Who told you that?

[alatar]

I think that in many mythologies/belief systems that the god or gods are the possessors of all knowledge. He/She/It/They have this information from the beginning by definition ('Gods are typically all-knowing.'). All - or when there's a pantheon, some - things that are, were, to be and can be are already known.

The knowledge is then given to the lesser beings. There are Golden Ages when ancestors knew much more, but, being part of the world and not that of the gods, this knowledge is lost.

As examples, by the Third Age in Middle Earth, there are none that have the subtlety and understanding to make Silmarils (okay, so the Trees were gone too). The Dwarves surpass their ancestors in few ways, but as a whole, know and can do/make less than Durin I. The elves - those that haven't left - make not much more than lembas and cloaks. The men of Westernesse no longer make towers like Orthanc or knives like Sting.

"For it is the doom of men that they forget." - Merlin in Excalibur

So, in many mythologies, we're experiencing a knowledge entropy where, if one were to graph it, would be a downward asymptotic curve where we'll always know some things, but nothing like our ancestors or the gods.

To me, however, in the real world, it's the exact opposite.