Wildness as an Act of Preservation?

In researching my paper, I'm coming to glean some meaning from the seemingly crazy antics of Shaman (The Crooked Line) and Bertha/Antoinette (Jane Eyre/Wide Sargasso Sea). Shaman and Bertha are both described at some point as being wild, like animals. I postulate that as they have no other ways to transgress from their fates, they turn within themselves and become wild in order to avoid having the restraints of human construction thrown onto them. For example, when Manjhu moves into her husband's home, no one bothers to take responsibility for Shaman. She is wild to begin with, and after Manjhu leaves, she is neglected to such an extent that she becomes completely matted in grime and filth. She eats dirt and plays in the mud and refuses to be comforted by the humans around her, thus alienating herself from them and their customs. Bertha, thrown into marriage by her father (and against her wishes by her step-father in Rhys's version), can see no way out of the marriage. In Rhys's novel, Rochester even strips Antoinette of her rightful name, instead calling her Bertha. She goes mad trying to remember herself and she attacks her oppressors like an animal to keep them from compromising her sense of self.