Burtele Foot Linked to Australopithecus deyiremeda — A Little-Known Contemporary of Lucy

Scientists say they have solved the long-standing mystery of the “Burtele” foot: a set of 3.4-million-year-old bones unearthed in Ethiopia in 2009. A new study published November 26 in Nature reports that those foot bones, together with a jaw bearing teeth and additional fossils, belong to Australopithecus deyiremeda, a little-known hominin that lived alongside the famous Australopithecus afarensis specimen known as Lucy.

The fossils were excavated at the Burtele locality in Woranso-Mille, in Ethiopia’s Afar region — close to the site where Lucy’s partial skeleton was found in 1974. The Burtele assemblage includes eight pedal bones and a lower jaw with well-preserved teeth. When first discovered, the foot’s anatomy, notably an opposable big toe, suggested a species adapted both for climbing and for a form of upright walking, but there were too few remains to assign it to a species with confidence.

Lead author Yohannes Haile-Selassie, a paleoanthropologist at Arizona State University, and colleagues later recovered more fossil material dated between about 3.33 and 3.59 million years old. In 2015 they proposed the name Australopithecus deyiremeda for that material; the new paper links the Burtele foot to that species, strengthening the case that A. deyiremeda was distinct from A. afarensis.

The study concludes that A. deyiremeda was bipedal but walked differently from modern humans and from Lucy’s species. Its foot anatomy suggests the species pushed off primarily with the second toe rather than a dominant big toe, indicating that early bipedality took multiple forms. "Bipedality in these early human ancestors came in various forms," Haile-Selassie said, noting that different locomotor adaptations coexisted for millions of years.

Researchers also used carbon isotope analysis on eight teeth to infer diet. The results suggest A. deyiremeda relied mainly on trees and shrubs, whereas A. afarensis had a broader diet that included more grass-based foods. This dietary difference could have reduced direct competition and helped both species coexist in the same region and time period.

Implications for the Hominin Family Tree

External commentators say the new finds complicate the previously simple narrative that Lucy’s species was the single ancestor of later hominins. Fred Spoor of the Natural History Museum in London, who wrote a commentary accompanying the study, suggested that A. anamensis — an older species — may have given rise to multiple sister lineages, including A. afarensis, A. deyiremeda and A. africanus. If true, that would make the hominin tree bushier and less linear than traditionally depicted.

"The new research suggests that A. anamensis wasn’t just the ancestor of Lucy, but that many other human species could descend from it as well," Spoor wrote.

Not all researchers are ready to redraw the family tree. Ryan McRae of the Smithsonian cautioned that the idea A. afarensis might be an evolutionary dead end remains a hypothesis, and more fossils will be needed to clarify relationships.

Haile-Selassie and his team plan further fieldwork in Ethiopia to recover more fossils of A. deyiremeda and related species. More material will be crucial to test the new attribution and to refine our understanding of locomotion, diet and evolutionary relationships among early hominins.

Key facts: The Burtele foot dates to about 3.4 million years ago; it is now attributed to Australopithecus deyiremeda. The species walked bipedally with a distinct foot push-off, ate mostly trees and shrubs, and coexisted with A. afarensis, highlighting early diversity in locomotion and diet among hominins.