Final answer:
Homo ergaster skull features include small jaws and teeth, a third molar larger than other molars, a skull shape similar to H. erectus or H. habilis, and a sagittal keel. Homo ergaster also had bipedal locomotion and human-like feet with arches and ankles.
Step-by-step explanation:
Homo ergaster, an extinct species of hominin believed to have lived around 1.9 million years ago, exhibited distinct features in its skull. Some notable characteristics include a long and low skull with a more pronounced forehead than earlier hominins. The face was relatively flat, lacking the pronounced prognathism seen in some earlier species. The brow ridges were prominent, and the braincase was larger and more rounded, indicating increased brain size compared to earlier ancestors. The teeth were smaller and more human-like, suggesting dietary adaptations. These features collectively indicate advancements in cognition, tool use, and adaptation to changing environments in the evolutionary timeline.