Is human sleep naturally polyphasic? Research on tribal people has indicated that it is. Many natives throughout the world either nap regularly or split their night sleep, which is not only evidence for their sleep being naturally polyphasic, but also towards the claim that human sleep is alterable. In this post the sleeping patterns of native people throughout the world will be examined, from the amazonian rainforest to Africa, as shown in Figure 1. This post will be split into two parts: The first part will center on native people that have been examined in peer-reviewed papers, and the other will focus on the tribal people that are discussed in non-peer-reviewed books and articles.
Hadza and Malagasy
Here we will take a look at the sleep patterns of Hadza people and people living in a small-scale non-electric agricultural society on Madagascar, to see how native people around the equator sleep when they aren’t being subjected to artificial light. These two tribes are quite different from each other, both in terms of lifestyles and sleep.
“Segmented sleep in a nonelectric, small‐scale agricultural society in Madagascar” (Samson et al.) explored the sleep pattern of people living on Madagascar, and what they found is quite interesting. Their sleep patterns resemble Dual core 1-extended (DC1-ext). In other words, they split their night sleep and nap during the day. There are not many populations that split their night sleep in today’s society, yet this population does. Additionally, they also utilize the midday energy dip to sleep almost every day. The sleep schedule of these people is perhaps like this because they don’t have the same environmental pressures as hunter-gatherer societies like the Hadza or Piraha people, so they can allow themselves to sleep during the optimal times of the night.
The study about the Hadza people is called “Hadza sleep biology: Evidence for flexible sleep‐wake patterns in hunter‐gatherers” (Samson et al). These people have very inefficient sleep – they spend a lot of time in bed but only sleep for a short duration while also taking opportunistic daytime naps. Unlike the Malagasy people, the Hazda don’t regularly wake up in the middle of the night for long durations. They also have very long sleep onset, or it takes very long for them to fall asleep. Samson proposes that is most likely to ensure that they don’t get attacked when they are sleeping. Predators are more dangerous when you are asleep, and if they attack you’ll want to be alert enough to defend yourself. This is may why it takes longer for these people to fall asleep when they try to go to sleep.
Like the Malagasy people, the Hazda do wake up in the middle of the night, but only for short durations at a time. The reason why the Hadza people wake up during the night more may also be so that someone is always awake in case of surprise attacks. This is similar to the theory why humans have different sleep chronotypes. Some people enjoy being awake longer, some wake up earlier, others have bouts of wakefulness in the middle of the night and so on. This way, it is unlikely that everyone in a tribe sleeps at the exact same hours, which presumably boosts their survivability. As mentioned previously, the Malagasy people don’t find it necessary to be awake around the clock, so they have stricter sleep times.
While on the topic of strict sleep times, Hadza people’s sleep is rather strange. They have a flexible sleep pattern, which changes quite frequently. This may also serve to increase their survival chances. They may have a daytime nap on some days but not everyday, but that’s not all. Their wake and sleep times also change daily, so one day they may go to sleep at 21:00 and 23:00 the next day. And this flexible sleep pattern is most likely an adaptation to coping with more vulnerability during their sleep.
Even though these two tribes have different sleep patterns, where the Malagasy people practice segmented sleep and the Hadza have siesta-like patterns, both are still biphasic in nature.
Tribal people from books and articles
The sleeping patterns of certain tribal people are well-explored in an article called “Toward a Comparative Developmental Ecology of Human Sleep”, and it is one of the best pieces of literature out there if you are interested in an introduction to how tribal people sleep across the world. The available information presented in this part is only a fraction of everything that is covered in that article, so you are highly encouraged to read it if you want to learn more.
The Gabra people live around Kenya and Ethiopia. They take frequent naps and do not care about what the surface they sleep on. This means that they can nap on the ground, leaves and so on. Their naps usually span between 15 and 30 minutes, and they can occur at any time throughout the day. In this tribe, old men nap even longer, up to 2 hours.
This tribe originates in Pakistan. The people from this tribe take frequent naps, usually between 12:00 and 14:30. Thus, it can be said that they practice a Siesta lifestyle.
The Balinese is a group that live in Indonesia. They nap often and their naps are usually between 13:00 and 15:00. In addition to their Siesta lifestyle, they also practice late night rituals, which delay their bedtimes.
The Hiwi people live in Colombia and Venezuela. They nap very frequently during the day, but they also segment their core sleep from time to time. The sleep pattern of these people actually resembles that of the Malagasy people, who also practiced a similar lifestyle.
In Congo you can find the Efe people. These people won’t nap unless they are sick, and taking naps is actually a symbol of weakness for them. They don’t have strict bedtimes, but they sometimes wake up in the middle of the night and then finish their core sleep after staying awake for a few hours.
The !Kung tribe can be found in Namibia, Angola and Botswana. This is a very interesting tribe, since they do not abide by any bedtimes. In other words, they have fluctuating sleep schedules. These people also sometimes wake up after sleeping for a while and continue sleeping later, which means that they have Segmented sleep tendencies.
The Ache are a tribe that live in Paraguay. These people follow a Segmented-like sleep pattern on some days where they wake up in the middle of the night, stay awake for a few hours and then continue sleeping later.
In addition to the already mentioned tribes, the book “Don’t Sleep, There Are Snakes: Life and Language in the Amazonian Jungle (Vintage Departure)” by Daniel Everet briefly touches on the sleep patterns of the Piraha tribe. This tribe has a very unique sleep pattern, since it could be said that they almost follow a nap-only schedule with many short naps during the day and night. Their naps last from 15 minutes to 2 hours (which is classified as a core sleep but the principle still remains). They have no dedicated core sleep and instead chat throughout the night. The reason why they have this unique sleep pattern is that the Amazonian jungle is dangerous and filled with predators, and sleeping for long durations exposes them to attacks.
In various tribes around the world, diverse sleep patterns appear to serve survival advantages or cultural needs. Even where there are not known reasons, these examples demonstrate that polyphasic sleep has been natural and frequent throughout human history.
Main author: Crimson
Page last updated: 20 October 2020