Homo ergaster (meaning "working man") or African Homo erectus is an extinct chronospecies of the genus Homo that lived in eastern and southern Africa during the early Pleistocene, between about 1.9 million and 1.4 million years ago. Homo ergaster is variously thought to be ancestral to, or as sharing a common ancestor with, or as being the same species as, Homo erectus.
Some palaeoanthropologists consider H. ergaster to be a variety of H. erectus, while others call H. ergaster the direct ancestor of H. erectus. With the discovery of the Dmanisi skull 5 in the South Caucasus in 2005, the earliest evidence for H. ergaster in Africa and for H. erectus in Asia is now of virtually the same age, and it is unclear if the speciation of H. erectus (H. ergaster) from H. habilis took place in Africa or Asia.
The binomial name was published in 1975 by Groves and Mazák. The specific epithet, "ergaster", is derived from the Ancient Greek ἐργαστήρ ergastḗr - "workman", in reference to the advanced lithic technology developed by the species, thereby introducing the Acheulean industry.
South African palaeontologist John T. Robinson discovered in 1949 a mandible of a new hominin in southern Africa, which he named Telanthropus capensis and which today is classified as Homo ergaster. That taxon was first applied to a mandible found near Lake Rudolf (now Lake Turkana), Kenya, by Colin Groves and Vratislav Mazák in 1975; dubbed KNM-ER 992, it became the type-specimen of the species. A near-complete skeleton of H. ergaster, KNM-WT 15000, or "Turkana Boy", was discovered in 1984 at Lake Turkana by Kamoya Kimeu and Alan Walker. It is dated to 1.6 million years ago (mya) and is one of the most complete early hominin fossils found to date.
Paleoanthropologists debate the defining of H. ergaster and H. erectus as separate species. Some consider H. ergaster to be a variety of H. erectus, the so-called African Homo erectus; they propose that early on, H. ergaster emigrated out of Africa to Eurasia, branching into a distinct species.—and they offer the labels "Homo erectus sensu stricto" (strict sense) for the Asian species and "Homo erectus sensu lato" (broad sense) for the greater species comprising both Asian and African populations. Two major notions for classifying the two species still divide the scientific community; they are: 1) H. ergaster and H. erectus are the same species; or, 2) H. erectus is indeed an Asian species distinct from African H. ergaster. Thus, although "Homo ergaster" has gained some acceptance as a valid taxon, ergaster and erectus are often identified as separate (that is, African or Asian) populations of the larger species H. erectus (sensu lato).
Some scientists dispense altogether with using the specific epithet ergaster, making no distinction, for example, between Turkana Boy and Peking Man as H. erectus fossils; see Interpreting evolution—Springer graph-model. Sura et al (2007) declared that Homo erectus "was a likely source of multiple events of gene flow to the Eurasian continent". In 2003, Anton found the taxonomic issues surrounding Asian vs. African H. erectus somewhat "intractable", and reported: "The H. ergaster question remains famously unresolved" and that same condition persists till today.
The latest discoveries at Dmanisi, Georgia, (see Dmanisi skull) suggest that all the contemporary groups of early Homo in Africa—which include Homo habilis, H. rudolfensis, H. ergaster, and H. erectus—are of the same species, which evolved at least 1.9 million years ago in Africa and later expanded through Eurasia as far as China and Java, where it is documented from about 1.2 mya—and which species is best named H. erectus.Thus, debate continues about the classification, ancestry, and progeny of H. ergaster, but it is still widely accepted to be the direct ancestor of later hominins such as Homo heidelbergensis, Homo neanderthalensis, Asian Homo erectus, and Homo sapiens.