The Human ... Tail?

Faith & Science Conversation
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I was reading up on 29 Evidences for Macro-evolution as suggested by @Christy and came across the “Anatomical Vestiges” portion of the article.

“Yet another human vestigial structure is the coccyx, the four fused caudal vertebrae found at the base of the spine, exactly where most mammals and many other primates have external tails protruding from the back. Humans and other apes are some of the only vertebrates that lack an external tail as an adult. The coccyx is a developmental remnant of the embryonic tail that forms in humans and then is degraded and eaten by our immune system (for more detail see the sections on the embryonic human tail and the atavistic human tail). Our internal tail is unnecessary for sitting, walking, and elimination (all of which are functions attributed to the coccyx by many anti-evolutionists). The caudal vertebrae of the coccyx can cause extreme and unnecessary chronic pain in some unfortunate people, a condition called coccydynia. The entire coccyx can be surgically removed without any ill effects (besides surgical complications), with the only complaint, in a small fraction of patients, being that the removal of the coccyx sadly did not remove their pain (Grossovan and Dam 1995; Perkins et al. 2003; Postacchini Massobrio 1983; Ramsey et al. 2003; Shaposhnikov 1997; Wray 1991). Our small, rudimentary, fused caudal vertebrae might have some minor and inessential functions, but these vertebrae are useless for balance and grasping, their usual functions in other mammals.” (Emphasis Mine)

Digging further I clicked on the “embryonic human tail” link which took me to this…

“Humans are classified by taxonomists as apes; one of the defining derived characters of apes is the lack of an external tail. However, human embryos initially develop tails in development. At between four and five weeks of age, the normal human embryo has 10-12 developing tail vertebrae which extend beyond the anus and legs, accounting for more than 10% of the length of the embryo (Fallon and Simandl 1978; Moore and Persaud 1998, pp. 91-100; Nievelstein et al. 1993). The embryonic tail is composed of several complex tissues besides the developing vertebrae, including a secondary neural tube (spinal cord), a notochord, mesenchyme, and tail gut. By the eighth week of gestation, the sixth to twelfth vertebrae have disappeared via cell death, and the fifth and fourth tail vertebrae are still being reduced. Likewise, the associated tail tissues also undergo cell death and regress.” (Emphasis Mine)

This is something I never heard of before… so I clicked on the images for more details on the Embryology.

http://embryo.soad.umich.edu/index.html <<< this is the link to Embryonic photos of a developing baby.

The author states that the remnants of the tail are most visible in pictures 14, 15, and 16, — it’s called the Neural Tube. And, according to the author, this tail gets digested due to cell division, preventing an actual tail from occurring. In stage 23 you can see the extreme differences in the Neural Tube.

I further investigated and clicked on the “Avatistic Tail” link to show human babies actually born with tails (very rare however). The site provided links —

http://www.anatomyatlases.org/AnatomicVariants/SkeletalSystem/Images/19.shtml

So I’ve seen both the Embryonic tail and the “post-Embryonic tail” and it seems convincing to me. I’m not sure how to explain the existence of such of an expenditure without resorting to Common Descent explanations.

What do you guys think?

-Tim

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Tim,
Nice analysis. Now add the genetic evidence related to this and together they provide very convincing evidence of the fundamental truth of common descent.

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Tim, if I were a Young Earth Creationist … I don’t think I would find the tail as convincing as
having the same defective gene for making vitamin C as chimpanzees.

Having a tail is just one of those freaks of nature …

Not being able to make vitamin c is considered NORMAL for humans… and chimps!

George Brooks

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@Patrick
@gbrooks9

I know it may sound odd that I single out something like the “rare occurrence of a human tail”. But when it comes to explanations like genomic evidence and (as George points out), “We have the same defective gene for making vitamin C for other primates, such as chimpanzees.” — a YEC can simply say, “That’s evidence for Common Designer not Common Descent.”

I agree that the genomic evidence is pretty convincing … but I have too also consider the mindset of different people that would disagree.

A human tail is a “freak of nature” but not in the same way as other things: having extra toes or fingers, having tumors (like the Elephant Man) or having a bizarre hair disorder that encases your whole body (as I’ve seen some unfortunate girls have). All those things can more easily be explained as genetic disorders … too much “hair grow gene” (yes, that’s not the technical term, but I’m a layman) or too many fingers and toes … it doesn’t prove anything other then there being some sort of disorder.

