Temperature regulates sleep more than light

Research has shown that body temperature, not just light, plays a key role in regulating our biological clock. The natural cooling of the night helps signal to the body when it is time to sleep.

Modern homes disrupt natural cooling

Studies by neuroscientists Jerome Siegel and Gandhi Yetish, published in Current Biology in 2015, found that people living without electricity sleep in line with nighttime temperature drops, not sunset. Modern heated and insulated homes, however, maintain similar temperatures day and night, removing this natural signal.

Ancient sleep patterns observed in traditional communities

To understand historical sleep habits, Siegel and Yetish studied three communities without electricity: the Tsimane in Bolivia, the Hadza in Tanzania, and the San in southern Africa. Their findings showed that these groups did not sleep immediately after sunset, contrary to common belief.

Sleep follows temperature changes

In these communities, sleep began when the air cooled and ended when it was coldest. The body’s blood vessels constrict in the cold to retain heat, suggesting that temperature significantly influences sleep cycles and biological rhythms.

Cultural perspectives on sleep

Interestingly, some of these communities do not have a common term for insomnia, highlighting how their natural sleep patterns may not align with modern sleep disorders.