How Did Ancient Humans Sleep in the Heat? No Fans, No Ice, No AC

Seventy-seven thousand years ago, a young man lies awake in a rock shelter above a river in what is now South Africa. The stone at his back is still warm, the air is as warm as his skin, and a mosquito is whining by his ear. No fan, no ice. So how did ancient people get through nights too hot for sleep? In this illustrated story, we follow one sleepless night in the shelter, and then the evidence: why falling asleep depends on losing heat through your hands and feet, why human skin is packed with sweat glands, when our ancestors may have lost their fur, savanna chimpanzees at Fongoli that hide from the heat in caves, the oldest known grass beds laid on ash at Border Cave, insect-repelling leaves in the bedding at Sibudu, what activity trackers revealed about sleep among the Hadza, San and Tsimane, midday naps and the debate over "two sleeps", why someone in a camp is almost always awake, raised bark beds, sleeping on flat roofs, and the fishing-net mosquito nets that Herodotus described in Egypt. Along the way we keep track of what we actually know and what is still debated. ⏱ Chapters 0:00 A sleepless night in a rock shelter 1:14 A fresh bed of leaves 2:36 Why a hot night is so hard 3:28 Built to sweat 4:22 When did we lose our fur? 5:52 Savanna chimps and cool caves 6:55 The oldest beds: grass and ash 7:35 Sibudu: leaves against mosquitoes 8:33 Sleeping when the night cools 9:47 Midday naps 10:05 Did people really sleep in two shifts? 10:38 Someone is always awake 12:06 Raised beds 12:28 Up on the roof 13:27 Herodotus and the fishing net 14:07 So how did they cope with the heat? 14:59 Back to the rock shelter 📚 Mentioned in this video: skin temperature and falling asleep (Kräuchi and colleagues, Basel, 1999); eccrine sweat gland density in humans, chimpanzees and macaques (Kamberov and colleagues, 2018); the age of the dark-skin variant of the MC1R gene (Rogers, Iltis and Wooding, 2004); the Fongoli savanna chimpanzees, Senegal (Jill Pruetz and colleagues); grass bedding on ash at Border Cave, South Africa/Eswatini (Wadley and colleagues, 2020); sedge bedding with river wild quince leaves at Sibudu, South Africa (Wadley and colleagues, 2011); sleep in the Hadza, San and Tsimane (Yetish, Siegel and colleagues, 2015); segmented sleep in historical Europe (Roger Ekirch); the "poorly sleeping grandparent" study of Hadza sleep (Samson and colleagues, 2017); rooftop sleeping in Mesopotamia and in Baghdad in the 1950s; Herodotus, Histories 2.95. The rock shelter scenes are an illustrated reconstruction based on the Sibudu finds, not a description of a specific night. 💬 What's your own trick for a hot night: a fan, a wet towel, a cold shower? Tell us in the comments. 🔔 Subscribe to Cave Ink — ancient life, everyday questions. #history #prehistory #sleep #archaeology #stoneage