A mysterious foot fossil from 3.4 million years ago has been tied to a little-known human relative that lived alongside Lucy. New findings, incorporating additional fossils uncovered since the initial discovery, place the Burtele foot and accompanying jawbone squarely with Australopithecus deyiremeda, a more primitive lineage than Lucy’s Australopithecus afarensis, according to a study published November 26 in Nature.
If these conclusions hold up under further examination, Lucy—the iconic symbol of early human evolution—might lose some of her irreplaceable status within the family tree.
In 2009, paleoanthropologist Yohannes Haile-Selassie, then leading a team at Arizona State University, recovered eight foot bones from Burtele near Woranso-Mille in Ethiopia’s Afar region, within sediments dating to about 3.4 million years ago. The site sits near the area where Lucy’s partial skeleton was found back in 1974.
The researchers initially recognized the Burtele foot belonged to a different species because it featured an opposable big toe, a trait that would have aided grasping and tree climbing. Yet the fossil record at that time wasn’t enough to name a new species based on the foot alone.
Shortly after, Haile-Selassie’s team identified teeth and other fragments dating from roughly 3.33 to 3.59 million years ago, which, in 2015, were attributed to Australopithecus deyiremeda. This designation faced skepticism due to the relatively small number of fossils available at the time.
The newest study expands the fossil record for A. deyiremeda and formally includes the Burtele foot among its attributed remains. Lucy’s species was long believed to be the sole hominin occupying that 3.8–3.0 million-year window, but these discoveries demonstrate that two related species coexisted in the Woranso-Mille region, prompting questions about how they shared a landscape.
According to the study, A. deyiremeda walked upright, though its second digit—rather than the big toe—likely provided the main push-off during locomotion.
“Bipedality in these early ancestors manifested in multiple forms,” Haile-Selassie explained in a news release. “There wasn’t just one way to walk on two legs until much later.”
Isotope analysis of eight A. deyiremeda teeth offered a glimpse into their diet, revealing a reliance on trees and shrubs, contrasting with Lucy’s broader diet that included a variety of grasses. Haile-Selassie noted that the coexistence was plausible because the two species differed in locomotion and diet, reducing direct competition.
Fred Spoor of the Natural History Museum in London, who wrote a commentary accompanying the new study, welcomed the broader recognition of A. deyiremeda as a distinct species. He highlighted that incorporating this lineage into the human family tree could introduce unexpected twists that might even shift Lucy’s position in the lineage leading to Homo sapiens.
Lucy, at about 3.3 feet tall, had a face closer to an ape than to a modern human, and a brain roughly one-third the size of ours. Her discovery in 1974 provided the first strong evidence that upright walking existed around 3.2 million years ago and reinforced the idea that her species was a key ancestor for later hominins.
For decades, Lucy’s species was viewed as the sole common progenitor for later hominins. The newer discoveries, however, suggest a more complex picture in which multiple, contemporaneous species contributed to the evolutionary mosaic, challenging a straightforward, linear lineage that places Lucy at the root.
Spoor cautioned that these interpretations could alter the traditional narrative about descent, noting that A. anamensis may sit at the base of this family tree, from which at least three sister lineages emerged: A. afarensis, A. deyiremeda, and A. africanus. If correct, this would complicate the long-held view that a single lineage leads directly to later humans.
Some researchers, like Ryan McRae of the Smithsonian, described the study as an early step toward entertaining the possibility that Lucy’s species could be a side branch rather than an outright ancestor. He emphasized that more fossil findings are needed before declaring a definitive shift in the evolutionary story.
Haile-Selassie plans to return to Ethiopia and nearby regions to search for additional Australopithecus fossils, hoping to clarify how these species relate and to expand the known roster of specimens.
Further discoveries of A. deyiremeda and A. anamensis would help answer lingering questions about their connections and trajectories within the broader hominin family tree, ultimately painting a richer, more nuanced portrait of human origins.
