Homo ergaster

Homo ergaster is an extinct species or subspecies of archaic humans who lived in Africa in the Early Pleistocene. Whether H. ergaster constitutes a species of its own or should be subsumed into H. erectus is an ongoing dispute within palaeoanthropology. Proponents of synonymisation typically designate H. ergaster as "African Homo erectus" or "Homo erectus ergaster". The name Homo ergaster roughly translates to "working man", a reference to the more advanced tools used by the species in comparison to those of their ancestors. The fossil range of H. ergaster mainly covers the period of 1.7 to 1.4 million years ago, though a broader time range is possible. Though fossils are known from across East and Southern Africa, most H. ergaster fossils have been found along the shores of Lake Turkana in Kenya. There are later African fossils, some younger than 1 million years ago, that indicate long-term anatomical continuity, though it is unclear if they can be formally regarded as H. ergaster specimens. As a chronospecies, H. ergaster may have persisted to as late as 600,000 years ago, when new lineages of Homo arose in Africa.

Those who believe H. ergaster should be subsumed into H. erectus consider there to be too little difference between the two to separate them into distinct species. Proponents of keeping the two species as distinct cite morphological differences between the African fossils and H. erectus fossils from Asia, as well as early Homo evolution being more complex than what is implied by subsuming species such as H. ergaster into H. erectus. Additionally, morphological differences between the specimens commonly seen as constituting H. ergaster might suggest that H. ergaster itself does not represent a cohesive species. Regardless of their most correct classification, H. ergaster exhibit primitive versions of traits later expressed in H. erectus and are thus likely the direct ancestors of later H. erectus populations in Asia. Additionally, H. ergaster is likely ancestral to later hominins in Europe and Africa, such as modern humans and Neanderthals.