‘Lucy’ was not alone: ​​a mysterious foot from 3.4 million years in the past complicates human evolution | Science | EUROtoday

There are solely eight bones, however they complicate the already complicated historical past of human evolution. In 2009, fragments of the foot of a person who walked upright virtually 3.4 million years in the past had been found on the Woranso-Mille website (Afar, Ethiopia). It was believed that solely Australopithecus afarensisgroup to which he belonged Lucythought of the frequent ancestor of the upright primates that got here later, together with people. Its discoverers didn’t know what species that foot belonged to, however they had been certain that it was not the species of the Grandma Lucy. The skepticism of paleoanthropologists was such that the foot remained an orphan till now. A piece revealed this Wednesday in Nature and led by the identical one who found these eight bones, he discovered an proprietor: it was one other kind of australopithecus (I do not say Australopithecus). and lived with Lucyand he was bipedal like her, however he nonetheless confirmed a love for bushes.

“This work is supported by new findings that clearly associate the foot with a A. I don’t say“, says the director of the Institute of Human Origins and professor at Arizona State University (United States), Yohannes Haile-Selassie, in an interview. In 2015, his group found a large number of teeth, a maxilla and incomplete jaws of a new species of australopithecus that they named I don’t say. In the Afar language of the region, it means something like close relative. The relevance of that discovery was that it was included in the list of possible ancestors of all humans. Haile-Selassie was convinced that the foot must have belonged to one of those close relatives, but he was unable to draw the dotted line until this new work.

Thanks to the new consignment of teeth, especially an almost complete jaw from a young individual who still had baby teeth, the 2009 foot is now seen in a different light. Among paleontologists and anthropologists there is a kind of unwritten law: without a new skull, it is difficult to accept a new species. But by combining the foot with what was discovered in 2015 and the new remains, its discoverers can tell much more about the A. I don’t say. The eight bones of the limb, in particular more elongated phalanges and the portion of the big toe that they found, which is reminiscent of that of chimpanzees, indicate that it walked on two legs, but was still arboreal. And this is reinforced by the study of his teeth.

“Teeth give us a lot of information,” summarizes the researcher on the University of Michigan (United States) and co-author of the research, Naomi Levin. The relationship of the stays of A. I do not say present in three totally different locations, however all a number of kilometers from Hadar, the place the skeleton of Lucysignifies that they coincided in time and house. “However, the chemistry of the teeth shows that these two closely related hominids had different behaviors, although their development was similar,” Levin continues in an e-mail.

The analysis of the carbon isotopes present in the enamel reveals that the afarensis Not only did they eat a greater variety of foods, but many of them already came from the soil, grass, grasses, etc. Meanwhile, the teeth of the I don’t say They suggest that they still fed on leaves and fruits, that is, up the tree.

Haile-Selassie maintains that there were two species coexisting, although they had different locomotor adaptations. “Now we are able to affirm that the A. y A. I do not say They had been neighbors, however they did various things.” With differentiated mobility and diet, both lineages were able to coexist without having to compete, that is, without having to kill each other. Otherwise, “one of many two would have grow to be extinct,” concludes Haile-Selassie.

Geologist Lluís Gibert, from the University of Barcelona, ​​has been accompanying Haile-Selassie in his excavations in northern Ethiopia for years. Co-author of the new work, remember that fossils are found within sediments and those sediments indicate what the environment was like. “The evolution of the physical environment is what conditions human evolution,” he highlights. “Africa was splitting in two,” Gibert recalls. “This rupture process conditioned the evolution of the landscape, going from a more jungle-type forest environment, like the one where gorillas currently live, to another savannah type.” It is in that transition, in that place, where the roots of human evolution would be.

To know the role that the owner of that foot had in this evolution, they lack the head. It is summarized by Fred Spoor, from the Natural History Museum in London, in a comment he makes to the study also published in Nature. “Attributing limb or trunk bones to a species is a matter of probability, unless they are part of an individual skeleton that preserves diagnostic features of the species, which are usually restricted to the skull,” he writes.

Even more skeptical is Leslea Hlusko, a paleobiologist at the National Center for Research on Human Evolution (Cenieh) and a great expert on the dental variation of early hominids. Your first objection has to do with bipedalism. “The dilemma lies within the issue of conclusively decoding the angle of the massive toe from the bottom of the foot, utilizing solely the metatarsal. You want the bone with which it articulates: the cuneiform,” he says in an email. And they have not yet found these bones in Woranso-Mille.

“It would be extraordinary to have two almost identical-looking apes living next to each other without interbreeding,” acknowledges Hlusko, something that has not been seen “in current primates, which is why I am extremely skeptical of all these interpretations of extreme biological diversity,” she adds. Although the Cenieh scientist highlights the new findings, she remembers that “fossil evidence is the only information we have about the appearance of these animals and to determine when and where they lived.” And he concludes about the new work: “It doesn’t give us any new perspective on the biology of our ancestors 3.5 million years in the past; for that, we nonetheless want extra fossils.” We should wait till they discover a cranium of a A. I do not say.