Chimpanzee beds are cleaner than human beds
Researchers have suspected for a long time that the elaborate beds and nests where the great apes spend the night provide efficient protection against predators and bloodsuckers. “That is certainly true. But the big surprise is that chimpanzee beds are cleaner than most human beds”, says Adriana Hernandez-Aguilar from the CEES.
Ape beds are complex structures built by interweaving branches into a secure foundation covered by a leafy mattress. The apes can even cover themselves with a nice duvet made from leaves, and CEES Researcher Adriana Hernandez-Aguilar confirms that chimpanzee beds are quite comfortable.
“I only have lain down on a bed to test it, but my colleague, anthropologist Fiona A. Stewart, has slept in them overnight. She reported that these beds are quite comfortable – and definitely more comfortable than sleeping on the ground, which she also tried in a safe area”, says Hernandez-Aguilar.
Comparing beds and surroundings
Adriana Hernandez-Aguilar, Fiona Stewart and other researchers have taken samples from 41 recently abandoned chimpanzee beds in the Issa Valley in Tanzania, and compared the amounts of bacteria and arthropods in the beds with those of surrounding vegetation and the ground – and human beds. The results give food for thought.
“Before we started our investigation, we thought that the chimpanzee beds would be richer in bacteria and arthropods than the branches found on surrounding trees. We used special swabs, almost like Q-tips, in order to take samples of bacteria, and we used a special vacuum cleaner that was designed to extract insects, spiders and other arthropods from the nests and branches. We were looking for these small creatures because many of them live as parasites and bloodsuckers on mammals”, Hernandez-Aguilar explains.
Cleaner than a human bed
The researchers didn’t find what they were expecting: The differences between beds and surroundings were instead very small. The number of arthropods were actually larger on the ground than in the beds.
“But the really big surprise was that we found almost no fecal bacteria in these beds. When you sample a human bed for comparison, it contains a lot of fecal bacteria and other bacteria. That’s why we say that chimpanzees’ beds are in a way cleaner than a human bed”, she adds.
Adriana Hernandez-Aguilar is actually impressed by the cleanliness of chimpanzee beds.
“The chimpanzees defecate and urinate over the sides of their beds, and they are very effective in doing this without soiling the beds themselves. They are also constantly cleaning themselves and other members of the group through grooming”, Hernandez-Aguilar comments.
Flushing toilets without closing the lid
One important reason for the amount of fecal bacteria in human beds, is that we have our toilets inside the house.
“Many people don’t close the lid before they flush the toilet, and this causes the bacteria to start flying around. They usually settle down on the bathroom floor, and many people like to go around barefoot inside the house. From there, it is only a short way for the bacteria from the bathroom to the bed”.
Adriana Hernandez-Aguilar adds that chimpanzees make themselves a new bed nearly every evening, while most people don’t change the linen on their beds very often.
“Young chimpanzees sleep with their mother, but they start making their own beds when they are around 3,5 years old. They spend a lot of time playing and practicing the technique, and the result is that they can make a nice new bed in only a few minutes”.
Hernandez-Aguilar and Stewart climbed a lot of trees in order to collect samples from chimpanzee beds. This could be hard work because the beds are quite high up in the trees, and chimpanzees in this area would never build a nest in a tree with branches lower than four meters above ground. That makes it hard for leopards and lions to attack them.
Shedding light on human evolution
The indoor environment created by the construction of homes and other buildings is often considered to be uniquely different from other environments. It is composed of organisms that are less diverse than those of the outdoors and strongly sourced by, or dependent upon, human bodies.
Yet, no one before Hernandez-Aguilar and her co-researchers have compared the composition of species found in contemporary human homes to that of structures built by other mammals. Therefore, the results from studies of chimpanzee beds can also shed some light on human evolution.
“The bed is an invention of the great apes – including humans, gorillas, chimpanzees, bonobos and orangutans – because we all make beds to sleep in. That separates us from the monkeys, the primates with the tails, who only sleep on the bare branches”.
“The invention of beds may be linked to the development of intelligence and the need for falling into deep sleep in order to “clean” the brain after a hard day's work. All the great apes need a certain amount of deep sleep, and without a nest, they could risk falling from the trees”, she explains.
The chimpanzees don’t use their beds only for sleeping, because the nights in areas close to equator last for 12 hours all year round. The apes go to the trees and their nests when darkness falls, and then they spend a lot of time vocalizing, socializing, eating, grooming each other – and finally, sleeping.
Adriana Hernandez-Aguilar adds that the current great apes are not the ancestors of humans in evolutionary terms. We did however have a common ancestor some 8 to 10 millions of years ago, and it may have been this ancestor who invented the bed.
The invention of fire
Most scientists believe that the early hominins had to sleep in trees to avoid being eaten. After the invention of fire some two million years ago, our human ancestors were able to sleep on the ground – but the great apes stayed in the trees.
Little is known about the origin of human houses and homes, but archaeologists believe that we started building homes – probably primitive huts – at least between 20 000 and 300 000 years ago. According to the “hygiene hypothesis”, the urban lifestyle, with its relatively limited exposure to infectious agents during childhood, might be behind the current epidemics of asthma, eczema and food allergies.
The chimpanzee lifestyle, with regard to their microbes, is probably a good match for our ancestral exposures. But the chimpanzee beds do not mirror the beds humans sleep in today. When Washington Post reporter Ben Guarino wrote a commentary about the chimpanzee beds, his conclusion was that the cleanliness of chimpanzee beds is an unattainable goal for most humans – unless you live in an IKEA warehouse, where you can find a new place to sleep every night.
“The microbial difference between chimp and human bedding is remarkable. Human beds are rife with microbes associated with our own bodies. Most of the germs in chimpanzee nests are not coming from their own bodies, but from the forest environment”, concludes Hernandez-Aguilar.
Thoemmes MS et al.: Ecology of sleeping: the microbial and arthropod associates of chimpanzee beds. Royal Society Open Science, 16 May 2018.
Hernandez-Aguilar, R. A., Moore, J., and Stanford, C. B. 2013: Chimpanzee nesting patterns in a dry habitat: Ecological influences and preferences. American Journal of Primatology 75:979-994
Stewart, F. Brief communication, 2011: Why sleep in a nest? Empirical testing of the function of simple shelters made by wild chimpanzees. American Journal of Physical Anthropology 146: 313-318.
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