...in how to survive in the wilderness, how to read the stars for directions, etc.

When we were in Peru, they explained to us how they were able to move gigantic rocks and boulders... and how they built things and terraces for agriculture, etc. They had math skills and much knowledge in prehistoric times! When we were in Greece, we saw amazing ruins on the islands that had been buried underground for thousands of years, that had advanced water pipes, toilets, baths, etc. Truly amazing. Archeaologists continue to uncover ruins that no one even knew were there from thousands of years ago. They could have had languages and record keeping for all we know that have been lost or buried deep. Civilizations rise and fall.