The study, published in the anthropological journal Proceedings of the Royal Society B, studied the Hazda people, a group of modern hunter-gatherers from Tanzania. Research indicates that varying sleep cycles in its population, usually associated with age, allow at least some members of the community to remain awake and attentive to danger throughout the night. Similar studies have previously drawn such conclusions about animals like birds and mice, but this is the first study to identify this behavior in humans.
