Wow, I'm impressed with your ability to cut-and-paste pages worth of stuff from biological websites. Oh, wait, no I'm not.
You can't make up in volume what you lack in substance. Your points will stand or fall on their own (or is that the problem?) If you feel that you need to support a point, a URL is sufficient to provide a link for further reading. And if you can't put something into your own words, perhaps you don't understand it well enough to use it.
Now on with the show...
As I've long said, properly understanding something is the first requisite of having a chance of actually rebutting it.
Unfortunately, you clearly did not understand my post. Please go back and reread it now before you repeat the mistakes you make here, keeping in mind the following highlights:
1. Contrary to your claim, the egg-laying to placental transition NEED NOT have happened in "one generation". The reason is:
2. As the hammerhead shark method of gestation makes entirely clear, it's perfectly workable to have placental feeding IN ADDITION TO egg-style yolk-feeding of the embryo. Thus:
3. Rather than needing to do the "switchover" in, as you preposterously claim, "one generation", what you have overlooked is the mechanism of: A) start with egg-based yolk-feeding. B) Over however many generations it takes, *add* placental feeding to yolk-feeding. C) Over however many generations it takes, phase out yolk-feeding and leave placental feeding as the primary embryonic nutrition source.
Thus, you were flatly wrong when you declared that there was no "gradualistic" way to transition from one to the other, because there *is* a workable, *gradualistic* pathway which you failed to consider as a possibility. QED.
As a sidebar issue, note that:
4. I don't need to demonstrate that it *did* happen that way, since that wasn't the claim being examined. The claim was *your* claim that it *couldn't* happen in *any* gradualistic way, period. In order to prove you wrong, I only need to demonstrate a *workable* gradualistic pathway that you had overlooked which allowed multi-generational change to occur without "breaking" the system. I did that.
And:
5. Evolution isn't even on the table here, since you claimed to have ruled out any "gradualistic" development BY ANY METHOD -- and my counterexample works as a gradualistic development method NO MATTER WHAT DRIVES IT.
Now let's look over your response...
While your detailing of live birth in sharks and other species is very interesting, for the sake of brevity, I shall not discuss it here since not even evolutionists would claim that mammals descended from sharks.
Boggle... Did you actually not understand the point being made there, or are you just trying to misrepresent what I actually said in the hopes anyone will swallow it? Or perhaps you're just trolling.
Hint: "Descent" wasn't relevant to the point being made, nor did I in any way claim that it was, or that descent was even involved.
Hint #2: It was a good point, and your dodging of it doesn't help your case any. You can't weaken a point by closing your eyes and hoping it'll go away. An honest debater would concede the point, or rebut it head-on.
According to you all that is needed for a change from egg laying is to get rid of the egg shell and attach the baby to the uterus and there you are!
I said those were the only "major" steps necessary, yeah.
A complete change in mode of reproduction.
I spent several thousand words explaining in detail why you were wrong when you claimed it was a "complete change" in the method of reproduction -- did you not bother to read it?
Problem is that science tells us it is not that easy.
To borrow an old phrase, you use science the way a drunk uses a lamppost -- for support instead of illumination. You frequently argue against science and scientific methods when it suits you, but then you aren't shy about digging frantically for "scientific" support when your own concepts start eroding.
Ok, let's look at what you've got...
[biology primer cut-and-paste snipped]
Without the above happening - with the cooperation of both the baby and the mother, there will be no pregnancy and no reproduction.
Some of it yes, some of it no (for example, the interdigitation limiters aren't necessary for non-deciduate placentas, so they're hardly a necessary "starter feature").
But you're just trying to muddy the waters. That in no way invalidates any of the points I made in my post to you, nor repairs any of the multiple flaws in your original erroneous claim.
See point #3 above: Retention of the yolk-feeding method allows "gradualism" however long it takes to cobble together a combination of changes which enables the first successful placenta. It's not true that th ere would be "no pregnancy and no reproduction" until all the changes were in place, since the *pre-existing* reproduction method would work just fine until a new method became workable.
