Of Beorn

[Iargwath]

I believe Beorn is the son of a Maia and a human. More specifically Radagast and a human woman.

Could be so. But it is said that Beorn is in distant relation to the Edain of the first age. Also your assumption may be correct Maia and human...But i think Luthien and Beren would be more probable. After all Beren did love animals and he also went under the spell of skin-changing as u mentioned Keeper of Dol Golder (sorry about that) you are correct...it was a spell.
But what was this spell? Did it remain within a man's body to be passed on to generations? Did the spell inflicted on Beren stay within him...myb leading to Beorn's skin-changing?
These are my assumptions which you probably dont care for...but will create a bit of a debate if possible...