I'm currently reading Why We Sleep and just finished a chapter on how humans' ancestors came out of the trees and started sleeping on the ground. It's speculat

I'm currently reading Why We Sleep and just finished a chapter on how humans' ancestors came out of the trees and started sleeping on the ground. It's speculated that early humans' use of fire made this non-suicidal - keeping away the big nocturnal predators and also reducing the number of ticks, etc, preying on them.