H. ergaster is supposed to be the direct ancestor of later hominids such as Homo heidelbergensis, Homo sapiens and Homo neanderthalensis. It is one of the earliest members of the genus Homo, possibly descended from, or sharing a common ancestor, with Homo habilis.

Homo ergaster used more diverse and sophisticated stone tools than Homo erectus. He refined the inherited Oldowan stone tools and developed the first Acheulean bifacial axes.