower post orbital ones Neck constriction, narrower skull base . "

The brain volume of Homo ergaster was between 750 and 900 cm 3 . However, some of the finds assigned to this species had a significantly smaller brain, for example only 582 cm 3 were calculated for the fossil KNM-ER 1805 . It is unclear whether this large range is to be interpreted as an expression of an actually existing range of variation, for example as a result of gender-specific differences, or whether the fossils belong to two related species.

If one assumes the Nariokotome boy , then when he died, this individual, about 1.50 to 1.60 m tall, would have probably measured 1.85 m when fully grown and would then have weighed almost 70 kg. Arm and leg lengths are the same as those of modern humans. From the construction of the shoulder blades and the shinbones, however, it was concluded that young specimens moved longer on four legs than today's toddlers.

In contrast to some of the original features in the area of ​​the head, the bones of the legs are suitable for persistent upright walking ; there are no indications of frequent stays in trees.

Tool use

Homo ergaster was ascribed tool manufacture and tool use, whereupon the art epithet stands out. However, some of the Oldowan -type finds come from layers from which fossils have also been recovered that were brought to Paranthropus boisei . Other ergaster fossils come from layers from which no tools are known; therefore the use of tools for Homo ergaster is considered probable, but not certain.

classification

Homo ergaster and the species of the genus Homo derived from it

The first description by Groves and Mazák was not based on newly discovered fossils; the naming of the new species Homo ergaster in 1975 was based on a regrouping and reorganization of numerous fossils, some of which were described decades earlier. In the years following the first description, the publication by Groves and Mazák was very rarely cited by other paleoanthropologists and the name Homo ergaster was only very rarely mentioned, as this species name was considered a synonym for Homo erectus . In the 1990s, however, some researchers pointed out that the fossils identified as African Homo erectus differ significantly from the "classic" finds from Asia ( Java man and Peking man ). These scientists therefore regard Homo rudolfensis as a possible ancestor of Homo ergaster ; Homo erectus is said to have emerged from Homo ergaster . From the same epoch and from the same regions of Africa there have been finds of other species of hominini with whom Homo ergaster shared his habitat: Paranthropus boisei , Homo rudolfensis and possibly Homo habilis .

Whether Homo ergaster was rightly granted the status of an independent species or whether the fossils can only be classified as early and regional variants of Homo erectus is still controversial in paleoanthropology - between so-called rags and splinters . Many fossils that are identified by certain researchers today on Homo ergaster were - as mentioned in the section First description - previously classified as Homo erectus and are still attributed to Homo erectus by other researchers . In addition, the holotype specimen is considered to be an unfortunate choice due to the presumably large and, above all, size-dependent variation range of the lower jaws of Homo erectus / Homo ergaster : “When the namesake of H. ergaster described the features of the jawbone KNM-ER 992, they showed no characteristic differences through which other fossils , which they also ascribed to H. ergaster (...) would differ from H. habilis . ”However, a non-characteristic holotype specimen quickly leads to discrepancies when assigning other finds to this species.

In a review article in the journal Nature in 1992 , Bernard Wood classified other finds from Homo ergaster , for example the well-preserved fossil skulls KNM-ER 3733 and 3883, which were identified by their discoverers as Homo erectus ; In the same place he classified the Nariokotome boy as a representative of Homo ergaster . The holotype KNM-ER 992 - conversely - is assigned to Homo erectus by individual paleoanthropologists and to Homo habilis by others . John T. Robinson even wrote in Nature in 1972 that this fossil could not be distinguished from Australopithecus africanus . Some of the other fossils that were placed on Homo ergaster are so incomplete that they have only been classified based on their age, but not on the basis of their morphological properties.

Nutrition and habitat

It is not yet clear what food Homo ergaster consumed; its molars , which are smaller in comparison with the australopithecines, suggest, however, that the food is softer than that of the Australopithecines, or that food has been processed by tools. "Similarities in teeth, jaws and muscle attachment points suggest that his diet was similar to that of Homo habilis ." Accompanying finds suggest that Homo ergaster stayed in a mosaic of habitats, including forests with thick undergrowth, open water areas and - at times flooded - grasslands belonged. From these ecological findings it was in turn concluded that animals living in water - easily accessible in seasonally drying waters - have contributed to the supply of protein-rich food.

A bone find from Koobi-Fora (archive number: KNM-ER 1808) shows changes that can occur with excessive vitamin A consumption. It is most likely that this vitamin A comes from the liver of animals; Whether the animals were hunted or captured as carrion is not known from fossil records. The American evolutionary biologist Marlene Zuk pointed out that Homo ergaster was the first kind of hominini to be able to run for long distances due to his physique. This presumably made it possible for the individuals of this species to quickly get to the remains of the prey of large predators and, as scavengers , to feed themselves with protein-rich food - also thanks to sophisticated stone tools.

