I thought it was already established that the genes for photosensitivity led to the formation of eyes in all animals. And that the proposed benefit in the early

I thought it was already established that the genes for photosensitivity led to the formation of eyes in all animals. And that the proposed benefit in the early Earth's oceans was to keep bacteria from frying themselves if they got too close to the surface (due to there being no ozone layer way back then). So, I'm not sure if this is all earth shattering knowledge at this point, but it's still a fun read.