For centuries, the inability to fall asleep and stay asleep has been treated as a medical failure. A careful reading of history, however, suggests that this modern view may be fundamentally wrong, and that what we call insomnia was once a vital survival advantage rather than a biological flaw. The contemporary expectation of an uninterrupted eight-hour sleep block is a relatively recent invention. Research into pre-industrial records indicates that our ancestors actually slept in a segmented pattern, waking naturally for an hour or two during the middle of the night before returning to sleep.
Dr. A. Roger Ekirch, a historian at Virginia Tech, spent 16 years examining diaries, court records, and literature from medieval times back to ancient Greece. He consistently found references to a biphasic sleep rhythm involving a “first sleep” and a “second sleep,” with a period of wakefulness between them.
During this middle gap, people were not frustrated or anxious. They prayed, talked, visited neighbors, and engaged in quiet activities. This suggests that the panicked wakefulness many experience at 2:00 a. m.
today may actually be an ancient biological program attempting to resume a schedule that modern life has suppressed. This pattern raises an important question: why would evolution favor a broken sleep cycle in a dangerous world? Researchers propose the “sentinel hypothesis” as a possible answer. In ancestral environments, it was risky for an entire group to be unconscious at once.
A 2017 study of the Hadzabe people, a hunter-gatherer community in northern Tanzania, provided striking data. Researchers led by Dr. David Samson tracked the sleep of 33 villagers over 20 days. Across more than 200 hours of recorded sleep, there were only 18 total minutes when every adult was asleep simultaneously.
On average, at least eight individuals were awake at any given time. This staggered wakefulness provided the group with near-constant protection against nocturnal predators and raids. In this context, the person who could not sleep was performing a critical role: guarding those who could. Archaeological evidence shows that ancient humans actively managed their sleep environments.
In Sibudu Cave in South Africa, archaeologist Lynn Wadley found fossilized bedding dating back 77,000 years. The layered mattress structure was topped with leaves from the Cryptocarya woodii tree, which contain chemical compounds that repel mosquitoes. This shows that early humans engineered their beds to reduce sleep disturbance from pests and disease, addressing physical discomfort while maintaining the useful alertness of the sentinel role. They did not view all wakefulness as a problem to be eliminated.
Ancient medicine also offers insight into how sleeplessness was managed. Many cultures developed botanical remedies, including opium poppy in the classical world, and valerian root or chamomile earlier in the Neolithic period. Physicians like Dioscorides documented the use of mandrake root to induce sleep before surgery. This knowledge suggests that ancient people distinguished between productive sentinel wakefulness and anxious wakefulness that required intervention.
They used plants not to forcefully shut down the mind, but to manage the specific type of alertness that was burdensome rather than useful. The psychological environment of the ancient night was also different. For people at greater risk from predators, hyper-vigilance was adaptive. The brain in high-risk environments tends to remain in lighter sleep stages, remaining reactive to sounds and movement.
Anthropologist Polly Wiessner found that among the ! Kung people of the Kalahari, daytime conversation centered on logistics and social matters. Nighttime talk, however, focused on stories, myths, and the supernatural. This turned unwanted wakefulness into a cultural activity, with the sleepless serving as storytellers and keepers of tradition.
This transformation of wakefulness into shared ritual meant that the night hours were not lonely or wasted. They were sacred, communal, and meaningful. The person awake was not isolated but connected to the group’s history and mythology. Modern society has taken a different approach.
Attempts to force a rigid, single eight-hour sleep block have removed the sentinel, replaced the communal fire with screens, and made the night a solitary struggle. The insomnia many experience today may be an ancient survival instinct seeking purpose in a world that no longer requires it. The evidence from the Hadza, from Sibudu Cave, and from historical archives points to a consistent conclusion: humans are designed for a staggered, partially awake collective existence, not for uniform unconsciousness. The night was divided into time for rest, time for watching, and time for ritual.
Ancient people did not expect perfect, continuous sleep. They integrated wakefulness into their lives as a practical tool for protection, a time for social bonding, and an opportunity for cultural transmission. Their alertness was not a disorder but a valuable asset. The modern struggle with sleep may reflect a mismatch between an environment that has become safe and predictable and biology that evolved for very different conditions.
A body that still produces sharp alertness at 3:00 a. m. may simply be doing exactly what it was designed to do.
This reframing suggests that the next time sleep fails to come, it may be worth remembering that this state of mind was, for most of human history, a vital contribution to the community’s safety and cultural continuity.
