Final answer:
The genus Australopithecus was the first to show human-like obligate bipedalism, as evidenced by the Laetoli footprints, which date to about 3.5 million years ago.
Step-by-step explanation:
The genus that was first to show human-like obligate bipedalism is Australopithecus. The Laetoli footprints, discovered by Mary Leakey in the 1980s, provide conclusive evidence of bipedalism in Australopithecus afarensis around 3.5 million years ago. This genus exhibited key changes such as longer legs, changes in spinal curvature, and the development of arches in the feet which are imperative for bipedal locomotion, similar to that of modern humans. The Australopithecus genus, therefore, marks a significant transition point towards the human-like bipedalism observed in our own species as well as in other hominins like Homo erectus.