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Author Topic:   Foot bone further supports that A. aferensis walked upright
DBlevins
Member (Idle past 59 days)
Posts: 652
From: Puyallup, WA.
Joined: 02-04-2003


Message 1 of 5 (604281)
02-10-2011 9:11 PM


Analysis of the fourth metatarsal remains of A. Aferensis individuals now seem to provide solid evidence that A. afarensis habitually walked upright. The fourth metatarsal bone was found to have a 'twist' such that when one end is attached to the toe the other end rises up, this torsion is found in feet with an arch. This also shows that 'Lucy's' feet had evolved away from the flexible midfoot found in apes, that enables them to grasp branches.

Exciting news! Maybe not as exciting as the discover of a new species of humans but close.


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 Message 2 by Coyote, posted 02-10-2011 9:26 PM DBlevins has not yet responded

  
Coyote
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Message 2 of 5 (604284)
02-10-2011 9:26 PM
Reply to: Message 1 by DBlevins
02-10-2011 9:11 PM


Bones!
For those of who have studied the bones of our fossil ancestors, this is exciting news.

Lucy was found after I finished my graduate classes so I didn't get to study those particular specimens, but I have seen pictures and casts in museum displays.

Interesting how all of the details of these bone finds are supporting the theory of evolution, eh? And that none of them are contradicting the theory (as in a Cambrian rabbit).

Might be something to that science stuff after all!


Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge.
This message is a reply to:
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RAZD
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Message 3 of 5 (604287)
02-10-2011 9:42 PM
Reply to: Message 2 by Coyote
02-10-2011 9:26 PM


Re: Bones!
Indeed Coyote, indeed.

For those of who have studied the bones of our fossil ancestors, this is exciting news.

But not entirely unexpected, eh? It is just what one would expect via evolution.

quote:
thanks to an analysis of about 35 new individuals of A. afarensis uncovered at Hadar, Ethiopia, in the past 15 years. The key is the fourth metatarsal, a long bone that connects the toe to the rest of the foot. The way the two ends of the bone were twisted in relation to each other in the fossils suggests that when one end was on the ground, the other end was raised about 8˚ to attach to the rest of the foot,

The composite skeleton of A. afarensis becomes more and more complete.

http://www.sciencemag.org/content/331/6018/750.abstract
http://www.sciencemag.org/content/331/6018/750.figures-only
http://www.nature.com/.../2011/110210/full/news.2011.85.html

quote:

The fourth metatarsal, a small bone that makes up the inner part of the fourth toe, is useful to palaeontologists because of the way that it differs in shape between tree climbers and land walkers. Ward's team found that Lucy's metatarsal was more like that of a modern human than a chimpanzee.

"This paper presents the most convincing skeletal evidence yet that A. afarensis had well-developed, modern human-like, arches," says Jeremy DeSilva, a functional morphologist at Boston University in Massachusetts.


Enjoy.


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Taq
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Message 4 of 5 (604334)
02-11-2011 11:42 AM


The hot debate right now is focused on the evolution of bipedalism in hominids. Was the common ancestor of chimps and humans functionally bipedal or arboreal? Of course, Lucy can't really answer the question with any confidence, but does finding adaptations for bipedalism so close the common ancestor indicate a bipedal common ancestor?

At the same time, australopithecines also have adaptations for tree climbing, most noticebly in the range of motion for the shoulder and adaptations in the wrist.

Edited by Taq, : No reason given.


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DBlevins
Member (Idle past 59 days)
Posts: 652
From: Puyallup, WA.
Joined: 02-04-2003


Message 5 of 5 (604387)
02-11-2011 5:14 PM
Reply to: Message 4 by Taq
02-11-2011 11:42 AM


Was the common ancestor of chimps and humans functionally bipedal or arboreal?

You're right that there is still a good amount of debate on why/how humans evolved bipedal motion. Some of the hypotheses that I recall were the thermoregulation model, the behavior model, food-transportation model, and the savannah hypothesis. I also think there was the climate model. oh yes, the aquatic theory also.

As far as whether our common ancestor with the chimps was functionally bipedal or arboreal, it would seem evident that it would have been arboreal yet, like chimpanzees today, spent time on the ground foraging. After the split, bipedalism developed in our lineage.

...but does finding adaptations for bipedalism so close the common ancestor indicate a bipedal common ancestor?

I would say no, for the simple fact that fossil evidence suggests that we evolved from an arboreal ancestor, and I don't know of any evidence that suggests apes reverted back to knuckle walking after being bipedal.

At the same time, australopithecines also have adaptations for tree climbing, most noticebly in the range of motion for the shoulder and adaptations in the wrist.

Iirc A. anemensis's foot bones were more primitive than A. aferensis and still retained features that allowed it to be arboreal.


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