How Did Every Sleep Stage Stay Non-negotiable?

On Huberman Lab, a face-value reading treats sleep as profoundly detrimental. During sleep a person is not finding a mate, not reproducing, not foraging for food, not caring for the young, and is vulnerable to predation. Dr. Matt Walker says sleep probably should have been selected against on any single one among lost mating, lost reproduction, lost foraging, neglected young, or predation risk. Sleep was not selected against.

Sleep has fought its way through every step along the evolutionary path. Dr. Matt Walker says every sleep stage has also survived, as best he can tell, and states outright that the stages are non-negotiable. He is sure vast evolutionary benefits would have followed if Mother Nature had thin-sliced some of the sleep away. He says it looks as though she has not, and he is usually in favor of her wisdom after 3.6 million years.

Each stage stays non-negotiable because the stages survived the evolutionary path. He draws that conclusion from survival of the stages, while the missing thin slice of sleep remains his reading of the record rather than a settled removal.