Creationist response to cetacean femur, leg atavism, and limb bud.

In another thread, a few others and myself engaged in a discussion about whale evolution and morphology. The issue of vestigial pelvises and limbs arose. I took some time to research these issues further. I’d like to lay out a summary of my findings — a more detailed version will be forthcoming in a paper. In the midst of this I will try and answer some direct questions posed to me by Granny Magda.These questions include:
1.) How much of a role does sexual dimorphism play in the size and shape of cetacean pelvises?
2.) Why do some whales have femur remnants and/or tibia remnants while others don’t?
3.) How similar is the whale’s pelvis to its ancestors?
4.) Why are some modern whales born with protruding rear legs?
5.) What about the molecular and DNA basis for limb loss?I’ll start with the question: How similar is the whale pelvis to its proposed ancestors?While the pelvis of land mammals up to Basilosaurus are composed of three distinct bones fused together, the pelvis of modern whales is only composed of one single bone — as noted by several authors who note a single ossification center found in cetacean embryos. This single bone is thought to be the ischium.Granny Magda brought to my attention the picture of the fin whale pelvis with a few small bone nodules fused to it, labeled the femur. This example was different from the other fin whales in Dr. David Taylor’s pelvis gallery. It is difficult to say for certain if this is the femur or not. The femur of whales is always connected to the pelvis via a ring of cartilage or short tendon strands — not fused directly to it — which is why none of the other fin whale pelvises show an attached femur. The bony nub could also be a bone spur or bone tumor. If the nub represents a femur fused to the pelvis, this would highlight another departure from the typical pelvic structure. In other mammals, the leg bones develop and ossify at different developmental stages than the pelvis does - eliminating the possibility that the femur could fuse to the pelvis.The other obvious structural departures of the modern whale pelvis include the lack of an acetebular cavitity in which the head of the femur typically resides. Struthers notes the head of the cetacean femur is in the position which in human surgery we would call dislocation backwards. The other point of difference is the lack of an obturator foramen in — or the hole in the pelvis through which nerves and muscles pass.There are other lesser known departures. The pelvic bone in modern whales has rotated about 120 degrees so that the illium end now points to the posterior end instead of to the anterior end, as in typical quadrupeds. In addition, the pelvis is rotated about 90 degrees inward so that the femur bones point towards each other. This illustration attempts to illustrate how the transition in position must have taken place.Since the shape of particular bones and the attachment points of specific muscles can differ between families of mammals, the nerve structure of the surrounding muscles are often examined to try and determine homologies between the bones of different animals. However, in the case of whales, the nerves associated with the pelvic musculature are so greatly altered, that it is utterly impossible yet to homologize them with muscles of terrestrial mammals according to author Alfred Brazier Howell, a professor of comparative anatomy. I will go into more detail about the musculature differences later.There is a significant sexual dimorphism in the structure of the male and female pelvis — a fact that Granny Magda tried to downplay saying individual variation is at least as big a variable.While it is true that individual body part variation is probably higher in whales than in other mammals — this is not a reflection of the necessity of those body parts. An example of this is the fluke. Individual variations in fluke shape is one-way researchers can easily tell one specific whale from another.Even though the pelvic bones can differ between individuals, definite generalizations can still be made. Struthers notes: Differences within a species can also be age related. The pelvis undergoes a dramatic growth spurt around the age of sexual maturity — which varies from 6-20 years old, depending on the species. The pelvis is the last bone to ossify in whales — the same for humans. Therefore, in younger whales, large portions of the pelvis may be completely cartilaginous. These cartilaginous parts would not be preserved in the museum samples recorded in Dr. Taylor’s gallery. galleryFemur and Tibia in Modern WhalesAs noted earlier, an important difference between the pelvic structures of different whale species is the presence of an attached femur in some whales — and even a tibia in others. Is this diversity random? Or is there a pattern to what we see? Most of the marine biologists whom I polled about this diversity hadn’t considered the question before and didn’t have an answer.Russian zoologist Alexy Yablokov began to classify mysticetes according to the presence of a femur or tibia. He noted the presence of a femur and tibia in right whales and bowhead whales. We can also include sperm whales in this category.He noted the presence of only a femur in humpbacks, blue whales, and fin whale. We can also add brydes whale, sei, and minke whale to this category. The only other mysticete without a record of a femur remnant is the pygmy right whale — which is the smallest of the baleen whales.Overall, the femur remnant is far more similar to an epipubic bone than to a typical femur.
Is the Cetacaean Pelvis Vesitigial?Granny Magda stated: She rightly states that an organ labeled vestigial isn’t necessarily a useless organ. Yablakov takes up this issue in his discussion of the cetacean pelvis. Historically, vestigiality is defined by a drastic change in form and function from an ancestral state. However, if usefulness isn’t a critical criterion, one wonders how you can discern a vestigial organ from a specialized one — a question that Yablakov poses. If your only criteria is to find examples where an organ exists in an altered state from the ancestral one, then vestigiality becomes a meaningless term. Why not call the front flippers vestigial forelimbs? Or call feathers vestigial scales? If you consider feathers specialized structures adapted to a specific purpose and not vestigial scales, why call the cetacean pelvis vestigial? The most you could say is that it has a specialized function different from the previous function, and if its structure were closer to that of a typical quadruped, it would not be able to perform its adapted function.After linking the cetacean pelvis to reproductive success, Yablakov makes this claim: Atavistic Hind LimbsYablakov questions whether any structure in whales can be considered vestigial if it performs a necessary function. Indeed, he suggests that the term vestigial should only be attached to structures that are not universally shared by all members of a single species. The only example in this category he can give is the occasional presence of hind protrusions in whales. Yablakov observed cases of external cetacean hind limbs during his experiences with the whaling industry. Edited by Aaron, : Removed large sections to eliminate any potential publishing conflict.

