Aren't all scriptures essentially human creations?
The Vedas themselves explain that although they appear within human society for our benefit, they weren't written by ordinary humans, but have always existed. They're like the instruction manual for how to live in this world; and most instruction manuals aren't written by the inventors themselves.
In Sanskrit the scriptures are called apaurusheya, not of human origin. According to Vedic wisdom, the Supreme Person empowers various other persons—sages, prophets, and acharyas—with the necessary vision for distributing and teaching the scriptures.
The validity of scriptural directions can be tested the same way as scientific theories. If 1) they appear reasonable and 2) they don't contradict anything we know to be true, and 3) if by acting according to them we get the predicted result, we may have more confidence in them. Blind doubt is just as un-beneficial as blind faith.