Final answer:
The cranial capacity of Homo erectus ranged from 1,000 to 1,250 cubic centimeters, marking an increase from earlier specimens and reflecting significant evolutionary changes in brain size.
Step-by-step explanation:
Homo erectus, a species that originated in East Africa approximately 1.9 million years ago, exhibited a progressive increase in brain size during its existence. Early specimens had cranial capacities of about 550 cubic centimeters (cc), which expanded over time. The adult Homo erectus had brain sizes ranging from about 1,000 to 1,250 cubic centimeters, demonstrating significant evolutionary growth in brain capacity. These capacities are smaller than modern humans, who average about 1,400 cubic centimeters. The increased brain size of Homo erectus was one of several adaptations, including reduced tooth and jaw size due to dietary changes, such as the consumption of cooked meat.