The empirical evidence that is in the link from Gunnar_Zarncke’s post is:
And throughout the book’s description of these events, there was one constant:
All of the white people who joined Indian tribes loved it and refused to go back to white civilization. All the Indians who joined white civilization hated it and did everything they could to go back to their previous tribal lives.
The empirical evidence that is in the link from Gunnar_Zarncke’s post is:
This is not just from introspection.