Ancient Foot Bone Proves Prehuman Lucy Walked Tall…

[wolftrax]

Linked article

The single lateral metatarsal bone somehow proved that? It should have already been largely established by Lucy's pelvis, legs and arms. Even if you somehow deduce a humanlike arch from a single bone on the outside of the foot, it doesn't translate into proof by itself.

If you read the linked article you would see that is a different article discussing another find where a big part of afarensis skeleton was found, including the pelvis, collarbone, shoulderblade, parts of the arms and legs, shown here:

http://www.sciencenews.org/view/access/id/60468/name/bb_bones_vertical.jpg

The fact of the matter is that a flat foot could function fine so calling that proof of anything even if it were somehow true is what I was complaining about. The feet are stiffened into the arch by tendons and they don't show up in fossils besides grove marks sometimes.

You haven't read the parts of the paper posted here, have you?

[Guest vilnoori]

I used the term "super arch" to describe what I am seeing there. In the H. erectus and the bigfoot prints, there is an arch even on the outside of the foot--there is a distinct area where the sole doesn't put pressure on the ground. This has been described as a midtarsal break, but it is not really the same as what you see in gorilla or chimp feet when they make a footprint. It could be confused for it, though, because the sole does put some pressure on the ground on the instep of the arch, where ours does not. It is still an arch, but it is a differently strung arch than our own. Can anyone else see that?

Similarly with the Laetoli track, there is still some arch there, but it is subtle, allowing for all over pressure of the foot on the ground. There is a valley that runs between the big toe and its metatarsal and the adjacent one which we just don't see in modern feet. I suspect that this allowed for more flexibility in the hallux for climbing, and that it was rigidly held together during walking or running to produce a firm step. The arch that goes from the back of the foot to the front is a much gentler one than ours, a flatter one, but it is still present. Again, what we are seeing is a differently strung arch system than our own.

Obviously it is all in the ligaments--though the 2-5 toes in both the Laetoli track and the H. erectus track are unusually long compared to ours (though some people still have them).

Edited March 1, 2011 by vilnoori

[BobZenor]

If you read the linked article you would see that is a different article discussing another find where a big part of afarensis skeleton was found, including the pelvis, collarbone, shoulderblade, parts of the arms and legs, shown here:

http://www.sciencenews.org/view/access/id/60468/name/bb_bones_vertical.jpg

You haven't read the parts of the paper posted here, have you?

I read all the articles posted in the OP and every post. I gathered that there were a few new afarensis fossils and the evidence that convinced them that it had an arch was the outside metatarsal. I will admit that I didn't pay any attention to the Hallei Salassi article after the "knuckle dragging" and "conclusive proof" part. That is what I complained about and if YOU read the links that should have been obvious. It is still just an assumption that the foot bone is what he was talking about as proof. What else could it be different from Lucy that could prove bipedalism. I don't actually care what he or that article have to say, you know, the first linked article in OP. Then the first link I followed was another fossil and they talked about calling it a missing link.

If you or someone else posted something different, then I didn't read it besides the one where you claimed they had a good anatomy background. That didn't impress me. What you don't seem to believe, is that I am not buying their interpretation even though I wasn't talking about them when I was criticizing the livescience or whatever article. I understood every word they said in the article you posted about anatomy. Did you read every link posted in this thread. If so how come you are so confused when I quoted the problems that I had and apparently transferred it to someone else. I tried to be perfectly clear. I was responding to different articles or your direct or quoted statements. You act like they are all the same when they aren't and all my comments apply to all of them. I am just not interested in delving deeply into something that is flawed from the basic premise.

Edited March 1, 2011 by BobZenor

[wolftrax]

Hallei Salassi didn't work on the paper with the metatarsal bone that is discussed in the opening post. His conclusion that afarensis was upright was based on an entirely different find. The article in the OP had all kinds of links in it to articles on entirely different papers. I didn't confuse that, apparently you did.

You are saying that the arch is made up of ligaments and the writers of the paper on this metatarsal, Carol V. Ward, William H. Kimbel, Donald C. Johanson, are making an interpretation based off of bias, but grant that muscle attachments do show on the bones. There is this whole section posted that talks about the shapes of the bones and their heads, how they interact with each other, how apes and humans are different because of the arch and midtarsal break, and how the afarensis metatarsal is more similar to humans. Thsi is the entirety of the bone and almost every aspect of it.