Good point. I realize this article is a little much for this type of venue. I was mostly using it as an opportunity to flesh out some thoughts.Basically, I'm tackling three aspects of whale anatomy that have previously been considered only explainable from an evolution standpoint.1.) The presence of a femur/tibia in certain whales
2.) The occasional presence of a hind "limb" in cetaceans
3.) The emergence and regression of a "limb bud" in cetaceansI believe each of these has been misrepresented and errantly used as evidence of cetacean quadruped ancestry.There is good evidence that the limb buds are not limb buds at all, but are involved in forming the mammary region.This helps explain why the femur and tibia in whales (as well as the pelvis) are so dramatically different in their orientation when compared to a quadruped pelvis and limb. Their developmental process and function are quite different.Also, if the hind buds are not limb buds, then the occasional hind "limb" can't be a leg reversion - and indeed the physical and chemical evidence strongly suggests these limbs are not at all atavistic reversions.

I'm happy to discuss stuff, but I'm still working on the main paper - so I don't want to take too much time away from it until it is finished.I didn't go into all the detail I could have. I didn't say never fused (although I did say always separate - so my word choice could have been better). "Always" separate as in "humans always have two arms" - which could be contradicted by the occasional human born with 3 arms.There are cases of the femur fused to the pelvis in cetaceans, but this is an abnormality, not the normal case. This also highlights another departure from the typical quadruped pelvis. Typically, the pelvis ossifies at a different time frame than the femur, so you don't find cases of people with a femur fused to the pelvis.Just looking at pictures doesn't give you the whole "picture" - so yes, it seemed to me that the femur was just a bony nub attached to the pelvis - but now I realize that the fin pelvis we examined was an anomaly, and not the typical condition. The fused nub could very well be the femur in the fin example - or it could be a bone tumor - either way it is an anomaly.I'm certainly not saying that all cases of femurs are bone tumors. The cetacean femur connects to the pelvis with an acetabular like patch of cartilage. The pelvis might have a slight indentation, but a true acetabular cavity is a deep recess forming part of the ball and socket joint with the femur. This is certainly not the case in cetaceans and isn't really a debatable point. Papers both old and recent acknowledge that modern cetaceans don't have an acetabular cavity.The acetabular cavity is formed by different parts of the 3 main pelvic bones - the ischium, the ilium, and the pubis. Modern whales don't have these three bones - they have one bone (known because of a single ossification center which makes up the bone), considered to be the ischium. The attempts to label one end the ilium and one end the ischium is a superficial, deceptive attempt to homologize the bones to a quadruped pelvis. It would be like calling one end of a femur a different bone than the other end.This is another strike against the similarity to a quadruped pelvis. Take the last proposed ancestor - the basilosaurids, if you really want to compare them. The pelvis of a basilosaurus is composed of an ilium on the most distal portion, close to where the femur attaches. Inward from there is the ischium - which forms the upper arch of the obturator foramen. Then comes the pubis, the largest of the three fused bones, which is attached to the pubis of the the opposing side. Anyhow, the ischium is a small arched piece of bone - maybe 4 