Lucy is a transitional form

[philadiddle]

I posted the following on another forum but it was dominated by creationists who posted nonsense in response. I'm reposting it here in hopes of getting some use out of it since it took me some time to make. There was one reasonable objection that was raised in the other forum and I'll add that onto the end. Unfortunatley I used the word "believe" in the first sentence which was an excuse for some to ignore the evidence. I found it quite ironic that someone supporting a religious view over science would be so picky about someone using the word "believe". Here it is as I posted it in a different forum:

I believe that Lucy is a transitional form, and in this post I’m am going to try to objectively back that up (which will make it a conclusion, not just a belief).

Sorry for belaboring the need to define what “transitional fossil” means, but I feel that it’s necessary to define or else my entire post could be disregarded because you think of “transitional fossil” in a different way than I do.

I’ll use a definition from a creationist website to try to avoid bias issues:

What is a transitional fossil? “A transitional fossil is one that looks like it’s from an organism intermediate between two lineages, meaning it has some characteristics of lineage A, some characteristics of lineage B, and probably some characteristics part way between the two. Transitional fossils can occur between groups of any taxonomic level, such as between species, between orders, etc. Ideally, the transitional fossil should be found stratigraphically between the first occurrence of the ancestral lineage and the first occurrence of the descendent lineage...” Source

To add to this, a transitional form does not have to be proven to be the single crown species that both lineages evolved from. We can never conclusively prove that. What a transitional fossil will show is that a species did once exist that shows characteristics of both of the currently existing species. Because of allopatric speciation, an overlap is possible.

The Lucy fossil has 14 morphological characteristics that are similar to chimpanzees, and 22 that are similar to humans. The following is a list of these features.

Features similar to a chimpanzee skeleton:
-Shape of mandible
-Protruding chin
-Lateral facet for canine on first lower premolar
-Size of first lower premolar
-Transverse processes of 10th through 12th thoracic vertebrae
-Medial margin of capitate (the carpal bone at the base of finger III)
-Arching of metacarpals and manual phalanges
-Orientation of acetabulum
-Diameter of femoral head
-Orientation of greater trochanter
-Lateral malleolus of fibula in lateral view
-Distal process of talus (tarsal bone that supports the tibia)
-Arching of metatarsals and of pedal phalanges other than distal phalanx
-Shape of proximal margin of proximal phalanx of toes I–III in lateral view

Features similar to a human skeleton:
-Simian shelf of mandible
-Slope of mandibular symphysis in lateral view
-Orientation of left and right postcanine tooth rows
-Incisor size
-Diastema (toothless space) between lower canine and first lower premolar
-Size of first lower premolar
-Spinous process of 4th through 10th thoracic vertebrae
-Displacement of postzygapophyses beyond caudal margin of centrum on 11th and 12th thoracic vertebrae
-Spinous process of 2nd and 3rd lumbar vertebrae
-Transverse width of centrum of 2nd through 5th lumbar vertebrae
-Number of fused vertebrae in sacrum
-Maximum transverse (side-to-side) width of sacrum (not counting 6th sacral vertebra of chimp)
-Lateral supracondylar ridge of humerus
-Lateral epicondyle of humerus
-Shafts of radius and ulna
-Proximal extension of olecranon process of ulna
-Dimensions of ilium beyond acetabulum (hip socket)
-Shape of greater sciatic notch
-Height of tip of greater trochanter
-Middle part of distal margin of tibia in posterior view
-Transverse width of medial malleolus of tibia
-Medial process of talus medial and plantar to tibial facet

Source

The evidence here is observed to be intermediate. The morphological features are factually divided between chimps and humans. This is not an assumption, it’s an observation. It also fits into the expected curve that we would expect to see if the cranium size of hominids was increasing.

The fossil does show evidence of being a basal form of both modern humans and chimpanzees from its morphology. Also, with the fossils found before and after it, it fits where it would be expected to fit if evolution occurred. It appears to fit after the original common ancestor of chimps and humans as it started to become more human-like. Again, this is not an assumption, but a conclusion based on the morphology of the bones.

This does not prove evolution, because as I’m sure it’s been explained a thousand times on this board, proof is something for mathematics, not science. However, the evolution of all apes from a common ancestor is the best explanation for what we observe. This allows us to make predictions about what other species we will find and where we find them (in Africa). It also allows us to make predictions about what we will find genetically, but we can save genetics for another thread.

Science always seeks the best explanation. If I am wrong about evolution being the best explanation for what we are observing here, then you need to not only explain how the evidence does not support evolution, but you also need to give a better explanation that takes into account all of the facts. Multiple features indicate that it walked more like humans, so if you think it’s a chimp you will need to explain that. Other features are clearly more chimp-like, like its jaw, so if you think it’s human you will have to explain that.

I’ve seen a certain video about Lucy posted on this forum several times and I expect it to be one of the first responses to this post so I’ll post it here and respond to it right away.

YouTube - Why do people laugh at Evolutionists?

The main points of this clip that I get out of it are the following:

1) The two bones were fit together so well, that they’re in an anatomically impossible position. This was laughed at.

