'Homo ergaster'[1] is an extinct hominid species that lived in eastern and southern Africa beginning about 1.9 million years ago during the late Pliocene epoch. Long-standing debate about the classification of H. ergaster has categorised it as a subspecies of Homo erectus, a separate species of African erectus, a broader-defined species (including H. erectus and H. heidelbergensis), or in strict species definition as temporal form of Homo sapiens. Thus dates for its extinction are often subjective to the definition of the species.[2] H. erectus and H. heidelbergensis are probably the migratory descendants of H. ergaster. H. ergaster may be distinguished from H. erectus by its thinner skull bones and lack of an obvious supraorbital sulcus. It may be distinguished from H. heidelbergensis by its thinner bones, more protruding face, and lower forehead. Derived features separating it from earlier species include reduced sexual dimorphism (around 25%), a smaller, more orthognathic (less protruding) face, a smaller dental arcade, and a larger cranial capacity (700 - 850 cm³). It is estimated that H. ergaster stood at 1.9 metres (6.2 ft) tall. Remains have been found in Tanzania, Ethiopia, Kenya, and South Africa.
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