Joined: May 2002
It seems clear to me that you are ignoring the details provided by me about possible pathways for evolution.
If you claim that front loading explains Pecten then you accept that evolution can generate the eye as found in Pecten unless you are not talking really about front loading but intervention.
Perhaps you can first share with us your front loading hypothesis wrt for instance Pecten and the Lobster? In fact you suggested that Pax-6 gene 'supports front loading' but if that is the case your argument seems to be that given the existence of Pax-6 at an instant t=t_0 you expect evolution to lead to the large variety of eye 'designs' as found in nature. Is that correct or are you backtracking your claims that let's say every species/family/genus/ or at whatever level was 'front loaded' independently at different instances in time/space?
I doubt that one can make a logically consistent claim of front loading that is not contradicted by the data other than through the Pax-6 gene. But Pax-6 seems to be going back in time quite some distance, long before the family Pectinidae arose.
To me it seems that you are not arguing for front loading but rather intervention since your objections seem to be terribly ad hoc and seem to refuse to recognize natural pathways to these structures. If that is the case then you cannot be arguing for front loading since teleological front loading is defined to be at t=t_0 the necessary information was inserted so that at a given time t1, with t1>t0, a certain feature arises in a certain family/species. Non teleological front loading would be that at a certain instance t=t_0 an initial state exists and we can trace back to such an initial state showing how the various eye 'designs' all seem to trace back to ancestral forms.
As far as the references to Korthof et al, they are meant to help the interested reader understand many of the problems found in Denton's work.
It seems evident to me that Nelson has not familiarized himself with the papers he quotes but rather that he is relying on second hand information which may or may not be relevant or even accurate. As I have shown, Dakin's 1908 statements are explained in more detail in 1967 and onwards where it was shown that the Pecten eye is very likely an evolutionary continuation of the single retina eye with the addition of a reflecting layer. The transition is even better to understand from a selective evolutionary viewpoint when realizing the advantage of these changes namely the ability to see both in and outside water. Combine this with the fact that the Pecten resides in a tidal affected area and thus may be exposed to both water and air and one realizes the selective advantage of the Pecten eye. Thus we have found the answer to Dakin's uncertainties. Nelson complains that I do not provide sufficient detail how natural selection and mutation built these eyes but if Nelson were to argue for front loading he would have no choice but to accept that natural forces can lead to the Pecten eye or Nelson should drop his claims about Pecten and front loading. Surely our ignorance of certain details should not be taken as evidence for front loading. In fact although we have not yet obtained all the necessary evidence a plausible pathway has been provided. Nelson may be complaining about 'sufficient details' but the amount of detail so far already exceeds any alternative hypothesis. And since Nelson seems to want to argue front loading he also by default has to accept some time period in which evolutionary processes shaped the eye of Pecten to what it is right now.
Nelson then raises the spectre of Spondylus, which attaches to rocks as if this forms a problem. Until Nelson can show us from the original research papers what the eye of the Spondylus looks like as compared to Pecten we have no real way to discuss this. Secondly until Nelson shows that there is actually a problem explaining the evolution of the eye in Spondylus and Pecten, we merely can speculate about what Nelson's 'argument may be'. Since Nelson seems to accept the evolutionary history of Pecten and Spondylus one may wonder why he seems to oppose that evolutionary processes led to the eye 'designs' since he does seem to accept front loading and common descent. Perhaps Nelson believes that another mechanism than evolutionary mechanisms played a role? He mentions front loading but as I have shown that merely states that at a given stage in time t=t_0 information was injected into the genome to allow Pecten and Spondylus to form their respective eyes. The fact the pectinacea were ancestral to Spondylidae surely supports the evolutionary pathway. So it is not clear to me how Nelson suggests front loading could have helped Pecten and Spondylidae. In fact, if Nelson is correct about the location of the Spondylus and its eyes (so far the data seem to be vague on either aspect) then Nelson may have to explain why a front loader would lead to a system which is now defunct namely the ability to see in air.
Nelson then confuses the issue of front loading and intervention even further when he states
|If these biological features were poised to evolve into greater complexity through an intelligent agent then it wouldn't have been as difficult as a blind force tinkering with such a complex system. |
Is Nelson suggesting that evolution is guided through an intelligent agent. Then he should not be arguing for front loading but instead for intervention.
Nelson still seems to be unwilling to deal with the available evidence which includes intermediate stages for the varieties of simple and compound eyes. Perhaps Nelson wants to argue that the details are not sufficient but that's just a matter of time for science to find all the common genes and variations that have led to the variety of eyes as found in nature. So far the evidence strongly suggests both evolutionary mechanisms and at least for many basic components a common ancestor.
If Nelson had taken the time to look at the pictures then he would have noticed how these portray the variety of intermediate paths likely to have been taken in the evolution of the various eye forms.
Nelson still repeats his so far unsupported assertion that
|Again, none of this shows how blind natural forces would, nor does it even explain why, natural selection would guide the organism down the difficult road of refraction to reflection in my particular examples|
1. Could Nelson show that the road of refraction to reflection is difficult
2. Could Nelson show that the road of refraction to reflection is even relevant for the lobster?
Nelson confuses the situation even further by claiming that
However, what I would expect from a Front-Loading persepective is that every step of the way was every bit more complex then the last, however, through the help of pre-positioned elements the evolution of these eyes was directed through intelligent agency.
So is it front loading or is it intervention? If it is front loading then we have the situation that at a certain time the information needed for evolution to play out was injected into the genome of a common ancestor and that from this common ancestor all the descendants arose with the large variety of eyes. Ignoring for the moment the grasping at straw nature of such a front loading scenario which would have to play out through an inherent chaotic and thus unpredictable system and interactions to eventually lead to the eye of the Pecten. Nelson presents no more evidence than that a some moment the basic building blocks were present that eventually would allow the Pecten or any other organism to evolve an eye design. No effort is made by Nelson to show that the eyes of the lobster are optimal for the functioning of the lobster. In fact Nelson merely argues that for the lobster eye, the eyes are perfect squares that are fine-tuned for the vision of lobster. No further information is presented to support this case. And if Nelson wants to consider fine-tuning and continue to argue for front loading then Nelson de facto has accepted the fine tuning power of evolutionary processes.
Given the contradictory stance of Nelson on the issue of front loading I would encourage Nelson to address the following issues.
1. Explain the hypothesis of front loading as it applies to Pecten.
2. If Nelson accepts front loading then does Nelson accepts that natural processes are responsible for the shaping of the eyes of Pecten? In absence of such an acceptance, Nelson cannot be talking about front loading here.
3. Can Nelson explain in detail the similarities and differences between Pecten and Spondylus and can Nelson provide us with the arguments proposed by Dakin? Do the findings apply to the whole family of Spondylus or just some particular species? After all the various species of Spondylus do seem to occupy a large variety of ecological niches
4. Can Nelson show that the lobster eyes are perfect squares or is Nelson using stylized drawings to reach these conclusions?
Perhaps Nelson may want to explain why the squares in the following picture are all but perfect?
Perhaps Nelson was confused by the resulting drawings?
Perhaps Nelson can also appreciate what perfect squares really would look like?