2) Lovejoy decided he could restore the pelvis to its natural shape. This too was laughed at.

3) The speaker says he’s removing whole parts, not just cutting.

4) Then they laughed at the way the pieces fit together.

There are other more general points made in the video but I’ll stick to the points about Lucy. So, here is my response to each of those points with a link to a pelvic anatomy diagram so that you can visualize what I’m describing:

http://radiology.usc.edu/Presentations/Sad...ANAT_FINAL2.HTM

1) The two bones that fit together too well (the sacral promontory and the iliac fossa) were deemed to be anatomically impossible because they were missing the sacroiliac joint. Instead of just laughing at the video, he should have studied pelvic anatomy to see why that claim was made. I am open to hear how the original bone was actually anatomically correct if anyone is willing to look objectively at the evidence with me.

2) The part of the fossil that was deformed was the blade along the iliac fossa right by where the sacroiliac joint should be. This is consistent with the idea that the sacral was pushed into the iliac causing the damage to occur. The damaged piece was at a 90 degree angle and was obviously crushed. If anybody cares to look at the actual fossil found and explain to me why it didn’t need fixing I would be open to hear that as well.

3) The speaker was mistaken. Lovejoy didn’t remove whole parts, he rearranged them by adding appropriate space for the sacroiliac joint, and he straightened out the bones that were crushed at an angle to make the blade of the iliac fossa straight.

4) The best way to overturn a scientific model is to have a better explanation. The speaker should have demonstrated a better way for the fragments to fit together. Even on the video the fragments were put together in a way that made the blade of the iliac straight, like it should be. Why did they just laugh at this? Was it put together wrong?

If this is difficult to visualize with text, I found a youtube video that has a great 3d model of the reconstruction so that you can see how it is broken and why it was fixed the way it was. I’ve taken the time to watch the video that you guys put up and I’ve taken the time to analyze and explain why I think it is an invalid argument, so hopefully you will return this by watching the following video and criticizing it:

YouTube - About the Reconstruction of the Lucy Pelvis - Final point.

That is the end of my original post. It was pointed out that Lucy's bones were found spread out and merely assumed to be the same creature. The bones actually make up 40% of the skeleton, and despite that many bones, there are no duplicate parts, indicating it is the same individual. There are also more fossil skeletons found of that species, it's not just Lucy that we have to study.

Lucy meets the definition of a transitional form, even by creationist standards.

 

[Agonaces of Susa]

What 2 species do you claim Lucy (a so-called Australopithecus afarensis) is a transition between?

 

[Targ]

Thanks for the post philadiddle, very useful.

 

[Blayz]

Seriously, you took the definition of transitional from a creationist web site, and then spent never-to-be-got-back hours munging science to fit it?

All fossils are transitional.

Next!

 

[juvenissun]

Seriously, you took the definition of transitional from a creationist web site, and then spent never-to-be-got-back hours munging science to fit it?

All fossils are transitional.

Next!

All fossils are transitional, and at the same time, are not transitional.

 

[Greg1234]

Seriously, you took the definition of transitional from a creationist web site, and then spent never-to-be-got-back hours munging science to fit it?

All fossils are transitional.

Next!

So are all vehicles.

 

[Wiccan_Child]

All fossils are transitional, and at the same time, are not transitional.

Well there's a logical fallacy. Either they are, or are not, transitional. Which it is, depends on who you ask, but they're one or the other.

 

[Naraoia]

All fossils are transitional, and at the same time, are not transitional.

???

Philadiddle: beautiful!

Obligatory terminological quibbles:

(1) What do you mean by "crown species"? In cladistic parlance, a crown group is one that includes the most recent common ancestor of all living members of a group, and all of its descendants. Lucy would be a member of the human + chimp (crown) clade. The way you used the term, though, doesn't make sense with that definition.

(2) "The fossil does show evidence of being a basal form of both modern humans and chimpanzees from its morphology." A basal form of both modern humans and chimpanzees would branch off before the last common ancestor of humans and chimps. I'm pretty sure that's not the accepted position of Lucy or what you are trying to say.

 

[philadiddle]

Seriously, you took the definition of transitional from a creationist web site, and then spent never-to-be-got-back hours munging science to fit it?

All fossils are transitional.

Next!

No, not all fossils are transitional. Some are dead ends. Your statement is incorrect.

 

[philadiddle]

???

Philadiddle: beautiful!

Obligatory terminological quibbles:

(1) What do you mean by "crown species"? In cladistic parlance, a crown group is one that includes the most recent common ancestor of all living members of a group, and all of its descendants. Lucy would be a member of the human + chimp (crown) clade. The way you used the term, though, doesn't make sense with that definition.

(2) "The fossil does show evidence of being a basal form of both modern humans and chimpanzees from its morphology." A basal form of both modern humans and chimpanzees would branch off before the last common ancestor of humans and chimps. I'm pretty sure that's not the accepted position of Lucy or what you are trying to say.

