[missedthecue]

Interestingly they don't name the phenomenon they describe with the eyeball. The concept is called "irreducible complexity" and applies to lots of other different areas, such as wings and the flagella of bacteria.

To quote Darwin, it seems "absurd in the highest possible degree" to posit that a fully functioning set of wings + the necessary fine motor skills and brain function required to effectively utilize them would ever evolve in just one generation, but a partially evolved wing one generation on the way to becoming the wings we see today would be a liability more than a benefit. Just a useless flappy dead-weight which would quickly cause the owner to fall prey to hungry predators.