Monday, July 23, 2007

A creationism vs. evolution discussion,. Part 3

A tale of tails...

My question:
Human embryos have tails.
Possible Answers- True or false
Correct answer- True
A delicious (although not entirely accurate) witticism on this situation is that 'Ontogeny recapitulates phylogeny,' or embryonic development mirrors the evolutionary process. Although the human embryo doesn't entirely follow the evolutionary path, it does in some respects. If we never had creatures in our background with tails, why would our embryos ever have them?

Marcsana’s response
7. Embryos don't have tails. You may want to do a bit more research and see how the whole of idea of vestigial organs is debunked.

My response:
There is absolutely no question that tails in humans do exist- both in all embryos and occasionally as vestigial tails in babies. Here are some links and information from scientific sources:

Fetal development: What happens during the first trimester?
“[At 9 weeks post-gestation] the embryonic tail at the bottom of your baby's spinal cord is shrinking, helping him or her look less like a tadpole and more like a developing person.”

The Fetus- Tail
“True vestigial tails… contain normal skin, connective tissue, muscle, vessels and nerves.”
“Fetal tail is a normal feature during embryonic development that should regress by the 8th week. Its persistence has been described beyond the 8th week… During the 5th-6th week, the human embryo has a tail with 10 to 12 vertebrae. Then, it starts to regress, reducing the number of vertebrae by fusion, leaving the vestigial coccyx. By this process, at 8 weeks, it disappears, although the exact moment varies. The persistent tail probably arises from the most distal non-vertebrate remnant of the embryonic tail.”

Human tails
“Bartels …described five types of rudimentary
caudal appendages in man: three of these are variations
of a “soft” tail presumably arising from the embryonic
tail, the fourth is a bony tail caused by hypertrophy of the
sacrococcygeal vertebrae and the fifth is a true animal
tail containing additional vertebrae. “

Human tails and pseudotails.
“The true, or persistent, vestigial tail of humans arises from the most distal remnant of the embryonic tail. It contains adipose and connective tissue, central bundles of striated muscle, blood vessels, and nerves and is covered by skin. Bone, cartilage, notochord, and spinal cord are lacking. The true tail arises by retention of structures found normally in fetal development.”

I should mention here an argument found on many anti-evolution and anti-abortion websites- claims such as “the end of the spine sticks out noticeably in a one-month embryo, but that's because muscles and limbs don't develop until stimulated by the spine . As the legs develop, they surround and envelop the coccyx, and it winds up inside the body”

This is a misstatement. See the source “The Fetus-Tail” above for an explanation of what really occurs- dynamic change in the structure that becomes the coccyx. The same source goes on to state that humans never have true tails- “It doesn't have any bones in it; it doesn't have any nerve cord either.” which is also proven false above.

Modern-day scientists do not claim that the coccyx is vestigial, in the sense of “now useless.” The point is, the coccyx evolved from vertebrae that were once part of a tail, now fused together into something that is called “a tailbone” for a reason.


Anonymous said...

Maybe you should have worded all that embryonic tail stuff in your own words. I want to hear it in your own words!
Of course, I'm being silly. You deferred to people who know more about this than you do. That is GOOD! So stop trying to call me out for it! Furthermore, you seem not to recognize correct debating format. It doesn't matter where the SOURCES come need to refute them. For example, if I were to quote a source that said the Earth was flat, I would expect you to cite sources that proved the Earth was round. It isn't the SOURCE of the's the argument. As I said, if the creationists are so off base, then show it. It should be easy. All your sarcastic comments, even though they are really rude, do not constitute real science. Anyway, we press onward to vestigial tails.
I am going to group the first four references into the same thing...the case for a tail. I would like to point out one thing before I begin. Here is a quote from a source, "T he persistent tail probably arises from the most distal non-vertebrate remnant of the embryonic tail." Because this part of the embryo looks like a tail, we have a comment on how it probably evolved??? That's like saying it looks like the earth is flat as far as my eye can see down three blocks through my neighborhood. Therefore, the whole world is flat. That is a gigantic leap and I don't accept the assumed evolution based on something like this. But more importantly, neither do other scientists as I'm going to show below.
You write, "Modern-day scientists do not claim that the coccyx is vestigial, in the sense of "now useless."
This is a purely argumentative change in definition by evolutionists. It DID use to mean organs once thought to be useless by evolutionists. Now, however, these two definitions seem to be a modern variant:
'Any part of an organism that has diminished in size during its evolution because the function it served decreased in importance or became totally unnecessary. Examples are the human appendix and the wings of the ostrich.'
Martin, E., Dictionary of Biology, Warner, New York, p. 250, 1986

"Any organ that during the course of evolution has become reduced in function and usually in size'."

Hale, W.G. and Margham, J.P., The Harper Collins Dictionary of Biology, Harper Perennial, New York, p. 555, 1991.
As the following article will indicate, this is just one more way for evolutionists to try and stuff their theory into changing evidence. It is purely argumentative and absolutely relative.

To address tails even more specifically, you misquoted the creationist argument in your rebuttal. I'm going to quote the full argument regarding the bones and nerve cord. And then I'll cite a source, although you already did.