I see what you're saying with both points. I agree with you but I'll still leave the OP unedited. Next time I talk about it I'll know to watch the use of those words.

Thanks

 

[philadiddle]

What 2 species do you claim Lucy (a so-called Australopithecus afarensis) is a transition between?

It is transitional between a "common ancestor of chimps and humans" and "humans".

 

[Naraoia]

No, not all fossils are transitional. Some are dead ends. Your statement is incorrect.

Let me be pedantic again. A dead end can still be a transitional form. Dromaeosaurs are a dead end - they left no living descendants. However, they branched between birds and the rest of Dinosauria, and they exhibit many features that are intermediate between the two.

I guess whether all fossils are transitional depends on what you mean by transitional

 

[philadiddle]

I guess whether all fossils are transitional depends on what you mean by transitional

Exactly, the definition really matters which is why I used a definition from a creationist website.

Is a T-rex a transitional form? What about a triceratops?

 

[Naraoia]

Exactly, the definition really matters which is why I used a definition from a creationist website.

Is a T-rex a transitional form? What about a triceratops?

IMO it's up to subjective judgement, and there are no sharp lines. Tyrannosaurs in general - well, all dinosaurs, really - can be considered transitional forms with respect to birds (depends on where you put the starting point for the transition, of course). Even ceratopsians, since they also show some "birdy" characters (for example, an erect gait) that aren't found in the closest living relatives of birds.

I think what you regard as transitionals depends on the number of unique derived traits that the creature possesses. Early tyrannosaurs, the small, protofeathered ones with a more conventional small theropod look, I would regard as fairly decent transitional forms. T. rex, on the other hand, isn't a particularly good one because of its specialisations (huge size, reduced arms, whatnot), despite the fact that it's exactly as far up the tree as its earlier relatives. Basically, I'd call anything that is (1) in the right phylogenetic position (2) a good illustration of the transition in question a transitional form.

Well, that's my personal view at this point in spacetime, anyway

 

[Agonaces of Susa]

It is transitional between a "common ancestor of chimps and humans" and "humans".

LOL.

Darwinists say that there is no common ancestor between chimps and humans: Oldest Skeleton of Human Ancestor Found

Move over, Lucy. And kiss the missing link goodbye.

Scientists today announced the discovery of the oldest fossil skeleton of a human ancestor. The find reveals that our forebears underwent a previously unknown stage of evolution more than a million years before Lucy, the iconic early human ancestor specimen that walked the Earth 3.2 million years ago. ...

The fossil puts to rest the notion, popular since Darwin's time, that a chimpanzee-like missing link—resembling something between humans and today's apes—would eventually be found at the root of the human family tree. Indeed, the new evidence suggests that the study of chimpanzee anatomy and behavior—long used to infer the nature of the earliest human ancestors—is largely irrelevant to understanding our beginnings.

Methinks you have no idea what you're talking about.

 

[rockaction]

Methinks you have no idea what you're talking about.

Oh the irony!

 

[Naraoia]

LOL.

Darwinists say that there is no common ancestor between chimps and humans: Oldest Skeleton of Human Ancestor Found


Methinks you have no idea what you're talking about.

Methinks he has a lot more idea than you do.

The article - a National Geographic news feature, not a scientific publication - doesn't even remotely say what you claim it does. Quoting a quote:

"This find is far more important than Lucy," said Alan Walker, a paleontologist from Pennsylvania State University who was not part of the research. "It shows that the last common ancestor with chimps didn't look like a chimp, or a human, or some funny thing in between."

This does not say there was no common ancestor. It says the common ancestor didn't look like all the things listed.

(By the way, the notion that the common ancestor wasn't chimplike is old news. Dawkins discusses several fossil taxa that may upset the view of the chimp-like common ancestor in The Ancestor's Tale, which was published five years before Ardi invaded Science. Orrorin and Sahelanthropus date to around/before the likely age of said common ancestor, and especially Orrorin is quite un-chimplike. Ardipithecus ramidus was likewise already known, and considered possibly bipedal, at that time. See the chapter titled "Ape-men" in The Ancestor's Tale.)

 

[Cabal]

The article - a National Geographic news feature, not a scientific publication - doesn't even remotely say what you claim it does.

Is anyone really surprised by that...?

 

[Split Rock]

It is transitional between a "common ancestor of chimps and humans" and "humans".

Lucy is just a big chimp. I have proof: Big Daddy?

 

[Agonaces of Susa]

The article - a National Geographic news feature, not a scientific publication - doesn't even remotely say what you claim it does.

This does not say there was no common ancestor. It says the common ancestor didn't look like all the things listed.

I know what it says because I read it.

Here is what it says:

The fossil puts to rest the notion, popular since Darwin's time, that a chimpanzee-like missing link—resembling something between humans and today's apes—would eventually be found at the root of the human family tree. Indeed, the new evidence suggests that the study of chimpanzee anatomy and behavior—long used to infer the nature of the earliest human ancestors—is largely irrelevant to understanding our beginnings.

No wonder you think Australopithecus afarensis is the missing link between chimpanzees and modern humans...