Homo ergaster

Homo ergaster Fossil range: Pleistocene, 1.8–1.3 Ma PreЄ Є O S D C P T J K Pg N ↓
Skull KNM-ER 3733 discovered by Bernard Ngeneo in 1975 (Kenya)
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Primates Family: Hominidae Genus: Homo Species: H. ergaster
Binomial name
†Homo ergaster Groves and Mazák, 1975

Homo ergaster is an extinct species or subspecies of hominin that lived in eastern and southern Africa from about 1.8 million years ago (mya) to about 1.3 mya. It is variously considered to be (1)another name for Homo erectus

[ a separate African species distinct from the Asian Homo erectusm and perhaps ancestral to or sharing a common ancestor with H. erectus; (2)

a subspecies of H. erectus, H. erectus ergaster; (3) another name for H. erectus; and, most currently popular, (4) the African variety of H. erectus, with "Homo erectus sensu stricto" for the Asian H. erectus, and "Homo erectus sensu lato" for the larger species comprising both the early African populations and the Asian populations

African species distinct from the Asian erectus,

Asian species distinct from African ergaster It is one of the earliest members of the genus Homo ancestral to, or sharing a common ancestor with, Homo erectus

. ergaster and H. erectus are still usually defined as distinct African and Asian populations of larger species H. erectus.

lived in eastern and southern Africa during the early Pleistocene, between 1.8 million and 1.3 million years ago

Some call H. ergaster the direct African ancestor at H. erectus, proposing that H. ergaster emigrated out of Africa and into Asia, branching into a distinct species.[6] Most dispense with the species-name ergaster, making no distinction between such fossils as the Turkana Boy and Peking Man. Though "Homo ergaster" has gained some acceptance as a valid taxon, H. ergaster and H. erectus are still usually defined as distinct African and Asian populations of larger species H. erectus. (For the remainder of this article, the name "Homo ergaster" will be used to describe a distinct species for the convenience of continuity in reading.)

There is still disagreement on the subject of the classification, ancestry, and progeny of H. ergaster, but it is now widely accepted to be the direct ancestor of later hominids such as Homo heidelbergensis, Homo sapiens, and Homo neanderthalensis and Asian Homo erectus

Homo ergaster skull reconstruction of the Turkana Boy/Nariokotome Boy from Lake Turkana, Kenya. Museum of Man, San Diego.

Homo habilis is generally accepted as the putative ancestor of the genus Homo, and often of H. ergaster most directly. This taxon's status as a legitimate species within "Homo", however, is particularly contentious. H. habilis and H. ergaster coexisted for 200,000-300,000 years, possibly indicating that these species diverged from a common ancestor. It is unclear what genetic influence H. ergaster had on later hominids. Recent genetic analysis has generally supported the Out-of-Africa hypothesis, and this may designate H. ergaster the role of ancestor to all later hominids.

Origin and extinction

H. ergaster is believed to have diverged from the lineage of H. habilis between 1.9 and 1.8 million years ago; the lineage that emigrated from Africa and fathered H. erectus diverged from the lineage of H. ergaster almost immediately after this. These early descendants of H. habilis may have been discovered in Dmanisi, Georgia. H. ergaster remained stable for ca. 500,000 years in Africa before disappearing from the fossil record around 1.4 million years ago. No identifiable cause has been attributed to this disappearance; the later evolution of the similar H. heidelbergensis in Africa may indicate that this is simply a hole in the record, or that some intermediate species has not yet been discovered.

or it is seen as a subspecies of H. erectus, Homo erectus ergaster (Mayr 2001). Although H. erectus was originally believed to have disappeared roughly 400,000 years ago, the dating of deposits thought to contain H. erectus fossils in Java were placed at only 50,000 years ago, meaning that at least one population would have been a contemporary of modern humans (Smithsonian 2007a).

• There is still disagreement on the subject of the classification, ancestry, and progeny of H. erectus, with two major alternative classifications: erectus may be another name for Homo ergaster, and therefore the direct ancestor of later hominids such as Homo heidelbergensis, Homo neanderthalensis, and Homo sapiens; or it may be an Asian species distinct from African ergaster.

