A new paper describes a case of a monkey mother having her birth assisted by another monkey -- in other words, a monkey midwife
The head, once fully exposed, was grabbed by the midwife, who pulled the baby out with both hands. She progressed to rip open the birth membranes. The new mother reclaimed the infant within a minute, and severed the umbilical cord. She ate the placenta as the midwife descended.
Black snub-nosed monkeys are Old World monkeys (cercopithecoid primates) native to China. I think this is cool not because it shows that monkeys need midwives (they don't) but because it shows that the behavioral flexibility that may have enabled midwifery in early humans is very extensive among primates. A delicious placental incentive may seem inventive, but humans are mystifyingly strange in being among the few mammals who don't regularly consume the placenta after birth.
Primate births are still rarely enough observed that the comparative dataset is quite small. As field studies extend this area of observation more broadly, we may yet discover more behavioral flexibility in different primates.