On their own 2 feet: 3.2 million-year-old fossil foot bone supports humanlike bipedalism in Lucy's species

Feb 10, 2011
This image shows the position of the fourth metatarsal Australopithecus afarensis (AL 333-160) recovered from Hadar, Ethiopia, in a foot skeleton. Credit: Carol Ward/University of Missouri

A fossilized foot bone recovered from Hadar, Ethiopia, shows that by 3.2 million years ago human ancestors walked bipedally with a modern human-like foot, a report that appears Feb. 11 in the journal Science, concludes. The fossil, a fourth metatarsal, or midfoot bone, indicates that a permanently arched foot was present in the species Australopithecus afarensis, according to the report authors, Carol Ward of the University of Missouri, together with William Kimbel and Donald Johanson, of Arizona State University's Institute of Human Origins.

The research helps resolve a long-standing debate between paleoanthropologists who think A. afarensis walked essentially as modern humans do and those who think this species practiced a form of locomotion intermediate between the quadrupedal tree-climbing of chimpanzees and human terrestrial . The question of whether A. afarensis had fully developed pedal, or foot, arches has been part of this debate. The fourth metatarsal described in the Science report provides strong evidence for the arches and, the authors argue, support a modern-human style of locomotion for this species. The specimen was recovered from the Hadar locality 333, popularly known as the "First Family Site," the richest source of A. afarensis fossils in eastern Africa, with more than 250 specimens, representing at least 17 individuals, so far known.

"This fourth metatarsal is the only one known of A. afarensis and is a key piece of evidence for the early evolution of the uniquely human way of walking," says Kimbel. "The ongoing work at Hadar is producing rare parts of the skeleton that are absolutely critical for understanding how our species evolved."

Humans, uniquely among primates, have two arches in their feet, longitudinal and transverse, which are composed of the midfoot bones and supported by muscles in the sole of the foot. During bipedal locomotion, these arches perform two critical functions: leverage when the foot pushes off the ground and shock absorption when the sole of the foot meets the ground at the completion of the stride. Ape feet lack permanent arches, are more flexible than human feet and have a highly mobile large toe, important attributes for climbing and grasping in the trees. None of these apelike features are present in the foot of A. afarensis.

Paleoanthropologists report in the Feb. 10 edition of Science on the recovery of a fossilized foot bone recovered from Hadar, Ethiopia, locality 333, popularly known as the "First Family Site," the richest source of Australopithecus afarensis fossils in eastern Africa. Credit: Donald Johanson/Institute of Human Origins/Arizona State University

"Understanding that the foot arches appeared very early in our evolution shows that the unique structure of our feet is fundamental to human locomotion," observes Ward. "If we can understand what we were designed to do and how natural selection shaped the human skeleton, we can gain insight into how our skeletons work today. Arches in our feet were just as important for our ancestors as they are for us."

This species, whose best-known specimen is "Lucy," lived in eastern Africa 3.0𔃁.8 million years ago. Prior to A. afarensis, the species A. anamensis was present in Kenya and Ethiopia from 4.2 to 4.0 million years ago, but its skeleton is not well known. At 4.4 million years ago, Ethiopia's Ardipithecus ramidus is the earliest human ancestor well represented by skeletal remains. Although Ardipithecus appears to have been a part-time terrestrial biped, its foot retains many features of tree-dwelling primates, including a divergent, mobile first toe. The of A. afarensis, as with other parts of its skeleton, is much more like that of living humans, implying that by the time of Lucy, our ancestors no longer depended on the trees for refuge or resources.

This is the fossilized foot bone -- fourth metatarsal of Australopithecus afarensis (AL 333-160) -- recovered from Hadar, Ethiopia. Credit: Elizabeth Harmon/Arizona State University

The Hadar project is the longest running paleoanthropology field program in the Ethiopian rift valley, now spanning more than 38 years. Since 1973, the fieldwork at Hadar has produced more than 370 fossil specimens of Australopithecus afarensis between 3.4 and 3.0 million years ago – one of the largest collections of a single fossil hominin species in Africa – as well as one of the earliest known fossils of Homo and abundant Oldowan stone tools (ca. 2.3 million).

Through ASU's Institute of Human Origins, the Hadar project plays an important role in training Ethiopian scholars by offering graduate degree and postdoctoral opportunities in the U.S. Promotion of local awareness of the global scientific importance and Ethiopian cultural heritage value of the Hadar site is also a project priority. Additionally, the fundraising phase of a planned "Hadar Interpretive Center" at Eloaha town, 30 kilometers from the site, was successfully completed in January 2011.

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jmcanoy1860
4.1 / 5 (9) Feb 10, 2011
Interesting study. Most interesting is the number of specimens which have been recovered. Of course, beating the creationists here is always a plus.
kevinrtrs
1.5 / 5 (17) Feb 10, 2011
"If we can understand what we were designed to do and how natural selection shaped the human skeleton, we can gain insight into how our skeletons work today

If evolutionists ever get to understand what humans were DESIGNED to do they'll have to acknowledge the existence of a superintelligent creator - and that could be extremely problematical. So maybe it's best that evolutionists do NOT get to such an understanding.

I have to repeat this mantra: The theory absolutely forbids DESIGN. So will the researchers please find some other words thru which to express their intentions?

