Final answer:
A branch of the genus Australopithecus evolved to become bipedal, exhibiting adaptations such as upright walking which were crucial for the evolution of early hominins. Homo erectus, a descendant of Australopithecus, continued these adaptations, and their benefits contributed significantly to survival and evolution.
Step-by-step explanation:
A branch of the hominids of the genus Australopithecus evolved to become bipedal. This evolutionary step was significant as it marked a transition towards upright walking, which is one of the defining characteristics of our lineage. Australopithecus species, such as Australopithecus afarensis, are well-known for their bipedal locomotion, as evidenced by the famous Laetoli footprints discovered by Mary Leakey. Homo erectus, a descendant of Australopithecus, continued this bipedal tradition and exhibited further adaptations that supported efficient upright walking, such as a broader pelvis and longer legs.
The transition to bipedalism offered numerous advantages, such as the ability to cover long distances more efficiently and the liberating of hands to carry objects and use tools, which were significant factors in the survival and evolution of early hominins. Although there are multiple hypotheses regarding the reasons behind this shift to bipedalism, it remains one of the key developments in the story of human evolution.