n equatorial east Africa some footprints have been found -- they are about 3.5 million years old, calculated by the potassium-argon dating method:

Whatever made the footprints on the left walked on two feet, and the feet have an arch, toes and a rounded heel. This small individual at the left is calculated to have been about 3'10" tall (1.2 metres). Because the larger track is said to have a smaller one stepping in it, heights cannot be calculated for those prints. Something with a human-like foot was walking through volcanic ash, upright and barefoot, 3.5 million years ago. Whether this was any of the Australopithecenes we just don't know.

At first you might think these were very like human footprints. But the smaller prints on the left are splayed out at an angle of about 42 degrees which probably means the creature was bent forward at the waist like an ape walking on two legs. We walk with our feet pointing almost straight ahead. And it's just possible that the larger prints are double because the creature on the right used its knuckles or hands as it walked on all fours. The smaller footprints to the left match the stride and placement of the larger ones to the right. This is something one would not expect of a child today walking beside an adult, unless deliberately doing so for fun. But this was probably not a fun situation. The makers of the footprints may have been trying to escape from the source of the volcanic ash. The ash on the ground may have been hot, and this the reason for not walking on all fours.

The smaller prints in the larger ones, if made by a separate creature, may have been because the heat was less once the larger foot had absorbed some of the heat and the larger creature may have provided some protection from searingly hot wind or rain.. The volcano is today identified as Sadiman, about 20 kilometres to the east of the footprints. Unfortunately we are not told the direction of the prints in relation to the volcano. We should be able to reconstruct the scene using our modern experiences with significant volcanic eruptions at Krakatoa, Mount St. Helens and Montserrat. One further point is that the smaller prints to the left are so close to the larger ones that they are less than the length of the larger foot away. This would seem to make walking together difficult if the prints were made at the same time, and if, as is said, the smaller creature was almost 4 feet tall.

The small tracks to the extreme right are said to be those of an extinct three-toed horse. Its tracks are not parallel to the footprints.

As the footprints and fossil remains of various animals we are told

are similar in type to the animals found in the area today....

....antelopes, hares, giraffes, rhinoceroses, horses, pigs and elephants

it's quite possible in my view that the hominid footprints were made by precursors of bonobos, a type of chimpanzee living in Africa today that frequently walks about upright and has been filmed carrying food bundles under one arm as it walks on two feet. But great apes are not human beings.