What are some political and social changes that the Joads go through in The Grapes of Wrath?
Tom Joad and Ma Joad come to the poignant realization that where they once were a single unit as a family, clearly defined geographically and economically, once they get out on the road and become migrant workers they become part of a larger group. No longer are they a single family. They are now members of a class.
This can be seen in direct statements made by both Tom and Ma in the novel as well as in the family's actions. They share their food and they offer to help those in need. The novel ends with a great act of generosity from Rose of Sharon that demonstrates this expansive sense of connection to others who share their material plight.
These changes in perspective equate to political and social change as the characters learn to see that their material situation is a political and social one. Instead of tending to "their own business", the family realizes that their problems are actually collective problems with collective solutions.
Tom reflects on this in his final scene in the book:
“...I been all day an’ all night hidin’ alone. Guess who I been thinkin’ about? Casy! He talked a lot. Used ta bother me. But now I been thinkin’ what he said, an’ I can remember—all of it. Says one time he went out in the wilderness to find his own soul, an’ he found’ he didn’ have no soul that was his’n. Says he foun’ he jus’ got a little piece of a great big soul. Says a wilderness ain’t no good, ‘cause his little piece of a soul wasn’t no good ‘less it was with the rest, an’ was whole. Funny how I remember. Didn’ think I was even listenin’. But I know now a fella ain’t no good alone.”
Coming to believe in a collective identity shows that the sense of being a single, well-defined unit has been replaced by a new socio-political identity - a significant change from the self-reliance the family begins with.