Final answer:
The Laetoli footprints were likely made by Australopithecus afarensis, an early human ancestor known for bipedal locomotion, evidenced by footprints discovered by Mary Leakey dating back 3.5 MYA.
Step-by-step explanation:
The ancestor responsible for the Laetoli footprints is likely Australopithecus afarensis. This is supported by the discovery of a 75-foot trail of footprints in East Africa at the site of Laetoli, which were uncovered by English paleoanthropologist Mary Leakey in the 1980s. These footprints date back to about 3.5 million years ago (MYA). The analysis of these prints suggests a modern striding gait similar to that of humans.
Australopithecus afarensis is one of the earliest known ancestors to have shown bipedalism, as exemplified by the famous specimen known as Lucy, who lived approximately 3 million years ago. Their foot structure, along with long arms and curved fingers, indicates both their bipedal movement as well as arboreal abilities. Therefore, the Laetoli footprints represent significant evidence of early hominin bipedal locomotion and provide insight into the early stages of human evolutionary history.