In the movie, after George tells Ape that his courtship displays aren't working, Ape notes that he found a book of human mating rituals and reads off a pickup line: "What's a nice girl like you doing in a plane like this?" It's highly possible that Ape found this book among the wreckage of the plane that crashed in the Bukuvu that brought George there in the first place.
Doubles as potential Fridge Horror. George is much less intelligent than Ape despite heavy hints that Ape raised him and thus George, if he has normal human brain function, should at least be as intelligent as Ape. However, this makes sense if you remember that George has been smashing into trees repeatedly since he was young; his stupidity is probably the result of a large amount of head trauma leading to brain damage.
