Final answer:
Bipedalism in hominins may have been selected for benefits such as freeing the hands, increasing energy efficiency, and improving thermoregulation. These advantages led to significant anatomical reorganizations like the development of spinal curves and the valgus angle of the femur, facilitating bipedal balance.
Step-by-step explanation:
Reasons for the Selection of Bipedalism in Hominins
Bipedalism, the ability to walk on two legs, may have been originally selected for due to its various adaptive benefits in early hominins. One hypothesis for this adaptation is the savanna hypothesis, which suggests that bipedalism evolved as an adaptation to a savanna habitat. This way of locomotion freed up the hands for carrying tools, food, or offspring, which could have been advantageous for survival. Additionally, bipedalism increased energy efficiency and improved thermoregulation by exposing more of the body's surface to the air. Anatomical changes, like the angling of the femur at a valgus angle and the evolution of spinal curves, facilitated bipedal balance and stability. Over time, adaptations such as a broader pelvis, longer legs, and arched feet emerged, increasing the efficiency of bipedal locomotion seen in Homo erectus and modern humans.
Although the brain size of later species such as H. floresiensis did not increase significantly, their bipedalism was somewhat different, characterized by a high stepping gait and slower walking speed, indicating diverse expressions of bipedalism in hominin evolution.