The only back history a cat has is his own. As does any animal, actually. We are, with perhaps the exception of whales and dolphins, the only species that remembers what happened before we were born by word of mouth, reading, poems, family histories.
You can, if you're careful and patient, figure out why that dog you just got from the shelter is so afraid of pianos, or resents men wearing hats, or why that lovely cat will quietly disappear when strangers show up wearing boots.
I wonder what he remembers beyond the bad stuff.