The footprints were formed 3.5 million years ago when at least two individuals walked over wet volcanic ash. The wet ash hardened like cement and was then covered by more ash. The footprints show that the individuals had perfect, two-footed strides. They also reveal that one hominid was larger than the other. And because the footprints fall next to each other, they indicate that the two hominids were walking side by side and close enough to each other to be touching.
Apes sometimes walk on two legs.
When an ape walks upright, weight is transmitted from the heel, along the outside of the foot, and then through the middle toes. The imprints left behind at Laetoli clearly show the weight distribution of true upright walkers. The footprints also look remarkably like a human's.