system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do people find the dark so fearful?

Of course there can be many reasons, but is there any ultimate characteristic that is most common or something?
gpt
Evolution. Darkness presents increased risk. We as a species depend strongly upon vision, which is in particular very hindered by darkness. The same is not true of every other species, some of which are formidable predators, nor is it an inconvenience to risks like falls and other sources of injury.

So us being strongly active (ranging and the like) at night, for much of our evolutionary history, would face a greater danger to our survival than if we were to sit down and shaddup. Fear is a natural 'discourager.'