New evidence from Ethiopia suggests that multiple hominin species, including the recently identified Australopithecus deyiremeda, lived side-by-side roughly 3.4 million years ago. The discovery, centered on remarkably well-preserved foot bones, reshapes our understanding of early human evolution and challenges the notion of a strictly linear progression of species.
The Burtele Foot: A Mystery Solved
In 2009, researchers led by Yohannes Haile-Selassie unearthed eight hominin bones forming a right foot at the Burtele site in Ethiopia’s Afar region. This “Burtele foot” stood out due to its gorilla-like opposable big toe – a feature indicating arboreal climbing ability. Initial analysis made it clear the foot didn’t belong to the better-known Australopithecus afarensis (the species of “Lucy”), prompting a search for its true owner.
The puzzle centered on whether the foot belonged to another Australopithecus species or a more primitive genus, Ardipithecus, which predated Australopithecus by over a million years. The discovery of jaw and teeth remains from the same location in 2015 led to the naming of a new species: Australopithecus deyiremeda. While suspected to be the foot’s owner, age discrepancies initially prevented definitive confirmation.
Confirmation Through Fossil Evidence
Further excavations in 2016 yielded a lower jawbone of A. deyiremeda just 300 meters from the original foot discovery, and at the same geological age. This established conclusively that the Burtele foot belonged to A. deyiremeda.
Dietary Differences and Peaceful Coexistence
Analysis of carbon isotopes in A. deyiremeda teeth revealed a diet primarily based on tree and shrub vegetation. In contrast, A. afarensis teeth suggest a preference for grasses. This dietary divergence implies minimal competition for resources, supporting the hypothesis that the two species coexisted peacefully in the same environment.
Haile-Selassie suggests that A. deyiremeda may have spent time in trees while A. afarensis roamed the grasslands nearby, minimizing direct conflict. This challenges the long-held belief that early hominin evolution was strictly linear, with one species always replacing another. The new evidence demonstrates that multiple closely related species thrived concurrently, even in close proximity.
Implications for Human Evolution
This discovery broadens our understanding of human ancestry. It suggests that coexistence, rather than constant competition, may be deeply ingrained in our evolutionary history. As Carrie Mongle of Stony Brook University notes, the findings are vital for gaining a more complete picture of hominin diversity during the Pliocene era.
The evidence underscores that human evolution was not a simple ladder, but a complex, branching bush with multiple species sharing the landscape for extended periods.
