Sleep is something we have evolved to do - it is part of our biology to need sleep to rest and recover for so many reasons we don’t even know yet but nature has chosen to preserve this genetic need across all organisms to sleep or have some sort of sleep like activity. 

It should come as no surprise that our modern lifestyles and bad habits have made us neglect the biological programming we have from our ancestors to wake and rest with the rising and setting of the sun. Whilst once upon a time we rose with daylight and hunted and gathered food, and watching the sunset we would retire to sleep or perhaps tell stories by a campfire, we are now on our phone and laptop screens until just before bedtime, exposing our eyes to blue light triggering the secretion of cortisol. 

Our eyes have cells in them which trigger the hypothalamus in the brain which is the Suprachiasmatic nucleus. This tells our bodies whether to release cortisol or melatonin. Imagine there are two taps in your brain and when your eyes see blue long wave light during the day they tell your brain to release the cortisol tap to keep you alert and awake because its daylight and there could be predators and food and other things to be aware of. Then as the sun sets and the day ends your eyes see red short wave lights and tells your brain okay the day is ending its time to rest lets release that melatonin tap to make me nice and sleepy and get ready for some restoration. Ingenious isn’t it. Well our 21st century lifestyle has all but overridden natures well written rules in our biology. We have black out blinds and fall asleep with cell phones still in our hands and sleep late in the mornings long past dawn. But you know who does sleep perfectly like we were intended to? Babies. 

Once babies develop their circadian rhythms, they are not yet affected by our bad habits and socialised to sleep in later in the day and stay up later at night, so like our ancestors before us, and undoubtedly like us as babies, they get up at the crack of dawn seeing all this glorious blue long wave light and are cortisol filled and ready for their day. Similarly, they sleep again in the early evening when the sun sets. 

Research by Ekirch suggests that our ancestors would sleep in two segments over night with a first sleep and a second sleep. Each period of sleep would be approximately 4 hours with an hour or 2 between sleeps at around midnight to 2am when people would socialise, do activities and make babies. The book Why your sleep matters by Sarah Ockwell Smith suggests that the reason babies often wake up at about 1 - 2am is for this very reason - because they are following a biological preset need in our bodies. 

However, Matthew Walker, one of the worlds sleep experts and Author of ‘Why we need sleep’ states that this phenomenon occurred largely in the Western world and was not present in any other ancient civilisations, suggesting it was more of a social fad rather than any biological need. And that what is more normal is for humans to have a long night sleep and a second sleep in the afternoon such as a siesta. Either way humans are meant to have a biphasic sleep. 

Studies performed in countries like Greece where shopkeepers were used to having an afternoon nap found that as tourism impacted these tiny villages and old men were forced to keep their shops open in the afternoon, the impact this had on their health was terrible. Those that were sometimes napping had 12% lower coronary mortality and those that were systematically napping had 37% lower coronary mortality. 

It just goes to show how important it is to follow the direction we receive from our instinctual babies who rise with the sun, nap in the afternoon and sleep early at night. If only more businesses allowed us to have a 30 minute nap after lunch think about how much healthier, happier and rested we would be. And productive. Cause lets face it that’s probably all they care about. 

Research

Why your baby’s sleep matters - Sarah Ockwell Smith

Why does sleep matter - Matthew Walker 

https://bigthink.com/robby-berman/for-1000s-of-years-we-went-to-bed-twice-a-night-2 

https://www.ncbi.nlm.nih.gov/pubmed/17296887 

https://www.health.harvard.edu/newsletter_article/Siestas_and_your_heart_Can_you_nap_your_way_to_health

https://www.sciencealert.com/humans-used-to-sleep-in-two-shifts-maybe-we-should-again

Cover Image by Giani Pralea from Pixabay