Final answer:
Bipedalism traditionally has been viewed as an adaptation to open grassland or savannah country, but current research suggests it evolved primarily in heavily forested environments. Anatomical changes, including the angling of the femur and spinal curves, facilitate successful bipedalism. The exact adaptive significance of bipedalism is still not fully understood.
Step-by-step explanation:
Bipedalism traditionally has been viewed as an adaptation to open grassland or savannah country. However, current research suggests that bipedalism evolved primarily in heavily forested environments. This is supported by the fact that many early hominin fossils have been found in forested areas. The hypothesis that bipedalism evolved as an adaptation to the savanna habitat is called the savanna hypothesis.
One of the most important anatomical changes that facilitate successful bipedalism is the angling of the femur (upper leg bone) inward at what is referred to as a valgus angle, which positions the knees and feet under the center of the pelvis. Bipedal hominins have also evolved spinal curves that make it possible for the hips to balance the weight of the upper body. The evolution of the arch in the foot as well as the realignment of the big toe so that it is parallel to the other toes is also instrumental in transmitting weight during the step phase of bipedal locomotion.
The adaptive significance of bipedalism is still not fully understood. There have been many hypotheses proposed, such as freeing hands to carry tools or food, increasing energy efficiency, or thermoregulation. However, none of these hypotheses are testable, making it challenging to determine the exact reason why bipedalism evolved.