A mysterious foot fossil discovered in Ethiopia many years ago belongs to a mysterious and controversial human relative who lived at the same time as our ancestor Lucy, a new study has revealed.
This discovery took many years. In 2009, scientists discovered a 3.4-million-year-old foot fossil with toes designed for living in trees. Newly discovered fossilized teeth and jawbones near the so-called Bartele’s Foot suggest that Lucy’s species, Australopithecus afarensis, lived side-by-side with another now extinct human relative, Australopithecus deiremeda, which lived about 3.5 to 3.3 million years ago.
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But like Lucy, oh. Deiremeda walked on two legs on land, showing that different humans living at the same time moved very differently from each other.
“What we’re learning now is that while bipedalism was certainly an important part of our evolutionary history, there were many ways to walk on two legs on land,” study lead author Johannes Haile Selassie, paleoanthropologist and director of the Institute of Human Origins at Arizona State University, told Live Science.
He said there had been “many experiments with bipedalism” in which different elements of the feet, pelvis and leg bones evolved at different rates and times.
Until the discovery of Bartele’s feet, humans were thought to have been fully bipedal by Lucy’s time, as she had a big toe that lined up with the other four toes. However, the adult Bartele’s feet have long, curved toes that are used for grasping tree branches.
Researchers previously also discovered a jawbone with teeth at the same location in Ethiopia. However, it was unclear whether these fossils belonged to the same species as Brutere’s foot, as it was unclear whether they came from the same time period.
In 2015, Au. deiremeda was named based on this jawbone and other features. However, the new species caused controversy because the shape and size of its teeth resembled Lucy and an older hominin, Australopithecus anamensis.
Meanwhile, Haile Selassie said the species of Brutere’s leg was unknown for many years because a skull is required for species designation. So he and his team returned to the Wolanso Mil site in the Afar region to search for more fossilized remains.
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Researchers found 13 new teeth and jaw fossil fragments of the same age near where Bartele’s foot was found. When compared with tooth remains from other hominid species, these were “confidently” attributed to gold. Dayremeda, the researchers write in a new study. The researchers believe the teeth and feet belong to the same species because of their similar age and location.
Chemical analysis of the tooth enamel revealed both Lucy’s seeds and gold. Dayremeda called Wolanso Mir home, they did not have to compete for resources. ah. Daylemeda lived in forest environments and fed mainly on trees and shrubs, while Au fed mainly on trees and shrubs. afarensis had a wide range of diets and lived in more open habitats.
“I think this is the best way for differences in diet and differences in exercise adaptation to coexist,” said Haile Selassie. “Is that surprising? Probably not, because we know that today’s modern primates, closely related primates, live together in the same areas.”
controversial coexistence
Reaction to Au-affiliated Brutele foot. Dayremeda was mixed.
Zelai Alemseged, a paleoanthropologist and professor of organismal biology and anatomy at the University of Chicago who was not involved in the new study, is not convinced that the foot and tooth remains are from the same species. He pointed out that this association is based on circumstantial evidence: proximity in time and space.
Alemseged told Live Science that if Au. Dilemeda is a separate species, and for him it is unclear whether it belongs to the genus Australopithecus or a late survivor of the older genus Ardipithecus, which is now known to have lived until about 4.4 million years ago.
However, other experts agree that Lucy and her species shared the landscape with this other australopithecine species. Oh said Jeremy DeSilva, a biological anthropologist at Dartmouth College who was not involved in the study. “They’re distinctive anatomically, but what’s more valuable to me is how distinctive they are behaviorally, such as being more selective about what they eat and spending more time in trees,” Deiremeda said.
In fact, de Silva is now a convert and believes that A. deiremeda is a separate species and that the foot belongs to it. “Australopithecus deiremeda has always been next to a question mark for me since it was first proposed as a species,” he told Live Science. “That’s not the case anymore. The question mark is gone.”
“For me, this paper is a ‘welcome to the family tree’ to Australopithecus deiremeda,” DeSilva added. “Right now we have our hands full trying to figure out where this fits.”
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