Researcher Stephanie Melillo holds the fourth metatarsal of the Burtele partial foot right after its discovery. The team found eight bones from the front half of a right foot. Such hominin fossils are rare, because they are fragile and are often destroyed in the face of carnivores and decay.
Image: The Cleveland Museum of Natural History. Photo courtesy: Yohannes Haile-Selassie
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A fossil discovered in Ethiopia suggests that humans' prehistoric relatives may have lived in the trees for a million years longer than was previously thought.
The find may be our first glimpse of a separate, extinct, branch of the human family, collectively called hominins. It also hints that there may have been several evolutionary paths leading to feet adapted for walking upright.
The fossil, a partial foot, was found in 3.4-million-year-old rocks at Woranso-Mille in the Afar region of Ethiopia. Bones of the hominin Australopithecus afarensis — the species to which the famous 'Lucy' skeleton belongs — have also been found in this location and from the same period.
But unlike Au. afarensis, the latest find has an opposable big toe — rather like a thumb on the foot — that would have allowed the species to grasp branches while climbing. Modern apes have similar toes, but the youngest hominin previously known to have them is Ardipithecus ramidus, which lived about 4.4 million years ago. The details of the discovery are published today in Nature.
Au. afarensishas a big toe that is more closely aligned with the other digits on the foot, an adaptation that provides support during upright walking. Au. afarensis "was fully bipedal and had already abandoned life in the trees", says study author Yohannes Haile-Selassie of the Cleveland Museum of Natural History in Ohio, whereas the newly discovered creature had not seemingly committed to life on the ground.
Other features of the fossil foot show that it did not belong to an ape, but that it is truly a member of the hominins, says Haile-Selassie. The latest specimen is "very much like the Ardipithecus foot, which I believe had many hominin features, so it's likely to be a hominin", agrees Daniel Lieberman, an anthropologist at Harvard University in Cambridge, Massachusetts, who was not involved in the study.
Good grasp of history
The discovery shows that one hominin lineage had grasping feet for at least a million years after Ar. ramidus. The creature was probably more agile in the trees than Au. afarensis but less nimble on two feet, says William Harcourt-Smith, an anthropologist at the City University of New York's Lehman College. "We can only get a tantalizing glimpse at this, but its bipedal gait is likely to have been very different from Lucy's and was probably a lot less efficient," he says.
The finding will force a rethink regarding the course of early hominin evolution, Harcourt-Smith adds. The addition of a mystery hominin species at this crucial time period suggests that the new species' lineage split from that leading to Lucy earlier in hominin history, and provides further evidence against the idea that modern humans evolved via a linear progression of species from apes. "This [finding] is fascinating, and makes the evolution of this defining behavior not a single, linear evolutionary event, but a far more complex affair," Harcourt-Smith says.
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13 Comments
Add Comment"The addition of a mystery hominine species at this crucial time period suggests that the new species' lineage split from that leading to Lucy earlier in hominine history"
Reply | Report Abuse | Link to thisAnother possibility is that this new species is an intermediate between Aridpithecus & Australopithecus that managed to hang on for a while after the Australopithecines emerged.
The more the merrier! : )
Reply | Report Abuse | Link to thisPerhaps it's just another species of monkey that went the way of so many, and not any relation to Humans?
Reply | Report Abuse | Link to thisIt's becoming more and more apparent that evolution was experimenting with more hominin lines at the same period of time that we ever thought. Another nail in the straight-line version of human evolution.
Reply | Report Abuse | Link to thisI would like to see confirmation of the " Long Ear " . I believe they dominated earth during the construction of the sphinx etc.
Reply | Report Abuse | Link to thisancient humans had feet like those of an ape not
Reply | Report Abuse | Link to thisancient humans had feet like an ape
Perhaps the hominin's native ecological niche in the rain forest became sparse, and overpopulation drove some to commute among island forests, still living in the trees but commuting through grassy plains. These conditions would favor a foot adapted for both walking upright and tree climbing.
Reply | Report Abuse | Link to thisLater the grasslands might have overtaken the forests, favoring the Lucy foot - better optimized for upright walking.
BTW, the Nature video was clear and informative. Thanks for not using any annoying video editing effects to zoom in & out, speed up, etc., although you might have lost some of the potential audience...
Reply | Report Abuse | Link to thisApparently the lessons from A. Sediba haven't sunk in yet. An individual can be a mosaic of mismatched features. For all we know this individual could look quite modern except for some really funny looking feet. (overstated--but you get the point.)
Reply | Report Abuse | Link to thisTo take back a bit of my own critique--I read the article and commented before viewing the video. The video is very good and expresses a more conservative opinion of what can be learned from the fossil.
Reply | Report Abuse | Link to thisMost modern humans can pick up a pencil with their toes, if they haven't crippled their feet with high heels.
Reply | Report Abuse | Link to this"Later the grasslands might have overtaken the forests, favoring the Lucy foot - better optimized for upright walking."
Reply | Report Abuse | Link to thisOr the "mystery hominine" evolved during an early phase of the "savannah-fication" of the forest, when an intermediate foot would be advantageous in an environment that was sort-of-woodsy & sort-of-grassy. And Au. afarensis emerged later, when the savannah had (almost) completely taken over, so the climbing foot was no longer beneficial.
"Ancient Human Had Feet Like an Ape"
Reply | Report Abuse | Link to thisDuh, it was an ape.