LogFAQs > #908029771

YoshitoKikuchi posted...

dolomedes posted...

an eyeball didn't just show up out of nowhere. it began as a single cell that could respond to light stimulus.

That doesn't answer how it came to take the shape and form it currently has.

Or, how did sight develop in the first place?

Well it happened over a very very long time with gradual improvements. With something so important as sight (and basic senses in general), the better an individual can orient themselves to the world, which is a significant advantage that is certain to be passed down in animals that rely on it.

The first "eyes" were little bumps on the surface of an organism's head that simply reacted to light. These organisms couldn't really "see" but more like they were able to sense very vague shadows.

Over time, eventually there arose organisms with greater visual definition with more clumps of cells. Then some had a bulb of translucent skin over those cells, focusing the light a little better. Eventually, more and more improvements kept adding up, until it reached a high level of complexity.

Also remember, the eye didn't have to evolve independently in every single creature that has them today. For example, all vertebrates (fish, amphibians, reptiles, birds, mammals) come from a common ancestor, who would have developed the groundwork for the basic eye blueprint we all share.