system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is it so much more difficult for humans to fall asleep, compared to other species?

I already have the understanding that stress is a factor, but why did humans evolve into beings that typically need a "winding down" period in order to fall asleep? Evolutionarily speaking, I can understand the need for us to be on alert as hunter-gatherers. But why do the majority of us need at least anywhere from 5-30 minutes to actually lie in bed with our eyes closed in order to fall asleep?
gpt
A lot of this is psychologically stress related. Many of us are on our computers or otherwise staring at a screen right before bed. the blue light from our screens messes with our circadian rhythm, sometimes being more stimulating than sunlight.

We're also distracted right before bed. As our head hits the pillow all we can do is think and for some of us, that's when the worrying starts and we begin working it over in our heads for solutions to our problems. All this combined with lack of adequate exercise, caffeine, and dozens of other issues make it much harder to fall asleep.

Animals might not need this "winding down" period that we do, but they're not asleep the moment they close their eyes either. Animals go through the same sleep cycles as humans with differing lengths of each stage depending on their sleep requirements (ex. a cat that sleeps 10 hours at a time vs. a giraffe that sleeps 4 minutes at a time).  If you have a pet at home and some free time, you can watch them lay down to sleep and then try to wake them, chances are if you do within 10min. they'll pop their heads right up but if let them go for 30-45min. it may take some shaking to rouse them.