Eight Hours of Uninterrupted Sleep May Be a Modern Fantasy, Anthropologist Says

The ideal of eight uninterrupted hours of sleep has become a modern expectation, but a leading anthropologist argues this notion is overly rigid compared to historical human sleep patterns. Alyssa Crittenden, an anthropologist at the University of Nevada, Las Vegas, contends that the idea of resting eight hours without interruption is “physiologically, a fantasy.”

Crittenden’s perspective stems from her extensive research with the Hadza, a hunter-gatherer community in Tanzania. Over two decades, she has witnessed firsthand how the Hadza’s sleep patterns differ significantly from the contemporary expectation of a single uninterrupted block. In an interview with HuffPost España, she explained that healthy human sleep does not necessarily have to occur in one continuous period.

The Hadza, who live in close contact with their environment, have sleep patterns that align closely with natural changes in light, temperature, and daily activity. A 2017 study led by Crittenden’s team equipped 33 Hadza volunteers with activity monitors for a total of 393 days. The researchers found that Hadza adults averaged just 6.25 hours of sleep per day, with a 68.9% sleep efficiency rate.

Interestingly, sleep among the Hadza was highly flexible. Naps were a common occurrence, happening on about 54% of observed days, with each nap lasting approximately 47.5 minutes. This pattern of sleeping in shorter blocks throughout the day contrasts with the modern expectation of uninterrupted nighttime rest.

Crittenden emphasizes that the Hadza’s sleep patterns highlight the importance of sleep quality alongside duration. While the study examined one population living in a specific ecological and social context, it challenges the notion that humans “only need six hours” of sleep. The research suggests that human sleep has historically been adaptable, shifting to suit different environmental and cultural conditions.

Historical evidence, such as that provided by historian Roger Ekirch, indicates that people in preindustrial societies often experienced multiple sleep periods, separated by a period of quiet nighttime activity. However, some scholars caution against interpreting historical sources as uniformly supporting a two-phase sleep routine. Regardless, the historical record demonstrates that human sleep schedules have evolved in response to cultural and environmental factors.

The Hadza findings also shed light on the role of napping in modern sleep. The researchers noted that the Hadza’s daytime naps were generally opportunistic, rather than a response to poor nighttime sleep. This suggests that sleep can be distributed across different parts of the 24-hour cycle, rather than being confined to a single nighttime block. Modern sleep guidelines, such as those from the CDC, emphasize the importance of total sleep duration while accommodating individual circadian rhythms.

While eight hours of uninterrupted sleep is often recommended, the Hadza research underscores that this is not a universally applicable standard. The concept of eight hours as a single uninterrupted block may contribute to unnecessary anxiety about sleep. Instead, the flexibility observed in the Hadza’s sleep patterns suggests that sleep can be adapted to meet both biological and environmental needs.

Ultimately, the Hadza case illustrates that human sleep has taken various forms throughout history, from consolidated nighttime sleep to segmented sleep patterns and the incorporation of daytime naps. These observations suggest that the modern expectation of a perfect, uninterrupted eight-hour night may not be a biologically necessary requirement. Instead, the scientific focus should be on understanding how sleep interacts with biology, environment, culture, and individual needs.