• Some palaeoanthropologists consider H. ergaster to be simply the African variety of H. erectus. This leads to the use of the term "Homo erectus sensu stricto" for the Asian H. erectus, and "Homo erectus sensu lato" for the larger species comprising both the early African populations (H. ergaster) and the Asian populations. (see numerous references)

It is one of the earliest members of the genus Homo, possibly ancestral to, or sharing a common ancestor with, Homo erectus. Some paleoanthropologists consider H. ergaster to be simply the African variety of H. erectus; this leads to the use of the term "Homo erectus sensu stricto" for the Asian H. erectus, and "Homo erectus sensu lato" for the larger species comprising both the early African populations (H. ergaster) and the Asian populations.

The binomial name was published in 1975 by Groves and Mazák. The second part, "ergaster", is derived from the Ancient Greek ἐργαστήρ "workman", in reference to the comparatively advanced lithic technology developed by the species, introducing the Acheulean industry.

Notes:

• Homo erectus ("upright man") is an extinct species of the genus Homo. It lived from about 1.8 million years ago (mya) to 50-70,000 years ago. However, often the early phase, from 1.8 to 1.25 (or 1.6) mya, is considered to be a separate species, Homo ergaster, or it is seen as a subspecies of H. erectus, Homo erectus ergaster (Mayr 2001). Although H. erectus was originally believed to have disappeared roughly 400,000 years ago, the dating of deposits thought to contain H. erectus fossils in Java were placed at only 50,000 years ago, meaning that at least one population would have been a contemporary of modern humans (Smithsonian 2007a).

There is still disagreement on the subject of the classification, ancestry, and progeny of H. erectus, with two major alternative classifications: erectus may be another name for Homo ergaster, and therefore the direct ancestor of later hominids such as Homo heidelbergensis, Homo neanderthalensis, and Homo sapiens; or it may be an Asian species distinct from African ergaster.

Some palaeoanthropologists consider H. ergaster to be simply the African variety of H. erectus. This leads to the use of the term "Homo erectus sensu stricto" for the Asian H. erectus, and "Homo erectus sensu lato" for the larger species comprising both the early African populations (H. ergaster) and the Asian populations.

• Fossil findings of early hominids is often fragmentary and inferences speculative, and although fossils of Homo erectus are much more common and complete than those of Homo habilis, researchers are not even sure into how many species the fossils can be placed. Nonetheless, it is clear that Homo erectus was a major stage in the history of human evolution. Just as in the stage-by-stage development of individuals (egg, baby, child, adolescent, adult) and the history of life on Earth (Precambrian, Cambrian, Ordovician, etc.), Homo erectus served as a foundation for subsequent stages, and it is considered to have given rise to Neandertals and Homo sapiens (Mayr 2001). H. erectus is thought to have been the first human ancestor to walk truly upright.

• Homo erectus was apparently very successful, considering that fossils of the species have been found in Africa, Asia (Indonesia and China), and Georgia (Caucasus region of Europe)(Mayr 2001). It is considered to be the first hominid to spread out of Africa. The differences between the early populations of H. erectus in Africa and the later populations found in Asia, Europe, and Africa are substantial enough for the separation by many researchers into the early African H. ergaster and the mainly Asian populations H. erectus (Smithsonian 2007b).

• The first fossils of Homo erectus were discovered by Dutch physician Eugene Dubois in

1891 on the Indonesian island of Java. He originally gave the material the name Pithecanthropus erectus based on its morphology that he considered to be intermediate between that of humans and apes. A famous example of Homo erectus is Peking Man, unearthed in China.

• Mayr (2001) notes that H. erectus existed without major change for at least one million years.

Overview

The earliest delineated member of the genus Homo is H. habilis, which lived from 2.33 to 1.44 million years ago, although some authorities do not consider it should be included in Homo, considering it more worthy, for example, to be retained in Australopithecus (Wood and Richmond 2000). Homo erectus is considered to have arrived around 1.8 million years ago, with fossils supporting its existence to 143,000 years ago. Homo ergaster is another early Homo species that has been delineated, and traced to about 1.8 to 1.3 million years ago. H. ergaster is possibly ancestral to or shares a common ancestor with H. erectus; it is widely considered to be the direct ancestor of later hominids such as Homo heidelbergensis, Homo sapiens, Neanderthals, Denisovans, and even Asian Homo erectus. Homo erectus and H. ergaster were the first of the hominina known to leave Africa. For example, H. erectus is known to have spread as far as Georgia, India, Sri Lanka, China and Java.

