Irreducible Complexity

One popular argument in favor of intelligent design is the idea of irreducible complexity. The idea is that certain biological systems are so complicated and interdependent that a piece-wise  incremental development of the type evolution suggests is not possible. The most common example given is that of the eye. The eye is a fantastically sophisticated sensory organ and we with all our industry have not yet matched it, but is it irreducible? No, of course not.

The short argument is that you probably know people with less complicated eyes: the colorblind. Colorblindness is an example of what happens when you remove one of the parts of the eye (in this case one of the three types of cones). These eyes work just fine and have been reduced in complexity.

We can take it much further though.

• Suppose we removed all cones. Now you see in black and white - still very useful.
• Remove the ability to swivel the eye. Now you must move your head around to look - fine.
• Now we remove the ability of the iris to adjust the pupil size. Now you don't see as well in low or very bright light, but that's not bad.
• Remove the ability to adjust focal depth. Now things near or far are fuzzy, but these are still eyes you would be glad to have.
• Remove the lens entirely. Now everything is fuzzy, but you can still tell if a predator is pouncing toward you.
• Remove the eyeball itself, leaving rod sensors in a depression on your face. You now collect less light and lose more focus, but some sight remains.
• Remove the indentation. Now it's just light sensors on skin. The sensors are less shaded so you get more noise and less sensitivity and protection, but they still work.
• Simplify the rods to just cells slightly reactive to light. You still know if it's daytime - that's something.