In a striking account from National Geographic, primatologist and CARTA partner Fiona Stewart emerges as the central figure in unraveling one of evolution’s quiet mysteries: why humans—and our primate relatives—sleep the way we do. Stewart’s unusually immersive research saw her spend nights both in chimpanzee nests and on the forest floor, transforming her own body into a scientific instrument. Her findings were clear and compelling: elevated nests dramatically reduce sleep disturbances and insect exposure, suggesting that these woven structures function as sophisticated “sleep technology”—possibly one of the earliest innovations in the human evolutionary story.
While Stewart highlights the engineered benefits of the nest, evolutionary biologist and CARTA Executive Co-Director Pascal Gagneux provides a stark reminder of the physical risks and environmental dangers associated with these structures. Having climbed into more than 300 nests to collect DNA samples, Gagneux warns that nests can "explode" if jostled incorrectly and shares harrowing accounts of being attacked by grieving chimpanzees or the threat of ground predators like hyenas. Together, their insights illustrate the evolutionary tension between the safety of the trees and the eventual transition to cooperative ground-sleeping, which experts believe finally unlocked the cognitive capacity for human intelligence and language.