There is also support for the idea that that the numerous distinct species being recognized in the fossil record, such as H. erectus and H. habilis, are actually just morphological variation among members of a single evolving lineage among early members of the Homo genus, and that perhaps even only one species with a lot of variability emerged from Africa (Wilford 2013; Watson 2013; Lordkipanidze et al. 2013).

Modern human beings, Neanderthals, and Denisovans are believed to have shared a common ancestor about 400,000 years ago (Marshall 2013). One theory is that these three groups all descended from Homo heidelbergenesis, which lived between 600,000 to 250,000 years ago (Marshall 2013) (other species suggested as ancestral are H. rhodesiensis and H. antecessor). One branch of H. heidelbergenesis are theorized to have left Africa about 300,000 to 400,000 years ago and split shortly thereafter to become Neanderthals, which settled in West Asia and Europe, and Denisovans, which settled farther to the east (NG 2013).

Neanderthals are considered to have lived from at least 230,000 years ago. Neanderthals disappeared from the fossil record about 30,000 years ago. Based on the DNA sequences for the nuclear genome of Neanderthals and modern humans, the population split between Neanderthals and modern humans took place 270,000 to 440,000 years ago (Reich et al. 2010).

Archaic Homo sapiens, the forerunner of anatomically modern humans, appeared between 400,000 and 250,000 years ago (O'Neil 2013). Anatomically modern humans are believed to have evolved from archaic Homo sapiens in the Middle Paleolithic, about 200,000 to 130,000 years ago (SA 2005; NG 2013), then migrated out of Africa some 50,000 to 100,000 years ago (Recent African Ancestory Theory) and replaced local populations of H. erectus, H. floresiensis, H. heidelbergenesis, and the Denisovan and Neanderthal populations.

The transition to behavioral modernity for Homo sapiens with the development of symbolic culture, language, and specialized lithic technology happened around 50,000 years ago according to many anthropologists (Mellars 2006), although some suggest a gradual change in behavior over a longer time span (Mcbrearty and Brooks 2000). Until about 50,000 to 40,000 years ago, the use of stone tools seems to have progressed stepwise: Each phase (habilis, ergaster, and neanderthal) started at a higher level than the previous one, but once that phase had started, further development was slow. After 50,000 years ago, in what Jared Diamond, author of The Third Chimpanzee, and other anthropologists characterize as a "Great Leap Forward," human culture apparently started to change at much greater speed: "Modern" humans started to bury their dead carefully, made clothing out of hides, developed sophisticated hunting techniques (such as pitfall traps, or driving animals to fall off cliffs), and made cave paintings. This speed-up of cultural change seems connected with the arrival of modern humans, Homo sapiens sapiens. Additionally, human culture began to become more technologically advanced, in that different populations of humans begin to create novelty in existing technologies. Artifacts such as fish hooks, buttons, and bone needles begin to show signs of variation among different population of humans, something what had not been seen in human cultures prior to 50,000 BP.

The Denisovans are not well delineated anatomically, given the very limited fossils found. The first fossils were discovered in 2008, when a small bone fragment of a finger was found. Two teeth were subsequently found. The lack of fossils has made anatomical representations of the group difficult. However, the DNA was preserved and was able to be extracted and has yielded excellent genetic analysis. As noted in a 2013 article in the Dartmouth Undergraduate Journal of Science, "Although Denisovans are thus far only represented by one finger bone and two teeth, they are currently the most well-known archaic human genetically – including Neanderthals of which there are hundreds of fossil records" (DUJS 2013). As a result, it was found that the Denisovans appear to be a unique group that shares a common origin with Neanderthals. DNA analysis further revealed that the Denisovans lived among and interbred with the ancestors of some present-day modern humans, with up to 6% of the DNA of Melanesians and Australian Aborigines deriving from Denisovans (Zimmer 2010; Callaway 2011).

In 2013, mitochondrial DNA was extracted from a 300,000- to 400,000-year-old sliver of hominin femur bone from Spain, which had been seen as either Neanderthal or Homo heidelbergensis. An almost complete mitochondrial genome was retrieved, the oldest human DNA sequenced. The DNA surprising yielded ancestral Denisonian DNA (Callaway 2013; Gibbons 2013).

