Thanks for your interjection, it’s nice to have a fresh view presented.
Firstly could we nail down this point.
The introduction of vestigial organs is an argument for degeneration in an already existing function, whatever the cause of that degeneration.
It does not stand up as an argument against functional design.
However canalon and now you both make the same point about essentially keeping up with new information as this is the way science proceeds. You also say that old information isn’t necessarily outdated or wrong. I completely agree.
However simply reading reviews does not advance your knowledge of a subject. Reading the papers themselves is what matters and that is what I encourage you to do.
So let examine what the latest papers are revealing about evidence on this subject.
Of necessity this post will be somewhat long, because in science the detail of evidence is important.
It is still not known how cave fish have lost eyesight and pigmentation. This is not just my view.
W. R. Jeffery (2005
) Adaptive Evolution of Eye Degeneration in the Mexican Blind Cavefish put it this way.http://jhered.oxfordjournals.org/content/96/3/185.full
Today, the mystery still persists, although the field of possibilities has been narrowed to two opposing hypotheses… The neutral mutation hypothesis (Kimura and Ohta 1971) suggests that eye regression is caused by random mutations in eye-forming genes, which accumulate in cave animals under relaxed selective pressure
Remember this is the hypothesis that Professor Deamer offered in1964.
In contrast, the adaptation hypothesis suggests that loss of eyes is adaptive and has a selective advantage in the cave environment (Culver 1982; Poulson 1963;Poulson and White 1969). As implied in the Darwin quote, however, the actual benefits of blindness have been difficult to understand.
This hypothesis is the one favoured by Jeffrery along with others, and is a Darwinian explanation.
Jeffery summarises the very interesting discoveries in the molecular changes that take place during this process. (new information) The paper is a fascinating read.
Eye formation does commence in the embryo but is arrested at a certain stage in development. ( Deamer in 1964 referred to Vandel’s (1961) discovery of this fact.)
This arresting takes place during lens formation.
However no genes understood to function during eye formation, appear to be damaged.
Also when the lens of an embryo of a surface fish is transplanted into the embryo of a cave fish at the same stage development the eye in the cave fish continues to develop normally. When a reverse transplant takes place the eye of the surface embryo is arrested, suggesting that the lens is the central controller of eye formation.
It has also been discovered that many genes are up regulated in cavefish relative to surface fish, rather than vice versa. The expanded regulation in particular of the hh genes seems to be quite central in the degenerative process.
It is for these reasons that Jeffery hypothesises that Natural selection is at work and not mutation.
In his 2008
paper Jeffery rows back a little in his assessment especially in the case of loss of pigmentation.http://www.life.umd.edu/labs/jeffery/Pu ... o.2008.PDFcavefish and microevolution of development
Surface ﬁsh and caveﬁsh brains are remarkably different, much more than expected from phenotypic variation within the same species. Page 270 2nd column
…The evolutionary forces that generate these changes are not understood. …page 271 1st column
How and why behavioral changes have evolved is almost completely uncharted territory.
The relative simplicity of caveﬁsh behaviors may reﬂect the short time since their original divergence, underscoring the importance of a micro evolutionary perspective. Astyanax has the potential to make signiﬁcant contributions to understanding the evolution of behavior at the molecular level.
H Wilkens University of Hamburg, Germany has a view that favours the mutation or neutral theory. (introduced by Deamer in 1964) in his 2010
Genes, modules and the evolution of cave ﬁshhttp://amec.glp.net/c/document_library/ ... -21261.pdf
This is what he says.
Therefore, it is likely that in cave ﬁsh with a transplanted lens from surface ﬁsh the retina remained in its reduced state characteristic of other cave ﬁsh. This result is supported by the observation that these specimens did not respond to light (Romero et al., 2003). This ﬁnding suggests that for the restoration of an eye two subunits, lens and retina, would be necessary. Thus the ‘complete restoration of the eye’ as hypothesised by Jeffery (2005) has not been shown and hence there is no support for the hypothesis that the lens alone has a ‘central role in cave ﬁsh eye development’.
Thus, I suggest that eye regression in Astyanax seems to be mainly because of down regulation of structural genes by the expanded hh gene expression,
which was suggested to have a causal role in eye development of the cave ﬁsh (Yamamoto et al., 2004).
However, the question of what causes downregulation of hh genes remains unsolved.
Keeping in mind that expanded expression of the hh genes may have a causal role in eye reduction of the parental cave ﬁsh, the development of ‘back to surface eyes’ could be explained by the secondary restriction of expression and downregulation of hh genes. I suggest that this could be due to as yet unidentiﬁed genes. In contrast to the hh genes, it is likely that these genes show loss-of-function mutations. In ‘back to surface eyes’ they could be expressed again because of the complementary restitution of their function.
I suggest that the variability of regressive traits is attributed to the loss of selection. Explanations of the reduction of biologically functionless traits in cave ﬁsh based on selection seem to be less probable because natural selection usually acts strongly to eliminate phenotypic variability. Therefore, variability of regressive traits in cave animals would be one of the rare cases, in which random mutations can manifest and are not eliminated by natural selection acting to preserve the functional capability of a module.
Incidentally the paper of (Romer 2003
) Wilkens refers to is herehttp://www.ncbi.nlm.nih.gov/pubmed/14984036
Romero A, Green SM, Romero A, Lelonek MM, Stropnicky KC. 2003One eye but no vision: cave fish with induced eyes do not respond to light.
So despite the passing of nearly 50 years Professor Deamer’s hypothesis is still very much in alive and kicking.
Both the eyeless epigean fish and cave fish with induced eyes are indifferent to the illumination whereas the surface forms are scotophilic, suggesting that optic development and phototactic behavior are decoupled.
The last point I make is this.
Jefferies (2008) makes good mention of cave fish as being a natural lab for the study of evolution since here we have both ancestor (suface) fish and their descendents (cave fish)
Also note that he recognises this process as micro evolution
(variation within a species)
Now lets return to Deamer’s reference to (Woods1956
) the evidence from which can be downloaded here. http://libsysdigi.library.uiuc.edu/OCA/Books2008
CHICAGO NATURAL HISTORY MUSEUM BULLETIN November 1954 page 4
Here is first hand evidence of the gradation of this degeneration that Deamer used to support his hypothesis. Evidence from the natural habitat.
Another kind well-known to aquarists is the cave tetra from San Luis Potosi, Mexico. This species reveals a fourstep gradation in the degeneration of the eyes from perfectly eyed, normally pigmented, surface-dwelling individuals to totally blind ones with the eye socket covered with tissue and no evident eye structure
So it is from the evidence of the natural environment that Deamer claims support for his view.
Even today we are unable to identify the actual theoretical mechanism of natural selection at work.
How does Jeffery he put it?
The evolutionary forces that generate these changes are not understood
If even within micro evolution (which as far as I know everyone accepts) natural selection cannot be identified at work, how is it that the Darwinian process of macro evolution is so certainly propounded as fact?
Therefore and with great respect, I would encourage both you and canalon to keep away from sweeping statements, unless you are confident you can back them up with evidence.
btw I have not yet received a reply from Professor Deamer. It is after all the holiday period.