According to the physician William Whitty Hall, author of a popular 19th-century sleep hygiene book, individuals in co-sleeping societies were like “wolves, hogs and vermin” who “huddle together,” whereas in the civilized West, “each child, as it grows up, has a separate apartment.” Where social sleeping persisted among white people, it was usually associated with poverty and considered a social ill — as in Jacob Riis’s 1890 How the Other Half Lives. One hundred and fifty tenement dwellers, he observed with horror, slept “on filthy floors in two buildings,” and tramps dozed off in the doorways.
Anyone who’s had a baby in the last few decades knows how strenuously doctors warn against co-sleeping. In many states, it’s even illegal to sleep in the same bed with your infant. Parents are warned over and over of the dangers of co-sleeping, and even subjected to hyperbolic ads that liken sleeping with your baby to letting your baby sleep with a butcher knife.