How Did Ancient Humans Sleep at Night With No Walls or Locks?

How did ancient humans sleep at night with no walls, no locks and no roof? In one Tanzanian camp, researchers tracked sleep for twenty days, and everyone was asleep at the same moment for just eighteen minutes in total. This video follows the evidence from chimpanzee tree nests to 200,000-year-old grass beds, insect-killing leaves and a 23,000-year-old hut floor, and explains what that number means. All research and sources are linked below. CHAPTERS 0:00 No walls, no locks: the question 0:40 The cartoon cave and Border Cave 1:47 Three dangers: teeth, people, the ground 3:12 Chimpanzee nests, fire and insect-killing bedding 4:57 Sleep intensity and three societies 6:25 The 23,000-year-old bedroom plan 6:56 Back to the 18 minutes 8:11 The four-step answer 8:27 The lock is new, the listening is old PEOPLE & SITES MENTIONED People (lead researchers): Lyn Wadley: grass bedding at Border Cave (Science, 2020) and bedding at Sibudu (Science, 2011). David Samson: Hadza sleep studies (2017), chimpanzee nests with Kevin Hunt (2014), the sleep intensity hypothesis with Charles Nunn (2015). Gandhi Yetish: sleep in three preindustrial societies (2015). Francesco Berna: fire at Wonderwerk Cave (2012). Dani Nadel: bedding at Ohalo II (2004). Masako Tamaki: the first-night effect (Current Biology, 2016). Christine Sievers: plant bedding at Border Cave (2022). Bob Brain: matched the two puncture marks on the Swartkrans skull to a leopard's lower canines (per a museum article). Sites: Border Cave, South Africa: grass beds on ash layers, 200,000+ years old. Sibudu, KwaZulu-Natal, South Africa: sedge beds with insect-killing leaves, about 77,000 years ago. Wonderwerk Cave, South Africa: burned bone and ashed plants, about 1 million years old. Swartkrans, South Africa: a young Paranthropus robustus skull with two puncture marks. Semliki, Uganda: 1,844 chimpanzee night beds sampled. Ohalo II, Sea of Galilee, Israel: a hut floor with bedding, about 23,000 years old. Jebel Irhoud, Morocco: early Homo sapiens fossils, 315,000 years old. SOURCES Samson DR and colleagues (2017). Chronotype variation drives night-time sentinel-like behaviour in hunter-gatherers. Proceedings of the Royal Society B 284:20170967. https://doi.org/10.1098/rspb.2017.0967 Samson DR and colleagues (2017). Hadza sleep biology: evidence for flexible sleep-wake patterns in hunter-gatherers. American Journal of Physical Anthropology 162:573-582. https://doi.org/10.1002/ajpa.23160 Yetish G and colleagues (2015). Natural sleep and its seasonal variations in three pre-industrial societies. Current Biology 25:2862-2868. https://doi.org/10.1016/j.cub.2015.09... Wadley L and colleagues (2020). Fire and grass-bedding construction 200 thousand years ago at Border Cave, South Africa. Science 369:863-866. https://doi.org/10.1126/science.abc7239 Wadley L and colleagues (2011). Middle Stone Age bedding construction and settlement patterns at Sibudu, South Africa. Science 334:1388-1391. https://doi.org/10.1126/science.1213317 Sievers C and colleagues (2022). Plant bedding construction between 60,000 and 40,000 years ago at Border Cave, South Africa. Quaternary Science Reviews 275:107280. https://doi.org/10.1016/j.quascirev.2... Berna F and colleagues (2012). Microstratigraphic evidence of in situ fire in the Acheulean strata of Wonderwerk Cave. PNAS 109. https://doi.org/10.1073/pnas.1117620109 Nadel D and colleagues (2004). Stone Age hut in Israel yields world's oldest evidence of bedding. PNAS 101:6821-6826. https://doi.org/10.1073/pnas.0308557101 Samson DR, Hunt KD (2014). Chimpanzees preferentially select sleeping platform construction tree species with biomechanical properties. PLoS ONE 9:e95361. https://doi.org/10.1371/journal.pone.... Samson DR, Nunn CL (2015). Sleep intensity and the evolution of human cognition. Evolutionary Anthropology 24:225-237. https://doi.org/10.1002/evan.21464 Tamaki M and colleagues (2016). Night watch in one brain hemisphere during sleep associated with the first-night effect in humans. Current Biology 26:1190-1194. https://doi.org/10.1016/j.cub.2016.02... Hublin J-J and colleagues (2017). New fossils from Jebel Irhoud, Morocco and the pan-African origin of Homo sapiens. Nature 546:289-292. https://doi.org/10.1038/nature22336 Swartkrans SK 54: Ditsong National Museum of Natural History, Tawane M (2021), "Fossils and the evidence they provide: the tale of SK 54 and SK 349" (cites Brain CK 1970, Nature 225:1112-1119). Hypotheses (the sleep intensity hypothesis, sentinel-like vigilance, the first-night effect as a night watch) are presented as the authors' proposals, not settled facts.