So again, far from being a useless evolutionary leftover, the "tail bone" is quite important in human development. True, the end of the spine sticks out noticeably in a one-month embryo, but that's because muscles and limbs don't develop until stimulated by the spine (Fig. 8). As the legs develop, they surround and envelop the "tail bone," and it ends up inside the body.
"Once in a great while a child will be born with a "tail." But is it really a tail? No, it's just a bit of skin and fat that tells us, not about evolution, but about how our nervous systems develop. The nervous system starts stretched out open on the back. During development, it rises up in ridges and rolls shut. It starts to "zipper" shut in the middle first, then it zippers toward either end. Once in a while, it doesn't go far enough, and that produces a serious defect called spina bifida. Sometimes it rolls a little too far. Then the baby will be born, not with a tail, but with a fatty tumor. It's just skin and a little fatty tissue, so the doctor can just cut it off. It's not at all like the tail of a cat, dog, or monkey that has muscle, bones, and nerve, so cutting it off is not complicated. (So far as I know, no one claims that proves we evolved from an animal with a fatty tumor at the end of its spine.)"
Here's the source.>
I would like this article to be examined. It's not very long.
I have to insert one more thing before closing. Evolution, obviously, says life came from non-life, then simple life, and then complex life. Prove the original formation of the first cell. One may also want to prove information-adding mechanisms. Otherwise, it looks like design. Consider this quote:
"Now here's an engineering problem for you. In the adult, you want to have the blood cells formed inside the bone marrow. That makes good sense, because the blood cells are very sensitive to radiation damage, and bone would offer them some protection. But you need blood in order to form the bone marrow that later on is going to form blood. So, where do you get the blood first? Why not use a structure similar to the yolk sac in chickens? The DNA and protein for making it are "common stock" building materials. And, since it lies conveniently outside the embryo, it can easily be discarded after it has served its temporary-but vital-function.
Notice, this is exactly what we would expect as evidence of good creative design and engineering practice. Suppose you were in the bridge-building business, and you were interviewing a couple of engineers to determine whom you wanted to hire. One person says, "Each bridge I build will be entirely different from all others." Proudly he tells you, "Each bridge will be made using different materials and different processes so that no one will ever be able to see any similarity among the bridges I build." How does that sound?
Now the next person comes in and says, "Well, in your yard I saw a supply of I-beams and various sizes of heavy bolts and cables. We can use those to span either a river or the San Francisco Bay. I can adapt the same parts and processes to meet a wide variety of needs. You'll be able to see a theme and a variation in my bridge building, and others can see the stamp of authorship in our work." Which would you hire?
As A. E. Wilder-Smith21 points out, we normally recognize in human engineers the principles of creative economy and variations on a theme. That's what we see in human embryonic development. The same kind of structure that can provide food and blood cells to a chicken embryo can be used to supply blood cells (all that's needed) for a human embryo. Rather than reflecting time and chance, adapting similar structures to a variety of needs seems to reflect good principles of creative design." The article is cited below.
I'll close with this,
"It was even once believed that the fertilized egg represented our one-celled ancestors, sort of the "amoeba stage." Sure enough, we start as small, round single cells. But notice how superficial that argument is. The evolutionists were just looking at the outside appearance of the egg cell. If we look just on the outside appearance, then maybe we're related to a marble, a bee bee, or a ball bearing-they're small, round things! An evolutionist (or anyone else) would respond, of course, "That's crazy. Those things are totally different on the inside from a human egg cell."
But that's exactly the point. If you take a look on the inside, the "dot" we each start from is totally different from the first cell of every other kind of life. A mouse, an elephant, and a human being are identical in size and shape at the moment of conception. Yet in terms of DNA and protein, right at conception each of these types of life is as totally different chemically as each will ever be structurally. Even by mistake, a human being can't produce gills or a tail, because we just don't have, and never had, those DNA instructions.
The human egg cell, furthermore, is not just human, but also a unique individual. Eye color, general body size, and perhaps even temperament are already present in DNA, ready to come to visible expression. The baby before birth is not even a part of his or her mother's body. From conception onward, we may have genes for a blood type or hair color different from our mothers'. We may be a sex different from our mothers'-about half of us are. Our uniqueness begins at conception, and blossoms continuously throughout life.
Embryonic development is not even analogous to evolution, which is meant to indicate a progressive increase in potential. The right Greek word instead would be entelechy, which means an unfolding of potential present right from the beginning. That's the kind of development that so clearly requires creative design. That's why evolutionists don't use the change from tadpole to frog as an example of evolution. Unlike the supposed evolution of fish to frog, all the genes necessary to change a tadpole into a frog are present right from the very beginning."
(This link was already referenced above, but I'm citing the source again)

Cris Waller said...

Wow, Marcsana, that's a lot of words- absolutely none of which refute what I have already stated:

1- Embryos have tails.
2. Some humans have tails that include nerve tissue and other structures and are not "fatty tumors."

So where did those 10 vertebrae that are present in the embryo but fuse and reduce to form the coccyx come from? Wouldn't it be a more intelligent design to not have 10 vertebrae in the first place if they are going to be fused and reduced in number to make the coccyx?

And why do some humans have what are indisputably tails? You repeat the same utterly false AiG source that states " But is it really a tail? No, it's just a bit of skin and fat...a fatty tumor. It's just skin and a little fatty tissue." As I already pointed out, that assertion is wrong.

You've failed to answer this- to reword your own argument, "For example, if I were to quote a source that said that some human tails do have nerve tissue and other complex structures, and are not fatty tumors, I would expect you to cite sources that prove that they never do."