Scientists Identify Lucy’s Long-Lost Neighbor as Australopithecus deyiremeda

Researchers Reassign Controversial Burtele Foot to a Distinct Tree‑Climbing Hominin

Lucy remains one of the most famous early human ancestors—catalogued as Australopithecus afarensis—and she walked the Afar region of Ethiopia more than three million years ago. For years, paleontologists debated the identity of nearby fossil material, especially a partial foot discovered in 2009 called the Burtele (BRT) foot. New analysis now links the BRT foot and nearby dental remains to a different species: Australopithecus deyiremeda.

The BRT foot was controversial because its anatomy did not match the classic A. afarensis foot. Some researchers argued it reflected variation within australopithecines; others suggested it belonged to a more primitive genus like Ardipithecus. Yohannes Haile‑Selassie and colleagues re‑examined the foot alongside dentognathic (tooth and jaw) material from the same geological horizon and concluded the remains most likely belong to A. deyiremeda.

“One of the reasons why the BRT foot [was] not assigned to A. deyiremeda…was the lack of diagnosable dentognathic specimens that could be directly compared with the holotype and paratype specimens of the species,” Haile‑Selassie writes in the Nature report.

The reassignment is supported by multiple anatomical features: an opposable, thumb‑like big toe that would aid grasping, strongly curved lesser toes suited to wrapping around branches, and a foot capable of hyperflexion—adaptations indicating a life more oriented to climbing than Lucy’s partly terrestrial A. afarensis. Dental traits from the same sites are also more primitive than those of A. afarensis, including patterns of incisor development more like great apes.

Isotope analyses of tooth enamel reveal ecological differences between the two species. While A. afarensis shows a mixed diet of C3 and C4 plant resources, A. deyiremeda appears to have relied more heavily on C4 plants—species adapted to hotter, drier environments. This suggests the two hominins occupied different ecological niches even as they lived in the same region.

These findings reinforce the picture of the mid‑Pliocene as a time of hominin diversity, with multiple forms experimenting with different combinations of arboreal skill and bipedal movement. Haile‑Selassie and colleagues stress that more postcranial fossils are needed to fully understand how and when human‑like, obligate bipedality evolved.

Why It Matters

The study clarifies an important anatomical puzzle and highlights that several bipedal adaptations could coexist with strong climbing abilities. By identifying the BRT foot with A. deyiremeda, researchers gain a clearer sense of how varied Pliocene hominins were—both in locomotion and diet—underscoring that human evolution was not a simple, linear path.