system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is watching a campfire or fireplace burn so relaxing?
gpt
Since fire seems to have been developed by our ancestors at least a million years ago, before they were even human - *homo erectus* was thought to have had fire - the experience certainly goes deep with us.

A campfire was a deterrent to predators who would otherwise sneak in and snatch people.  Fear of fire is an even deeper instinct that goes back to the first land animals, because the high oxygen content of the atmosphere at times made random forest fires an utter apocalypse.  So even the smell was and is a deterrent.

But by whatever process, hominids overcame that and came to use fire as a tool, and the same glow and dancing light that sparked fear in *everything* else became a source of security to the hominid line.  As long as that fire danced and crackled, the leopards would keep their distance.

It's the same thing with the sound of a soft rain.  Sitting at the entrance to a cave mouth with soft rain trickling outside, you were secure that no leopard was going to be out in that rain looking for you or your children.  It was taking it easy somewhere the same as you were, and couldn't smell you even if it was hungry.