system
A chat on 4chan
human
My personal beliefs on this is many souls 'immigrated' here from other places. Maybe they died here accidentally while on a mission or during battle, or were sent here to 'learn' or chose this life to teach or help others.
I think they can get stuck in a reincarnation cycle hear when their souls 'gain weight' so they can't escape Earth's gravity. They reincarnate here over and over just like most souls, and don't have any memories except what they gain in their mortal lifetime so maybe they're not much different from anyone else, at least materialistically they are very similar. 
How they're different? I'd assume spiritually they're very different, but also similar as they're human too. Other than that I dunno.
How many are like this? Also dunno, but it's probably more than most people realize.
gpt
That's basically the view of Robert Monroe. Have you read his books?