inches or so long. Compare that to the pelvis of a modern whale which is typically around a foot long, and is composed entirely of an ischium, and is a completely different shape than the bassilosaurus ischium. If you really want to compare actual bones, you have to compare ischium to ischium - and there is no comparison. You're missing the point and misusing the term "homology."Certainly every animal has a specific muscle for a specific role - but just because two animals have a muscle that makes the penis erect doesn't mean they are homologous. Examples of convergent evolution refute this notion from an evo perspective. Just because we call them by the same name, doesn't mean the muscles are similar in structure or are derived from a common ancestor. The muscles don't come with names on them. We give them names for simplicity sake. Imagine if we had a different name for the pectoral muscle for every species that has one. In depth analysis is done on the nerve patterns in the muscles - the only type of "name tag" the muscles have.There's no reason to disagree with Dr. Brazier on the in-depth point he was making - its not really a debatable issue. You found the right paper. Yes, drastic transformation indeed. Why should this drastic transformation sway the author? He already accepts as fact the common dogma. This is just one more large stepping stone evolution happened to climb.Just to be sure, I'm not saying my paper is supposed to refute whale evolution. You can accept all the points I make and still hold to the scenario. But, it should be clear that some of the prime evidence listed for whale evolution has been misinterpreted. That argument is not meant to refute the evolutionary origin of whales - just to highlight how the term "vestigial" can be more of a propaganda term than a useful term.Edited by Aaron, : not finished

If you are referring to the positioning of the pelvis and femur in this picture, it is not accurate. What they are doing (I'm assuming) is rotating the pelvis so you can get a better view of what the bone looks like. If you looked at it straight on from this angle, you wouldn't see very much. But, if they don't give you a disclaimer telling you that is what they are doing, you are left to reason that they are accurately showing you the true orientation.If you want to see a paper with the true orientation, check out this: link It's on page 14 and coincides with the diagram I already provided. Hox mutations don't always produce an exact duplicate - and I wasn't indicating that these hind flippers are perfect duplications of the front flipper. Usually the duplicated part is abnormally developed. For example, my son was born with an extra digit growing from below his thumb, yet it was nothing more than a nub - a single phalange with no nail.Dorudon has three foot digits (which is less than his forelimb). The sperm whale mutation has two digits. So either way, it is an incomplete mutation. Notice how the round carpal bone in the x-ray matches the round carpal bone in the sperm flipper. You see no such thing in Dorudon.And what about the 4 foot long hind limb in the humpback whale example? How is that at all like Dorudon? Several misrepresentations of what I've said.I didn't claim that the hind limbs of Dorudon were sexual claspers - the guy who discovered the fossil did.My thought is that these types of mutation more readily occur in regions where there are already similar genes at work. The formation of the genitals and the mammary gland include several genes that are also involved in limb formation.Can you even explain how an atavistic reversion occurs? How does an ancestral gene get turned back on?you might find this interesting: http://www.epigeneticscomesofage.com/Chapter_16.html

