Final answer:
Homo erectus had larger jaws and teeth, a smaller brain, and a prominent brow compared to modern humans. Although they were efficient bipedal walkers, their facial structure and skull shape were notably different.
Step-by-step explanation:
The anatomical features of H. erectus differed from those of modern humans. While H. erectus was nearly as efficient at bipedal locomotion as modern humans, with a broader pelvis, longer legs, and arched feet for walking upright, the differences were more pronounced from the neck up. Notably, H. erectus had larger jaws and teeth, a sloping forehead, and a smaller brain compared to humans today.
Their brain size ranged from about 775 to 1,100 cubic centimeters, substantially smaller than the modern human average of 1,130 to 1,260 cubic centimeters, despite showing a progressive increase over their time. H. erectus also displayed a prominent brow, and unlike other primates, they had a nose with downward-facing nostrils which may have been an adaptation to colder climates.
Physical adaptations such as a larger brain and smaller facial features like teeth and jaws emerged over time, likely due to changes in diet and increased use of tools. The gradual decrease in prognathism and the shift towards smaller jaws and teeth also coincided with dietary changes that included softer foods made possible by the cooking of meat and plants. Nevertheless, H. erectus were uniquely adapted to their environment, with their long legs suggesting the ability to run great distances, which could be beneficial in endurance hunting.