The footprints of our predecessors
The Laetoli footprints were most likely made by Australopithecus afarensis, an early human whose fossils were found in the same sediment layer. The entire footprint trail is almost 27 m (88 ft) long and includes impressions of about 70 early human footprints.
3.6 million years ago in Laetoli, Tanzania, two early humans walked through wet volcanic ash. When the nearby volcano erupted again, subsequent layers of ash covered and preserved the oldest known footprints of early humans.
Team members led by paleontologist Mary Leakey stumbled upon animal tracks cemented in the volcanic ash in 1976, but it wasn’t until 1978 that Paul Abell joined Leakey’s team and found the 88ft (27m) long footprint trail referred to now as “The Laetoli Footprints,” which includes about 70 early human footprints.
The early humans that left these prints were bipedal and had big toes in line with the rest of their foot. This means that these early human feet were more human-like than ape-like, as apes have highly divergent big toes that help them climb and grasp materials like a thumb does. The footprints also show that the gait of these early humans was "heel-strike" (the heel of the foot hits first) followed by "toe-off" (the toes push off at the end of the stride)—the way modern humans walk.
The close spacing of the footprints is evidence that the people who left them had a short stride, and therefore probably had short legs. It is not until much later that early humans evolved longer legs, enabling them to walk farther, faster, and cover more territory each day.
How do we know these are early human footprints?
The shape of the feet, along with the length and configuration of the toes, show that the Laetoli Footprints were made by an early human, and the only known early human in the region at that time was Au. afarensis. In fact, fossils of Au. afarensis were found nearby to the footprints and in the same sediment layer, telling scientists that Au. afarensis was in the area at the same time the footprints were left.