Prehistoric foot bones finally linked to our early ancestors
In a groundbreaking discovery that sheds light on human evolution, paleoanthropologists have finally linked a mysterious foot bone found in Ethiopia to the extinct species Australopithecus deyiremeda, one of humanity’s oldest known evolutionary relatives. This revelation comes after 16 years of research, beginning with the initial discovery of the Burtele foot in 2009 at the Woranso-Mille paleontological site. Although the foot was identified as human-like, its exact species remained elusive until recent studies provided clarity. The findings, published in the journal *Nature* on November 25, reveal that A. deyiremeda co-existed with the famous hominin species Australopithecus afarensis—best known for the iconic fossil named Lucy—approximately 3.4 million years ago.
The Burtele foot, characterized by its unique anatomical features, offers significant insights into the evolution of bipedalism. Unlike its more advanced relatives, A. deyiremeda possessed a more primitive foot structure, including an opposable big toe that facilitated climbing while still allowing for bipedal locomotion on the ground. This contrasts with modern humans, as A. deyiremeda’s walking style relied on the momentum generated by its second toe. According to Arizona State University’s Yohannes Haile-Selassie, a co-author of the study, this discovery underscores the complexity of early human locomotion, suggesting that there were multiple ways of walking upright among our ancestors. The research also indicates that A. deyiremeda and A. afarensis shared the same geographic region without competing for resources, hinting at a diverse ecosystem that allowed both species to thrive.
The study of the Burtele foot not only enhances our understanding of early human evolution but also highlights the significance of fossil evidence in reconstructing the past. As researchers continue to uncover new findings, they are reshaping the narrative of how human ancestors adapted to their environments. This discovery emphasizes the importance of interdisciplinary collaboration in paleoanthropology, as scientists combine fieldwork with advanced laboratory analysis to piece together the intricate puzzle of human ancestry. The ongoing exploration of Ethiopia’s rich fossil record promises to reveal even more about our evolutionary journey, offering a deeper appreciation for the diverse adaptations that have shaped the story of humankind.
Sixteen years ago, paleoanthropologists stumbled upon an errant foot bone at a dig site in Ethiopia. It was clearly human-like, but which species it belonged to remained a mystery. Now, we finally know that the foot belongs to one of humanity’s
oldest known evolutionary relatives
. The 3.4-million-year-old bones belong to the now extinct
Australopithecus deyiremeda
.This opposable-toed ape co-existed with the same hominin species as one of our
most famous ancestors–Lucy
. The findings are detailed in a study published on November 25 in the journal
Nature
.
The Burtele foot (left) and the foot embedded in an outline of a gorilla foot. Credit: Yohannes Haile-Selassie / Arizona State University
Feet first
In 2009, paleoanthropologists discovered the initial eight unidentified fossils—collectively referred to as the
Burtele foot
, at the Woranso-Mille paleontological site in Ethiopia’s Afar Rift. Researchers announced their findings in 2012, but while they knew the bones didn’t belong to the hominin species
A. afarensis
, they couldn’t pinpoint exactly which species the errant foot belonged to. What’s more, they weren’t ready to identify the hominin based on foot bones alone.
“It is not common practice in our field to name a species based on postcranial elements–elements below the neck–so we were hoping that we would find something above the neck in clear association with the foot,” Arizona State University paleoanthropologist and study coauthor Yohannes Haile-Selassie
said in a statement
. “Crania, jaws and teeth are usually the elements used in species recognition.”
Although researchers previously discovered teeth near the site of Burtele foot, they weren’t entirely certain that they originated from the same sediment layers. Three years later, Haile-Selassie’s team
announced the discovery of
A. deyiremeda
nearby based on additional fossils. These new finds still did not include examples of the species’ feet. However, after a decade of additional excavation work and laboratory analysis, Haile-Selassie and his team are now confident the Burtele foot discovered in 2009 belongs to
A. deyiremeda
.
Standing up on two feet
In terms of evolutionary development,
A. deyiremeda
possessed a more primitive foot than those belonging to Lucy and her
A. afarensis
family. While the Burtele foot still has an opposable big toe vital for tree climbing, it allowed
A. deyiremeda
to still walk on two legs while on the ground. But unlike
Homo sapiens
,
A. deyiremeda
’s bipedal walking relied on the momentum generated using its second digit.
Haile-Selassie explained that the foot’s form was particularly striking given what they know about
Ardipithecus ramidus
, an early predecessor of both
A. deyiremeda
and
A. afarensis
.
“The presence of an abducted big toe in
Ardipithecus ramidus
was a big surprise, because at 4.4 million-years-ago there was still an early hominin ancestor which retained an opposable big toe, which was totally unexpected,” he said. “Then 1-million-years later, at 3.4-million-years ago, we find the Burtele foot, which is even more surprising.”
With the revised fossil record, Haile-Selassie said that paleoanthropologists now know early human bipedality “came in various forms.”
“The whole idea of finding specimens like the Burtele foot tells you that there were many ways of walking on two legs when on the ground, there was not just one way until later,” he added.
Remarkably, the recent fieldwork and radiocarbon dating further confirms that
A. deyiremeda
and
A. afarensis
co-existed in the same geographic area. Given their differing anatomies and diets, they were able to do so without pushing either species towards extinction.
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Prehistoric foot bones finally linked to our early ancestors
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