Why do Jung insist on collective unconscious when we have more plausible explanations? When you have same world, same relationships and same organism, same brains across humans, isn't it natural to have same myths?

Instead of creating an alternative world for myths, where they live independent of our biological existence, it's more believable to find cues in biological systems to create similar characters. Maybe we are preprogrammed to see white bearded men as a sages and they represent knowledge for us. This is rather developed version of falling from tree dreams.