July 16, 2007

The Human Eye


I'm currently reading the book, "A Briefer History of Time" by Stephen Hawking. Not to be confused with a "Brief" History, this is an updated version for the really stupid people. And yet it still goes over my head from time to time. Hence today's question from a thought brought up recently by jmc.

How did the human eye evolve from nothing? I can't comprehend the natural selection of a human eye. I understand the Darwinian idea that tall giraffes beat out short giraffes, hence, only tall giraffes today. But, I don't understand how an eyeless creature formed an eye? Any evolutionists out there?

8 comments:

JMC said...

I actually stole that eye idea from someone else. I think it was in some article in a news magazine talking about intelligent design. But it stuck with me as a good example for that viewpoint. And a good reminder to people that evolution is still an unproven theory (though well-supported by lots of scientific evidence). Plus it gets people all up-in-arms, which can be entertaining. :)

Aaron said...

Believing in the idea that the human eye can evolve from nothing takes more faith in a belief system than you or I have my friend.

Sabai said...

Be that as it may, I still want to hear the best argument for it. There's got to be one, right?

JMC said...

Okay, let's see. How 'bout this:

One day, a bunch of multiple-celled organisms were swimming around in the primordial soup, bumping into each other, which would often result in the bumper being eaten by the bumpee. At some point one of the cells in one of the organisms had a mutation that made it become a light receptor. After a while there were a lot of these things with light receptor cells, and they survived better because the light receptors gravitated toward light, thus avoiding bumping into things that registered as darker and could eat them. So, over time, the light receptor cells became more numerous on each organism. Then they became more sensitive to varying degrees of light. Then somewhere along the line when a brain evolved (I know, a whole other discussion), nerve cells developed that connected the light receptors and the brain, so that the organisms could make sense of the light. The light receptors became more specialized, etc., etc., etc. And voila!! The human eye!

Aaron said...

So, in "theory" by random chance, one organisms mutation made it have light rececptors... but how does that explain that exact same mutation will even ever happen again? Wouldn't it have to be that multiple organisms mutate exactly the same and then mate to create an offspring?

Plus, nature abhors change. Look at animals. Hybrids are for the vast majority sterile. Other than plants, there is only 1 insect that is not sterile through hybridization. Random chance mutations being passed down to the next generation doesn't seem all that likely to me.

Again, there must be a lot of faith to believe in the unproven theory of macroevolution.

JMC said...

Well, hey, at least I tried. :)

Sabai said...

ok, i requested help from an evolutionist-friend of my mine.

(here is his response.)

As far as the vertebrate eye discussion goes, I could you refer you here, where there's a lot of good information:

http://en.wikipedia.org/wiki/Evolution_of_the_eye

A range of eye forms--from simplest spot of pigmented cells to the very acute eyes of hawks & octopuses & about everything in between--already exist in animals in nature. This sample of structures makes it relatively straightforward to propose a simple series of steps to illustrate how "more complex" eyes evolved. Such a proposed sequence also is logical because each minor innovation that would increase visual acuity in any way would have been beneficial to its bearer & would have been selected for. The development of such an organ would have been under intense selection, & there is a lot of evidence that features under strong selection can accumulate traits much more quickly than features not under (or under weak) selection. Hence, scientists propose that a relatively "complex" eye evolved in a relatively short (geologically-speaking) period of time (say, less than a million years).

Just as a side note, proponents of Intelligent Design have often proposed that the eye is an example of an "irreducibly complex" structure that has an optimal design. At the end of that Wikipedia link, its described how the irreducible complexity argument doesn't really hold any weight, & many people would argue that the human eye has a less-than-optimal design (e.g. the "backwards retina" argument).

(I'm not smart enough to follow that, but hopefully it'll help some of you) :)

Aaron said...

Then why hasn't the eye evolved into a more optimal design?

Surely along the way there has been a mutuation that made the eye more optimal? Shouldn't it have survived?