This post is inspired by Jessa Gamble, an internationally recognized science writer who gave an interesting TED Talk about how our natural sleep cycle is nothing like our modern sleep cycle.  Watch the video here. 

Gamble’s bio from Wikipedia:

Jessa is a Canadian and English author and co-owner of the science blog The Last Word on Nothing. Her book, The Siesta and the Midnight Sun: How Our Bodies Experience Time, documents the rituals surrounding daily rhythms. Along with local languages and beliefs, these schedules are losing their global diversity and succumbing to what Gamble calls “circadian imperialism.

Horseshoe Crabs and Sleep Cycles

We can learn a lot about sleep by studying the resilient and venerable horseshoe crab. This incredible blue-blooded crustacean (good Radiolab podcast about this amazing crab here) has survived all mass extinctions. A half a billion years of evolution.

It turns out that if you take a horseshoe crab that lives on the East Coast, put it in a sloped cage and fly it to the West Coast, it will scurry up the cage as if the tide was rising. It will continue to scurry up the slope for weeks until the crab’s internal clock adapts to the new surroundings. Gamble states that “Life evolved under the conditions of light and darkness.” All plants and animals that have more than two cells have these internal clocks that have evolved over time. Often taking cues from the surrounding environment.

Human Evolution and The Great White North

Like the horseshoe crab, humans too have an internal body clock. Gamble talks about what we can learn about sleep from experiments involving subjects who live in a bunker deep underground in complete darkness for a couple of months at a time. Similarly to the horseshoe crab in the sloped cage, the subjects living in the bunker start waking up 15 minutes later every day as their internal clocks start slowly adjusting to their new external environment. 

Gamble states that “[the internal body clock] is incredibly important in our lives. It’s a huge driver for culture and I think that it’s the most underrated force on our behaviour.” She goes on to say that humans evolved as a species primarily near the equator which means that our internal body clocks are well-adjusted to the typical 12-hour day and 12-hour night cycle. As humans spread around the planet, they started to experience different natural light cycles.

It is important to note that Gamble lives in Arctic Canada, where there is perpetual daylight in the summer and perpetual darkness in the winter. The indigenous culture in Arctic Canada is highly dependent on the seasons. In the winter darkness, people get lots of sleep and primarily spend time indoors with family. In the summer, people are very active and work very long hours. Gamble describes the heightened activity in the summer as “manic”. People that live in constant darkness might also give us clues to perhaps the most productive sleep pattern.

Is there an Ideal Sleep Pattern?

People that live in constant darkness without any artificial light actually sleep twice per night. Wait… what? Apparently people in these conditions tend to go to sleep at 8:00PM and sleep until midnight. Then they fall back asleep from 2:00AM until sunrise. Gamble describes these two awake hours as a “meditative quiet” where there is a surge of prolactin, a chemical produced in the pituitary gland that influences sleep by promoting rapid eye movement sleep (REMS).

If this actually is the ideal sleep pattern, it is very different the sleep pattern found in modern society. The modern, fast-paced, globalized culture promotes jet lag, 24-hour businesses, and shift work. Gamble questions whether the benefits of modernization outweigh the benefits of the ideal sleep cycle. We live in a society that often values productivity over health. Maybe we can learn something from the humans whose internal clocks evolved to become less reliant on daylight.