Contrary to assumption, it appears that sleep duration in the absence of electricity is not significantly longer than it is in contemporary Western society

Chapter 21 - Hunter-Gatherer Sleep and Novel Human Sleep Adaptations. Gandhi Yetish, Ronald McGregor. Handbook of Behavioral Neuroscience, Volume 30, 2019, Pages 317-331. https://doi.org/10.1016/B978-0-12-813743-7.00021-9

Abstract: In this volume, we review sleep in diverse, nonelectric populations worldwide and present some background on the different lifestyles of these populations. In particular, we focus on hunter-gatherers and foragers, because humans lived as foragers, exclusively, since we first evolved, 315,000 years ago, until the first recorded instance of agriculture, 9500 years ago. While modern foragers cannot be seen as an analogue for the past, they do present a unique lens to study how people's biology and behavior respond to contemporary hunting and gathering conditions. Rather than advance arguments that one population sleeps better than all the rest, we approach sleep as an adaptation, shaped by natural selection, that allows people to best fit their sleep into their specific conditions. We discuss how this approach can improve our understanding of worldwide variation in sleep and suggest some ways it may apply to sleep patterns in the West as well.