Discovery and representative fossils

The South African palaeontologist John T. Robinson first discovered a mandible of a new hominid in southern Africa in 1949; he named the species Telanthropus capensis, though it is now recognised as a member of Homo ergaster. The name was first applied by Colin Groves and Vratislav Mazák to KNM-ER 992, a mandible discovered near Lake Rudolf (now Lake Turkana), Kenya in 1975, which became the type-specimen of the species. The most complete skeleton of H. ergaster (and one of the most complete extinct hominids to date), KNM-WT 15000, was discovered at Lake Turkana, Kenya, in 1984 by paleoanthropologists Kamoya Kimeu and Alan Walker. They nicknamed the 1.6-million-year-old specimen "Turkana Boy".

Classification and special distinction

Many paleoanthropologists still debate the definition of H. ergaster with H. erectus as separate species. Some call H. ergaster the direct African ancestor at H. erectus, proposing that H. ergaster emigrated out of Africa and into Asia, branching into a distinct species. Most dispense with the species-name ergaster, making no distinction between such fossils as the Turkana Boy and Peking Man. Though "Homo ergaster" has gained some acceptance as a valid taxon, H. ergaster and H. erectus are still usually defined as distinct African and Asian populations of larger species H. erectus. (For the remainder of this article, the name "Homo ergaster" will be used to describe a distinct species for the convenience of continuity in reading.)

• separate species, Homo ergaster, or it is seen as a subspecies of H. erectus, Homo erectus ergaster (Mayr 2001).

H. ergaster may be distinguished from H. erectus by its thinner skull-bones and lack of an obvious supraorbital foramen. It may be distinguished from Homo heidelbergensis by its thinner bones, more protrusive face, and lower forehead. Derived features separating it from earlier species include reduced sexual dimorphism, a smaller, more orthognathous(less protrusive) face, a smaller dental arcade, and a larger cranial capacity (700–900 cm³ in earlier ergaster-specimens, and 900-1100 in later specimens). It is estimated that male H. ergaster stood 1.89 meters (6 ft 2 in) tall^{[citation needed]}. Remains have been found in Tanzania, Ethiopia, Kenya, and South Africa.

Divergence

Homo ergaster skull reconstruction of the Turkana Boy/Nariokotome Boy from Lake Turkana, Kenya. Museum of Man, San Diego.

Homo habilis is generally accepted as the putative ancestor of the genus Homo, and often of H. ergaster most directly. This taxon's status as a legitimate species within "Homo", however, is particularly contentious. H. habilis and H. ergaster coexisted for 200,000-300,000 years, possibly indicating that these species diverged from a common ancestor. It is unclear what genetic influence H. ergaster had on later hominids. Recent genetic analysis has generally supported the Out-of-Africa hypothesis, and this may designate H. ergaster the role of ancestor to all later hominids.

Origin and extinction

H. ergaster is believed to have diverged from the lineage of H. habilis between 1.9 and 1.8 million years ago; the lineage that emigrated from Africa and fathered H. erectus diverged from the lineage of H. ergaster almost immediately after this. These early descendants of H. habilis may have been discovered in Dmanisi, Georgia. H. ergaster remained stable for ca. 500,000 years in Africa before disappearing from the fossil record around 1.4 million years ago. No identifiable cause has been attributed to this disappearance; the later evolution of the similar H. heidelbergensis in Africa may indicate that this is simply a hole in the record, or that some intermediate species has not yet been discovered.

Use of tools

Homo ergaster used more diverse and sophisticated stone tools than its predecessor, Homo habilis. H. ergaster refined the inherited Oldowan developing the first Acheulean bifacial axes: while the use of Acheulean tools began ca. 1.6 million years ago, the line of H. erectus diverged some 200,000 years before the general innovation of Acheulean technology. Thus the Asian migratory descendants of H. ergaster made no use of any Acheulean technology.^{[citation needed]}

Sociality

Sexual dimorphism in H. ergaster is greatly reduced from its australopithecine ancestors (around 20%), but still greater than dimorphism in modern humans. This diminished dimorphism is speculated to be a sign of reduced competition for mates between males, which may also correspond to the more modern social practices of ergaster ^{[citation needed]}. Not only was H. ergaster like modern humans in body, but also more in organisation and sociality than any earlier species. It is conceivable that H. ergaster was the first hominin to harness fire: whether as the containment of natural fire, or as the lighting of artificial fire, is still a matter of contention. It is now assumed, however, that erectus did have control of fire, as well as each other hominin sharing a common ancestor with ergaster.

