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Laetoli footprints
3.66 million years ago (found 1978)· Fossil or site· Human ancestors & us
Well establishedStrong fossil, genetic or geological evidence.
Trails of footprints left about 3.66 million years ago in volcanic ash in Tanzania by upright-walking hominins.
See it on the Life map →What happened
A nearby volcano, Sadiman, dusted the landscape with fine ash. Light rain turned it into a cement-like layer that recorded the tracks of many animals and of at least two hominins walking side by side for about 27 meters, roughly 70 prints in all. Fresh ash then buried and preserved them. Mary Leakey's team exposed the main trail in 1978; prints of two more individuals were found nearby in 2015.
Why it matters
The prints are direct evidence of behavior: hominins were walking upright with a humanlike stride long before stone tools or large brains.
Think of it like
Like a fresh concrete sidewalk: someone walked across it before it set, and the impressions hardened in place.
The evidence (fossils, genes, rocks)
Argon–argon dating of ash layers above and below the prints; casts, 3D scans and experiments comparing them with tracks made by modern people and chimpanzees.
Still debated
How closely the stride matched ours, how many individuals made the main trail, and whether all the hominin prints at Laetoli were made by one species.
Connections (3)
▸Laetoli footprints record Walking on two legsWell established
The connection
Footprints capture behavior, not just anatomy. The Laetoli trails show a heel striking first, a raised arch, and a big toe in line with the other toes: a walking style close to ours, already in place about 3.66 million years ago.
When and how
Laetoli, northern Tanzania, about 3.66 million years ago; the main trail was found in 1978 by Mary Leakey's team, with more prints added in 2015.
The evidence
Experiments comparing the prints with those of people and chimpanzees walking in wet sand point to an upright, humanlike stride rather than a bent-knee ape gait.
Debates and open questions
Studies differ on how humanlike the stride was; some find a slightly bent knee or a less efficient walk than ours.
▸Laetoli footprints were probably made by AustralopithecusStrong evidence
The connection
The only hominin fossils known from Laetoli at that time belong to Australopithecus afarensis, Lucy's species, so the footprint makers are usually identified as afarensis. The prints suggest small, upright walkers of different sizes moving together across the ash.
When and how
Laetoli, Tanzania: afarensis jaws and teeth were found there in the 1970s in the same rock layers as the trails.
How sure are we?
The match of age, place and foot shape with afarensis foot bones from Hadar is strong but circumstantial; footprints carry no bones or DNA.
Debates and open questions
A 2021 restudy of a separate Laetoli trail (site A), once thought to be a bear's, argued that a second, different hominin also walked there.
▸The Leakey family uncovered Laetoli footprintsWell established
The connection
Mary Leakey led excavations at Laetoli from the mid-1970s, and in 1976 her team spotted fossil animal tracks. In 1978 they exposed the hominin trail, carefully cleaned it, cast it and reburied it, adding footprints to the family's long record of East African discoveries.
When and how
Laetoli, northern Tanzania, 1976–1979; Mary Leakey's team, with geochemist Paul Abell spotting the first hominin print in 1978.
The evidence
Mary Leakey and Richard Hay's 1979 Nature paper and field records document the find; the trail was re-excavated and conserved in the 1990s with the Getty Conservation Institute.
Debates and open questions
Little about the discovery is disputed. The open question is conservation: reburial protects the trail, but tree roots and erosion have damaged parts of it.