As for the finding - that there is a uniquely human trait [double arches] with no corresponding ancestor located yet should surely by now have raised more than just a mild suspicion that there simply isn't ANY? We were designed and created by a mastermind so superior it's unfathomable.
JRDarby
4.2 / 5 (5) Feb 10, 2011
You have to repeat your mantra because without that you might see how unreasonable you're being. The fact that we don't know of an ancestor with double arches raises absolutely no problems for evolutionary theory because evolution by genetic mutation through natural and sexual selection explains it perfectly. A cosmic designer doesn't have any explanatory power at all. Where with evolution you can say both how generally and specifically a phenomenon occurred, with a cosmic designer it's just nebulous magic--especially if you think that one cannot work through evolution.
T2Nav
4 / 5 (4) Feb 10, 2011
I am confused about this magical fellow that DESIGNED us-- who designed him?
scenage
3.5 / 5 (2) Feb 10, 2011
The classic Chicken or the Egg paradox.
Eventually you'll get to what came before the big bang. To be honest, I'm going with both arguments. God / being of some sort, set in motion something that would allow us to evolve to as we are. Now that we're all happy, lets get back to talking about bipedalism and what this means.
SgntZim
5 / 5 (1) Feb 10, 2011
I'm not a scientist so please don't jump down my throat. I thought we diverged from apes about 4mya. Has anyone got a good link I could look at to describe the time-scale?
Skultch
4.2 / 5 (5) Feb 10, 2011
there simply isn't ANY?


So, there's a trait we haven't found yet, so we should throw out the whole theory. In that case, I guess you'll be quick to reply that you no longer think your god exists since there's no evidence of the flood he created.

When was the flood, Kevin?

Oh, yeah...you only do drive-byes now.

Coward.
gvgoebel
4.3 / 5 (6) Feb 10, 2011
If evolutionists ever get to understand what humans were DESIGNED to do they'll have to acknowledge the existence of a superintelligent creator - and that could be extremely problematical.


Problematic? I wouldn't have the LEAST problem in accepting the existence of the Flying Spaghetti Monster. I would be absolutely pleased to find out that, as I have always suspected, the Universe really DOES have a sense of humor.

malapropism
4.5 / 5 (4) Feb 10, 2011
I have to repeat this mantra: The theory absolutely forbids DESIGN. So will the researchers please find some other words thru which to express their intentions?

Though it pains me somewhat to admit it, you are partially correct in the assertion that, "The theory [of evolution through natural selection]... forbids design [by an intelligent operator]."

However it seem to me that you make the mistake of supposing that the fault lies with the theory whereas I'd suggest in this case that rather it lies with the language: it is simply the case that there are few commonly used words in English that connote 'utility of purpose' (check a thesaurus) more effectively, and in a manner understandable by pretty much everyone, than "designed". It's just unfortunate that this word also carries implications of some notion of a "designer" when that seems clearly not the intent in Ward's quote.
gvgoebel
5 / 5 (6) Feb 10, 2011
It's just unfortunate that this word also carries implications of some notion of a "designer" when that seems clearly not the intent in Ward's quote.


He should have said "adapted", but apparently he's not used to bickering with creationists and isn't aware of the "loaded" words.

It's actually difficult when writing about evo science to avoid being tripped up by what amounts to a bias to see nature as designed: "Mesmerized by a mental mirror that imposes human ways of doing things on a Universe that, as all admit, isn't run by humans."

Even Dawkins has noted this: "It is almost as if the human brain were specifically designed to misunderstand Darwinism [sic], and to find it hard to believe."

DamienS
5 / 5 (4) Feb 10, 2011
Even Dawkins has noted this: "It is almost as if the human brain were specifically designed to misunderstand Darwinism [sic], and to find it hard to believe."

Not just Darwinian principles, but anything that is outside of our direct and immediate experience. Things which are slow to change compared to a lifetime. For example, this includes, evolution, geology & plate tectonics, astronomical phenomena...
carter
3.7 / 5 (3) Feb 11, 2011
How can science even consider evolution when it is so much easier to believe that a great and powerful being just snapped his fingers and created the universe. just don't care if the insurmountable energy it would have taken this being to create the universe is impossible as long as I believe it, it is so. Isn't it really easier to believe in religion that was brainwashed into me as a kid rather than try to actually figure out the truth. So what if the bible contradicts itself and no one can agree on what version of the truth is right. If I shout loud enough and tell you how religious I am, I will be right.
Donutz
5 / 5 (3) Feb 11, 2011
We were designed and created by a mastermind so superior it's unfathomable.


Please show evidence -- any evidence, anything at all -- of the existance of a deity or deities. Then please show evidence -- anything, anthing at all -- that it's *your* particular sky fairy. Then please show evidence -- anything, anything at all will do -- that your magical sky fairy actually dictated or inpired the collected set of stone-age shepherd's tales called the 'bible'. Then show evidence -- anything, anything at all -- that your sky fairy intended these fairy tales to be taken literally.

Until you do that, expect to continue to be lauged at. You're comic relief kevin. You and all the other creotards. You can't prove your POV by picking away at the other POV. Process of elimination simply doesn't work. If you had a working brain you'd understand that.