Current state of whose world? At 13 many of us had been intimately involved in raising infants and toddlers for years. It's not surprising that the 13-year-old in question is a girl.
She was able to do it in the Amazon because that's an environment she knows. Many, many others may not be able to do it in the Amazon specifically, but would be able to do so in a wilderness that they know.
I mean, right now what I'm reading from you is that all the teenagers today who could in fact keep an infant sibling alive in a wilderness environment they're familiar with are not part of reality, which is probably not your intention. So there's room enough for more clarity
