You're dodging again. When I point out specific problems in your claims, you dodge and shift to grandiose generalities. When I point out the problems with your generalities, you dodge by xeroxing page after page of vaguely related minutiae from various websites.
You clearly love dancing, but since you keep stepping on your own feet, let's turn off the music and cut to the chase.
Your original claim was that "gradualistic" development of placental birth from an egg-laying predecessor was "impossible" because it couldn't have happened in "one mutation" or "one generation". You asserted that it *must* have happened "all at once" (or else not at all) because otherwise the embryo would have "starved" for lack of nourishment.
I demolished this on several grounds.
First, I showed that you had completely overlooked the mechanism of developing placental feeding *in addition to* the pre-existent yolk-feeding method, not as an immediate *replacement* for it to which you had simplistically limited your thinking. This opens the door for a *multi-generational* development of the placenta instead of the "single generation" method you had considered to be the "only" possibility.
To date, you have not attempted to refute that point at all. Nor, unfortunately, have you conceded it. Instead, you've just danced around it hoping to distract attention from it by reprinting pages of various websites for us, while *continuing* to cling to your flawed "one mutation, one generation" scenario.
Second, you have grasped for as much as you can get your hands on (including the aforementioned spews of website cut-and-pastes) and flung it against the wall in the hopes that something sticks. Your hope was that you could find something that would show that a placenta is (allegedly) so much more complex than egg-laying mechanisms that its development would boggle the mind (well, *your* mind, anyway).
Unfortunately, all of your specific examples have so far fallen into the following categories:
1. Structures or processes *already present* in egg-hatched reproduction. Sorry, no cigar, since these hardly need to be "developed" in order to be put into service for placental birth.
2. Structures or processes which clearly are not necessary for a primitive placenta, they are merely improvements (albeit sometimes great improvements) on the minimum configuration, and could be added at any later point after the "first" successful placenta was developed. I include in this category those structures/processes which you simply *declare* to be absolutely necessary but for which you have not provided any sort of actual evidence. *You're* the one making the claim of impossibility, *you* document the alleged impossibilities and demonstrate that they are, indeed, absolutely necessary steps. You have the burden of proof.
3. Structures or processes which may have been necessary novel developments for the first primitive placenta, which you claim (without any real support) are somehow impossibly difficult. See #2 for a discussion of your responsibility for a burden of proof. I'm afraid that your just saying, "gosh-a-roony, that sure looks hard to me" doesn't even begin to approach the standards of actual evidence.
And as a further flavor of error in your argument:
4. We haven't even yet touched on the topic of your presumptions of "irreducible complexity". For example, the placenta could have started out as something else useful before it became useful as a nutritional conduit. For just one scenario, it may first have served as just an "anchor" to the womb while the embryo subsisted off its yolk prior to early (e.g. marsupial-like) birth. Only many generations later, once it was already reliably attaching to the uterine wall, might it have developed a way to pass nutrients. I don't think this is necessarily what happened, but the point is that in order to actually cover all bases in your "can't get there from here" claims, you need to make sure you've considered and examined *every* possible series of stages, and then eliminated each and every one of them. Otherwise, your claims are just empty declarations, devoid of any real rigorous support.
The above is the evolutionist 'leap of faith' through a chasm the size of the Grand Canyon.
No, sorry, *you're* the one claiming that it *couldn't* have worked without *all* modern features in place. *You're* the one making a "leap of faith" if you haven't already examined and discredited *every* possible pathway by which one could get to "here" from "there". My job in this discussion is simply to point out all the possibilities you clearly *hadn't* already considered.
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,
Oh? Prove it. Prove that the embryo-side of the placenta couldn't "leech" enough nutrients out of an *unmodified* uterine wall to be at least partially useful (especially since this is pretty much how the ruminant placenta works *now*). Until you have proven this, you *can't* claim that you've made your case. Admit it -- you're operating off of feelings, without evidence (and until I informed you of a great deal and corrected your many errors, without any real knowledge of how the whole system actually works).
the attachment of the placenta to the uterine wall,
Hardly a major feat, due to point #1 above ("already works that way in eggs").
and the non-rejection of the 'foreign' body by the mother.
We already dealt with that in a prior post, don't pretend we haven't. That problem would already have been addressed long before placental development commenced.
