[exDemMom]

And the numbers would seem more difficult with all the little bits and pieces that make up the eye but which until they come together to produce vision seem to have very little survival advantage.

The process is not quite as random as some people seem to think. The laws of physics put a very strong constraint on what is and is not possible. Vision is based on the fact that some chemicals absorb specific wavelengths of light. Even single-cell organisms have eyespots. Eyes have arisen many times, in many different forms.

[1010RD]

Even single-cell organisms have eyespots. Eyes have arisen many times, in many different forms.

Why do eyespots develop and what is the environmental advantage of an eyespot? I am curious about this because the human eye is so complex in and of itself, but you also need the processing power of the brain to have it all come together. What's the value of a partial eye?