In AL 333-160, the metatarsal head is twisted

laterally relative to the base, producing shaft torsion

characteristic of modern humans (2) and later

fossil hominins, including Homo habilis specimen

OH 8 (22, 23) and the H. erectus foot bones

from Dmanisi, Republic of Georgia (24). This

torsion contrasts with the ape condition, in which

the head and base exhibit minimal relative rotation

(Fig. 2). Torsion allows the plantar surface of

themetatarsal head to contact the ground in a foot

with a strong skeletally supported transverse arch

(2, 25, 26), an everted posture characteristic of a

foot adapted for the modern human terminalstance

phase of gait, rather than the inverted foot

postures of apes used in climbing. This degree of

torsion of the AL 333-160 metatarsal demonstrates

that a permanent bony transverse arch must

have been present in the foot of A. afarensis.

In AL 333-160, the diaphysis is angled plantarly,

rather than dorsally, relative to the base, as

in humans and H. habilis [OH 8; see (11)] and

unlike in African apes (Fig. 3). This morphology

further indicates a permanent longitudinally arched

posture of the foot, because the fourth metatarsal

makes an angle of about 8° to the ground in a normal human foot (5). The metatarsal head in

AL 333-160 is flattened along the plantar portion

of its articular surface, which faces distally

relative to the diaphysis rather than being parallel

to the diaphysis as in extant apes, forming a

large plantar surface-diaphyseal angle (Fig. 3).

This reflects the overall more extended posture

of the metatarsophalangeal joints in the hominins

(2, 5, 23).

The AL 333-160 head exhibits another set

of distinctive hominin apomorphies observed also

in Ardipithecus ramidus (25), Australopithecus

(14, 19, 27), and later hominins [reviews in (1, 22)].

It is domed dorsally in medial and lateral views

(indicated by arrows in Fig. 3B), and there is a

deep transverse gutter along the dorsal margin

of the subchondral surface. In chimpanzees and

gorillas, the domed portion of the head inclines

plantarly, reflecting habitual loading in flexion.

The hominin configuration seen in AL 333-160,

and also in the AL 333-115 partial metatarsals

(14, 19), would allow an increased range of dorsiflexion

at the metatarsophalangeal joint as compared

with apes, as well as habitual loading of the

joint in extended postures that occur during the

push-off and terminal phases of striding bipedal gait.

The lateral column of the human midfoot is

relatively stiff, so that the mid- and hindfoot lift

off the ground during gait simultaneously (1).

In apes, however, dorsiflexion in the midfoot

ensures that the heel leaves the substrate before

the midfoot, a condition known as a “midtarsal

break,†which can be up to 28° in magnitude (28).

This dorsiflexion occurs primarily at the cuboidmetatarsal

joints (10, 26, 29) and is distinct from

the medial collapse in some human feet, which is

far less pronounced and occurs to a variable degree

at multiple joints (7, 11, 12). The transverse and

longitudinal pedal arches and metatarsophalangeal

dorsiflexion inferred fromAL 333-160 signal an

osteological pattern of midfoot stability and lateral

foot rigidity unknown in the apes.

Dorsoplantar curvature of the lateral tarsometatarsal

joint surfaces contributes to the distinctive

midtarsal dorsiflexion in great apes

(8, 10, 26, 29). These surfaces on the human

proximal fourth and fifth metatarsals are flatter.

The proximal articular surface of AL 333-160 is

nearly flat (Fig. 4B), matching the mean of the

modern human sample. Limited dorsiflexion at

the lateral tarsometatarsal joints (10, 30), which

would contribute to a relatively stiff lateral foot

like that of modern humans, can be inferred for

A. afarensis. AL 333-160 also has dorsoplantarly

deep metatarsal bases, a condition also described

for Ardipithecus ramidus (25) (Fig. 4B). This

would limit dorsiflexion and plantarflexion at the

lateral tarsometatarsal joints, additional evidence

of a human-like relatively stiff lateral foot fundamentally

different from that seen in apes.

A rigid lateral foot in A. afarensis is further

suggested by the orientation of the facet for the

lateral cuneiform on the base of the AL 333-160

fourth metatarsal (Fig. 4C), mirroring the complementary

facet seen on the lateral cuneiform

(14, 19). In A. afarensis, as in modern humans,

H. habilis [OH 8 (31)], and the Dmanisi H. erectus

feet (24), the lateral cuneiform is elongated, extending

distally past the cuboid, so that it articulates

with the proximomedial corner of the fourth

metatarsal at an obliquely oriented facet (14, 19).

In apes, the lateral tarsometatarsal joints are aligned

in the same coronal plane in such a way that the

distal end of the lateral cuneiform is coplanar with

the fourth tarsometatarsal joint, and the oblique

facet on the fourth metatarsal for the lateral cuneiform

is absent (Fig. 4C), a configuration that

facilitates dorsiflexion at the tarsometatarsal joints

(10). Thus, even if there wasmore calcaneocuboid

mobility in A. afarensis than in modern humans

(32, 33), this was evidently not the case for the

lateral tarsometatarsal joints [see also (34)].