Final answer:
Homo erectus has unique brain size, body size, and cranial shape. Their brain size increased progressively, their body size is taller than any previous hominin, and their cranial shape is characterized by a sagittal keel and a prominent brow ridge.
Step-by-step explanation:
Homo erectus is unique in terms of brain size, body size, and cranial shape. The brain size of Homo erectus increased progressively from about 550 cc to 1,250 cc. This increase in brain size is associated with an increase in behavioral, cognitive, and cultural complexity. In terms of body size, Homo erectus is taller than any previous hominin, with longer legs that allowed them to run long distances and chase prey. Their cranial shape is characterized by a sagittal keel, which is a small raised ridge on top of the skull, and a prominent brow ridge.