What actions in 1984, by George Orwell, signals the end of Winston's humanity?
I agree with the repudiation of Julia as one of the moments that indicates to us that Winston's humanity is over. The fact that both of them meet up in the park and so openly and honestly confess that they sold one another out and betrayed each other is painful to read and a moment where their humanity has ended to a great extent. The "change" that both of them speak is one where their humanity exits, and in its place is an existence where one's sense of identity disappears. This moment is a critical one in signaling the end of Winston's humanity. I would also say that the celebration of the news of an Oceanic victory is another moment where the reader fully grasps that Winston's humanity is over and that the gutted shell of a man that is there is one who is no longer the human being that once was.
In my opinion, the event that signals the end of Winston's humanity is when he betrays Julia. I think that this shows him giving up his human emotions so as to just be able to get along in his society.
During the earlier parts of the book, I think, Winston's relationship with Julia shows him trying to remain human. It shows him trying to have human relationships and human feelings. Once he gives this up, he is no longer fully human.
I think that the central message of this book is that totalitarian governments try to take away the humanity of their people. They try to take away people's ability to think, to have their own memories, and to have normal human relationships.