system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Lots of species developed eyes to "see" but how did they know there were something to see in the first place ?

My 9 yo surprised me with this question this morning. He sometimes got some showerthough but this one is over my level. Hope you can help us :).
gpt
They didn't "know" anything.

The first "eyes" in nature weren't eyes so much as they were simply pigment spots that detected light. The little floaty microbes that could detect light had a major advantage over the ones that couldn't because they could find bright spots to photosynthesize in. 

From there on it became an evolutionary arms race. Eyes were a big advantage and better eyes allowed a creature to hunt more effectively or avoid hunters more effectively. That went on for millions of years until today when there are animals like us kicking around with comparatively huge eyes and big parts of our brains devoted entirely to processing and interpreting the information those eyes gather.