Evolution of the Eye and Senses (formerly "Just Some Thoughts")

Hello, castis.Yes, this subject has been beaten to death. Darwin himself discussed a possible scenario for the evolution of eyes, based on the "partial eyes" that exist in the animal kingdom.No, the proto-eye did not have to begin so far back. It is believed that eyes evolved in 14 different linneages, independently of one another.The evolution of the eye from no eye has been modelled on a computer. In each step of the model, the new version of the eye is only very slightly different from the older version. And the new version is a little better at seeing than the old version. So it is possible for there to be a sequence of ever-so-slightly better eyes.You are correct (if I am reading you correctly) that the eye has to start with some cells have a photosensitive chemical. I think that the photosensitive pigments in the human eye are very slight variations of proteins involved in locomotion in single cells. I will let people more qualified than I discuss this more detail.

It would be hard to say. Eyes developed, I believe, before the Cambrian, before animals had easily fossilizable body parts.But, in a very technical sense, the first animal (or ancestor) that had a recognizable part that formed the first basis for an eye may have been something like Loudmouth's Blepharisma. I think this certainly counts.