ergaster

Homo ergaster is an extinct hominin species that lived in Africa during the early Pleistocene, roughly 1.9 to 1.4 million years ago. In some classifications it is treated as the African form of Homo erectus, while others recognize it as a distinct species. The best-known material includes the Turkana Boy skeleton (KNM-WT 15000) from Kenya, a nearly complete adolescent male dated to about 1.6 million years ago, which provides important insight into body size and proportions.

Anatomically, H. ergaster shows a transition toward a more modern body plan compared with earlier hominins: relatively long legs and a tall, lean physique suited to efficient bipedal locomotion. The skull is long and low with pronounced brow ridges. Brain size ranges roughly from 600 to 900 cubic centimeters, generally larger than earlier Homo species but smaller than modern humans. The dentition is reduced relative to australopithecines and early Homo, though teeth are still larger than in modern humans.

Behavior and tools associated with Homo ergaster include the Acheulean stone tool industry, featuring hand axes and cleavers, suggesting advances in tool manufacture and planning. Evidence for hunting or coordinated scavenging exists, though interpretations vary, and the use of fire remains debated. Material culture indicates increasingly complex foraging and possible social organization, though firm conclusions about language or symbolic behavior are elusive for this period.

Taxonomic status remains debated. If recognized as a separate species, ergaster represents an early African member of the Homo erectus lineage and a crucial link in human evolution; if treated as a subspecies, it is viewed as part of the broader H. erectus complex.