A human tail, on the other hand, should NOT happen if the human species isn’t related to other species … like primates for instance. In the mind of a person who does not believe in common descent it would almost (not quite) be as freaky as a person being born with gills behind their ears (like Mel Gibson from Water World).

As the article points out, YECs like Duane Gish, argue that it’s not a true tail. You would not make this argument if say someone was born with a sixth finger, “That’s not a true finger!”

-Tim

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Maybe what I should have said is I just don’t think the tail or the
defective vitamin c gene will influence any YEC.

These evidences are for helping the non-YEC feel good about their
position.

George Brooks

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Yeah considering that there is a critique on the very same article - - A Critique of ''29 Evidences for Macroevolution'' - Part 4 -

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hi tim. is think its actually simple: first- in rare cases shark also born with “legs”:

http://sarasotafins.weebly.com/shark-blog/how-sharks-show-err-love

so according to this we need to believe that sharks use to live on land.

secondly- human embrio also have gills-like structures. but they never evolve to gill but something else. so if we see 2 similar stuctures it cant prove that they have the same function. this process that you see in embrio development is actually very important:

by that way- see that some human “tails” have different shapes.

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@jahiddle

The link won’t load on my computer, unfortunately. There is criticisms and such left on the actual article of 29 Evidences for Macro-evolution — I admit that much of it goes way over my head, but I’m grasping onto “some” of it. More than the actual tail “surviving” clear up on through birth, was the idea of a tail-like structure that gets consumed (or ingested) very early on in the pregnancy. Perhaps it’s not much of anything “definitive” … just odd.

@gbrooks9

Maybe you’re right George. However I do distinctly remember, several years back, hearing about stories of humans being born with tails, and the prospect of it greatly disturbed me (much more than things like the elephant man had to go through, even though the “tail” is much more subtle) .

@dcscccc

Apoptosis is very interesting, Guy — and so some of my inferences may have been mistaken.

I agree that two similar structures don’t prove similar function. The ostrich wing is often defined as vestigial because of apparent design for something it is not capable of doing … i.e., flying. This does not mean “useless” or “without function” … but it does imply it’s vestigial-ness.

“For example, wings are very complex anatomical structures specifically adapted for powered flight, yet ostriches have flightless wings. The vestigial wings of ostriches may be used for relatively simple functions, such as balance during running and courtship displays—a situation akin to hammering tacks with a computer keyboard. The specific complexity of the ostrich wing indicates a function which it does not perform, and it performs functions incommensurate with its complexity. Ostrich wings are not vestigial because they are useless structures per se, nor are they vestigial simply because they have different functions compared to wings in other birds. Rather, what defines ostrich wings as vestigial is that they are rudimentary wings which are useless as wings.” - Douglas Theobald

Other historical sources …

“…for, although the latter [ostrich] does not fly, it still uses its wings as aids in running swiftly over the African plains and deserts … Retrogression is, however, not always carried so far as to do away with a structure altogether … But not infrequently the degenerating organ can be turned to account in some other way, and then retrogression either stops just short of actual elimination, as in the case of the wings of the ostrich, or so alters and transforms the structure as to fit it for new functions …” (Weismann 1886, pp. 5-9)"

And the historical definitions of “vestigial”

vestigial. a. Of, pertaining to, or of the nature of a vestige; like a mere trace of what has been; also, rudimentary. In biology vestigial has a specific application to those organs or structures which are commonly called rudimentary, and are rudimentary in fact, but which are properly regarded, not as beginnings or incipient states, but as remains of parts or structures which have been better developed in an earlier stage of existence of the same organism, or in lower preceding organisms, and have aborted or atrophied, or become otherwise reduced or rudimentary in the evolution of the individual or of the species.
(The Century Dictionary: An Encyclopedic Lexicon of the English Language 1911)

“Vestigial organs are sometimes pressed into a secondary use when their original function has been lost.”
(The Story of Evolution, Joseph McCabe, 1912, p.264)<<<

Some of the trouble I encounter is that people tend to say, “The Theory of Evolution says such ‘n’ such”. But there is no “one” theory of evolution. There are many proposed theories of evolution that entail different mechanisms to account for the varying degrees of changes in the overall shape of life over time.

— Lamarkian Evolution
— Darwinian Natural Selection
— Neo-Darwinian Evolution
— Niche Construction (directed evolution)
— Evolution through Symbiogenesis
— Self-Organization
— Evolutionary Developmental Biology (Evo-Devo for short)
— Process Structuralism

And the list goes on.

