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New fossil shows “Lucy” to have been steady on her feet

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lucy human ancestor foot bone modern walkingAt some point in the past five million years or so, our human ancestors traded in an arboreal existence for a dedicated two-legged life on the ground. A patchy fossil record, however, has frustrated researchers hoping to pinpoint the emergence of more modern human upright walking

Even the gait of the well-studied "Lucy" species, Australopithecus afarensis, has been the subject of some debate. Most of her 3.2-million-year-old skeleton suggests that Lucy was a fairly obligate biped, but without crucial foot bones, researchers could not confidently reconstruct the hominin’s stride.

Now, a newly described fossil foot bone might help solidify the case for A. afarensis‘s bipedal abilities. The fourth metatarsal, a pivotal bone for distinguishing human feet from ape feet, is the first of its kind to be described for the species. 

Uncovered in 2000 in Hadar, Ethiopia, the fossil is "nearly perfectly preserved," according to the researchers behind the new study, published online February 10 in Science. And the slim bone, less than 60 millimeters long, suggests the species had stiff arched feet—much more like those of Homo habilis and H. sapiens than like those of African apes or earlier hominins—better adapted to hoofing it on the ground than seeking refuge in the trees.

foot bone fossil from A. afarensis"Arches in the feet are a key component of human-like walking because they absorb shock and also provide a stiff platform so that we can push off from our feet and move forward," Carol Ward, of the pathology and anatomical sciences department at the University of Missouri, Columbia, and lead author of the new paper, said in a prepared statement. "Arches in our feet were just as important for our ancestors as they are for us."

Such a rigid foot stands in contrast to that of Ardipithecus ramidus, the 4.4-million-year-old hominin described in 2009. Although scientists are still debating how often "Ardi" would likely have walked upright, some of the specimens’ foot bones—including a large grasping great toe—point to a highly capable climber with flatter, more flexible feet.

The new analysis also supports the theory that A. afarensis was indeed the primate to have left the 3.6-million-year-old two-legged tracks in Laetoli, Tanzania.

"Now that we know Lucy and her relatives had arches in their feet, this affects much of what we know about them, from where they lived to what they ate and how they avoided predators," Ward said. "If we can understand what we were designed to do and the natural selection that shaped the human skeleton, we can gain insight into how our skeletons work today."

Image of foot placement courtesy of Kimberly A. Congdon/Carol Ward/Elizabeth Harman; image of side views of fossil courtesy of Science/AAAS

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  1. 1. lennyshelby 12:57 pm 02/11/2011

    your last statement: "If we can understand what we were designed to do and the natural selection that shaped the human skeleton, we can gain insight into how our skeletons work today."

    you used the word "designed". do you believe in design, or a Designer/Creator? if not, are you saying that a random mutation such as arched feet, would have forced a subject to no longer be a tree-dweller like the rest of her species, and would have forced her to live on the ground more and adapt to a totally new lifestyle?

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  2. 2. Telrunya 3:55 pm 02/11/2011

    Nice slant SciAM. Emphasis on slant though. Not everyone agrees with this assessment. William Harcourt-Smith, from the City University of New York and the American Museum of Natural History, disagrees with Ward and DeSilva.

    "You look at this one bone, it looks very humanlike, and you can’t disagree with the analysis, but it only tells part of the story," Harcourt-Smith told LiveScience. "If you want to know how it [Australopithecus] walked around you have to look at all of the evidence available."

    Lets take a look at the knuckles and enlongenated hands. Let’s take into account that this bone is not the most indicative of an arch. Let’s take into account this isn’t corroborated by another fossil.

    You can’t make a rule from one example. There are far too many unknowns and yet SciAm is printing it as if it’s a universally accepted truth in the scientific community when it is far from that.

    SciAm: one word. Perspective. Get some

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  3. 3. karlt10 11:41 pm 02/13/2011

    Telrunya, if you read the above piece and interpret it as being SciAm, or it’s writer, as having made (a) conclusion, you’ll have to explain just how. The piece is a report of findings by others; it is not the conclusion of a study performed by SciAm.

    Telrunya; two words: Reading comprehension. Learn it.

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  4. 4. Telrunya 1:31 pm 02/15/2011

    I comprehend quiet well Karl. I comprehend that you have no real reply to my statements so you must resort to flaming. If you read through all the articles ever printed by SciAm reguarding evolution and you dont see an editorial slant then I suggest you are the one who needs a little comprehension training. If this were a balanced article then they would have printed the fact that there are those in the scientific community that disagree with the findings of these others as I pointed out in my OP. I return it to you. Prespective. Get some

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