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No lead - toeing around it , this foot bone could change the story of human evolution , or at least the story of human groundwork evolution .
The ivory is extra grounds thatAustralopithecus afarensis , an ancient human root who go around 3 million year ago , spent most of its clip walking , instead of climb trees like Pan troglodytes .
The “first family” excavation site in Hadar, Ethiopia, where the foot bone was discovered.
" Lucy and her congener were bipedal , but there had been a disputation as to how versatile they were in the trees , " said lead investigator Carol Ward , at the University of Missouri in Columbia , referring to the most famousA. afarensismember nicknamed Lucy after a Beatles song . " If they did climb in the trees , they would n’t have been able to do it any well than you or I would . "
One human origins expert does n’t corrupt the conclusions , however , sayingother Lucy - aged bonespoint to a combining of tree climbing and undercoat walking .
infantry bone
The fossilized arch bone, called the fourth metatarsal, thought to belong to an early human ancestor and discovered in Hadar, Ethiopia.
The osseous tissue in question belonged to one of Lucy’sA. afarensiskin who give way about 3.2 million years ago . It was discovered in Hadar , Ethiopia , on a plateau so fertile with fossils from this earned run average that it ’s called the " first kinsperson site . "
The bone comes from the exterior of the foot , near the little finger toe , and is a stiff part of the arch bone that act like a lever when walking on two feet .
arch were an important part of our evolution into humans , because they make climbing tree diagram much harder . The arches on the inside of the foot , nearer to the big toe , serve as a jolt absorber when we plant our invertebrate foot back on the footing . All other living prelate havefeet made for prehension and bendingto hang up onto tree branches and their new , more like our hands than our metrical foot .
Fourth-metatarsal bone Bones of a human foot showing the arched configuration and the location of the fourth metatarsal (the type of bone thought to belong to an early human ancestor some 3.2 million years ago).
Their analyses revealed the ivory matched up best with human foot bones , suggesting , Ward said , that Lucy and herAustralopithecuskin would have spent time in the tree only when chased there by predators or to harvest nutrient from its arm . " Selection was n’t favoring the ability to be effectual in the trees , it was favoring being effectual on the priming coat , " Ward said .
" That ’s a braggy deal because that think arches , and not just precursors , material full - grown arches , go back three , three and a one-half million twelvemonth , " said Jeremy DeSilva , from Boston University , who was not involved in the study . " It really helps us understand this unambiguously human feature , this arch . "
Down from the tree
An inkling of Lucy ’s saunter came in 1976 , when scientist discovered footprints in volcanic ash left behind 3.5 million years ago by three fauna in Laetoli , Tanzania . Though the footprints had distinguishable arches , figuring out who made themwas tricky and has been long debated in the archeological earth .
And only a few arch bones from early humans have been found , making it difficult to make up one’s mind if Australopithecus had arches .
" Those of us who exploit on feet and other human foot morphology , arches have been tough because they are soft tissue , and they do n’t really fossilize , " DeSilva , who contemplate motivity in the earliest copycat and early human ancestors , told LiveScience . " What you bet for are haggard hints , or correlates of the presence of an arch , and as a orbit we have n’t really been able to agree on what those are . "
Scientists do n’t have a very clear grasp on how bones develop , either , DeSilva state . Use of bone during motion can influence the bone staging laid down by gene during development . And so it ’s tough to sequester features of these fossilized bones that would ’ve been the result of the walk style of a few individuals versus an adaptation that develop in a group of organisms .
Butprevious studiesof ankle , toe and heel finger cymbals convinced DeSilva . " I would n’t say that from a individual metatarsal [ foot bone ] you could restore the entire motive power of an animal , but from all of the other evidence that ’s been presented from the waist down , they were obligate baby-walker , " DeSilva said .
" These thing are move very standardized to the way we are , the way we do today and they were not spending much metre up in the tree diagram , " DeSilva said , though he observe that there are differences in the pelvic region that suggest Lucy and her kin might have walk with a slimly unlike pace .
Or still hanging around ?
But this novel grounds has n’t swayed everyone .
William Harcourt - Smith , from the City University of New York and the American Museum of Natural History , disagrees with Ward and DeSilva . Though he read the analytic thinking of the off-white is well - done , he still believes that Lucy could have spend as much as 50 pct of her clip climbing , and would have been comfortable in the trees .
" You front at this one bone , it appear very anthropomorphic , and you ca n’t disagree with the analysis , but it only tells part of the history , " Harcourt - Smith told LiveScience . " If you want to bed how it [ Australopithecus ] walk around you have to look at all of the evidence available . "
Harcourt - Smith also notes that a bone from the inside of the foot , where the arch is the strong , would be more convincing . When Harcourt - Smith look at other function of Australopithecan anatomy , including its curved toe bones and another ft osseous tissue send for the navicular bone , he comes to unlike conclusions .
" It [ Ward ’s osseous tissue ] is obviously quite anthropomorphic , " Harcourt - Smith said . " But you look at the other bone and you have a mosaic of adaptive feature , " think of feature for Sir Herbert Beerbohm Tree climbing as well as take the air on the reason .
DeSilva observe thatAustralopithecusdoes have climb adaptations , including indication of a strong upper eubstance , which would have encouraged climbing , but which he say could also be used as adaptations to carry food or babies when walk on two understructure .
" They have their own interesting version and shape and peculiar single which have been difficult to calculate out if they are evolutionary carryovers or if they are adaptations , " DeSilva said . " These are not scale - down humans . "
An analysis of the off-white will be publish in the Feb. 11 emergence of the diary Science .
you may adopt LiveScience Staff Writer Jennifer Welsh on Twitter @microbelover .
