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Homo ergaster ("working man") is an extinct hominid species (or subspecies, according to some authorities) which arose in Africa some 1.9 million years ago with the advent of the lower Pleistocene and the cooling of the global climate.
H. ergaster is sometimes categorized as a subspecies of Homo erectus. It is currently in contention whether H. ergaster or the later, Asian H. erectus was the direct ancestor of modern humans. H. ergaster may be distinguished from H. erectus by its thinner skull bones and lack of an obvious sulcus. Derived features include reduced sexual dimorphism, a smaller more orthognathic face, a smaller dental arcade, and a larger (800cc) brain. It is estimated that H. ergaster stood at 1.9m (6ft) tall. Remains have been found in Tanzania, Ethiopia, Kenya, South Africa, and out of Africa in Georgia.
The type specimen of H. ergaster is KNM-ER 992[1]; the species was named by Groves and Mazak in 1975.
The species name originates from the Greek ergaster meaning "Workman". This name was chosen due to the discovery of various tools such as hand-axes and cleavers near the skeletal remains of H. ergaster. This is one of the reasons that it is sometimes set apart distinctly from other human ancestors. Its use of advanced (rather than simple) tools was unique to this species; H. ergaster tool use belongs to the Acheulean industry. H. ergaster first began using these tools 1.6 million years ago. Charred animal bones in fossil deposits and traces of camps suggest that the species made creative use of fire.
Physiology
The Turkana Boy
In 1984 near the banks of Nariokotome in Lake Turkana, a team lead by Richard Leakey, Alan Walker and his Kenyan assistant Kamoya Kimue, trained a few local Kenyans on how to spot Hominid fossils and were nicknamed “the Hominid gang”. Kamoya Kimue had the sharpest eye for fossil hunting; he could spot a tooth fragment from 100 yards away. Only tiny remains of skull were scattered around a few locations. On August 22, 1984 traveling on the hot dry terrains of this once rich organic area on their Jeep one day, Kamoya spotted of pieces of skull sticking out from the dusty ground. As Kamoya, Richard Leakey and Alan began to dig on the sediments, more and more bones were found including, a skull with teeth and jaw, femurs a spin, ribs and tibia. In about three weeks of hard work digging with the Hominid gang, the skeleton began to take shape. The almost complete 90% skeleton of a young boy was uncovered from the sediments in great condition and given its name KNM WT-15000 nicknamed “Nariokotome Boy” or “Turkana Boy”.
For further information visit Turkana boy for a more indepth look at the anatomy.
Unlike Lucy’s (Australopithecus afarensis) ape like body, there is a large gap between the small ape-men and the tall hairless Human stature. The major gap in sizes between Homo habilis and Homo ergaster/erectus is quit puzzling for anthropologists, since Homo ergaster appeared relatively short after Homo habilis 2 to 1.9 million years ago. Homo habilis may as well be a separate species of Homo, and so we must look at the missing gap to find the missing link of which hominid came right before Homo ergaster.
There is no way of knowing if whether these early hominids scavenged or hunted more, but meat became a crucial role for the development of the ever increasing brain capacity. Meat contains large amounts of porteins and nutrients all the energy required for the more demanding body, especially for the brain. Homo ergaster’s brain sizes were about 700 to 900cc a bit larger than Homo habilis and Homo rudolfensis who had 750cc. It was perhaps the nutrition of meat that made our ancestors grow larger brains. Homo ergaster/erectus became the first hominids known to use the Archeaulan stone tool industry found alongside remains form the fossils uncovered.
Clearly, these were not the ape-men creatures as Eugene Dubois was the first to discover Homo erectus remains in South Eastern Asia (Island of Java, Indonesia) . Unlike the first hairy species of Homo such as habilis and rudolfensis living 2.5 to 2 million years ago, the ergaster were very likely dark and smooth skinned. This adaptation was a necessity because living under the ever-increasing dry and hot African terrain; ergaster developed one difference in comparison to their predecessors. The likely dark skin pigmentation acted as a shield in order to protect the skin from the Suns ultraviolet rays. This adaptation is seen in dark skinned Africans of today who have well adapted bodies for the hot conditions. Homo ergaster must have sweated; in combination with the lost hair and taller height, sweating kept the body cool from the Suns intense heat range.
As Africa became dryer 2 million years ago, more savannah would cover the continent making Homo ergaster capable of traveling longer distances in order to find water sources from lakes and vegetation. One crucial difference between these himinids and the previous Homo habilis ape-men was the size of the dentation. Homo ergaster seemed to have the right fit bodies made for hunting meat instead of having to scavenge.
Rise of Homo erectus
Evidence suggests that Homo ergaster began to make long migrations and would ultimately leave the African home continent in a matter of less than 100,000(?) years. Over the millennia the species eventually reached as far as the Europe (evidence suggests the new genus Homo georgicus) Middle East, Eastern and Southern Asia became inhabited 1.9 million years ago) Asia would become a major advantage for these early hominids as being rich in resources and would help them become the longest living known hominid species Homo erectus.
Yhe variation in comparison to the Javanese fossils and African specimens from Eastern and Southern Africa differ in post-cranial shape. Specimen Sangiran 17 for example is more robust and larger brow ridges protrude over the eye orbits in comparison with KNM 1808-3733 .
Reference
- Tattersall, Ian and Schwartz, Jeffrey. "Extinct Humans". Westview Press, Boulder, Colorado and Cumnor Hill, Oxford, 2000. ISBN 0-8133-3482-9 (hc)
Footnote
- ^ KNM-ER 992 is short for: Kenya National Museum (where it is housed); East Rudolf (where it was found); and 992 (the museum acquisition number)
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