Granny M,Thanks for the thoughtful reply and good questions. Not quite. Even without Shh, the mice still developed front and back limbs - just not complete limbs. And yes, they did die early. So minor, they can't duplicate it in the lab. When scientists want to explore the affects of silencing Shh or Hand2, they have to silence it completely. They don't have a way to selectively silence it in just the hind bud. Yes, because if you knock out Shh, Hand2, or Fgf8, you still get a limb that develops much more thoroughly than the cetacean condition. It certainly is comparable - especially since the Hand2, Fgf8, and Shh would not be eliminated from the whole body if you cut off the AER - just silenced in the one region. These proteins are intertwined. One promotes the production of the other. Removing the AER stops these proteins from being expressed. They are limb buds why? Because they have an AER? An AER is just a thickened area of ectoderm at the end of the limb bud - a situation just like the early formation of the mammary gland - even in humans. In fact, even in humans, the formation of the mammary gland begins as protruding ridge - the mammary hillock. Later, this ridge regresses. After it regresses, a secondary bulge emerges which becomes the external part of the mammary gland. Sounds familiar to what happens in cetaceans.Contrary to what you said, the hind buds in cetaceans do not look or behave like limb buds. The AER is much smaller and more localized to a small spot. The buds themselves are much smaller than a typical hind limb bud - despite how long they are actively developing. Chemically, they are lacking Shh and Hand2 - as you pointed out.The only similarity is the presence of an AER and Fgf8. As I mentioned, an AER is also part of a developing mammary gland - and Fgf8 is also a critical protein for the earliest stages of mammary gland development.Here are some more problems for you to chew on. Studies have also been done on the limb buds of gray whales and minke whales. You see the same situation where the buds regress into a fold of skin without developing any skeletal elements. Yet, both of these whales have femur bones. Where did they come from if the "limb buds" regress? If they didn't come from the "limb buds," can you call them limb bones? Seems like they are something entirely different. Except that the femur is always there in sperm whales. No need for this conjecture. Seriously? You're evidence for this is what? Actually, when I presented this information to a marine biologist, he commented on how much great work in anatomy came from that time period.Consider this before you make such a nonsensical comment: Back in the 1880s, whaling was big business. As such, it provided scientists with many more specimens to study if they were looking to study embryos. If you want to study whale embryos, you are limited to the chances of a killed whale being pregnant - and then if it happens to be pregnant at the developmental stage you are interested in.The chances of obtaining beneficial specimens were much greater back then than they are now in our age of very regulated cetacean specimens.

Granny M, Maybe I wasn't clear enough. I don't think the femur bones are bone tumors. My only mention of anything being a tumor was the one specific fin whale pelvis with the small nodule fused to the edge of the pelvis. I said in that case that it was difficult to tell if the nub was a tumor or the femur fused to the pelvis - and either way, that was an abnormal case, since a normal cetacean pelvis doesn't have anything fused to it. Calculating homology between muscles involves more than identifying common connection points - I'm sure its more complicated than either of us could really debate at length. Either way, the paper you cited doesn't dispute Brazier's point about nerve differences in the muscles between cetaceans and other mammals. The author disputes Arvy's contention that there is no homology - not Brazier's point that homology is extremely difficult to decipher. The author also cites a paper by Bejder and Hall which cites Brazier's comments - but does not disagree with him. I don't disagree with Tajima. He says the aponeurotic sheet has a similar connection point. That's the straight up data. How he interprets that data evolutionarily is another matter. I'm sure there are similar muscles in similar positions that play similar roles. When you read Struthers, you see how some muscles have similarities, but others he has a hard time labeling because of how drastically different they are in their connection points from a terrestrial animal. Either way, it is not a major building block of my arguments.Edited by Aaron, : No reason given.