Did you not understand post #378?
Eggs of course do not have a placenta. Without it though, mammalian reproduction would be impossible.
Wrong again. As I pointed out in my post #378 (you *did* read it, didn't you?) marsupials don't have placentas (most of them, anyway) and yet their "mammalian reproduction" is, obviously, not "impossible".
Furthermore, *again* as I showed in my post #378 (try *reading* it before you try to rebut it, please), eggs actually *do* have "placentas" in a sense -- the extraembryonic tissues that allow an embryo to develop successfully in an egg are the *same* structures that make placentas workable.
Are you ignoring these issues, or just pretending to? Neither option inspires confidence...
There is a quite a bit necessary for a placenta to do its job:
[Cut-and-paste says:] The placenta is the link between a fetus and its mother about the exchange of substances and the thermoregulation. At the childbirth it will be replaced by digestive system, lungs and kidneys of the newborn, for the exchange of substances. The thermoregulation will be driven by the central nervous system through the control of the blood circulation and of the metabolism.
...all of which is the case for egg-hatched reproduction as well. So much for requiring a "change"...
[Cut-and-paste says:] Other placental functions: * Production of hormones * Transmission of chemical messages * Regulation of the resistances of the fetal circulation * Regulation of oxygenation of the fetal blood. How and how much these functions are achieved is still mainly unknown.
...all of which are refinements to the reproductive process which were made possible after primitive placental birth was developed, and are not necessary requirements for the first appearance of placental feeding. Immaterial to the argument, which I shouldn't have to remind you, is about whether placentas could *first* arise *at all*.
The proper perfusion of the placental vessels is a prerequisite for the complete growth of the fetus. From: Physiology of Fetoplacental Circulation
Again, if you had *read* my post #378, you'd see examples demonstrating that "complete" growth of the fetus is not a necessary function of the first placenta in order for it to be highly useful. Some marsupials are examples of this.
Does not seem like something you can just say 'abracadabra' and arise by random chance!
Straw man. It happened neither by "abracadabra", nor by "random chance" acting alone. NOR is a Darwinian origin even at issue here, refer back to point #5 above if you're still unclear on that point. You're wrong even *apart* from any argument about Darwinian evolution as a method.
At birth there has to be a complete change from blood circulation through the mother to circulation through the baby,
Horse manure, fetal blood circulation is *never* "through the mother". From the start, the embryo has its *own*, *self-contained* blood system.
this includes a complete switch in the lung function of the baby from its being a consumer of oxygen to an acquirer of oxygen:
Gee, just like in a hatching egg... Again, no change necessary there. And again, just as I had *already* pointed out in post #378. Try understanding it next time.
[cut-and-paste says:] In the fetus, the systemic, pulmonary and umbilical circulations have several links. The umbilical and placental circulations are a temporary system for the life and the growth of the fetus, that is abandoned at the childbirth, when drastic changes take place transferring the function of gas exchange from the placenta to the lungs.
Gee, again, just like *also* happens in an animal hatching out of an egg. *Again*, no change necessary there. I covered this already -- do you need a refresher course?
Does not seem like it could have happened with a single mutation does it?
Sigh. There you go with your "single mutation" fetish again. See point #3 above.
Furthermore, I again refer you to the fact that the "switchovers" you focus on are *already* present and working in egg-hatched species. So they hardly have to be added by *any* number of mutations in order to be put into identical service for placental birth.
The transfer of blood requires a very complex system:
Again you are in error -- there is no "transfer of blood".
[Cut-and-paste says:] we can classify the placental vessels as follows: + chorionic vessels; + vessels of the cotyledons; + capillary vessels in the villi; + paravascular capillary network. The villi can be classified in 5 main groups: stem villi, mature and immature intermediate villi, terminal villi and to mesenchimal villi [20]. From: Anatomy of the Fetal Side
Again, all present in egg-hatched vertebrates, except for the final branches of the villi, and while those increase efficiency, they aren't necessary for the success of a primitive placenta.
Amazing what can be done with a single mutation eh!
