What Good is Half an Eye?
I’m sure that by now, most readers will be aware of the debate that took place on ABC Nightline between Christians Ray Comfort and Kirk Cameron, and atheists Brian Sapient and Kelly of the Rational Response Squad. Many bloggers have put their two cents in on this one, and I don’t think there’s really anything I can add that hasn’t already been covered.
Having said that, I would just like to pick up on one point that Ray Comfort argued in his opening address – the human eye and its ability to prove without any shadow of a doubt, through its wondrous complexity, the existence of an intelligent creator. The irony of this claim, was that it caused my wondrously complex human eyes to roll uncontrollably in disbelief that this argument is still being used!
The argument is supposed to go that the eye is so complex and intricate, that it could not possibly have evolved through natural selection. Each part is useless without the other parts, and it either works as a complete unit, or not at all. This argument, which has also been applied to other parts of animals’ bodies, has been refuted by evolutionists time and time again. For more on this, Ebonmusings has a particularly good article, What Good is Half a Wing?.
We know that the human eye evolved from more primitive forms. This Wikipedia article explains how early eyes worked.
The earliest predecessor of the eye was a simple patch of photosensitive cells, physically similar to receptor patches for taste and smell, called an “eyespot”. Eyespots can only sense ambient brightness: they can distinguish light from dark, but can not distinguish shapes or determine the direction light is coming from. Some organisms covered the spot in transparent skin cells for protection. Eyepatches are found in nearly all major animal groups, and are common among lower invertebrates such as the unicellular euglena. The euglena’s eyespot, called a stigma, is located at its anterior end, has a red pigment, and allows the organism to move in response to light, often to assist in photosynthesis.
I would like to add to the evidence illustrating this passage, by pointing out that we still have eyespots today. What’s more, I can prove it. Please take part in this fun, simple experiment. All you will need to do is find a lamp, and then follow these instructions.
1. Have the lamp next to you, plugged in, but switched off. Make sure that you can see the bulb directly. Remove the shade if necessary.
2. With the lamp still off, locate the switch and hold it in your hand ready.
3. With the lamp still off, stare at the bulb.
4. Now, close your eyes as tightly as you can. Really squeeze them shut, so absolutely no light can get through, although keep your eyes pointing in the direction of the bulb.
5. Keeping your eyes shut the whole time, switch the lamp on. Wait a few seconds. Switch it off again. Back on. Off again. On. Off.
What do you notice? You can see whether the light is on or not, even with your eyes shut. This is exactly the type of vision that earlier, less evolved versions of the eye offered their owners. It may seem primitive, and of course it is, but with predators in pursuit, it could easily have been the difference between life or death. It would definitely have increased chances of survival, and there is no question that natural selection would favour it. That’s how much use a lot less than half an eye is, Mr Comfort!
When open, our eyes are truly amazing in the detailed information they offer us. We see colours, shapes, perspective, etc. But when covered by our eyelids, they are effectively eyespots, the very tools that aided our ancient ancestors. While, for all intents and purposes, useless to us now, at least in comparison to what we’re familiar with, we cannot underestimate how much of an advantage this would have been in the past.
The much deeper irony of creationists like Comfort appealing to the eye as evidence of design, is that it is actually one of the most amazing examples of natural selection we have. It is an even more compelling example when you consider that, as Richard Dawkins points out, the vertebrate eye has evolved many times independently.
When one says “the” eye, by the way, one implicitly means the vertebrate eye, but serviceable image-forming eyes have evolved between 40 and 60 times, independently from scratch, in many different invertebrate groups. Among these 40-plus independent evolutions, at least nine distinct design principles have been discovered, including pinhole eyes, two kinds of camera-lens eyes, curved-reflector (“satellite dish”) eyes, and several kinds of compound eyes.
I really do wonder what more can we say? If the likes of Ray Comfort are still recycling this argument in the face of so much contradictory evidence, I doubt that our wondrous, complex eyes will ever see its long overdue demise.