I know it’s said in jest, but if your kid is attached while you’re sleeping, i.e. breastfeeding and cosleeping, which a hunter gatherer society would most certainly do, babies don’t fuss unless they’re sick or something. My wife slept soundly through the night and said “it’s amazing she doesn’t feed at night!” (Referring to our daughter), and I said, shocked, “she eats at night, she makes a soft noise and you just roll over and pop a boob in her mouth without waking up!” This is entirely a modern problem of our own creation and convenience.