In a remarkable turn in the story of human origins, scientists have confirmed that a mysterious fossilized foot unearthed in Ethiopia belongs to a previously unknown ancient relative, Australopithecus deyiremeda. This discovery, published in Nature on November 27 and 28, 2025, offers a fresh perspective on the evolutionary landscape of our ancestors and challenges long-held assumptions about the singularity of our lineage.
The saga began in 2009, when researchers digging in Burtele, a site in northeastern Ethiopia, stumbled upon a fossil foot unlike any previously seen. For decades, the region was considered the exclusive domain of Lucy’s species, Australopithecus afarensis, thought to be the direct ancestor of modern humans. But the Burtele foot, with its opposable big toe resembling a human thumb, was a clear outlier. This feature pointed to a creature adept at climbing, suggesting a lifestyle spent largely in the trees—a stark contrast to the ground-roaming habits of Lucy’s kind.
It wasn’t until the recent discovery of additional fossils at the same site—a jawbone with 12 teeth—that scientists could finally assign the enigmatic foot to a species. According to NBC News, the analysis led researchers to identify the remains as belonging to Australopithecus deyiremeda, a species first named in 2015 but whose relationship to the Burtele foot had remained unproven until now.
John Rowan, an assistant professor of human evolution at the University of Cambridge, who was not involved in the study, described the team’s conclusion as “very reasonable.” In an email to NBC News, Rowan explained, “Now we have much stronger evidence that, at the same time, there lived a closely related but adaptively distinct species.”
This revelation upends the tidy narrative of human evolution as a straight ladder, where one species neatly gives rise to the next. Instead, as Ashleigh L.A. Wiseman of the McDonald Institute for Archaeological Research at the University of Cambridge noted, “human evolution wasn’t a straight ladder with one species turning into the next.” Rather, she likened it to a family tree, “with several so-called ‘cousins’ alive at the same time, and each having a different way of surviving.”
The team, led by Yohannes Haile-Selassie of Arizona State University, carried out a detailed analysis of the new fossils. A CT scan of the teeth suggested that A. deyiremeda was more primitive than Lucy’s species. Isotopic analysis of the teeth revealed a diet rich in leaves, fruit, and nuts—foods abundant in the forested environments the species inhabited. In contrast, Lucy’s species likely spent more time foraging on the ground, possibly consuming a more varied diet.
“These differences meant that they were unlikely to be directly competing for the same resources,” Wiseman told NBC News. The implication? Two closely related hominins coexisted in the same region, each carving out its own ecological niche. Haile-Selassie emphasized the significance of this in an interview with AFP, stating, “co-existence is deep in our ancestry.”
The Burtele foot’s grasping big toe is a particularly striking feature. As reported by The Jakarta Post, this adaptation allowed its owner to grab onto tree branches much like modern apes, underscoring a climbing lifestyle. This stands in contrast to Lucy, whose anatomy was better suited for upright walking on two legs, a key milestone in human evolution. The discovery, therefore, not only broadens our understanding of the diversity of early hominins but also hints at the varied experiments with bipedality—walking on two legs—that occurred during this pivotal period.
But the find has also reignited debate within the scientific community. When the species A. deyiremeda was first named a decade ago, skepticism abounded, largely due to the scarcity of fossils. Assigning a new species based on limited remains is always contentious. As The Jakarta Post noted, “attempts to add a new branch to the human family tree usually provoke fierce debate.” Yet, the latest trove of fossils, and the clear anatomical links between the foot and the jawbone, have swayed many experts. “There will always be sceptics, but I think these new finds, and their validation of older ones, will help many researchers to be more accepting of A. deyiremeda,” John McNabb, a palaeolithic archaeologist at the University of Southampton, told AFP.
For decades, Lucy’s species was the prime suspect in the search for our direct ancestor. However, the existence of A. deyiremeda complicates this picture. The new species is more primitive and has a less human-like foot, making it unlikely to dethrone Lucy as the leading candidate. Still, as Haile-Selassie pointed out, the discovery “adds a new player into the mix” and “opens this possibility that we might still find more species within that time period because it looks like the Australopiths were experimenting with bipedality.” He mused, “Could there be another species which could be a better candidate to be the ancestor of the genus Homo? We don’t know—it depends on what we find.”
Rowan echoed this uncertainty, telling NBC News, “Which species were our direct ancestors? Which were close relatives? That’s the tricky part. As species diversity grows, so do the number of plausible reconstructions for how human evolution played out.”
Wiseman also cautioned against drawing firm conclusions from the available evidence, noting that definitive species assignments should rest on well-preserved skulls and fossils from multiple associated individuals. While the new research strengthens the case for A. deyiremeda’s existence, she added, it “doesn’t remove all other alternative interpretations.”
Ultimately, the discovery of the Burtele foot and its association with Australopithecus deyiremeda paints a far richer, more complex portrait of our ancient past. Rather than a lone ancestor marching steadily toward modern humanity, we see a bustling landscape of relatives—some climbing, some walking, all experimenting with survival in their own way. The search for our true ancestor continues, but with each new find, the story grows more fascinating—and more human.
