Answer
a.
Work Step by Step
Australopithecus afarensis footprints were found in Tanzania. This species seemed to have walked the earth from 3.9 to 3 million years ago. From the prints, scientists deduced that the australopiths walked in an upright manner because the footprints revealed a deep arch in the foot and that the big toes were aligned with the other toes; these two characteristics are essential to bipedal movement.
