Ancestor: a person from whom we descended, who lived generations ago.
Cognitive: relating to mental processes....more
Hypothesis: a possible reason or explanation for an observation.
Lesser apes: the group of apes least related to humans, that contains 16 species of gibbon apes; these apes spend a lot of time in the trees but can walk on two legs on the ground....more
Primate: a category of mammal that includes monkeys, lemurs, apes, and humans.
Scientists hypothesize that, over the course of human evolution, sleep patterns have changed as to benefit the development of high intelligence. Groups of apes that evolved earlier are thought to show sleep habits or patterns that also evolved earlier. For example, lesser apes slept on branches or on other temporary locations. This type of rest did not allow for long durations of sleep because the locations were vulnerable to predators or to other environmental disturbances.
Sleep patterns shifted in great apes that evolved later, like orangutans, gorillas, chimpanzees and bonobos. These primates still slept in trees, but slept in bed-like structures called nests. Scientists hypothesize that the stable environment of a nest allowed great apes to experience a deeper and longer sleep. Improved sleep quality eventually led to enhanced brain function, which increased intelligence in great apes.
While nests improved sleep for the apes, sleeping in trees still limited sleep quality. Scientists propose that early humans transitioned from sleeping in trees to sleeping on the ground. This move improved the stability of their nest-- which, at this point, began to resemble a house.
A highly stable nest greatly increased the duration and quality of sleep, which led to even more brain development in early humans. This brain development eventually allowed early humans to improve their cognitive abilities beyond that in other great apes. Higher quality sleep also enabled humans to sleep for a shorter part of the day, giving them more time for learning, socializing, and defending their communities.
More recently, scientists have begun to wonder whether this evolutionary explanation of sleep can also explain some of the more common sleep problems that people have today.
Insomnia - The inability to sleep
Narcolepsy - The tendency to fall asleep during the day without the desire to do so.
Seasonal Affective Disorder - Depression-like symptoms that appear during winter months
Sleep Apnea - Difficulty breathing consistently throughout the night.
Additional images via Wikimedia Commons. Yawning baby by Solangg.
Sisi Gao, Patrick McGurrin. (2017, June 21). Human Origins of Sleep. ASU - Ask A Biologist. Retrieved January 13, 2021 from https://askabiologist.asu.edu/human-origins-sleep
Sisi Gao, Patrick McGurrin. "Human Origins of Sleep". ASU - Ask A Biologist. 21 June, 2017. https://askabiologist.asu.edu/human-origins-sleep
Sisi Gao, Patrick McGurrin. "Human Origins of Sleep". ASU - Ask A Biologist. 21 Jun 2017. ASU - Ask A Biologist, Web. 13 Jan 2021. https://askabiologist.asu.edu/human-origins-sleep
Humans need a daily period of deep sleep to maintain health.