DavidMcC wrote:
Yeah, and I hope you two are going to withdraw your case against me over your claim that there must have been three identical, fully vertebrate eyes in an ancestral tuatara!

Given no one made this case, it would be odd to require anyone to retract it.

DavidMcC wrote:I sustopect that any ancestor with three eyes the same would be way pre-vertebrate, and the eyes woud not be vertebrate-type, but much simpler.

Yes. I already said that and clarified it repeatedly. You are late to the party.

In fact in this post http://www.rationalskepticism.org/evolution/birds-possibly-developing-selfconcious-brains-t52176-340.html#p2418081 I link back to an earlier post where I already stated this quite clearly and that you had already failed to understand what I wrote.

Sendraks wrote:

DavidMcC wrote:
Yeah, and I hope you two are going to withdraw your case against me over your claim that there must have been three identical, fully vertebrate eyes in an ancestral tuatara!

Given no one made this case, it would be odd to require anyone to retract it.

...

But you implied that a tuatara ancestor must have had three fully formed vertebrate eyes, did you not?
Of course, the three eyes would have been like the lamprey's three eyes - not all the same.

DavidMcC wrote:
But you implied that a tuatara ancestor must have had three fully formed vertebrate eyes, did you not?

No I did not. I suggest you go back to the previous posts and read what I wrote carefully rather than persist with this fiction. I will not re-write for your benefit what I have already linked to twice now and also provided further clarifying responses in my comments to SS.

DavidMcC wrote:Of course, the three eyes would have been like the lamprey's three eyes - not all the same.

The Tuatara's three eyes are already like the lampreys eyes, in that they are not all the same.

Look, Sendraks, can we agree that you were probably referring (apparently without realising it) to the lamprey, with its third eye (which has a lens and of course a retina, without which it would not even be an eye!)? The problem might be that lampreys aren't reptiles, and is only just a vertebrate (early lampreys are generally considered to be primitive to the "true" vertebrates), so you made a slip there, if you were indeed thinking of lampreys.
BTW, I wrote a thread about lampreys years ago, probably on this site, but, as the site search facilities are not what they once were, I will not dig it out just yet.

Sendraks, now that you know about lampreys, perhaps we can end this part of this thread.
(I infer that you did not know about lampreys before I told you, otherwise you would surely have mentioned them yourself.)

DavidMcC wrote:Look, Sendraks, can we agree that you were probably referring (apparently without realising it) to the lamprey,

No. I don't think we could agree to that. I was not thinking of lampreys, my comments are clearly about the tuatara, its ancestors and the specialisation of functions from basal forms.

*edit*

I'm not sure where this sudden fixation on lampreys has come from. If I was going to mention lampreys, I would have prior to this point.

Sendraks wrote:

DavidMcC wrote:Look, Sendraks, can we agree that you were probably referring (apparently without realising it) to the lamprey,

No. I don't think we could agree to that. I was not thinking of lampreys, my comments are clearly about the tuatara, its ancestors and the specialisation of functions from basal forms.

*edit*

I'm not sure where this sudden fixation on lampreys has come from. If I was going to mention lampreys, I would have prior to this point.

I am not fixated on lampreys, I just think you must have been thinking of them as the ancestral species with three eyes. You appear fixated on the existence of a tuatara (or near ancestor) with three similar eyes. That is not a rational conclusion from tuatara eye facts that you yourself have discussed, given that recapitulationism isn't true.

...The genetic structure for a third eye would have remained in the vertebrate lineages, expressed in various forms, such as our pineal gland in, and the parietal eyes of the reptiles.

DavidMcC wrote:
I am not fixated on lampreys, I just think you must have been thinking of them as the ancestral species with three eyes.

DavidMcC wrote:You appear fixated on the existence of a tuatara (or near ancestor) with three similar eyes.

In the context of discussing surface vertebrate eyes, it was the first example that sprang to mind of an extant near basal form that demonstrates two eyes for vertebrates was not always the norm.

DavidMcC wrote: That is not a rational conclusion from tuatara eye facts that you yourself have discussed, given that recapitulationism isn't true.

And I've pointed out, at least twice, that I am not talking about recapitulationism and never have been. I've already acknowledged that recapitualationsim was discarded long ago as being flawed, so it would neither be rational for me to refer to it (and I haven't outside of the context of responding to you) nor would it be rational for you to make reference to it in the context of my posts.

Recapitualationism =/= the study of embryos to determine basal traits held by common ancestors,

Recapitulationism = the theory that every organism in its ontogeny must pass through stages representing the forms of its phylogenetic forebears

DavidMcC wrote:...The genetic structure for a third eye would have remained in the vertebrate lineages, expressed in various forms, such as our pineal gland in, and the parietal eyes of the reptiles.

Yes. I already said as much.
http://www.rationalskepticism.org/evolution/birds-possibly-developing-selfconcious-brains-t52176-320.html#p2417552

Sendraks wrote:

DavidMcC wrote:...The genetic structure for a third eye would have remained in the vertebrate lineages, expressed in various forms, such as our pineal gland in, and the parietal eyes of the reptiles.

