In The Grapes of Wrath, what does John Steinbeck show about mankind's connection to others?

Steinbeck's overall message to humanity is about the
ability to transform reality.  Steinbeck uses Tom Joad to show how someone who is self-
exiled, seeking to not look after anything other than their own interests can rise to
being a collective being and be an agent of change.  The loudest point that Steinbeck
makes is that individuals do not have to be chained to their existence, modeling what it
is.  They have the power and can make conscious choices on any level in order to
transform their world into what it should be as opposed to what is might exist as.  In
the time period of the Great Depression, this is a poignantly powerful message.  Tom
Joad recognizes that he is a part of something larger than herself. Ma Joad recognizes
that she is a part of something larger than herself.  Even Rose of Sharon with the last
action of the novel finally acquiesces to the idea that she is part of something larger
than herself.  The message that Steinbeck wishes to deliver to the reader is that there
is a larger and more transcendent image of ourselves that has to be appropriated and
adopted in order to find and discover real and lasting social
change.