Final answer:
The first debated evidence for bipedality is found in the Australopithecines, supported by fossil records such as the Laetoli footprints and the early hominin genus Ardipithecus. The Pliocene epoch fossils show clear signs of bipedalism, and by about 2.8 million years ago, early Homo species were nearly as efficient at bipedal locomotion as modern humans.
Step-by-step explanation:
We find the first debated evidence for bipedality among the Australopithecines. This evidence comes from significant fossil findings, including the famous Laetoli footprints discovered by Mary Leakey in the 1980s, which likely belonged to Australopithecus afarensis. These showed a modern striding gait characteristic of bipedal locomotion. Furthermore, Ardipithecus, a very early hominin with fossil evidence dating back around 4.4 to 5.6 million years ago, demonstrated bipedality, although its classification as a direct human ancestor remains uncertain.
By the Pliocene epoch, hominins such as Australopithecus showed clear signs of bipedalism, and by about 2.8 million years ago, early Homo species like Homo erectus had evolved to be nearly as efficient at bipedal locomotion as modern humans. However, the genus Homo also encompasses not just our own species but also those closely related to us, including hominins with various degrees of bipedalism and diverse anatomical features, such as larger brain size and tool-making capabilities.