Final answer:
Cranial endocasts of Homo erectus show an increase in brain size over time, reflecting cognitive and cultural complexity with a range from approximately 550 cc to 1,250 cc, alongside physical adaptations for tool use and hunting.
Step-by-step explanation:
Cranial endocasts of Homo erectus show that the species had a progressively increasing brain size throughout its existence, suggesting cognitive and cultural complexity. These endocasts reflect a brain volume ranging from about 550 cubic centimeters (cc) to 1,250 cc, which is considerably larger than earlier hominins like Homo habilis who had a brain volume of about 800 cc. Unlike Homo habilis, whose brain capacity helped distinguish it from Australopithecus, the increased brain size in Homo erectus aligns with more advanced behaviors such as the increased use of fire, cooking of meat, and potentially the advent of rudimentary language.
With the wider adoption of tools and the development of hunting techniques, Homo erectus displayed physical adaptations that supported these activities, including smaller teeth and jaws due to softer diet provided by cooked food, taller stature, longer legs, and adaptation for endurance running. These physical characteristics, when considered alongside cranial endocasts, indicate a trend of encephalization that correlates with the hypothesis of increased behavioral, cognitive, and cultural developments in human evolution.