Final answer:
The Miocene and Pliocene environments, with changing landscapes and cooling climate, likely promoted bipedalism in early hominids for improved mobility and thermoregulation, among other benefits.
Step-by-step explanation:
The advantages of bipedalism are significantly tied to the environment of the Miocene and Pliocene epochs. During the Miocene, hominids began to exhibit traits enabling bipedal locomotion, possibly in response to environmental changes such as forest fragmentation which may have favored more efficient ground travel. The colder Pliocene environment, with its altered landscapes and reduced arboreal habitats, likely further incentivized bipedalism for energy efficiency, improved thermoregulation, and the ability to traverse open landscapes more effectively. Increased mobility also allowed for carrying tools, offspring, or food, giving bipedal creatures an evolutionary advantage. Key anatomical changes necessary for successful bipedalism, such as the valgus angle of the femur, spinal curves, and modification of foot structure, evolved to support a bipedal mode of locomotion.