Modern vs. Prehistoric Sleeping Patterns

Many individuals in today’s society report sleep deprivation, a trend believed to be correlated with the use of technology, particularly before going to bed. Theories suggest that caveman ancestors living in the prehistoric times (Cretaceous period 66 million years ago or hunter-gatherer societies in the Paleolithic Era 10,000 years ago) naturally slept much longer than we do now. In 2015 the Bureau of Labor Statistics reported that employed individuals 25-54 years old with children under 18 slept on average 7.8 hours per night. A study published by LiveScience sought to compare sleeping patterns between modern hunter-gatherer societies and modern individuals in order to analyze the potential difference.

94 members of three hunter-gatherer societies in rural parts of Africa and South America that live very similarly to how their ancestors did were studied for 1,165 days. Results indicated that these individuals slept approximately 6.5 hours a night whereas people in industrial societies slept about 7-8 hours a night. Although the light from smartphones, computers, or other screens suggests circadian rhythm disruption, scientists suggest “people do not get any less sleep today than they did in prehistoric times.” In fact, researchers found that unlike industrial people, hunter-gatherers did not go to sleep as soon as it got dark. Rather, they prepared for the following day, then went to sleep about 3 hours after sunset and usually woke up before sunrise. Scientists suggest that the amount of sleep has more to do with temperatures rather than the length of daylight hours.

Dr. Daniel Cavanagh, assistant professor at Loyola University Chicago, gave a talk about his research with Drosophila clock gate. He explained sleeping patterns as being determined by one’s circadian rhythm, which can be influenced by environmental factors. In particular, he introduced clock cells that help keep a particular circadian rhythm. His research with Drosophila clock cells stems from the study “Genetic Analysis of Sleep” conducted by Amanda Crocker and Amita Sehgal. Using mice, the researchers investigated a variety of genes and neurotransmitters contributing to sleep. They mention that the circadian rhythm, specifically in mammals, is maintained by molecular feedback loops, which can be maintained in cells in a 24-hour rhythm. The main components of the circadian clock are divided into positive regulators NAPS2/CLOCK, which drive the transcription of Per and Cry that feedback and inhibit the transcription of BMAL1, and negative regulators CLOCK/NPAS2 that follow degradation and initiate a new cycle. Mice with mutations in CLOCK, BMAL, and Cry genes demonstrated changes in sleep amount. These results suggest a strong genetic contribution to sleep. Additionally, neurotransmitter and receptors majorly contribute to the neurochemical analysis of sleep. The study analyzed particular genes and neurotransmitters that affected sleep such as: Orexin (stabilizes sleep, wake-promoting signal), Acetylcholine (critical for waking EEG and REM sleep), biogenic amines norepinephrine histamine, dopamine, serotonin (wake-promoting properties), GABA (sleep-promoting neurotransmitter), and somnogens (tells body to go to sleep).

Relating back to the article about sleep differences between modern and prehistoric individuals, it is interesting that sleep, having a significant genetic contribution that would have derived from prehistoric ancestors, varies so much in modern societies. Rather than using a modern hunter-gatherer society, it would be interesting to study the genetic composition of sleep for truly prehistoric hunter-gatherer individuals (of course, that is nearly impossible). Potential factors for this variance are the extremely different lifestyles, technological contribution, activity level, environmental composition, evolution, or others.

Pictures:

https://assets.entrepreneur.com/content/3x2/1300/20150709172101-sleeping-man-iphone-apple-bed.jpeg

http://www.123rf.com/photo_24226819_illustration-of-a-caveman-family-sleeping-together-under-a-wooly-blanket.html

References:
"American Time Use Survey." Bureau of Labor Statistics, United States Department of Labor, 20 Dec.2016,
                     www.bls.gov/tus/charts/#older. Accessed 27 Feb. 2017.

Choi, Charles Q. "Modern Hunter-Gatherers Probably Get Less Sleep Than You Do." Live Science, Purch, 15 
                     Oct. 2015, www.livescience.com/52495-hunter-gatherers-sleep.html. Accessed 27 Feb. 2017.

Crocker, Amanda, and Amita Sehgal. Genetic Analysis of Sleep. Cold Spring Harbor Laboratory Press, 2010.

"Modern Hunter-Gatherers Probably Get Less Sleep Than You Do." Scientific American, 2015, 
                     www.scientificamericna.com/articl/modern-hunter-gatherers-probably-get-less-sleep-than-you-do/.
                     Accessed 27 Feb. 2017.