How the placenta evolved from an ancient virus
Kelsey Coolahan's obsession began during her third year at Cooper Medical School, part of Rowan University in New Jersey. "I'm in the labor and delivery room, and I'm witnessing this whole miracle-of-birth thing, it's amazing," Coolahan remembered. "And then you have one lonely resident at the foot of the bed who is slowly pulling something out of mom's uterus ...
https://whyy.org/segments/the-placenta-went-viral-and-protomammals-were-born/