This mandible, which is in two pieces, is the type specimen of the species Homo ergaster. The gracile (light) build and relatively small cheek teeth set this specimen apart from more typical examples of Homo erectus, whose jaws were more heavily built and whose cheek teeth were quite large, relative to modern humans. In 1975, paleoanthropologists Colin Groves and Vratislav Mazák proposed a separate species for the early humans inhabiting Africa during this time period. The name Homo ergaster was proposed for this species; the word "ergaster" is Greek for "workman," which was a reference to stone tools found in the same geologic level.