All the symbols are simple, I wouldn't be surprised if many children around the world scribble similar signs while doodling. It seems likely to me that the sign

All the symbols are simple, I wouldn't be surprised if many children around the world scribble similar signs while doodling. It seems likely to me that the signs arose in disparate locations through sheer coincidence instead of through an active Paleolithic common culture or a miraculously preserved memory of some ancient heritage - the ultimate source of the symbols - shared by far flung groups.