New eyes for blind cave fish?
A remarkable experiment leads to much evolutionary misinterpretation
9 August 2000
Fish living in caves, in permanent darkness, are blind, with apparent ‘scars’ where their eyes should be. In the quarter of a century in which I have written and spoken on creation issues, I have often raised the matter of eyeless fish to argue against evolution, despite the fact that I believe that these fish arose from ones that originally had eyes. I also agree with evolutionists about the fairly obvious mechanism by which they think this happened. Nevertheless, I hope it will be clear from what follows that I find it exceedingly strange that some evolutionists would gloat about this as a ‘classic proof’ of evolution.1
Note that such fish often are, in all other respects, identical to the same species of fish living at the surface and having eyes.
Imagine a situation in which a group of such ‘normal’ fish swim into a stream which enters an underground cave, and become trapped in this pitch-dark environment. Their eyes are completely useless here.
But eyes do not ‘disappear’ just because they are no longer needed. The fish’s DNA would have programmed into it the instructions on constructing eyes, and the code on the DNA does not ‘know’ that the eye is no longer needed, so it will keep on manufacturing eyes, generation after generation.
However, due to the effects of the Curse on all creation (Genesis 3:19, Romans 8:20–22), genetic copying errors (mutations) arise in all living things. In fact, in a moderate-sized population, many of these errors occur in each generation. It is not hard to see how one of these could result in a gene that usually ‘switches on’ eye development being corrupted, or somehow ‘switched off’, via mutation.
In a normal above-ground situation, such eyeless fish would probably never survive much past early infancy, because they would be so handicapped both in locating food and escaping predators. So for all practical purposes, we never see eyeless fish in the wild where there is sunlight.
However, in the cave, it is a different matter. The eyeless type no longer suffers this disadvantage compared to its compatriots. Not only that, the eyeless ones even have an advantage over the others. This is because, as fish bumped into rocks and cave walls in the darkness, the eyed ones would be likely to injure their eyes. The delicate tissue of eyes is prone to injury, which would allow harmful bacteria to enter, leading to infection and often death.
The eyed fish would thus have a lesser chance of surviving to produce offspring. Those fish carrying the ‘eyeless’ genetic defect would have a greater chance of passing it on to the next generation, so it would not take many generations under such circumstances for all the fish to be of the ‘eyeless’ type.
But this classic example of mutation/selection causing adaptation to a new environment is also a classic example of a mutation causing a downhill change. It is not showing us how the first stages of a new, complex adaptation could arise, it is merely showing us how complex information coding for great engineering design is being corrupted or lost. The grand-scale theory of evolution—that microbes have become millipedes, magnolias, and microbiologists—demands that huge amounts of new information, of true genetic novelty, have arisen over millions of years. To show such information arising from natural processes is the real challenge for evolution. It is a challenge which the renowned Darwinist Richard Dawkins was unable to answer, as shown in the video From a Frog to a Prince (as well as refutation of Skeptic’s attack and refutation of Dawkins’ later response).
Even if one tiny example could be found where information had arisen by chance mutation, Dr Lee Spetner’s classic book Not By Chance (see right; as well as this review) shows that neo-Darwinian theory requires literally hundreds to be observable today. So far, all the examples studied (including the handful of ‘helpful defects’, like the loss of eyes in cave fish, or wingless beetles on windy islands [see Beetle bloopers]) show a loss of information.
The fascinating experiment (by researchers from the University of Maryland, USA) that has brought blind cave fish back into the news was one in which young eyeless fish had lenses implanted in them from the same species of fish (Astyanax mexicanus) living at the surface. Eight days later, the blind fish seemed to be regrowing eyes. After two months, they had a ‘large restored eye with a distinct pupil, cornea and iris. In addition, the retina of the restored eye showed rod photoreceptor cells …’.2
The researchers are not saying that the fish developed sight, which would require regrowth of nerve connections to the brain and more. This experiment is of great interest in helping us understand more about the pathways by which genes express the development of certain structures in the embryo. The following may be helpful in understanding what has taken place:
It has long been known that during the development of certain frog embryos, for instance, the lens not only appears first, it acts as an ‘inducer’ of the development of most of the rest of the eye. Thus, if the lens from one embryo is surgically embedded into another embryo at a spot different from where the eye normally develops, an eye will start to form at that location.
Both in the above example, and that of the cave fish, the development of the eye structures can only take place if the organism into which the lens is transplanted has the genetic instructions present in its DNA to manufacture such structures.
This indicates that the mutation by which the fish initially became ‘eyeless’ did not somehow ‘delete’ all of the ‘eye information’, but just interfered with the process leading to the eye’s development. An analogy with computers would be deleting files on a computer—the information is not deleted, just the record of its location on the hard disk. If the data as such were not still there, ‘undelete’ programs would not be possible.
In the example here, the mutation most probably just blocked the proper formation of the lens. Without the lens to induce the rest of the eye to form, it won’t. This is supported by the fact that in the embryos of eyeless cave fish, eyes start to form, but the lens that has started to form deteriorates, and the other structures remain undeveloped.
This is the first time, to my knowledge, that such optic induction experiments have been successful on any organism in a post-embryonic stage. As such it is important in future embryological research into the immensely ingenious, complex, and still very poorly understood, processes by which an adult organism develops from a tiny fertilized egg.
Sadly, though not surprisingly, this has been described in such a way as to promote the ‘evolution is fact’ idea—even though it has nothing to do with demonstrating that microbes could turn into man (and as shown, the change is in the opposite direction required). It has been described as ‘Eye parts lost during millions of years of evolution were restored in just a matter of days’.3 We have already seen that it is misleading to describe the loss of the ability to produce eyes as ‘evolution’, because it gives rise to the impression that it has something to do with how there came to be such things as fish with eyes in the first place. In addition, there is not the slightest bit of evidence that the process of losing them took millions of years. In fact, it would be surprising if it took more than a few dozen generations, or just a few short years, given the scenario described earlier.
Indeed, considering the supposed creative power of ‘evolution’, it is remarkable that these fish, allegedly separated for millions of years, are so near-identical to those living at the surface that even evolution’s most hardened ‘true believers’ concede that they should be given the same species name. The notion that they have not been cut off from each other for anywhere near as long, directly fits the facts.
- A recent example is Jerry Coyne, an evolutionist from the University of Chicago, who reviewed Niles Eldredge’s anti-creationist book The Triumph of Evolution in the Chicago Tribune, 30 July 2000 Sunday, Books; pg. 4. Among other things, Coyne berated Eldredge for not mentioning ‘some of the classic and most powerful arguments for evolution [including] the nonfunctional eyes of cave organisms, which evolved from sighted creatures.’ Return to text.
- www.sciencedaily.com/releases/2000/07/000728082041.htm, accessed 9 August 2000, 17 January 2017;
www.sfgate.com/cgi-bin/article.cgi?file=/examiner/hotnews/stories/28/fish.dtl&type=science, accessed 9 August 2000;
www.sfgate.com/news/article/Science-gives-eyes-to-blind-subterranean-fish-3052068.php, accessed 17 January 2017. Return to text.
- Ref. 2. Return to text.