The Laetoli footprints

1 minute read

The most striking piece of evidence for bipedality in our earliest hominin relatives is a series of footprint trails at Laetoli, a fossil-bearing site in Tanzania. The longest trail, known as trail G, was made by at least two individuals, one much larger than the other. These individuals were probably members of a species called Australopithecus afarensis, with fossil remains that have been found in other parts of the Laetoli area from nearly the same time, 3.5 million years ago. This species lived long before any that scientists call humans, they are different from us in many, many respects. But the evidence shows that they walked bipedally in a very humanlike way.

Studying these footprints poses many challenges to scientists. Their shape should give us clues about the shape of the feet, the way they struck the ground, the length and pattern of steps. Probably the most obvious aspect of these footprints are the big toes, which were aligned more or less with the other toes. This is a very different shape than a chimpanzee or gorilla foot, in which the big toe is relatively short and diverges from the foot, and the other toes are long and curving. Nevertheless, the toes of A. afarensis were not quite the same as ours, as you can compare as you make your own footprints.

A comparison of one of the Laetoli footprints (bottom) with a footprint from a later site attributed two modern humans (top and middle). The human (middle) is walking with a bent-knee, bent-hip (BKBH) gait, not a normal gait for a person. The image shows the depth of different parts of the print. From a research paper by David Raichlen and colleagues Raichlen:Laetoli:2010.

This lab station has you making footprints, to see how you might study the shape and conditions under which the Laetoli footprints were made. As you make footprints, try to use different styles of gait. Move fast or slow, maybe try to simulate a running step. Can you rule out some patterns of movement for the makers of the Laetoli footprint trail?