Yes. I already said as much.
http://www.rationalskepticism.org/evolution/birds-possibly-developing-selfconcious-brains-t52176-320.html#p2417552

I know you did, but you didn't seem to relate it to the tuatara, whose three eyes you claimed were all the same, originally.

DavidMcC wrote:I know you did, but you didn't seem to relate it to the tuatara,

Of course it relates to the Tuatara and indeed everything else included within the context of my posts in the discussion up to that point

DavidMcC wrote:whose three eyes you claimed were all the same, originally.

I'm getting tired of this bullshit David, because you seem unable to report what I said with any accuracy or honesty. I suggest that if you are going to refer to what I claimed, you simply quote what I said, rather than use your own unreliable interpretations.

http://www.rationalskepticism.org/evolution/birds-possibly-developing-selfconcious-brains-t52176-320.html#p2417515

http://www.rationalskepticism.org/evolution/birds-possibly-developing-selfconcious-brains-t52176-320.html#p2417545

The alternative to what I have said in these posts is that at some point, the Tuatara ancestors went from having two eyes to developing a third eye of limited function. I don't subscribe to this idea at all and it would inconsistent with evolution and what we know about the development of diapsids.

Sendraks wrote:

DavidMcC wrote:I know you did, but you didn't seem to relate it to the tuatara,

Of course it relates to the Tuatara and indeed everything else included within the context of my posts in the discussion up to that point

DavidMcC wrote:whose three eyes you claimed were all the same, originally.

I'm getting tired of this bullshit David, because you seem unable to report what I said with any accuracy or honesty. I suggest that if you are going to refer to what I claimed, you simply quote what I said, rather than use your own unreliable interpretations.

http://www.rationalskepticism.org/evolution/birds-possibly-developing-selfconcious-brains-t52176-320.html#p2417515

http://www.rationalskepticism.org/evolution/birds-possibly-developing-selfconcious-brains-t52176-320.html#p2417545

The alternative to what I have said in these posts is that at some point, the Tuatara ancestors went from having two eyes to developing a third eye of limited function. I don't subscribe to this idea at all and it would inconsistent with evolution and what we know about the development of diapsids.

If there is any unreliability in my posts, it relates to ambiguity in yours.

DavidMcC wrote:If there is any unreliability in my posts, it relates to ambiguity in yours.

If there is ambiguity, then you should have no problems directly quoting text that is such. As it is stands, all we have are your unreliable interpretations about what I have written.

*dual post*

*space for rent*

Sendraks wrote:

DavidMcC wrote:If there is any unreliability in my posts, it relates to ambiguity in yours.

If there is ambiguity, then you should have no problems directly quoting text that is such. As it is stands, all we have are your unreliable interpretations about what I have written.

Sendraks wrote:Actually my claim, such as it is, is that to be consistent with evolution all three eyes would at one point been equally rudimentary. The possibility of the third having more function then degrading, seems unlikely to me but was included for completeness.

You did not say whether "at one point" lies within the time-frame of tuataras, as such.

DavidMcC wrote:
You did not say whether "at one point" lies within the time-frame of tuataras, as such.

In all my previous comments I was referring to the ancestors of Tuataras and the evolution of those ancestors to the Tuatara as it appeared 200million years ago.

Sendraks wrote:

DavidMcC wrote:
You did not say whether "at one point" lies within the time-frame of tuataras, as such.

In all my previous comments I was referring to the ancestors of Tuataras and the evolution of those ancestors to the Tuatara as it appeared 200million years ago.

... Which would include ancient vertebrate fish. The only known fish group with three eyes is the lampreys, which were certainly around at 200mYa, according to most versions of evolution.

DavidMcC wrote:
... Which would include ancient vertebrate fish. The only known fish group with three eyes is the lampreys, which were certainly around at 200mYa, according to most versions of evolution.

The order Rhynchocephalia, of which the Tuatara is the last surviving member, existed 200million years ago. There were certainly lampreys around then and indeed the oldest lamprey fossils date back to 360million years ago, although I'm sure you already know that.

The existence of three eyes in basal reptile forms like Rhynchocephalia (the remains of which are found in many specialised extant forms) could be the product of convergent evolution. However, as Rhynchocephalia is a basal form, it is reasonable to conclude that all members of that order share common unspecialised features which in turn they inherited from a common ancestor, who would have been more basal still.

Sendraks wrote:

DavidMcC wrote:
... Which would include ancient vertebrate fish. The only known fish group with three eyes is the lampreys, which were certainly around at 200mYa, according to most versions of evolution.

The order Rhynchocephalia, of which the Tuatara is the last surviving member, existed 200million years ago.

I was going to point this out and was just looking for a reference to back it up. I like underscoring the hypocrisy of certain posters who seldom support their assertions by trying to support my own assertions more often.

Anyway, according to this source, Rhynochocephalia originated in the early Triassic, approximately 250-240 Mya.
http://www.ucl.ac.uk/museums-static/obl ... lians.html

Certainly no need to go to lampreys 200Mya when there were much more advanced three-eyed organisms running around on land prior to that.