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BiologyScience

The Laetoli footprints

Three hominins walk across wet volcanic ash in Tanzania, and the ash sets like plaster.

When
Known to
± 30 thousand years
Era
Pliocene, Cenozoic

A fall of carbonatite ash from the nearby Sadiman volcano is dampened by rain, walked over, and then baked and buried — preserving a 27-metre trackway of hominin footprints 3.66 million years old, discovered in 1978. The prints show a modern-looking gait with a well-developed arch, a non-divergent big toe and a heel-to-toe stride, in a species whose skeletons still show climbing adaptations. A separate set of prints found nearby indicates a second, differently-walking hominin at the same site. The originals are now reburied, and deteriorating.

Just before

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