Amazing how stubbornly you stick to the "single mutation" fallacy.
Nothing requires the changes to be a "single mutation" (nor in a "single generation"), nor do most of your alleged "changes" actually need to happen at all, because they *aren't* "changes" -- they are features and mechanisms *already* present in egg-hatched species.
But then, this was already explained to you in post #378. What's your excuse for not understanding it?
CHANGES IN THE MOTHER:
[cut-and-paste snipped]
Amazing what little is needed to change from egg laying to live bearing - just a complete change in the mother!
Sorry, but none of that is required for a primitive placental gestation. They can be added as refinements after the initial system is in place.
And the production of a few hormones is hardly a "complete change in the mother", so don't overstate the issue.
IMMUNOLOGICAL REJECTION PROBLEMS:
[Cut-and-paste snipped]
Of course the above problem had to be solved before a single baby was born since immunological rejection causes loss of pregnancy.
You really need to try reading your own sources before you offer them in alleged support of your claims. Your quoted material says no such thing. It only says that rejection sometimes occurs, *not* that there's a special system in place which "solves" the problem and that rejection would invariably occur without it.
Furthermore, it's clear that egg-hatched species already have immunosuppressive systems, since sperm cells are not rejected on their way to the ovum, and the fertilized ovum (which is likewise "foreign" to the mother) is not rejected as it passes down the birth canal and gets built into an egg.
One of the purposes of the amniotic sac is to prevent immunological problems with the mother:
[Cut-and-paste says:] since the bag of waters prevents bacteria from entering the uterus by acting as a barrier, membranes aren't usually ruptured until delivery is imminent.
That's sweet, but irrelevant, since eggs have amniotic sacs too.
Yet again, I must ask you to learn something about egg-laying as a method of reproduction before you make a fool of yourself declaring what might or might not be a big "change" when compared to placental birth.
The amniotic fluid plays an important part in the baby's development:
[Cut-and-paste snipped]
Seems the amniotic sac is a pretty essential part of the baby's excretory system.
Yup. Sure is. Just like it is in eggs, too. Yet again, you might want to learn something about it before you make yet another mistake about what does and does not need to be added/changed in order to go from eggs to placentas...
The umbilical cord is of course essential in this whole process. It is not as simple as one would think:
[cut-and-paste snipped]
Seems that the jelly around the umbilical cord is quite necessary. Even with the strong service Wharton's jelly provides in preventing knotting, babies die because of the cutting off of the blood supply.
Yup, sure is. By the way, eggs have umbilical cords and take care to prevent twisting as well...
CONCLUSIONS:
Seems we need quite a lot to happen for this transformation!
"Seems" not after all, once we snip out all the parts of your long list that a) are *already* present in eggs, thus requiring no "transformation", and b) weren't necessary for the first placenta but were later improvements.
In fact, gosh, once you take out all that hand-waving, we're left with the issues I already covered in my post #378. Amazing.
Even the individual processes within the system which are necessary to accomplish the change over are quite complex and could not have arisen as a result of a single mutation.
Big whoop-de-doo, since as I already spelled out in great detail in post #378, they need not happen in "a single mutation", nor "a single generation. Reread point #3 above if you're still unclear on this concept. Or hell, reread post #378, I already covered this.
So... Did you not read post #378 before you attempted to rebut it, or did you not understand it, or are you purposely avoiding the parts of it that you know cause problems for your claim? Inquiring minds want to know.
Further, all the processes are interrelated. The separation of the umbilical cord has to signal a changeover to breathing by lungs and blood circulation wholly within the baby.
Already present in egg-layers, fella.
The joining of the baby to the uterine wall starts the signaling of changes in the mother. In fact, the whole process can be seen as a very careful interaction between the baby and the mother.
Not necessary for the first placenta, although later development of such coordination certainly improves the system.
As a result of all the above, I think it should be pretty clear to those who have an open mind that at no point is there a possibility that the changes necessary to achieve a transformation of the reproductive system from egg laying to mammalian live birth can be achieved in a single generation.
