Final answer:
Homo erectus's adaptive success is evidenced by its increased reliance on material culture and apparent increased intelligence, as they developed sophisticated tools, increased brain size, and demonstrated complex social behaviors.
Step-by-step explanation:
The adaptive success of Homo erectus can be seen in key evolutionary changes such as an increase in brain size, use of fire, cooking meat, and creating sophisticated tools. These changes illustrate an increased reliance on material culture and an apparent increase in intelligence. These adaptations, including the ability to walk and run long distances, the development of complex social and cognitive abilities potentially linked to the emergence of language, and cooperative behaviors such as caring for the sick, enabled Homo erectus to adapt to changing climates and environments. Therefore, Homo erectus's high degree of adaptive success is evidenced by both (a) increased reliance on material culture and (b) apparent increased intelligence.