Final answer:
The increase in cranial capacity of Homo habilis is attributed to encephalization, indicating improved cognitive abilities and an adaptation to a changing environment.
Step-by-step explanation:
The increase in cranial capacity among Homo habilis populations is directly attributed to encephalization, which is a progressive increase in brain size over time. This evolutionary development suggests an increase in behavioral, cognitive, and cultural complexity. The changed brain size suggests advancements in cognitive ability, such as the use of symbolic and abstract language, tools, and fire use. Evidence of cooked food at Homo erectus sites, for example, implies a diet that supported brain growth. Furthermore, during a period of rapid climate change, larger brains may have helped our ancestors adapt to an unpredictable environment, facilitating the development of culture and technology.