sleep biology

How the Brain Cleans Itself During Sleep: The Glymphatic System

by
Brain cross-section showing cerebrospinal fluid flow through glymphatic channels during deep sleep

The glymphatic system pumps cerebrospinal fluid through the brain during deep sleep, clearing amyloid beta and tau proteins linked to Alzheimer’s. One night of sleep deprivation raises amyloid by 5% on PET scan. Here is the full mechanism and what disrupts it.

Why Sleep Didn’t Kill Our Ancestors: The Evolutionary Science of Human Sleep

by
Prehistoric human sleeping at night representing evolutionary sleep science and survival biology

Early humans slept just 6.4 hours per night on average, in two bouts, with individual sleep timing staggered across the group so that all adults were simultaneously unconscious for only 18 minutes per night. Read the evolutionary biology of sleep timing, predator evasion, and why unconsciousness survived selection pressure.