Homo ergaster
The KNM -ER 3733
Homo ergaster is an extinct hominid species of the genus Homo from the Early Pleistocene. This Chrono species are exclusively associated fossils from Africa, which are 1.9 to 1.4 Mio. years old and in Koobi Fora ( East Africa ) and were found in Swartkrans ( South Africa). However, some of the species attributed findings also come from younger strata and may be only 1 million years old.
Naming
The name of the genus Homo is derived from the Latin homo [ hɔmo ː ] = dt man. 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, which is attributed to this species. However, the oldest stone tools are much older than the fossils of Homo ergaster 2.4 million years ago and were probably made by Homo rudolfensis and Homo habilis.
Tool use
Homo ergaster was attributed to tool manufacture and tool use, to which also lifts the Style epithet. However, the findings from the Oldowan type originate partly from layers of which one has recovered fossils that have been found to Paranthropus boisei. Other ergaster fossils come from layers of which there are no known tools; Therefore, the use of tools for Homo ergaster may still be considered as probable, but not certain.
First description
The South African finds were discovered in 1949 by John T. Robinson and first Telanthropus capensis been named.
The first description of the species Homo ergaster was carried out by Colin Groves and Vratislav Mazák in a Czech journal and was based on a two-part holotype: the well-preserved lower jaw fragment KNM -ER 992 an adult, which discovered in 1971 by Richard Leakey in Koobi Fora (Kenya ) and whose age was dated at 1.5 million years; Leakey had the find published in 1972 and assigned to the genus Homo, but not assigned it to a certain type.
As a possible ancestor of Homo ergaster is considered Homo rudolfensis; Homo erectus is supposed to be evolved from Homo ergaster. From the same period and for the same regions of Africa, there are findings of other kinds of Hominini with which Homo ergaster therefore shared its habitat: Paranthropus boisei, Homo rudolfensis and possibly Homo habilis.
The finds from Koobi Fora are kept in the National Museum of Kenya in Nairobi, the finds from Swartkrans in the Transvaal Museum in Pretoria.
Classification
Whether Homo ergaster was awarded the status of an independent way of law or whether the fossils are classified merely as an early and regional variants of Homo erectus, is in paleoanthropology - between so-called Lumpern and splinters - controversial. Many fossils that are now provided by certain researchers to Homo ergaster were previously classified as Homo erectus and Homo erectus are still attributed by other researchers. In addition, the holotype specimen is considered due to the presumably large and especially size-dependent variation of the lower jaw of Homo erectus / Homo ergaster chosen as unfortunate: "As the namesake of H. ergaster the features of the jawbone KNM -ER described 992, they showed no characteristic differences would, through which other, they also H. ergaster fossils attributed to (...) of H. habilis differ. " However, a non- characteristic holotype specimen results in the assignment of other finds of this kind quickly to inconsistencies.
In a review article in the journal Nature Bernard Wood ordered in 1992 still further discoveries at a Homo ergaster, for example, the well-preserved fossil skull KNM -ER, which had been provided by their discoverers to Homo erectus 3733 and 3883; at the same place he considered also the Turkana Boy as a representative of Homo ergaster. The holotype KNM -ER 992 is - vice versa - to Homo erectus provided by individual paleoanthropologists from others Homo habilis. John T. Robinson wrote in 1972 in Nature even, this fossil is no different from Australopithecus africanus. Some other fossils that have been found to Homo ergaster, are so incomplete that they were filed only because of their age so, but not because of their morphological characteristics.
Features
Since Homo ergaster numerous fossils are attributed to other researchers apply as early Homo erectus, the characteristics of both species hardly differ. As typical for the head applies, inter alia, a continuous and moderately broad bony above the eyes are far apart, consisting of - in the upper part of the face - emerge almost perpendicular bone. The upper jaw protrudes yet far out to the front, so that the jaws form a kind of snout; the distance between the mouth and nose opening is quite large. " Some of the morphological characteristics features of H. ergaster compared with H. erectus: generally somewhat grazilerer skeleton, longer and narrower molars, complex roots of the premolars, thinner skull bones, no bones Kiel on the skull, weaker Überaugenwulst, higher cranial vault, lower postorbital Schädeleinschnürung, narrower skull base. "
The brain volume of Homo ergaster was 750-900 cm3. However, some of this kind associated findings had a significantly smaller brain, for KNM -ER 1805 were, for example, only 582 cm3 calculated. Whether these large margin can be interpreted as an expression of actually existing range of variation, for example, due to gender differences or whether the fossils might belong to two related species, is unclear.
Judging from the Turkana Boy, then this at death about 1.50 to 1.60 m wide individual would probably measured at full-grown 1.85m and would then have been almost 70 kg. Arm and leg length are similar to those of modern man. From the construction of the shoulder blades and the shin bone was, however, concluded that young specimens continued moving longer than the infants of modern man on four legs.
Unlike some original features in the head bones of the legs for upright perennial running are likely evidence of a frequent stay on trees missing.
Diet and habitat
What food Homo ergaster has taken, has not comprehensible; its smaller in comparison with the australopithecine molars suggest, however to a softer food than this or on a processed food with tools. " Similarities in teeth, jaw and muscle attachment points to the supposition that his diet resembled Homo habilis. " From accompanying findings it can be concluded that Homo ergaster was staying in a mosaic of habitats, to the forests with dense undergrowth, open water and - temporarily flooded - grasslands belonged.
A bone find from Koobi Fora - (archive number: KNM -ER 1808) has changes as they may occur with excessive vitamin A consumption. Most likely that this vitamin -A derived from the livers of animals; whether the animals were hunted or captured as carrion, fossil is not occupied.