"Single generation", eh? You're a broken record. Reread point #3 above, and post #378. WE ALREADY COVERED THAT. So why do you lamely pretend that we haven't?
There are way too many changes needed to make a claim that all these changes could have occurred in any sort of gradual manner
...so you claim, without actually making a case for it. All your arguments so far have been of the faulty "one mutation, one generation" variety. If you're going to shift gears now and insist that gradual change is ruled out, you're going to have to prove *why*. If you're going to try that now, be very sure that you're working on a *minimal* set of *necessary* changes, and *not* a laundry-list of *modern* features which are not only more advanced than any likely first placenta, but are even more advanced than many other mammalian placentas (e.g. cows). Good luck.
and that they are far too many to have occurred suddenly in a stochastic manner.
They didn't, nor did they need to, which is exactly why you were dead wrong in your post #257, and why you would be well advised to just admit that you were wrong and retract it rather than bluster on.
Your points will stand or fall on their own (or is that the problem?) Indeed it is a problem. The problem is that the differences detailed between egg-laying and live bearing animals are individual only for purposes of detailing, but they very much form a system which requires all the parts to work together:
The joining of the baby to the uterine wall starts the signaling of changes in the mother. In fact, the whole process can be seen as a very careful interaction between the baby and the mother. -me-
Not necessary for the first placenta, although later development of such coordination certainly improves the system.
The above is the evolutionist 'leap of faith' through a chasm the size of the Grand Canyon. The only purpose of a placenta is the transfer of nutrients from the mother to the baby through the uterine wall. This alone requires both changes in the uterine wall of the mother, the attachment of the placenta to the uterine wall, and the non-rejection of the 'foreign' body by the mother. This by itself requires numerous changes in the growing baby and the mother as well as numerous specific proteins to be secreted to achieve a successful change in nutritional system. As the following shows:
The mammalian embryo obtains nutrients directly from its mother and does not rely on stored yolk. This adaptation has entailed a dramatic restructuring of the maternal anatomy (such as expansion of the oviduct to form the uterus) as well as the development of a fetal organ capable of absorbing maternal nutrients. This fetal organ ---the chorion ---is derived primarily from embryonic trophoblast cells, supplemented with mesodermal cells derived from the inner cell mass. The chorion forms the fetal portion of the placenta. It will induce the uterine cells to form the maternal portion of the placenta, the decidua. The decidua becomes rich in the blood vessels that will provide oxygen and nutrients to the embryo.
From: Modifications for Development within Another Organism
Let's look at the above problem more closely:
While the embryonic epiblast is undergoing cell movements reminiscent of those seen in reptilian or avian gastrulation, the extraembryonic cells are making the distinctly mammalian tissues that enable the fetus to survive within the maternal uterus. Although the initial trophoblast cells of mice and humans divide like most other cells of the body, they give rise to a population of cells wherein nuclear division occurs in the absence of cytokinesis. The original type of trophoblast cells constitute a layer called the cytotrophoblast, whereas the multinucleated type of cell forms the syncytiotrophoblast. The cytotrophoblast initially adheres to the endometrium through a series of adhesion molecules. Moreover, these cells also contain proteolytic enzymes that enable them to enter the uterine wall and remodel the uterine blood vessels so that the maternal blood bathes fetal blood vessels. The syncytiotrophoblast tissue is thought to further the progression of the embryo into the uterine wall by digesting uterine tissue (Fisher et al. 1989). The uterus, in turn, sends blood vessels into this area, where they eventually contact the syncytiotrophoblast. Shortly thereafter, mesodermal tissue extends outward from the gastrulating embryo (see Figure 11.27D). Studies of human and rhesus monkey embryos have suggested that the yolk sac (and hence the hypoblast) is the source of this extraembryonic mesoderm (Bianchi et al. 1993). The extraembryonic mesoderm joins the trophoblastic extensions and gives rise to the blood vessels that carry nutrients from the mother to the embryo. The narrow connecting stalk of extraembryonic mesoderm that links the embryo to the trophoblast eventually forms the vessels of the umbilical cord. The fully developed extraembryonic organ, consisting of trophoblast tissue and blood vessel-containing mesoderm, is called the chorion, and it fuses with the uterine wall to create the placenta. Thus, the placenta has both a maternal portion (the uterine endometrium, which is modified during pregnancy) and a fetal component (the chorion). The chorion may be very closely apposed to maternal tissues while still being readily separable from them (as in the contact placenta of the pig), or it may be so intimately integrated with maternal tissues that the two cannot be separated without damage to both the mother and the developing fetus (as in the deciduous placenta of most mammals, including humans).