It seems more probable for me to come to the conclusion that some form of evolution is happening than it is for me to come to a concrete conclusion HOW it happens, and what are the mechanisms — that latter end of the discussion is much more complex.

-Tim

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hi tim. so the bottom line is that this tail cant be evidence for vestigial. otherwise we will need to conclud that shark ancestor was a land animal:)

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You’re utterly, spectacularly wrong. ALL MALE SHARKS have claspers. It’s not rare at all. They are neither “legs” nor legs.

[quote]so according to this we need to believe that sharks use to live on land.
[/quote]Since your premise is simply false, we don’t need to believe anything of the sort. You might remember that science isn’t about belief, it’s about evidence.

[quote=“dcscccc, post:7, topic:3314”]
secondly- human embrio also have gills-like structures. but they never evolve to gill but something else. so if we see 2 similar stuctures it cant prove that they have the same function.[/quote]
That’s a straw man. We’re pointing out that they have a common origin, not a common function. They are called brachial arches, pharyngeal arches, or gill arches.

[quote]this process that you see in embrio development is actually very important:
[/quote]It is, but it doesn’t support anything you’re trying to claim.

[quote=“dcscccc, post:7, topic:3314”]
by that way- see that some human “tails” have different shapes.
[/quote]They are all tail-shaped, and there’s no need to put scare quotes around it. They are no different histologically from other vertebrate tails at analogous stages of development.

Hey, where is the whale’s blowhole located in the analogous stage?

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No, because you’re mistaken when you claim that claspers are legs.

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I don’t think so. The statement you quoted from Theobald, “degraded and eaten by our immune system,” isn’t very accurate, but apoptosis wasn’t understood very well when he wrote that. A more accurate way to put it is that the cells are developmentally programmed to die (the process is apoptosis), THEN the dead cells are cleaned up by a part of the immune system (but there’s no real immune reaction to them).

Apoptosis is very common during development. For example, hands and feet, forepaws and hind paws, etc. all start out paddle-shaped. The cells between the digits die via apoptosis. Everything about that suggests an evolutionary process in which modifications are layered on, not that something intelligently designed anything (except maybe evolution itself).

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joao- you are wrong, because i gave an example of mutate claspers that look like a pair of legs. so look again in the picture down.

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No, you did no such thing. Claspers do not look like legs. You did not give any example of “mutate claspers,” whatever that might mean.

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look again here:

http://sarasotafins.weebly.com/shark-blog/how-sharks-show-err-love

lokk at the image with the lady hold a small shark with mutate clasper.

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I did. There’s nothing “mutate” or mutant about it. The ends unfold.

What part of [quote]“How does one do that, you may ask? Well, the claspers aren’t just sausage-looking all the time. The tip actually unfolds and is this… pointy, spur thing,”[/quote] don’t you understand?

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joao.first- do you have any source that show it a regular trait? any image of clasper that i found doesnt look like that at all.

even if its indeed true that its not a mutate clasper- its still look like small legs. so according to the logic of evolutionists we need to think that shark was a land animal in is past.

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[quote=“dcscccc, post:17, topic:3314, full:true”]
joao.first- do you have any source that show it a regular trait?[/quote]
Do YOU have any source to support YOUR claim?

So how do you go from your ignorance to your claim that this is “mutate”?

Do you have any support whatsoever for your claim?

Only superficially. If we sectioned it, do you predict we’d find homologues of a tibia and fibula in the distal part and a femur in the proximal part?

[quote] so according to the logic of evolutionists we need to think that shark was a land animal in is past.
[/quote]I don’t think that you understand the fundamental logic of science, much less the logic used by any specific group of scientists.

Science is about formulating and empirically testing hypotheses. Got any?

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@Joao
@dcscccc

I had no idea this topic would cause such a stir.

Guy - a few questions here.

  1. If the shark “pointy expenditures” is evidence of ancestral legs then why does it ONLY appear on male sharks? The tail example I gave was not gender specific.

  2. The site that you shared didn’t even say “legs” or even “leg-like appendages”. That’s what you said.

  3. Why are you putting the burden on Joao to look up sources to defend the claim that it’s not “ancestral legs”, when it’s YOU that brought it up in the first place?

-Tim

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Except in that case it would appear to be a design flaw. There’re no advantage to getting scurvy if you don’t eat enough citrus.

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