Final answer:
Fossil evidence indicates that bipedalism in hominins predated the evolution of large brains, as demonstrated by footprints and skeletal features of early Homo species and hominins like H. floresiensis.
Step-by-step explanation:
Recent fossil findings suggest that the evolution of bipedalism in early hominins occurred long before the development of large brains. The most significant evidence comes from Mary Leakey's discovery of footprints dated around 3.5 million years ago, believed to be from Australopithecus afarensis, which show a modern striding gait. Furthermore, analysis of early Homo species, including Homo erectus who lived about 2.8 million years ago, indicates that they had anatomical features supportive of efficient bipedal movement, such as a broader pelvis, longer legs, and arched feet, while still having relatively small brains. This evidence is reinforced by discoveries like H. floresiensis, which despite having small brains, exhibited anatomical features indicative of bipedalism.
Key changes in anatomy, such as the valgus angle of the femur and the evolution of spinal curves, facilitated bipedalism and preceded encephalization, the process of brain enlargement. The expensive tissue hypothesis suggests that the metabolic demands of a larger brain were met much later through dietary changes, indicating a decoupling of bipedalism and brain size in the human evolutionary timeline.