Homo ergaster

Species Information

Geographic Range: Africa and Eurasia, including sites such as Lake Turkana, Koobi Fora, Dmanisi, Nariokotome, and others (Tattersall) (A. de Sousa, B. Wood).
Paleoanthropologists: Groves and Mazak were the first to classify, but not the first to discover fossils of, Homo ergaster (Tattersall).
"Homo ergaster" - Work Man (Tattersall)
Paleoanthropologists Groves and Mazak were the first to introduce Homo ergaster as a species distinct from Homo erectus, after the discovery of KNM-ER 992 (Tattersall).

Homo ergaster shares many of the same traits with Homo erectus, but what makes Homo ergaster unique are in the cranium and mandible (A. de Sousa, B. Wood).
H. ergaster has a unique set of mandibular premolars. These molars are smaller than those of australopiths, and signals that H. ergaster had a different diet from previous hominids, or that they were preparing the food before eating. This is evidence of stone tools, cooking, or both (A. de Sousa, B. Wood).
H. ergaster is the first hominin to have modern human-sized teeth while also having a postcranial skeleton appearing to be a habitual biped. They also lacked climbing morphology (A. de Sousa, B. Wood).
Out of three Africa cranial specimens, H. ergaster had an average brain size of 762cc. This contrasts three Dmanisi cranial specimens, which display an average size of 675 cc (A. de Sousa, B. Wood). This is different from the KNM-ER 3733, which has a brain capacity of 848cc, which demonstrates the variation between H. ergaster groups (Tattersall).
In studying the vertebral column of the H. ergaster specimen KNM-WT 15000, it is noticeable that it has similar thoracic vertebral canals to earlier hominins and primates, signaling that H. ergaster likely was not able to produce speech. They do, however, seem to have been able to control their breathing to a larger extent (Tattersall).

Homo habilis is most likely the closest ancestor of Homo ergaster based on locational evidence, morphological evidence, and chronological evidence.

Homo habilis is likely a transitionary species going towards Homo ergaster based on morphological evidence. H. habilis has a smaller brain size and smaller body as compared to H. ergaster. H. habilis is also overall more ape-like than H. ergaster (Anton).
H. habilis and H. ergaster fossils are regularly found in similar locations. For example, the fossil specimen KNM-ER 1813, a 1.9 million year old H. habilis specimen, was found in the same location as KNM-ER 3733, a 1.6 million year old H. ergaster specimen (Anton). This displays both a locational and chronological line connecting the two species.

Type Specimen
Well-preserved adult mandible (A. de Sousa, B. Wood).
Discovered in Koobi Fora, Kenya, 1971 (A. de Sousa, B. Wood).
Specimen that helped create the distinction between H. erectus and H. ergaster (A. de Sousa, B. Wood).
Small molars and premolars (Rightmire).
Parabolic dental arcade (Rightmire).
More developed chin, but not close to modern human (Rightmire).

Adult mandible with worn teeth (A. de Sousa, B. Wood).
Discovered in Koobi Fora, Kenya, 1970 (A. de Sousa, B. Wood).
First discovery of Homo ergaster (A. de Sousa, B. Wood).
Added to the distinction between H. erectus and H. ergaster (A. de Sousa, B. Wood).

Homo ergaster shares almost all of its traits with Homo Erectus. One main distinction occurs in the geographic range of each species. Homo Ergaster came into being when paleoanthropologists believed that the African Homo Erectus was different enough from the Asian Homo Erectus that it warranted a new species (Tatterhall). The African Homo Erectus was therefore designated Homo Ergaster (Tattersall).
There are two main physiological differences between Homo ergaster and Homo erectus:
- 1) Homo ergaster is older, as evidenced by details in the mandibular premolars. This evidence comes from the type specimen, KNM-ER 922 (A. de Sousa, B. Wood).
- 2) Homo ergaster has a less advanced form of bipedal movement, as evidenced by the shape of the base of the skull (A. de Sousa, B. Wood).
There is a large debate as to whether H. ergaster should just be classified as an African H. Erectus due to there being so many similarities between the species. The consensus is slowly going towards merging the two species once again (Tattersall).

Antón, S.C. (2003), Natural history of Homo erectus†. Am. J. Phys. Anthropol., 122: 126-170. https://doi.org/10.1002/ajpa.10399
Antón, S. C. (2012). Early Homo: Who, When, and Where. Current Anthropology, 53(S6), S278–S298. https://doi.org/10.1086/667695
De Sousa, A., and B. Wood. “The Hominin Fossil Record and the Emergence of the Modern Human Central Nervous System.” Evolution of Nervous Systems, 2007, pp. 291–336, doi:10.1016/b0-12-370878-8/00018-5.
Rightmire, G. P. (1990). The Evolution of Homo Erectus. Cambridge University Press.
Tattersall, Ian. “Homo Ergaster and Its Contemporaries.” Handbook of Paleoanthropology, 24 Dec. 2014, pp. 2167–2187, doi:10.1007/978-3-642-39979-4_53.

KNM-Er 3733 | The Smithsonian Institution’s Human Origins Program, humanorigins.si.edu/evidence/human-fossils/fossils/knm-er-3733. Accessed 01 Apr. 2025.
“KNM-Er 730.” - Антропогенез.РУ, 15 July 2023, antropogenez.ru/fossil/105/. Accessed 01 Apr. 2025.
“KNM-ER 992.” Wikipedia, Wikimedia Foundation, 9 Aug. 2024, en.wikipedia.org/wiki/KNM-ER_992. Accessed 01 Apr. 2025.
“KNM-WT 15000.” The Smithsonian Institution’s Human Origins Program, 27 Sept. 2024, humanorigins.si.edu/evidence/human-fossils/fossils/knm-wt-15000. Accessed 25 Apr. 2025.
Tattersall, Ian. “History and Reality of the Genus Homo: What Is It and Why Do We Think So?” Mètode Science Studies Journal, 1 Jan. 1970, www.redalyc.org/journal/5117/511766757033/html/. Accessed 01 Apr. 2025.
Taylor, Illustrations by Keenan, and Barbara Helm Welker. “28. Homo Ergaster.” The History of Our Tribe Hominini, Open SUNY Textbooks, 13 June 2017, milnepublishing.geneseo.edu/the-history-of-our-tribe-hominini/chapter/homo-ergaster/. Accessed 01 Apr. 2025.

Written by Rafer Shaughnessy

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