Final answer:
Mary Leakey discovered 3-million-year-old footsteps in the 1980s, believed to be made by Australopithecus afarensis. Recently, older "ghost tracks" dated up to 23,000 years old were found in New Mexico, providing new insights into the human occupation of North America.
Step-by-step explanation:
The footsteps dating back 3 million years were found by English paleoanthropologist Mary Leakey in the 1980s. These significant footprints were uncovered in East Africa at the site of Laetoli, likely made by the species Australopithecus afarensis. The Laetoli footprints suggested a modern striding gait, providing compelling evidence of early hominin bipedalism.
More recently, in January of 2020, scientists reported the discovery of over 60 "ghost tracks" at White Sands National Park in New Mexico, which were radiocarbon dated to between 21,000 to 23,000 years old. These findings predate the human occupation evidence from sites like Monte Verde in Chile and Clovis, New Mexico, revolutionizing the understanding of early human presence in North America.