The social organisation of H. ergaster probably resembled that of modern hunter-gatherer societies. Unlike australopithecines, ergaster males presumably did not compete at all for females, which had themselves increased in size greatly in proportion to males. This reduced competition and dimorphism also coincided with an increase in brain size and efficiency of stone tools.

Linguistic use

According to the BBC series Walking With Cavemen, Homo ergaster was probably the first hominid to use "what we would recognise as a human voice," though its symbolic cognition was probably somewhat limited compared to modern humans. It was thought for a long time that H. ergaster was restricted in the physical ability to regulate breathing and produce complex sounds. This was based on Turkana Boy's cervical vertebrae, which were far narrower than in later humans. Discoveries of cervical vertebrae in Dmanisi, Georgia some 300,000 years older than those of Turkana Boy are well within the normal human range.

It has been established, furthermore, that the Turkana Boy probably suffered from a disease of the spinal column that resulted in narrower cervical vertebrae than in modern humans (as well as the older Dmanisi finds). While the Dmanisi finds have not been established definitively as H. ergaster; they are older than Turkana Boy (the only definite ergaster vertebrae on record), and thereby suggest kinship to ergaster. Turkana Boy, therefore, may be an anomaly.

There is no archaeological evidence that Homo ergaster made use of symbolic thought (such as figurative art), but the well-evolved brain and physical capabilities (along with reconfiguration of ergaster's breathing-apparatus) suggest some form of linguistic or symbolic communication.

See also

• Homo erectus
• Homo georgicus
• Homo habilis
• Telanthropus capensis

General:

• List of fossil sites
• List of human evolution fossils

References

ISBN links support NWE through referral fees

• Deacon, Terrence W. (1998). The Symbolic Species: The Co-evolution of Language and the Brain. W.W. Norton & Company. ISBN 0-393-03838-6. 
• Leakey, Richard (1992-09-01). Origins Reconsidered. ISBN 0-385-41264-9. 
• Ruhlen, Merritt (1994). The origin of language: tracing the evolution of the mother tongue. New York: Wiley. ISBN 0-471-58426-6. 
• Shreeve, James (1995). The Neandertal Enigma: Solving the Mystery of Modern Human Origins. Harper Perennial. ISBN 0-670-86638-5. 
• Tattersall, Ian and Jeffrey Schwartz (2000). Extinct Humans. Boulder and Cumnor Hill: Westview Press. ISBN 0-8133-3482-9. 
• Wood, Bernard (2001). The Meaning of Homo. Ludus Vitalis 9.

• Mayr, E. 2001. What evolution is. New York: Basic Books. ISBN 0465044255.
• Novaresio, P. 1996. The Explorers. Stewart, Tabori & Chang. ISBN 155670495X.
• Sawyer, G. J., and B. Maley. 2005. Neanderthal Reconstructed. Anat. Rec. (New Anat.) 283B: 23-31.
• Smithsonian National Museum of Natural History. 2007a. Homo erectus. Smithsonian Institution. Retrieved March 4, 2007.
• Smithsonian National Museum of Natural History. 2007b. Homo ergaster. Smithsonian Institution. Retrieved March 4, 2007.

External links

• Archaeology Info
• Smithsonian

Part of the series on Human evolution

Hominini

Sahelanthropus tchadensis • Orrorin tugenensis • Ardipithecus

Australopithecines

Australopithecus: A. anamensis • A. afarensis • A. bahrelghazali • A. africanus • A. garhi

Paranthropus: P. aethiopicus • P. boisei • P. robustus

Humans and Proto-humans

Kenyanthropus platyops

Homo: H. habilis • H. rudolfensis • H. georgicus • H. ergaster • H. erectus (H. e. lantianensis • H. e. palaeojavanicus • H. e. pekinensis • H. e. soloensis) • H. cepranensis • H. antecessor • H. heidelbergensis • H. neanderthalensis • H. rhodesiensis • H. floresiensis • Homo sapiens (H. s. idaltu • H. s. sapiens)

Topics: Timeline of human evolution • List of human fossils • Human evolutionary genetics

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