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A great deal can be learned from the actual traces of ancient human locomotion: the footprints of early hominids. The best-known specimens are the remarkable tracks discovered at Lactoli, Tanzania, by Mary Leaky. These were left by small hominids around 3.6 to 3.75 million years ago, according to potassium – argon dates of the volcanic rocks above and below this level. These hominids walked across a stretch of moist volcanic ash, which was subsequently turned to mud by rain, and which then set like concrete.
Examination of his shape of the prints revealed to Mary Leakey that the feet had a raised arch, a rounded heel, a pronounced ball, and a big toe that pointed forward. These features, together with the weight-bearing pressure patterns, resembled the prints of upright-walking modern humans. The pressures exerted along the foot, together with the length of stride, which averaged 87 centimeters, indicated that the hominids had been walking slowly. In short, all the detectable morphological features implied that the feet that left the footprints were very little different from those of contemporary humans.
A detailed study has been made of the prints using photogrammetry, a technique for obtaining measurements through photographs, which created a drawing showing all the curves and contours of the prints. The result emphasized that there were at least seven points of similarity with modern bipedal prints, such as the depth of the heel impression, and the deep imprint of the big toe. M Day and E. Wickens also took stereo photographs of the Lactoli prints and compared them with modern prints make by men and women
in similar soil conditions. Once again, the results furnished possible evidence of bipedalism. Footprints thus provide us not merely with rare impressions of the soft tissue of early hominids, but also with evidence of upright walking that in many ways is clearer than can be obtained from the analysis of bones.
The study of fossil footprints is not restricted to examples from such remote periods. Hundreds of prints are known, for example, in French caves dating from the end of the last ice age, approximately 10,000 years ago. Research by Leon Pales, using detailed silicon resin molds of footprints mostly made by bare feet, has provided information about this period.
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