A 3.4-million-year-old foot proves our ancestors walked in many different ways

Nature · Published 3 October 2026 Swipe more like this →

In short: For decades, we thought early human evolution was a straight line. But the discovery of the Burtele foot, now linked to the species Australopithecus deyiremeda, reveals a more complex reality. This ancient hominin lived alongside the famous Lucy, yet possessed a primitive, grasping big toe and a distinct, specialized diet.

In 2009, researchers led by Yohannes Haile-Selassie uncovered eight bones from a 3.4-million-year-old foot at the Woranso-Mille site in Ethiopia. For years, this 'Burtele foot' remained an enigma, as it did not match the anatomy of the well-known Australopithecus afarensis, the species to which the famous Lucy belongs. While A. afarensis was fully bipedal with an adducted big toe, the Burtele foot retained an opposable big toe, a trait more common in much older ancestors like Ardipithecus ramidus. This indicated that early hominins possessed diverse ways of navigating their environment, with some still relying on arboreal grasping while walking upright on the ground.

The mystery was finally resolved through a decade of persistent fieldwork. By recovering additional dentognathic specimens from the same stratigraphic horizon as the foot, the team established a clear link between the Burtele foot and Australopithecus deyiremeda, a species formally announced in 2015. This discovery provides definitive evidence that two distinct hominin species co-existed in the same landscape during the mid-Pliocene. The geological work, led by Beverly Saylor, was crucial in mapping these fossil layers to confirm that these species shared the same region at the same time.

Beyond locomotion, isotope analysis of tooth enamel has revealed significant ecological separation between these cousins. While A. afarensis utilized a mixed diet of C3 resources from trees and shrubs alongside C4 tropical grasses, A. deyiremeda relied more heavily on C3 foods. This dietary strategy mirrors that of earlier hominins like A. anamensis. Furthermore, the discovery of a juvenile jawbone, estimated to be about 4.5 years old, allowed researchers to study growth patterns, showing a disconnect in development between front and back teeth similar to that seen in living apes. These findings collectively paint a picture of a diverse, competitive, and highly adaptable early human lineage.

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