um... man was here LONG before writing was invented. Information from the garden of Eden HAD to of been passed down orally
Yes, some of the earliest info was orally transmitted. However your statement here is incorrect:
Moses wrote down what had previously been passed down orally.
Some of the info was oral. But other items in the book of Genesis were no doubt gleaned from written records. Stephen says in Acts 7 that Moses was educated in all the wisdom of the Egyptians; presumably this means being able to read and write what was in their libraries.
In addition,editor-surveyor correctly says Moses had the benefit of direct revelation as well which is stated many times in the Pentateuch.