At least indirect close contact with predators and scavengers can also be derived from genetic studies on tapeworms of the genus Taenia . The species Taenia saginata and Taenia asiatica , which also occur in humans, are closely related to a tapeworm found in African lions , and Taenia solium is closely related to a tapeworm in hyenas . If it was initially suspected that these tapeworms were only transferred to humans with the advent of cattle breeding around 10,000 years ago, the genetic studies were interpreted to mean that the transfer might have taken place 1.7 million years ago.

See also

Web links

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

Individual evidence

  1. ↑ Ulrich Welsch : The fossil history of humans. Part 1: How the first primates became homo. In: Biology in Our Time. No. 1/2007, pp. 42-50
  2. ↑ Illustration of the fossil KNM-ER 992 on: efossils.org
  3. ^ Richard Leakey : Further Evidence of Lower Pleistocene Hominids from East Rudolf, North Kenya, 1971. In: Nature. Volume 237, 1972, pp. 264-269 , doi: 10.1038 / 237264a0
  4. ^ Colin Groves and Vratislav Mazák: An Approach to the Taxonomy of the Hominidae: Gracile Villafrancian Hominids of Africa. In: Časopis pro mineralogii a geologii. Volume 20, 1975, pp. 225-247. Reprinted in: In: W. Eric Meikle, Sue Taylor Parker: Naming our Ancestors. An Anthology of Hominid Taxonomy. Waveland Press, Prospect Heights (Illinois) 1994, ISBN 0-88133-799-4 , pp. 107-125.
  5. ^ Robert Broom and John T. Robinson : A new type of fossil man. In: Nature . Volume 164, 1949, pp. 322-323, doi: 10.1038 / 164322a0
  6. ^ Gerhard Heberer : About a new archantropine type from the Oldoway gorge. In: Journal of Morphology and Anthropology. Volume 53, 1963, pp. 171-177.
    The name Homo leakeyi was picked up ten years later by Bernard G. Campbell: A new taxonomy of fossil man. In: Yearbook of Physical Anthropology. Volume 17, 1973, pp. 194-201.
  7. ↑ The archive name KNM stands for Kenyan National Museum .
  8. ↑ Ulrich Welsch: Die Fossilgeschichte des Menschen ... , p. 48
  9. ↑ Gary J. Sawyer, Viktor Deak: The Long Way to Man. Life pictures from 7 million years of evolution. Spektrum Akademischer Verlag, Heidelberg 2008, p. 104, ISBN 978-3827419156 .
  10. ^ A b Bernard Wood and Nicholas Lonergan: The hominin fossil record: taxa, grades and clades. In: Journal of Anatomy . Volume 212, No. 4, 2008, p. 361, doi: 10.1111 / j.1469-7580.2008.00871.x , full text (PDF; 292 kB) ( Memento from October 20, 2012 in the Internet Archive )
  11. ↑ Gary J. Sawyer, Viktor Deak: The Long Way to Man, p. 102.
  12. ^ W. Eric Meikle, Sue Taylor Parker: Naming our Ancestors. An Anthology of Hominid Taxonomy. Waveland Press, Prospect Heights (Illinois) 1994, ISBN 0-88133-799-4 , p. 106.
  13. ^ A b Gary J. Sawyer, Viktor Deak: The long way to people, p. 100.
  14. ^ Gary J. Sawyer, Viktor Deak: The Long Way to Man, p. 104.
  15. ↑ Such review articles usually represent the current state of the secured knowledge in a certain subject area; But they can also have the function of helping a certain position on an issue to break through in the research community.
  16. ^ Bernard Wood : Origin and evolution of the genus Homo. In: Nature. Volume 355, 1992, pp. 783-790; see also: Bernard Wood: Early hominid species and speciation. In: Journal of Human Evolution. Vol. 22, No. 4-5, 1992, pp. 351-365, doi: 10.1016 / 0047-2484 (92) 90065-H
  17. ^ John T. Robinson: The Bearing of East Rudolf Fossils on Early Hominid Systematics. In: Nature. Volume 240, 1972, pp. 239-240 , doi: 10.1038 / 240239a0
  18. ^ Ian Tattersall : Masters of the Planet. The Search for Our Human Origins. Palgrave Macmillan, 2012, p. 108, ISBN 978-0-230-10875-2 .
  19. ↑ Marlene Zuk : Paleofantasy. What evolution really tells us about sex, diet, and how we live. WW Norton & Company, New York and London 2014, pp. 27-28, ISBN 978-0-393-08137-4
  20. ↑ Tapeworms tell tales of deeper human past. In: Science News of July 1, 2009, doi: 10.2307 / 3981638
  21. ^ EP Hoberg, NL Alkire, AD Queiroz and A. Jones: Out of Africa: origins of the Taenia tapeworms in humans. In: Proceedings of the Royal Society B. Online publication of April 22, 2001, doi: 10.1098 / rspb.2000.1579