Final answer:
The debated evidence for bipedality in early hominins can be traced back to between 7 and 6 million years ago (MYA), with pivotal discoveries such as Ardipithecus fossils around 4.4 MYA and the Laetoli footprints at 3.5 MYA.
Step-by-step explanation:
The first (debated) evidence for bipedality in early hominins in the fossil record appears to be found in the time period between 7 and 6 million years ago (MYA). Some of the most significant evidence of early bipedalism is attributed to specimens from Ardipithecus, which date back to about 4.4 MYA, and to the notable discovery by Mary Leakey of Laetoli footprints around 3.5 MYA. Moreover, the genus Australopithecus, believed to have lived from about 4 MYA, provides evidence for upright walking in hominins that precedes the emergence of the genus Homo.