• UCLA Health
  • myUCLAhealth
  • School of Medicine
U Magazine

U Magazine

U Magazine
  • Home
  • Current Issue
  • Centennial Campaign for UCLA Issue
  • Browse U Magazine
  • Letters to the Editor
  • Subscribe
  • Contact
  • UCLA Health
  • myUCLAhealth
  • School of Medicine

U Magazine

Browse U Magazine

  1. Home
  2. Browse U Magazine
Share this
The Cutting Edge

Our Ancestors Probably Didn’t Get Eight Hours of Sleep a Night, Either

  Our Ancestors Probably Didn’t Get Eight Hours of Sleep a Night, Either  
 

Illustration: Maja Moden

A team of UCLA-led researchers studying sleeping patterns among traditional peoples whose lifestyles closely resemble those of our evolutionary ancestors found that the industrialized world’s sleep habits do not differ much from those of our pre-industrial forebears.

“The argument has always been that modern life has reduced our sleep time below the amount our ancestors got, but our data indicate that this is a myth,” says Jerome Siegel, PhD, professor of psychiatry and biobehavioral sciences.

The researchers monitored sleep patterns among the Hadza, hunter-gatherers who live near the Serengeti National Park in Tanzania; the Tsimane, hunter-horticulturalists who live along the Andean foothills in Boliva; and the San, hunter-gatherers in the Kalahari Desert of Namibia. It is the first study of sleep habits of people who maintain foraging and traditional hunting lifestyles in the present day. Measurements included length of sleep during the summer and winter, body temperatures, environmental temperatures and the amount of light exposure.

One myth dispelled by the results is that people in earlier eras went to bed at sundown. The subjects of the study stayed awake an average of nearly three-and-a-half hours after sunset. “The fact that we all stay up hours after sunset is absolutely normal and does not appear to be a new development,” Dr. Siegel says.

Most of the people studied by Dr. Siegel’s team slept less than seven hours each night, clocking an average of six hours and 25 minutes. The amount is at the low end of sleep averages documented among adults in industrialized societies in Europe and America. The amount they slept also was found to vary with the seasons — less in the summer and more in the winter.

One recent history suggested that humans evolved to sleep in two shifts, a practice chronicled in early European documents. But the people Dr. Siegel’s team studied rarely woke for long after going to sleep. Dr. Siegel chalks up the discrepancy to a difference in latitudes. The groups of people studied live near the equator, as did our earliest ancestors; by contrast, early Europeans migrated from the equator to latitudes with much longer nights, which may have altered natural sleeping patterns, he says.

Insomnia was so rare among those studied that the San and the Tsimane do not have a word for the disorder, which affects more than 20 percent of Americans. The reason may have to do with sleep temperature. The people studied consistently slept during the nightly period of declining ambient temperature, Dr. Siegel found. Invariably, they woke when temperatures, having fallen all night, hit the lowest point in the 24-hour period. This was the case even when the lowest temperature occurred after daybreak. The pattern resulted in roughly the same wake-up time each morning, a habit long recommended for treating sleep disorders.

The team was surprised to find that all three groups receive their maximal light exposure in the morning. This suggests that morning light may have the most important role in regulating mood and the suprachiasmatic nucleus, a group of neurons that serve as the brain’s clock. Morning light is uniquely effective in treating depression. “Many of us may be suffering from the disruption of this ancient pattern,” Dr. Siegel says.

“Natural Sleep and Its Seasonal Variations in Three Pre-industrial Societies,” Current Biology, November 2, 2015

 


Previous
A Better Stem Cell for Regenerative Medicine
Next
Progress toward Healing Scarred Hearts


YOU ARE VIEWING

Spring 2016

Spring 2016
E-Brochure
Printable PDF
IN THIS ISSUE
  • The Year that Was
  • A Joyful Return for Las Mariítas
  • A Better Stem Cell for Regenerative Medicine
  • Our Ancestors Probably Didn’t Get Eight Hours of Sleep a Night, Either
  • Progress toward Healing Scarred Hearts
  • BMI a Poor Measure of Health
  • Untapped Brain-cell Region Offers Goldmine of Drug Targets for Autism Treatments
  • Electric Patch Holds Promise for Treating PTS
  • New Strategy to Fight Ovarian Cancer
  • Frequent Use of Post-acute Care Associated with Higher Readmission
  • BPA Replacement in Plastic Accelerates Embryonic Development, Disrupts Reproductive System
  • Happy Feet, Happy Hearts
  • Healing the Invisible Wounds
  • Listen to the Voices Within
  • Rx for the Future
  • A Long and Winding Road
  • Honors & Awards
  • In Memoriam
  • A Late-in-Life Gift of Song
  • Reflections: Volunteering at the Venice Family Clinic
  • In Her Own Words: Blanca Samira Campos, MD (RES ’11)
  • Postcard from Guatemala
  • Celebrating the Generous Philanthropy of Wendy and Leonard Goldberg
  • Former UCLA Physician Establishes Neuroscience Chairs
  • Leaders of Tomorrow Scholars Dinner Honors Medical Students
  • Patient Center Named for Performers Lawrence and Gormé
  • World Presidents Organization Experiences UCLA Health for a Day
  • Advancing Research on Women’s Health
  • “Let’s Talk” Series Addresses Women’s Heart Disease
  • Holiday Spirit at Mattel Children’s Hospital UCLA
  • Gifts
  • In Memoriam
  • Special Delivery
Like Us on Facebook Follow Us on Twitter Subscribe to Our Videos on YouTube Follow us on Instagram Connect with Us on LinkedIn Follow us on Pinterest
UCLA Health hospitals ranked best hospitals by U.S. News & World Report
  • UCLA Health
  • Find a Doctor
  • School of Medicine
  • School of Nursing
  • UCLA Campus
  • Directory
  • Newsroom
  • Subscribe
  • Patient Stories
  • Giving
  • Careers
  • Volunteer
  • International Services
  • Privacy Practices
  • Nondiscrimination
  • Billing
  • Health Plans
  • Emergency
  • Report Broken Links
  • Terms of Use
  • 1-310-825-2631
  • Maps & Directions
  • Contact Us
  • Your Feedback
  • Report Misconduct
  • Get Social
  • Sitemap
Like Us on Facebook Follow Us on Twitter Subscribe to Our Videos on YouTube Follow us on Instagram Connect with Us on LinkedIn Follow us on Pinterest

Sign in to myUCLAhealth

Learn more about myUCLAhealth