As I was lying in bed, thinking about this (I have a brain that just NEVER shuts up), it occurred to me that there may be other similar cases; specifically some of the "feral children" or "wolf children" that crop up over the years. Not the ones who have been discovered in a state of neglect, but the ones found running around "wild" in the woods.

My memory is vague on this, but I recall a pair of sisters and I believe they never really learned to walk upright (and died fairly young) who had a 'secret language' and never learned to speak. A collection of these cases could show whether there was a possible parallel. And if memory serves, the bulk of these feral children came from that region of the world (a belt from India to the Middle East.)