Furthermore, it's clear that rejection isn't automatic failure for gestation, since equine (horse) gestation *always* involves immunilogical rejection of the "chorionic girdle" which develops at about 25 days into gestation, and becomes completely rejected by the mother at about day 100-140. But no matter, since by then it has already done its job. Didn't know that, did you?
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.
In *modern* placentas. Do get back to us when you show that they were a necessary component of the *first* eutherian placenta. For elucidation you might want to do some research and find out how many of them *aren't* present in the perfectly workable shark and marsupial placentas.
Ooh, better yet, let's compare your account to *other* eutherian mammalian placentas to see how much of that is actually "necessary", shall we?
Ruminant (cows, sheep, etc.) placentas work in a pretty straightforward manner, much simpler than human placentas which you erroneously focus on as if they were the *only* workable kind.
The uterine wall of the ruminant undergoes essentially *no* changes in preparation for the attachment of the placenta. The placenta nestles up to wavy tissues of the uterus which are *always* present in the ruminant uterus, pregant or not. It just plasters up against the uterine wall as it grows and doesn't do any kind of "invasion". And it doesn't do any of the fancy "coordination" you believe is necessary for a functioning placenta. Oops.
As the following shows:
[cut-and-paste snipped]
Um, it "shows" nothing of the kind, you might want to read your own sources more carefully. Note the following passage, "It will induce the uterine cells to form the maternal portion of the placenta, the decidua". See the mention of the "decidua"? This is discussing only *deciduate* placentas. Guess what? Ruminant placentas work just fine *without* all this rigamarole. So much for your presumption that this mechanism is a necessary ingredient of primitive placentas, eh? Oops again.
Let's look at the above problem more closely:
Let's not, since cows get along just fine without all that overcomplication.
[Cut-and-paste says:] While the embryonic epiblast is undergoing cell movements reminiscent of those seen in reptilian or avian gastrulation,
*AHEM*... Free clue for the clueless -- and from your own sources, too...
There are numerous 'little' problems within the above that need to be solved for the system to work properly, one of them is oxygen:
Why is this a "problem"? Sure, having a fetal hemoglobin with a higher oxygen affinity than the maternal hemoglobin increases the efficiency of the transfer, but can you demonstrate that it's *necessary*? Some lemurs, for example, appear to use the same hemoglobin throughout both their fetal and post-birth lives. Even theoretically, oxygen transfer would still take place with identical hemoglobins on both sides of the placental barrier, just not as efficiently.
But even if were actually a necessity before placentas became feasible, it's hardly an insurmountable step. A proliferation of hemoglobin types is the norm among animals, not the exception. For all you know, birds and reptiles may very well already use a fetal hemoglobin during the egg stage, where respiration is performed quite differently than during "post hatch" life (I wasn't able to find any specific information either way on that).
I could go on and on,
Oh, I'm sure you could... But wouldn't it be simpler to just admit holes in your original faulty claim? Like, say, admitting that it *needn't* have happened in "one generation" after all?
however, let's just show the problem of adhesion: [Implantation]
Cows don't bother with any of that and they work just fine... How many more times am I going to have to instruct you on basic biology?
Finally, lets show the developmental system of an egg: [picture snipped] Compare the above to the picture of the human developmental system in Post# 257 .
Looks pretty much the same to me -- did you have a point to make? And, by the way, it *really* looks like the intra-uterine cow embryo.
Again, each step requires numerous other steps as well as coordination of all the steps.
Again, cows do fine with about 3/4 fewer steps than you have listed as "essential". Try again.
The reductionism of evolutionists does not cut it.
And yet, cows still live... Maybe it's your assumptions that are wrong.
The steps are numerous and have to be precisely timed, they need various genes, proteins and organs.
Mooooooooooooo!
I'm going to summarize with the statement I used to start this whole discussion -- if you were smart, you'd have made sure that you actually *knew* enough about gestation to be able to discuss it intelligently and not trip over something that's already known, like for example how other animals already manage to reproduce.
Now that I've dealt with your latest round of "throw another website at the wall and hope something sticks", let's get back to basics...
Do you admit that your original presumption that it "had" to occur "in one mutation, in one generation" was faulty? Yes or no.
Do you admit that you erred when you presumed that mammals would have had to "develop" structures and processes which, oops, were already present in the egg-laying method of reproduction? Yes or no.
Do you withdraw your original claim that gradualistic development of placental birth would be "impossible"? Yes or no.
Note: This is a test of your intelligence and honesty. Respond accordingly.
