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  Topic: The Blind Leading the Blind, Berlinski on Eye Evolution< Next Oldest | Next Newest >  

Posts: 319
Joined: May 2002

(Permalink) Posted: April 05 2003,01:55   

Here is a bit of startling naivete from Berlinski's latest ("A Scientific Scandal").  I may send this bit as a letter to commentary or somthing.


Let us agree that in the development of an eye, an initial light-sensitive patch in a given organism becomes invaginated over time. Such a change requires a corresponding structural change to the organism's anatomy. If nothing else, the development of an eye requires the formation of an eye socket--hardly a minor matter in biological terms. Is it really the case that an organism otherwise adapted to its environment would discover that the costs involved in the reconstruction of its skull are nicely balanced by what would initially be a very modest improvement in sensitivity to light? I can imagine the argument going either way, but surely an argument is needed.

While Berlinski should be congradulated for pointing out Dawkins' inaccurate popularization of Nilsson and Pelger's article on eye evolution as a stochastic computer simulation (it was actually a mathematical model), Berlinski should remove the plank from his own (discussion of the) eye.  In "A Scientific Scandal" he asserts that one of the problems for eye evolution that Nilsson and Pelger did not consider was how the skull would be "reconstructed" to include eye sockets.

But as any decent student who has taken high school biology would know (at least as long as evolution was not expunged due to creationist political armtwisting), eyes evolved before bones!  Cephalochordates, the closest invertebrate relatives of vertebrates, have primitive eyes but no bones.  In fact, based on genetic evidence many biologists now think that vertebrate eyes share a common ancestral eyespot with insect eyes, the common ancestor being a perhaps millimeter-long, nearly transparent but eyespot-equipped worm.

Unfortunately, it is a typical creationist strawman to envision eye evolution as occurring on some kind of mythical eyeless fish with a fully-formed skull, brain, etc.  On the contrary, biologists (who actually know some biology) know that all manner of gradations of eye complexity exist in extant organisms, from creatures with an "eye" consisting of a single photoreceptor cell, through all of the various stages that Nilsson and Pelger depict, to the "advanced" camera eyes of mammals and cephalpods.  Sometimes the whole sequence from eyespot to advanced eye with lens can be seen in a single group (e.g. snails), yet another thing which Berlinski would have known if he'd followed the reference that Nilsson and Pelger gave to the actual classic work on eye evolution, a monster 56 page article by Salvini-Plawen and Mayr in the journal Evolutionary Biology (volume 10, 1977) that reviewed hundreds of papers on eyes across the animal kingdom, entitled "On the evolution of photoreceptors and eyes".  Complex eyes with lenses have even evolved in single-celled dinoflagellates, which have no brains, blood vessels, or numerous other features Berlinski is concerned about.

Berlinski on the other hand has a brain as well as eyes, but apparently does not see when it comes to biology.  He is not a creationist but he certainly seems to hang out with them and uncritically repeats many of their arguments, unaware of the biological facts which contradict them.  If Berlinski is going to declare as bunk the central organizing theory of biology, he should be taking the matter up with biologists in the professional literature, rather than in forums like Commentary, wherein elementary questions like "which came first, skulls or eyes?" can be botched and yet still get published.

Edited by niiicholas on April 05 2003,13:01

  17 replies since April 04 2003,23:50 < Next Oldest | Next Newest >  


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