Researchers at Duke University (North Carolina) have compiled a database of the sleep patterns of hundreds of mammals, including those of 21 species of primates –baboons, lemurs, orangutans, chimpanzees …–, as well as of human beings.
In return, human sleep is more efficient, since only a small proportion of the time we spend sleeping is spent in light sleep phases. Most of our time in bed is in deep sleep. For example, the REM phase constitutes 25% of our rest period. During this phase, so called because it uses the acronym for Rapid Eye Movemen t (Rapid Eye Movement, in English, due to the characteristic movement of the eyeballs under the eyelids), the brain is very active and we dream and capture a large amount of information of our environment.
In contrast, many primates only dedicate 5% of their sleep to this REM stage. According to anthropologist and study co-author David Samson, “humans are unique in our ability to enjoy shorter but higher quality sleep.” This scientist spent more than 2,000 hours observing orangutans sleeping in both REM and REM phases. Other states For the researchers , the shortening of the sleeping period in people compared to other animals is not only a result of the arrival of artificial light and screens , which have allowed us to take advantage of hours of darkness to be active.
Another different study conducted with hunter-gatherer societies living without electricity in Tanzania, Namibia, and Bolivia found that they stay with their eyes closed just a little longer than those of us who enjoy electronic gadgets. Therefore, the arrival of artificial light and other advances in modern life cannot be blamed for the shortened hours of sleep , according to Samson. He, along with fellow Duke anthropologist Charlie Nunn, suggests that humans replace quantity of sleep with quality long before we have televisions and cell phones.
These researchers believe that a qualitative change occurred when we went from sleeping in trees to sleeping on the ground. This allowed them to rest by the fire and in close proximity to other people to gain warmth and protect themselves from predators, which would help them sleep more soundly. At the same time, sleeping less enabled more hours to spend learning new skills and strengthening social ties , which in turn improved memory capacity and brain power.
