Konner, The Evolution of Childhood (Harvard University Press, 2010) + Small, Our Babies, Ourselves
Solitary infant sleep is a recent industrial cultural anomaly
Anthropologists documenting infant sleep across cultures. Continuous mother-infant contact day and night is the species norm. Separating mothers and infants for sleep is a recent industrial practice, largely confined to Western societies. Small's 'Our Babies, Ourselves' synthesized data from dozens of societies.
Melvin Konner (Emory) and Meredith Small (Cornell) are two anthropologists whose work documented infant sleep practices across cultures. Konner's work with the Ju/'hoansi people of the Kalahari documented continuous mother-infant contact day and night, with no separate infant sleep arrangements.
Small's book 'Our Babies, Ourselves' synthesized cross-cultural data from dozens of societies, including the rapidly shrinking number that still practiced traditional infant care. The pattern was consistent.
Separating mothers and infants for sleep is a recent practice, largely confined to industrialized Western societies, and it represents a sharp departure from what infants have evolved to expect. This does not by itself prove cosleeping is better. It does establish that the species norm is cosleeping, and that the burden of proof should sit on the practice that is the historical anomaly.
Continuous
Mother-infant contact, traditional cultures
Recent
Western separation practice
Industrialized
Limited geographic spread
Konner & Small
Primary anthropologists
Why it matters
Solitary infant sleep is not the default human practice. It is a recent industrial cultural choice. That does not settle the question of what is best, but it does change which side has to justify itself.
This is one finding from the research library behind How to Birth a Mother. Everything here traces back to a study, a dataset, or a systematic review.