From: Formation of Extraembryonic Membranes
There are numerous 'little' problems within the above that need to be solved for the system to work properly, one of them is oxygen:
The solution to the fetus's problem of getting oxygen from its mother's blood involves the development of a fetal hemoglobin. The hemoglobin in fetal red blood cells differs slightly from that in adult corpuscles. Two of the four peptides of the fetal and adult hemoglobin chains are identical ---the alpha (α) chains ---but adult hemoglobin has two beta (β) chains, while the fetus has two gamma (γ) chains (Figure 15.11). Normal β-chains bind the natural regulator diphosphoglycerate, which assists in the unloading of oxygen. The γ-chain isoforms do not bind diphosphoglycerate as well and therefore have a higher affinity for oxygen. in the low-oxygen environment of the placenta, oxygen is released from adult hemoglobin. in this same environment, fetal hemoglobin does not give away oxygen, but binds it. This small difference in oxygen affinity mediates the transfer of oxygen from the mother to the fetus. Within the fetus, the myoglobin of the fetal muscles has an even higher affinity for oxygen, so oxygen molecules pass from fetal hemoglobin for storage and use in the fetal muscles. Fetal hemoglobin is not deleterious to the newborn, and in humans, the replacement of fetal hemoglobin-containing blood cells with adult hemoglobin-containing blood cells is not complete until about 6 months after birth.
From: Fetal Hemoglobyn
I could go on and on, however, let's just show the problem of adhesion:
The mouse blastocyst hatches from the zona by lysing a small hole in it and squeezing through that hole as the blastocyst expands (Figure 11.25). A trypsin-like protease, strypsin, is located on the trophoblast cell membranes and lyses a hole in the fibrillar matrix of the zona (Perona and Wassarman 1986; Yamazaki and Kato 1989). Once out, the blastocyst can make direct contact with the uterus. The uterine epithelium (endometrium) “catches” the blastocyst on an extracellular matrix containing collagen, laminin, fibronectin, hyaluronic acid, and heparan sulfate receptors. The trophoblast cells contain integrins that will bind to the uterine collagen, fibronectin, and laminin, and they synthesize heparan sulfate proteoglycan precisely prior to implantation (see Carson et al. 1993). Once in contact with the endometrium, the trophoblast secretes another set of proteases, including collagenase, stromelysin, and plasminogen activator. These protein-digesting enzymes digest the extracellular matrix of the uterine tissue, enabling the blastocyst to bury itself within the uterine wall (Strickland et al. 1976; Brenner et al. 1989).
Implantation
Finally, lets show the developmental system of an egg:
This is a picture of a 4 day quail embryo. It is on the yolk with the some of the egg shell removed. Notice the large vessels which are required to provide the nutrients necessary for the rapid development if the embryo. The heart and eye are evident by somewhat obscured by the presence of a new membrane structure, the allantois. The allantois grows from the umbilicus (belly button) and has two primary functions. First it is a waste storage area for the embryo and it will be the gas exchange organ while the embryo is confined in the egg. After hatching, the chick will leave the allantois in the shell. The heart is the red structure in the middle of the embryo and the eye is visible as a dark area in the head.
Compare the above to the picture of the human developmental system in Post# 257 .
Again, each step requires numerous other steps as well as coordination of all the steps. The reductionism of evolutionists does not cut it. The steps are numerous and have to be precisely timed, they need various genes, proteins and organs.