[extropy-chat] why the vertebrate eye might not be suboptimal after all

[Damien Broderick]

At 03:50 PM 7/6/2006 -0500, I url'd:

>http://www.arn.org/docs/odesign/od171/retina171.htm

A medico pal, not on this list, comments:

<it's still crap. The "blind spot" is only one of the flaws in the 
vertebrate eye, and by far the least important one (which is, no 
doubt, why the author Ayoub concentrated on this). Basically, Ayoub 
has taken all the rejigs evolution has provided to make the 
vertebrate eye work and then complain that if the eye wasn't wired 
that way all the rejigs would make things worse. Well of course they 
would. If you fit a catalytic converter to a hydrogen-powered car 
it's only going to slow it down.

Perhaps the most important problem with the vertebrate eye is the 
fact that the design makes it easy for the retina to shear off the 
back of the eye. Retinal detachments are a common problem in humans. 
I don't see how anyone could possibly argue that retinal detachments 
are evidence of good design, which is no doubt why Ayoub doesn't even 
mention the fact.

The real test is this conclusion: "nor is it easy to conceive how it 
might be modified without significantly decreasing its function." In 
fact it's very easy. After all, we have a perfect example sitting 
around. It's called the mollusc eye. And it manages to be just as 
good at seeing as the vertebrate eye without all the stupid design 
features AND without the flaws that Ayoub claims would necessarily 
eventuate from a reverse design. You'll notice the hoops Ayoub jumps 
through specifically so that he doesn't even have to address the 
issue of the cephalopod eye. "Would hundreds of thousands of 
vertebrate species -- in a great variety of terrestrial, marine, and 
aerial environments -- really see better with a visual system used by 
a handful of exclusively marine vertebrates?" In other words, the 
vertebrate eye must be better because there are lots more 
vertebrates. Except of course, by that logic, the most successful eye 
of all time is the insect eye. Ayoub seems to be unaware that the 
very existence of multiple different eye designs poses a major 
problem for ID. >

[me:]

I don't defend theistic ID, which of course is horseshit. I was 
interested in some of his points attempting to counter alleged 
suboptimality. Your own points are compelling but don't dispose of 
some of his alternative-perspective pleading for the benefits of the 
way things are.

<It could be explained away if eye design followed the ecological 
niche of each creature, much the way arms become flippers in whales. 
But the eye doesn't follow that process. The eye appears to have 
evolved many different times (11 from memory), and it doesn't 
discriminate along ecological niche lines. Fish, with their 
vertebrate eye, live in water, alongside octopuses with their 
cephalopod eye and crabs with their arthropod eyes. This only makes 
sense from the "frozen accident" perspective. And even if Ayoub is 
right and the vertebrate eye is superior, then why do the cephalopod 
and arthropod eyes exist? Whatever eye is "superior", the others are 
not, and Ayoub's way of dealing with this is to play semantic games 
so that he doesn't even have to assess which design is superior. 
Which sort of defeats the purpose of his argument, don't you think? 
"I am only going to consider the vertebrate eye, and since that is 
the only eye I will consider, it follows that it is the best design I 
will consider."

Note also that he called cephalopods "marine vertebrates". Since 
Ayoub is a professor of biology who teaches marine biology, I can 
only conclude that thinking about ID in a positive light 
automatically shuts down the critical thinking parts of the brain. 
Which would certainly explain a lot. >

[me:]

It's obviously a typo. Interesting that none of his dopy acolytes 
hasn't pointed it out to him, though.

Damien Broderick