The stories of our Gods and goddesses are written down in the Prose Edda and the Poetic Edda. The Eddas are valuable resources, but they are symbolic, not historical. Their contents were subject to all sorts of factors that affect the way we use them religiously - human
Interpretation and bias being the main ones!
Nothing in our lore suggests that the Eddas are meant to be taken literally, and to do so puts us in the same category as those fundamentalist Christians who take the Bible, word for word, as the exact and infallible word of their God. To take the tales of our Gods and Goddesses as lessons urging us to mate outside our kind (or outside our species!) is as wrong as the Christian who argues that the Genesis creation story should be taken as scientific truth. Myth is bigger than that.
Books in PDF format to read:
Phil Hine - Devotions And DemonessesIrv Slauson - The Religion Of Odin
Michael Jordan - Dictionary Of Gods And Goddesses