In 1976, an excavation in Tanzania unearthed ancient footprints that changed what we know about how we walk

An ordinary day of fieldwork in the dry savanna of East Africa ended up changing the way science perceives human evolution. In their quest to study an arid region in northern Tanzania, a team of researchers led by palaeontologist Mary Leakey decided to investigate a layer of volcanic ash found across a large area. The area, called Laetoli, was already known to contain fossils, but what it really preserved was an ancient behaviour.

As investigators brushed away the loose surface dust, they noticed a series of distinct indentations deeply pressed into the prehistoric crust.

The field scientists were quick to realise that this was a clear record of evolution. Instead of providing skeletal pieces, such as jaws and teeth, the location offered an actual snapshot of how early humans walked around on their feet. A long time ago, an eruption from a local volcano covered the area in a layer of fine, powdery grey ash. Right after the volcanic activity, a downpour of rain created a perfect mould of the way these individuals walked until a second wave of ash was laid on top of the prints, sealing them.

Pushing upright walking further into the deep past

The discovery and preservation of this ancient trail quickly garnered attention throughout the world since it gave direct evidence of bipedalism. This is according to a study published in the journal PLOS ONE. The trails are estimated to be about 3.6 million years old.

This timeline established the trail as the oldest unequivocal evidence of obligate bipedalism in the human lineage available at that time.

Previous anthropological theories often speculated about the specific form of locomotion of our earliest ancestors and whether or not they were adapted to terrestrial bipedalism. The impressions found in the ash at Laetoli have been instrumental in settling the debate. This is explored in another study published in the scientific journal Proceedings of the Royal Society B: Biological Sciences, which states that these tracks reflect an extended limb and efficient gait. Although there are differences in mechanics in comparison with contemporary representatives, the gait is described as an upright posture that demonstrates the adaptation of our predecessors to bipedalism.

Reconstructing a journey across the savanna plains

This archaeological site continues to yield scientific information as modern technologies enable experts to investigate the characteristics of the individuals whose prints were found there. It is stated in an informative review published by the Smithsonian Institution Human Origins Program and titled Laetoli Footprint Trails that the trails were most likely made by individuals belonging to Australopithecus afarensis – the same species as the celebrated fossil named Lucy.

The spacing of the tracks reveals a clear behavioural snapshot, showing a trail of individuals walking across the volcanic landscape.

Today, this ancient African landscape is celebrated as a foundational milestone in evolutionary biology, demonstrating how insights into human behaviour can come from a simple set of marks in the crust. The enduring legacy of the 1976 discovery serves as a reminder that our collective lineage has a long history of bipedal travel. It shows that early hominins were moving across their world in a stable, upright manner, adapting to the challenges of their environment step by step.

It remains a striking reality that when people travel to Africa nowadays to see animals on the savannas, they are walking near the exact traces left by their early human relatives, which rest safely beneath the surface of the hardened volcanic ash.