Dr. A I just recently photographed the hind limbs of a Dorudon and Basilosaurus skeleton.The Dorudon limb is very much like this diagram of Basilosaurus - although it is hard to tell from this diagram how the femur articulates with the pelvis. It doesn't lay flat to it, but is extended perpendicular to it. I guessed at calling it a carpal bone - based on the typical bones in a hand. Whatever it is, the rounded shape is the same as the bone in a sperm whale front flipper. The 4 foot + limb atavism in the humpback can be found here:
Hind Limb Rudiments on Modern Whales Example Two What I meant is that I didn't pull the idea of sexual claspers out of my rear (not sure if you were insinuating that). The idea was first put forth by someone else. In that sense, the claim isn't mine - though I agree with him. Thanks for the link - that's a paper I hadn't read yet.The ridge extends between the forelimb and the hindbud, not between the two hindbuds (not sure if you thought this, but the wording is a little tricky.)And the milk line connects to the nipple. I didn't mean to imply that what we see in humans is an exact one to one comparison of the cetacean condition - just that the forming of the mammary glands involve the appearing, disappearing, and reappearing of certain structures. In cetaceans, the developmental process is more complex, involving the forming of mammary clefts - in which the nipple reside. The Ryder study I first cited wasn't linking the buds to the milk lines - but to other parts of the organ such as the rudimentary mammary clefts.BTW, I've run my main points by several marine biologists and none argued against them. I received some helpful comments and advice - and plenty of affirmation, including on this point of the mammary glands.Edited by Aaron, : No reason given.

I may not have all the details correct of how they thought the limbs turned into the tail - but this book by Ryder talks about how the tail fluke is related to the feet:On the Development of the Cetacea: Together with a Consideration of the ... - John Adam Ryder - Google BooksIn describing an embryo he says: "provided the fluke folds be regarded as representative of the hinder limb folds..."

Here's Dorudon. I wasn't focused on number of digits, so this isn't the best angle. I have a better shot of the digits but it is a bit blurry. Here's Basilosaurus: Yes. I had a nice back and forth with a scientist who examined the buds and wrote a widely cited paper on it. He now sees it my way.

Granny, I think you have done a good job raising questions and concerns.I've been a little vague with references and such because I'm not looking to "show my whole hand" so to speak. This isn't the primary outlet I'm looking to disseminate my theories through. Once I'm finished with the final paper and it has been published, I'll send you a copy to check out all the references and the additional details of my arguments.Speaking with you both has been helpful in seeing what details I need to refine.

Granny M, I don't think scientists should be able to mimic in the lab everything that God did and nature did. I only said what I did because your attitude seemed to be that the changes needed to eliminate the limb were rather simple. And that view is over-simplistic. Here's a link to the paper I was referring to: Developmental changes of the fore- and hind-limbs in the fetuses of the southern minke whale, Balaenoptera acutorostrata - PubMedThe whole paper isn't available for free. I got a copy from the author.Here's Edward Babinski's quote regarding that paper: from his popular websiteEd must not have ever read the paper, because it says no such thing. The paper isn't very long - it makes a point of highlighting the development of cartilage in the forelimb at a very early stage - but it says nothing about the development of any cartilage in the hind limb. At its largest state of development, the hind bud is called a small bump. Do you think they needed to understand the chemical basis behind a structure to physically see how it develops? Modern insight into the chemical happenings of the hind bud haven't offered support to the the traditional view of their nature.I haven't done much research into sirenian biology. Do you bring up their pelvic bones because a) you don't think they have any purpose?
or
b) the only way they could have bones like that is if they evolved from a four-legged creature?

jab
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generalized assertionSome of those old writings aren't the easiest thing to discern. They don't always use the same terminology as they do today.Some things I've stumbled through and I've had to make some adjustments. That's not too bad, given that I don't have a degree in science and have only been studying this particular subject for 3 months or so.What if I'm correct though, and scientists have been wrong about the hind buds for over 100 years? What does that say about their interpretations?Here's the quote from my source: I'll tell you who said it later.Here's a quote from a biologist who works on cetacean anatomy in response to my atavistic legs = hox mutation theory.

I'm used to criticism on this site. Here's the context of my email that he was directly responding to: