Freethought & Rationalism Archive

GeoTheo · 08-05-2002, 03:14 PM

Quote:

Originally posted by ps418:


What page? I want to look it up next time I go to the library, and see what Leakey says for myself.

I don't have it with me. It is at home. You could look it up in the index or wait till tomorrow.
I will point out that Johanson and Leakey are serious rivals.

ps418 · 08-05-2002, 03:25 PM

Quote:

Originally posted by GeoTheo:
How do you think lucy walked and on what do you base this? Paintings?

Paintings? Are you getting upset because I'm pressing you to back up your claims re: Leakey? Or is this just reflection of your knowledge of anthropology? At any rate, that Lucy in particular walked bipedally is based on the numerous anatomical features, including the positioning of the foramen magnum, the morphology of the knee joint and pelvus, and other characteristics as well.

Make sure you get back to me on Leakey. I want to see where exactly he expressed doubt that Australos. were bipedal.

Patrick

ps418 · 08-05-2002, 03:33 PM

Here's more on australopith locomotion from an old post. Maybe if we're lucky Ergaster will stop by and give her 2 cents also.

Quote:

There is no evidence whatsoever that the australopiths were quadrupedal, and they would not not need to develop the bipedal locomotor adaptations that they possessed in order to "lift its trunk and scan over savanna grasses." The humerofemoral relationship would have made quadrupedal locomotion quite akward and inefficient, and the hand bones lack any indication of knuckle walking adaptation. They lack transverse ridges at the base of the dorsal articular surface of the metacarpal heads, the widest transverse diameter of the metacarpal heads is located anteriorly, not dorsally as in chimps and gorillas, and the distal articular surface of the radius lacks the dorsal ridge that limits dorsiflexion of the wrist in knuckle walking posture (see Human Evolutionary Anatomy, p. 385 and refs therein). Interestingly, the relative length of the thumb is much more human-like than that seen in any ape (about 50% the length of digit II, whereas in apes it is about 36%).

And there are indeed a variety of indications in the long bones, distal fubula, etc. (for instance, bicondylar angle of the femur 5-10 times that seen in quadrupeds), pelvis (ilium wider than tall as seen only in humans, well-developed sciatic notch, totally different angular relationship between components of pelvis than that seen in qudrupeds) and foot (robusticity patterns of metatarsals, big toe much more adducted than in apes, showing only a little opposability) that the australopiths were well-adapted to bipedalism, although they also possessed adaptations for arboreal locomotion and retained many primitive features as well.

Bubba · 08-05-2002, 06:22 PM

Taking it from a purely non scientific intuitive basis I look elsewhere and see evidence that we evolved from ape like ancestors that didn't walk upright. The next time your at a shopping mall look at the way some old men and some teenage boys walk. Many of them are slouched and leaning forward a little bit. To me they seem to show not intelligent direct design but decent from ancestors that were quadrupel (or whatever the term is for how apes walk!)

Plus the similarity in homology between all other primates and humans is amazing. I love to take my family to the zoo and every time we go through the sections with chimps, bonobo's and so forth I'm astonished at the similarities.

Bubba

[ August 05, 2002: Message edited by: Bubba ]

MrDarwin · 08-06-2002, 05:27 AM

Quote:

Originally posted by ps418:

Make sure you get back to me on Leakey. I want to see where exactly he expressed doubt that Australos. were bipedal.

My impression was that Leakey (and pretty much everybody else) fully accepts the bipedality of australopithecines in general, and Lucy in particular.

(edited to add that I haven't kept up with the current literature on human evolution, so I could be wrong on this)

[ August 06, 2002: Message edited by: MrDarwin ]

Ergaster · 08-06-2002, 06:40 AM

You are correct. There are no paleoanthropologists who doubt that "Lucy" or any other australopithecine was bipedal. There is a debate over whether and how much time certain australos spent in trees, but no doubt at all that they were bipeds while on the ground.

It is really quite irrelevant what Richard Leakey or any particular individual might express as a personal opinion. It only matters if that opinion also happens to be supported by the physical evidence. The consensus in the field is and has been for over 30 years that australos were bipedal.

Quote:

Originally posted by MrDarwin:


My impression was that Leakey (and pretty much everybody else) fully accepts the bipedality of australopithecines in general, and Lucy in particular.

(edited to add that I haven't kept up with the current literature on human evolution, so I could be wrong on this)

[ August 06, 2002: Message edited by: MrDarwin ]

GeoTheo · 08-06-2002, 07:31 AM

Origins Reconsidered by Richard Leakey and Roger Lewin p. 193-6
Discusses Lucy's anatomy and points out that it was unlikely that she had a striding gait like humans or that she could run bipedally.
So....Choice:
1. They walked everywhere (slowly and awkwardly)
2. Did not run bipedally(ran some other way)
If it is number 2. Lucy was not fully bipedal.
Peter Scmid of the Anthropological Institute in Zurich points out the various features of her anatomy like the cranially oriented shoulder joint, funnel shaped thorax, curved phalanges, large pisiform and other features that point to tree climbing adaption. There is an illustration on p. 195 that shows how her skeleton appears to be adapted to tree climbing.

GeoTheo · 08-06-2002, 07:52 AM

Like I said earlier, I accept human evolution. I just think that some people are too optimistic about the signifigance of some of these finds.
Also If a.afarensis was contemporary to early homo which was fully bipedal, what is the signifigance of Lucy's gait anyway? It is obvious the australopithecines were an offshoot.

[ August 06, 2002: Message edited by: GeoTheo ]

Ergaster · 08-06-2002, 08:42 AM

Firstly, A. afarensis did not coexist with the genus Homo. Some species of australopithecines certainly did, but not that one.

Secondly, the fact that A. afarensis did not walk exactly like humans is not an argument against ancestry. Australopithecines were not humans, so of course they should not be expected to look or behave like humans. If you believe that humans arose from non-human ancestors, why should you expect these non-human ancestors to behave or locomote like humans? The features that define humans were acquired gradually. If you understand how evolution and speciation works, it is to be expected that the earliest members of the genus Homo will be very hard to distinguish from their closest australo relatives, and that may well include styles of bipedalism.

We know that by 1.6 million years ago humans had pretty much modern body proportions and bipedalism. But the genus Homo first appears in the fossil record almost a million years earlier. Unfortunately there is little postcranial material associated with those fossils, but what there is seems to suggest that human body proportions and possibly locomotor styles were still rather australopithecine-like. Which really should come as no surprise.

Quote:

Originally posted by GeoTheo:
Like I said earlier, I accept human evolution. I just think that some people are too optimistic about the signifigance of some of these finds.
Also If a.afarensis was contemporary to early homo which was fully bipedal, what is the signifigance of Lucy's gait anyway? It is obvious the australopithecines were an offshoot.

[ August 06, 2002: Message edited by: GeoTheo ]

Valentine Pontifex · 08-06-2002, 10:23 AM

Origins Reconsidered page 194:

Quote:

In other words, Lucy and other australopithecines were bipeds, but they weren't humans, at least in their ability to run.

There is nothing really unconventional here.

Lucy was a biped -- period. That her bipediality differed from anatomically modern humans is hardly suprising. I don't think that one day an ape decided to be a biped and from that point on walked and ran the exact same way as we do today.

There is still a lot of disagreements over how much time they spent in the trees versus walking on the ground, the exact mechanics of their locomotion, etc. But that australopithecines were bipeds is pretty obvious.

08-05-2002, 06:22 PM	#14
Bubba Veteran Member Join Date: Mar 2001 Location: Orient, OH USA Posts: 1,501	Taking it from a purely non scientific intuitive basis I look elsewhere and see evidence that we evolved from ape like ancestors that didn't walk upright. The next time your at a shopping mall look at the way some old men and some teenage boys walk. Many of them are slouched and leaning forward a little bit. To me they seem to show not intelligent direct design but decent from ancestors that were quadrupel (or whatever the term is for how apes walk!) Plus the similarity in homology between all other primates and humans is amazing. I love to take my family to the zoo and every time we go through the sections with chimps, bonobo's and so forth I'm astonished at the similarities. Bubba [ August 05, 2002: Message edited by: Bubba ]</p>

08-06-2002, 07:52 AM	#18
GeoTheo Veteran Member Join Date: May 2002 Location: Bemidji Posts: 1,197	Like I said earlier, I accept human evolution. I just think that some people are too optimistic about the signifigance of some of these finds. Also If a.afarensis was contemporary to early homo which was fully bipedal, what is the signifigance of Lucy's gait anyway? It is obvious the australopithecines were an offshoot. [ August 06, 2002: Message edited by: GeoTheo ]</p>

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08-06-2002, 07:31 AM	#17
GeoTheo Veteran Member Join Date: May 2002 Location: Bemidji Posts: 1,197	Origins Reconsidered by Richard Leakey and Roger Lewin p. 193-6 Discusses Lucy's anatomy and points out that it was unlikely that she had a striding gait like humans or that she could run bipedally. So....Choice: 1. They walked everywhere (slowly and awkwardly) 2. Did not run bipedally(ran some other way) If it is number 2. Lucy was not fully bipedal. Peter Scmid of the Anthropological Institute in Zurich points out the various features of her anatomy like the cranially oriented shoulder joint, funnel shaped thorax, curved phalanges, large pisiform and other features that point to tree climbing adaption. There is an illustration on p. 195 that shows how her skeleton appears to be adapted to tree climbing.

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