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. 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.
The type specimen of H. ergaster is KNM-ER 992 ; 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.
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