One of the most debated human fossil finds is that of a Homo ergaster. As explained by Science Daily, this species of human roamed eastern and southern Africa between 1.9 and 1.4 million years ago.

The argument over ergaster is whether it is its own separate species or if it is in fact just a subspecies of Homo erectus. Many sources, such as the Smithsonian, just lump ergaster and erectus together. Others, such as Michigan State University, state that ergaster may have been the direct ancestor of erectus or that ergaster was just the version of erectus that lived in Africa. Another related controversy is whether ergaster or erectus gave rise to the lineage that produced modern humans.

Because of the timeline, ergaster would have lived at the same time as erectus. However, ergasters were more slender with thinner skull bones, while erectus were more robust. Ergasters, like erectus, used tools and presumably had a similarly lifestyle.